mybatis-spring集成原理探究
- 主线
- 问题
- 1. MapperFactoryBean 怎么注入 sqlSessionTemplate
- 2. Mapper代理对象创建时机
- 拓展
- 1.自动注入方式
- 2. @Autowired 原理
- 源码记录
- @MapperScan
- MapperScannerRegistrar
- MapperScannerConfigurer
- ClassPathMapperScanner
- ClassPathBeanDefinitionScanner
- MapperFactoryBean
- SqlSessionTemplate
- Configuration
- InterceptorChain
- Interceptor
- Plugin
- MapperRegistry
- MapperProxyFactory
- MapperProxy
- MapperMethod
- DefaultSqlSession
- Executor
- CachingExecutor
- BaseExecutor
- SimpleExecutor
- StatementHandler
- BaseStatementHandler
- PreparedStatementHandler
- ParameterHandler
- DefaultParameterHandler
- ResultSetHandler
- DefaultResultSetHandler
主线
- MapperScan 注解 Import MapperScannerRegistrar
- MapperScannerRegistrar 注册 MapperScannerConfigurer
- MapperScannerConfigurer 扫描 baesPackage 所有的 Mapper,利用 ClassPathBeanDefinitionScanner 并注册 BeanDeifinition,随后在 ClassPathMapperScanner 修改 BeanDeifinition 的属性,影响 Spring 注册 Bean 的行为
- 当Spring开始注册Mapper的时候,实际上所有Mapper的 BeanDefinition.beanClass 在步骤3的时候都已经变为了MapperFactoryBean,而 MapperFactoryBean 又实现了 FactoryBean接口,因此Spring最终注册的是 MapperFactoryBean,注意此时并未返回代理对象。
- 当需要使用Mapper的时候,比如在Service通过@Autowired自动注入Mapper,或者通过BeanFactory.getBean(“xxxMapper”)的时候,spring会通过mapper的beanName或者beanType去查找Bean(如studentMapper),这时才会调用MapperFactoryBean.getObject方法去创建代理对象,然后注入给Service。
- Mybatis使用的是JDK动态代理
问题
1. MapperFactoryBean 怎么注入 sqlSessionTemplate
MapperFactoryBean.getObject()方法如下,先getSqlSession(),而getSqlSession() 返回的this.sqlSessionTemplate 是何时、如何注入到MapperFactoryBean的
public class MapperFactoryBean<T> extends SqlSessionDaoSupport implements FactoryBean<T> {
@Override
public T getObject() throws Exception {
return getSqlSession().getMapper(this.mapperInterface);
}
}
public abstract class SqlSessionDaoSupport extends DaoSupport {
private SqlSessionTemplate sqlSessionTemplate;
public SqlSession getSqlSession() {
return this.sqlSessionTemplate;
}
public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
if (this.sqlSessionTemplate == null || sqlSessionFactory != this.sqlSessionTemplate.getSqlSessionFactory()) {
this.sqlSessionTemplate = createSqlSessionTemplate(sqlSessionFactory);
}
}
protected SqlSessionTemplate createSqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
return new SqlSessionTemplate(sqlSessionFactory);
}
public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) {
this.sqlSessionTemplate = sqlSessionTemplate;
}
}
问题探索:
将断点打在 sqlSessionTemplate 成员属性上,当运行到使用该属性的代码时,就会停止下来,这时就可以往前追溯sqlSessionTemplate 是如何被注入的
调用栈如下:
setSqlSessionTemplate:93, SqlSessionDaoSupport (org.mybatis.spring.support)
invoke0:-1, NativeMethodAccessorImpl (sun.reflect)
invoke:62, NativeMethodAccessorImpl (sun.reflect)
invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
invoke:498, Method (java.lang.reflect)
setValue:332, BeanWrapperImpl$BeanPropertyHandler (org.springframework.beans)
processLocalProperty:463, AbstractNestablePropertyAccessor (org.springframework.beans)
setPropertyValue:278, AbstractNestablePropertyAccessor (org.springframework.beans)
setPropertyValue:266, AbstractNestablePropertyAccessor (org.springframework.beans)
setPropertyValues:104, AbstractPropertyAccessor (org.springframework.beans)
setPropertyValues:79, AbstractPropertyAccessor (org.springframework.beans)
applyPropertyValues:1740, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support)
populateBean:1452, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support)
doCreateBean:619, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support)
createBean:542, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support)
lambda$doGetBean$0:335, AbstractBeanFactory (org.springframework.beans.factory.support)
getObject:-1, 351028485 (org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$34)
getSingleton:234, DefaultSingletonBeanRegistry (org.springframework.beans.factory.support)
doGetBean:333, AbstractBeanFactory (org.springframework.beans.factory.support)
getBean:208, AbstractBeanFactory (org.springframework.beans.factory.support)
preInstantiateSingletons:936, DefaultListableBeanFactory (org.springframework.beans.factory.support)
finishBeanFactoryInitialization:918, AbstractApplicationContext (org.springframework.context.support)
refresh:583, AbstractApplicationContext (org.springframework.context.support)
<init>:93, AnnotationConfigApplicationContext (org.springframework.context.annotation)
main:14, MainTest (com.kingo)
可以看到 populateBean 方法,该方法为 Bean 属性赋值,在执行 applyPropertyValues 前(真正为 Bean 属性赋值),我们可以先探究属性值是如何获取的
protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
if (bw == null) {
if (mbd.hasPropertyValues()) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
}
else {
// Skip property population phase for null instance.
return;
}
}
// Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
// state of the bean before properties are set. This can be used, for example,
// to support styles of field injection.
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {
if (!bp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
return;
}
}
}
PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
int resolvedAutowireMode = mbd.getResolvedAutowireMode();
if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// Add property values based on autowire by name if applicable.
if (resolvedAutowireMode == AUTOWIRE_BY_NAME) {
autowireByName(beanName, mbd, bw, newPvs);
}
// Add property values based on autowire by type if applicable.
// 通过debug运行,可以找出 PropertyValues 在此处会发生变化,
if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);
PropertyDescriptor[] filteredPds = null;
if (hasInstAwareBpps) {
if (pvs == null) {
pvs = mbd.getPropertyValues();
}
for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {
PropertyValues pvsToUse = bp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
pvsToUse = bp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
if (pvsToUse == null) {
return;
}
}
pvs = pvsToUse;
}
}
if (needsDepCheck) {
if (filteredPds == null) {
filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
}
checkDependencies(beanName, mbd, filteredPds, pvs);
}
if (pvs != null) {
applyPropertyValues(beanName, mbd, bw, pvs);
}
}
贴上 populateBean 的代码,重点关注里面 PropertyValues pvs 变量的赋值过程,主要是在autowireByType() 方法
要想进入该方法,必须满足条件 resolvedAutowireMode == AUTOWIRE_BY_TYPE,而resolvedAutowireMode 作为 BeanDefinition 的一个属性,此前在 MapperScannerConfigurer 注册BeanDefinition 的时候,其实已经重新设置了 resolvedAutowireMode 的值为 AUTOWIRE_BY_TYPE,因此可以满足该条件并执行 autowireByType(),从而获取到了SqlSessionTemplate的实例。
但是autowireByType() 要能成功获取属性值,有一个很重要的前提:Spring 容器提前注册好 SqlSessionTemplate 实例,具体原因需要继续探究 autowireByType() 方法的运行,此文不做详细回答。
如果是 spring+mybatis 可以通过以下三种方式去注册 SqlSessionTemplate 实例
1. 注册SqlSessionFactory
2. 注册SqlSessionFactoryBean
3. 注册 SqlSessionTemplate
@Configuration
@MapperScan(basePackages = {"com.kingo.mybatis.mapper"})
public class MybatisConfig {
@Bean
public DataSource dataSource() {
DruidDataSource dataSource = new DruidDataSource();
dataSource.setDriverClassName("***");
dataSource.setUrl("***");
dataSource.setUsername("***");
dataSource.setPassword("***");
return dataSource;
}
@Bean
public SqlSessionFactory sqlSessionFactory() {
Environment environment = new Environment("dev", new JdbcTransactionFactory(), dataSource());
return new DefaultSqlSessionFactory(new org.apache.ibatis.session.Configuration(environment));
}
@Bean
public SqlSessionFactoryBean sqlSessionFactoryBean() {
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setDataSource(dataSource());
return sqlSessionFactoryBean;
}
@Bean
public SqlSessionTemplate sqlSessionTemplate() {
return new SqlSessionTemplate(new DefaultSqlSessionFactory(new org.apache.ibatis.session.Configuration(new Environment("dev", new JdbcTransactionFactory(), dataSource()))));
}
@Bean
public MyFactoryBean myFactoryBean() {
return new MyFactoryBean();
}
}
其中前两种方法是因为 MapperFactoryBean 的父类 SqlSessionDaoSupport 包含了 setSqlSessionFactory(SqlSessionFactory sqlSessionFactory)方法, Spring检测到包含setter方法,只要SqlSessionFactory 注册到spring容器中,就可以将 SqlSessionFactory 注入进去,然后 SqlSessionDaoSupport 通过 SqlSessionFactory 去创建 SqlSessionTemplate。
如果是springboot+mybatis,则无需手动注册 SqlSessionFactory,因为在 MybatisAutoConfiguration 中已经注册了 SqlSessionFactoryBean。
随后Spring 就调用 Bean 的 setter 方法为属性赋值,因此 MapperFactoryBean 在 getObject() 时 执行getSqlSession() 获取到的 SqlSessionTemplate 是有值的。
在平时的开发中,我们经常采用 @Autowired 注解为 Bean 注入依赖,但 Mybatis 通过修改 BeanDefinition 的方式,也能使 Spring 给自己注入想要的依赖。
但当 SqlSessionTemplate 为空时,并不会像 @Autowired 一样报错。因此需要自行判断属性是否注入成功,MapperFactoryBean 的父类 DaoSupport 实现了 InitializingBean 接口,通过 afterPropertiesSet() 去校验属性值是否赋值成功。
当然,不通过 @Autowired 这种方式去注入依赖,可以减少对 Spring 的依赖,通用性更强。
2. Mapper代理对象创建时机
通过debug发现,MapperFactoryBean注册到容器中的时候,其实代理对象并未创建。当需要使用到 Mapper 的时候,断点才会停在MapperFactoryBean.getObject方法。问题的关键在于getBean方法传过去的 name。
举例:
如果通过StuService调用StuMapper,并且StuService的注册先于StuMapper的话,Bean的注册顺序会是这样:
- StuService 注册,发现依赖于 StuMapper,于是getBean(“stuMapper”),此时的bean是一个普通bean,并没有FactoryBean前缀
- 先将 MapperFactoryBean 注册,然后再调用 MapperFactoryBean.getObject 方法将代理类创建出来并注册到容器中。可以关注此时 MapperFactoryBean 与后续注册 的Mapper(MapperFactoryBean)地址是否一样
- 当开始注册Mapper的时候,是通过**getBean(“&stuMapper”)**来获取FactoryBean,这里就会拿到先前已经注册好的 MapperFactoryBean,直接返回回去,不会再次创建代理对象
拓展
1.自动注入方式
平常开发的时候,如果需要注入Bean,一般都是通过@Autowired让spring自动装配进来。通过mybatis集成spring的源码分析,我们得知还可以设置Bedifinition.autowireMode让spring自动装配,但前提是所需注入的bean需要提前的在spring容器中注册好
public class MyFactoryBean implements FactoryBean<Account> {
private SqlSessionTemplate sqlSessionTemplate;
public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
if (this.sqlSessionTemplate == null || sqlSessionFactory != this.sqlSessionTemplate.getSqlSessionFactory()) {
this.sqlSessionTemplate = createSqlSessionTemplate(sqlSessionFactory);
}
}
protected SqlSessionTemplate createSqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
return new SqlSessionTemplate(sqlSessionFactory);
}
public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) {
this.sqlSessionTemplate = sqlSessionTemplate;
}
public Account getObject() throws Exception {
Account account = new Account();
account.setName("Jianguo");
account.setMoney(BigDecimal.valueOf(10000000L));
return account;
}
public Class<?> getObjectType() {
return Account.class;
}
}
public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
AbstractBeanDefinition beanDefinition = (AbstractBeanDefinition) registry.getBeanDefinition("myFactoryBean");
beanDefinition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
}
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
}
}
2. @Autowired 原理
在注册StuService的时候,需要调用populateBean方法为属性赋值,此时会遍历所有实现了InstantiationAwareBeanPostProcessor接口的BeanPostProcessor
其中AutowiredAnnotationBeanPostProcessor就实现了改接口(至于AutowiredAnnotationBeanPostProcessor是何时注册到spring容器的,可以后续探究),因此会执行其中的 postProcessProperties 方法,通过BeanFactory.getBean方法获取符合的Bean(如果Bean还未注册,就先将该Bean注册了再返回)
源码记录
@MapperScan
主要是注册 MapperScannerRegistrar
package org.mybatis.spring.annotation;
import java.lang.annotation.Annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Repeatable;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.mybatis.spring.mapper.MapperFactoryBean;
import org.mybatis.spring.mapper.MapperScannerConfigurer;
import org.springframework.beans.factory.support.AbstractBeanDefinition;
import org.springframework.beans.factory.support.BeanNameGenerator;
import org.springframework.context.annotation.Import;
/**
* Use this annotation to register MyBatis mapper interfaces when using Java Config. It performs when same work as
* {@link MapperScannerConfigurer} via {@link MapperScannerRegistrar}.
*
* <p>
* Either {@link #basePackageClasses} or {@link #basePackages} (or its alias {@link #value}) may be specified to define
* specific packages to scan. Since 2.0.4, If specific packages are not defined, scanning will occur from the package of
* the class that declares this annotation.
*
* <p>
* Configuration example:
* </p>
*
* <pre class="code">
* @Configuration
* @MapperScan("org.mybatis.spring.sample.mapper")
* public class AppConfig {
*
* @Bean
* public DataSource dataSource() {
* return new EmbeddedDatabaseBuilder().addScript("schema.sql").build();
* }
*
* @Bean
* public DataSourceTransactionManager transactionManager() {
* return new DataSourceTransactionManager(dataSource());
* }
*
* @Bean
* public SqlSessionFactory sqlSessionFactory() throws Exception {
* SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
* sessionFactory.setDataSource(dataSource());
* return sessionFactory.getObject();
* }
* }
* </pre>
*
* @author Michael Lanyon
* @author Eduardo Macarron
*
* @since 1.2.0
* @see MapperScannerRegistrar
* @see MapperFactoryBean
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(MapperScannerRegistrar.class)
@Repeatable(MapperScans.class)
public @interface MapperScan {
/**
* Alias for the {@link #basePackages()} attribute. Allows for more concise annotation declarations e.g.:
* {@code @MapperScan("org.my.pkg")} instead of {@code @MapperScan(basePackages = "org.my.pkg"})}.
*
* @return base package names
*/
String[] value() default {};
/**
* Base packages to scan for MyBatis interfaces. Note that only interfaces with at least one method will be
* registered; concrete classes will be ignored.
*
* @return base package names for scanning mapper interface
*/
String[] basePackages() default {};
/**
* Type-safe alternative to {@link #basePackages()} for specifying the packages to scan for annotated components. The
* package of each class specified will be scanned.
* <p>
* Consider creating a special no-op marker class or interface in each package that serves no purpose other than being
* referenced by this attribute.
*
* @return classes that indicate base package for scanning mapper interface
*/
Class<?>[] basePackageClasses() default {};
/**
* The {@link BeanNameGenerator} class to be used for naming detected components within the Spring container.
*
* @return the class of {@link BeanNameGenerator}
*/
Class<? extends BeanNameGenerator> nameGenerator() default BeanNameGenerator.class;
/**
* This property specifies the annotation that the scanner will search for.
* <p>
* The scanner will register all interfaces in the base package that also have the specified annotation.
* <p>
* Note this can be combined with markerInterface.
*
* @return the annotation that the scanner will search for
*/
Class<? extends Annotation> annotationClass() default Annotation.class;
/**
* This property specifies the parent that the scanner will search for.
* <p>
* The scanner will register all interfaces in the base package that also have the specified interface class as a
* parent.
* <p>
* Note this can be combined with annotationClass.
*
* @return the parent that the scanner will search for
*/
Class<?> markerInterface() default Class.class;
/**
* Specifies which {@code SqlSessionTemplate} to use in the case that there is more than one in the spring context.
* Usually this is only needed when you have more than one datasource.
*
* @return the bean name of {@code SqlSessionTemplate}
*/
String sqlSessionTemplateRef() default "";
/**
* Specifies which {@code SqlSessionFactory} to use in the case that there is more than one in the spring context.
* Usually this is only needed when you have more than one datasource.
*
* @return the bean name of {@code SqlSessionFactory}
*/
String sqlSessionFactoryRef() default "";
/**
* Specifies a custom MapperFactoryBean to return a mybatis proxy as spring bean.
*
* @return the class of {@code MapperFactoryBean}
*/
Class<? extends MapperFactoryBean> factoryBean() default MapperFactoryBean.class;
/**
* Whether enable lazy initialization of mapper bean.
*
* <p>
* Default is {@code false}.
* </p>
*
* @return set {@code true} to enable lazy initialization
* @since 2.0.2
*/
String lazyInitialization() default "";
/**
* Specifies the default scope of scanned mappers.
*
* <p>
* Default is {@code ""} (equiv to singleton).
* </p>
*
* @return the default scope
*/
String defaultScope() default AbstractBeanDefinition.SCOPE_DEFAULT;
}
MapperScannerRegistrar
获取@MapperScan属性值并注册 MapperScannerConfigurer
public class MapperScannerRegistrar implements ImportBeanDefinitionRegistrar, ResourceLoaderAware {
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
AnnotationAttributes mapperScanAttrs = AnnotationAttributes
.fromMap(importingClassMetadata.getAnnotationAttributes(MapperScan.class.getName()));
if (mapperScanAttrs != null) {
registerBeanDefinitions(importingClassMetadata, mapperScanAttrs, registry,
generateBaseBeanName(importingClassMetadata, 0));
}
}
void registerBeanDefinitions(AnnotationMetadata annoMeta, AnnotationAttributes annoAttrs,
BeanDefinitionRegistry registry, String beanName) {
// 这里将 MapperScannerConfigurer 注册到容器中
BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(MapperScannerConfigurer.class);
builder.addPropertyValue("processPropertyPlaceHolders", true);
Class<? extends Annotation> annotationClass = annoAttrs.getClass("annotationClass");
if (!Annotation.class.equals(annotationClass)) {
builder.addPropertyValue("annotationClass", annotationClass);
}
Class<?> markerInterface = annoAttrs.getClass("markerInterface");
if (!Class.class.equals(markerInterface)) {
builder.addPropertyValue("markerInterface", markerInterface);
}
Class<? extends BeanNameGenerator> generatorClass = annoAttrs.getClass("nameGenerator");
if (!BeanNameGenerator.class.equals(generatorClass)) {
builder.addPropertyValue("nameGenerator", BeanUtils.instantiateClass(generatorClass));
}
Class<? extends MapperFactoryBean> mapperFactoryBeanClass = annoAttrs.getClass("factoryBean");
if (!MapperFactoryBean.class.equals(mapperFactoryBeanClass)) {
builder.addPropertyValue("mapperFactoryBeanClass", mapperFactoryBeanClass);
}
String sqlSessionTemplateRef = annoAttrs.getString("sqlSessionTemplateRef");
if (StringUtils.hasText(sqlSessionTemplateRef)) {
builder.addPropertyValue("sqlSessionTemplateBeanName", annoAttrs.getString("sqlSessionTemplateRef"));
}
String sqlSessionFactoryRef = annoAttrs.getString("sqlSessionFactoryRef");
if (StringUtils.hasText(sqlSessionFactoryRef)) {
builder.addPropertyValue("sqlSessionFactoryBeanName", annoAttrs.getString("sqlSessionFactoryRef"));
}
List<String> basePackages = new ArrayList<>();
basePackages.addAll(
Arrays.stream(annoAttrs.getStringArray("value")).filter(StringUtils::hasText).collect(Collectors.toList()));
basePackages.addAll(Arrays.stream(annoAttrs.getStringArray("basePackages")).filter(StringUtils::hasText)
.collect(Collectors.toList()));
basePackages.addAll(Arrays.stream(annoAttrs.getClassArray("basePackageClasses")).map(ClassUtils::getPackageName)
.collect(Collectors.toList()));
if (basePackages.isEmpty()) {
basePackages.add(getDefaultBasePackage(annoMeta));
}
String lazyInitialization = annoAttrs.getString("lazyInitialization");
if (StringUtils.hasText(lazyInitialization)) {
builder.addPropertyValue("lazyInitialization", lazyInitialization);
}
String defaultScope = annoAttrs.getString("defaultScope");
if (!AbstractBeanDefinition.SCOPE_DEFAULT.equals(defaultScope)) {
builder.addPropertyValue("defaultScope", defaultScope);
}
builder.addPropertyValue("basePackage", StringUtils.collectionToCommaDelimitedString(basePackages));
registry.registerBeanDefinition(beanName, builder.getBeanDefinition());
}
}
MapperScannerConfigurer
扫描basePackage的Mapper并将其注册成BeanDefinition
/**
* BeanDefinitionRegistryPostProcessor that searches recursively starting from a base package for interfaces and
* registers them as {@code MapperFactoryBean}. Note that only interfaces with at least one method will be registered;
* concrete classes will be ignored.
* <p>
* This class was a {code BeanFactoryPostProcessor} until 1.0.1 version. It changed to
* {@code BeanDefinitionRegistryPostProcessor} in 1.0.2. See https://jira.springsource.org/browse/SPR-8269 for the
* details.
* <p>
* The {@code basePackage} property can contain more than one package name, separated by either commas or semicolons.
* <p>
* This class supports filtering the mappers created by either specifying a marker interface or an annotation. The
* {@code annotationClass} property specifies an annotation to search for. The {@code markerInterface} property
* specifies a parent interface to search for. If both properties are specified, mappers are added for interfaces that
* match <em>either</em> criteria. By default, these two properties are null, so all interfaces in the given
* {@code basePackage} are added as mappers.
* <p>
* This configurer enables autowire for all the beans that it creates so that they are automatically autowired with the
* proper {@code SqlSessionFactory} or {@code SqlSessionTemplate}. If there is more than one {@code SqlSessionFactory}
* in the application, however, autowiring cannot be used. In this case you must explicitly specify either an
* {@code SqlSessionFactory} or an {@code SqlSessionTemplate} to use via the <em>bean name</em> properties. Bean names
* are used rather than actual objects because Spring does not initialize property placeholders until after this class
* is processed.
* <p>
* Passing in an actual object which may require placeholders (i.e. DB user password) will fail. Using bean names defers
* actual object creation until later in the startup process, after all placeholder substitution is completed. However,
* note that this configurer does support property placeholders of its <em>own</em> properties. The
* <code>basePackage</code> and bean name properties all support <code>${property}</code> style substitution.
* <p>
* Configuration sample:
*
* <pre class="code">
* {@code
* <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
* <property name="basePackage" value="org.mybatis.spring.sample.mapper" />
* <!-- optional unless there are multiple session factories defined -->
* <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory" />
* </bean>
* }
* </pre>
*
* @author Hunter Presnall
* @author Eduardo Macarron
*
* @see MapperFactoryBean
* @see ClassPathMapperScanner
*/
public class MapperScannerConfigurer
implements BeanDefinitionRegistryPostProcessor, InitializingBean, ApplicationContextAware, BeanNameAware {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
if (this.processPropertyPlaceHolders) {
processPropertyPlaceHolders();
}
ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
scanner.setAddToConfig(this.addToConfig);
scanner.setAnnotationClass(this.annotationClass);
scanner.setMarkerInterface(this.markerInterface);
scanner.setSqlSessionFactory(this.sqlSessionFactory);
scanner.setSqlSessionTemplate(this.sqlSessionTemplate);
scanner.setSqlSessionFactoryBeanName(this.sqlSessionFactoryBeanName);
scanner.setSqlSessionTemplateBeanName(this.sqlSessionTemplateBeanName);
scanner.setResourceLoader(this.applicationContext);
scanner.setBeanNameGenerator(this.nameGenerator);
scanner.setMapperFactoryBeanClass(this.mapperFactoryBeanClass);
if (StringUtils.hasText(lazyInitialization)) {
scanner.setLazyInitialization(Boolean.valueOf(lazyInitialization));
}
if (StringUtils.hasText(defaultScope)) {
scanner.setDefaultScope(defaultScope);
}
scanner.registerFilters();
scanner.scan(
StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
}
}
ClassPathMapperScanner
调用Spring的ClassPathBeanDefinitionScanner完成扫描,并修改BeanDefinition的值
public class ClassPathMapperScanner extends ClassPathBeanDefinitionScanner {
/**
* Calls the parent search that will search and register all the candidates. Then the registered objects are post
* processed to set them as MapperFactoryBeans
*/
@Override
public Set<BeanDefinitionHolder> doScan(String... basePackages) {
Set<BeanDefinitionHolder> beanDefinitions = super.doScan(basePackages);
if (beanDefinitions.isEmpty()) {
LOGGER.warn(() -> "No MyBatis mapper was found in '" + Arrays.toString(basePackages)
+ "' package. Please check your configuration.");
} else {
// 重点: 修改了BeanDefinition的属性,影响了后续 Spring 初始化该 Bean 的行为
// 将所有BeanDefinition.beanClass 修改为 MapperFactoryBean.class
// 并且使用有参构造初始化 Bean
// 修改 BeanDefinition.AutowireMode = AbstractBeanDefinition.AUTOWIRE_BY_TYPE, 后续Spring会根据属性类型从容器中获取对应的Bean, 完成自动注入
processBeanDefinitions(beanDefinitions);
}
return beanDefinitions;
}
private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {
AbstractBeanDefinition definition;
BeanDefinitionRegistry registry = getRegistry();
for (BeanDefinitionHolder holder : beanDefinitions) {
definition = (AbstractBeanDefinition) holder.getBeanDefinition();
boolean scopedProxy = false;
if (ScopedProxyFactoryBean.class.getName().equals(definition.getBeanClassName())) {
definition = (AbstractBeanDefinition) Optional
.ofNullable(((RootBeanDefinition) definition).getDecoratedDefinition())
.map(BeanDefinitionHolder::getBeanDefinition).orElseThrow(() -> new IllegalStateException(
"The target bean definition of scoped proxy bean not found. Root bean definition[" + holder + "]"));
scopedProxy = true;
}
String beanClassName = definition.getBeanClassName();
LOGGER.debug(() -> "Creating MapperFactoryBean with name '" + holder.getBeanName() + "' and '" + beanClassName
+ "' mapperInterface");
// the mapper interface is the original class of the bean
// but, the actual class of the bean is MapperFactoryBean
definition.getConstructorArgumentValues().addGenericArgumentValue(beanClassName); // issue #59
// 在这里,Mybatis将beanDefinition的BeanClass 设置成了 MapperFactoryBean.class
definition.setBeanClass(this.mapperFactoryBeanClass);
definition.getPropertyValues().add("addToConfig", this.addToConfig);
// Attribute for MockitoPostProcessor
// https://github.com/mybatis/spring-boot-starter/issues/475
definition.setAttribute(FACTORY_BEAN_OBJECT_TYPE, beanClassName);
boolean explicitFactoryUsed = false;
if (StringUtils.hasText(this.sqlSessionFactoryBeanName)) {
definition.getPropertyValues().add("sqlSessionFactory",
new RuntimeBeanReference(this.sqlSessionFactoryBeanName));
explicitFactoryUsed = true;
} else if (this.sqlSessionFactory != null) {
definition.getPropertyValues().add("sqlSessionFactory", this.sqlSessionFactory);
explicitFactoryUsed = true;
}
if (StringUtils.hasText(this.sqlSessionTemplateBeanName)) {
if (explicitFactoryUsed) {
LOGGER.warn(
() -> "Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.");
}
definition.getPropertyValues().add("sqlSessionTemplate",
new RuntimeBeanReference(this.sqlSessionTemplateBeanName));
explicitFactoryUsed = true;
} else if (this.sqlSessionTemplate != null) {
if (explicitFactoryUsed) {
LOGGER.warn(
() -> "Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.");
}
definition.getPropertyValues().add("sqlSessionTemplate", this.sqlSessionTemplate);
explicitFactoryUsed = true;
}
if (!explicitFactoryUsed) {
LOGGER.debug(() -> "Enabling autowire by type for MapperFactoryBean with name '" + holder.getBeanName() + "'.");
// 这里设置了 AutowireMode = AbstractBeanDefinition.AUTOWIRE_BY_TYPE(2),后续MapperFactoryBean 的非普通属性(例如 sqlSessionFactory)将从spring容器中获取,然后通过 set 方法设置进去
// 具体代码在AbstractAutowireCapableBeanFactory.populateBean()的autowireByType()
definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
}
definition.setLazyInit(lazyInitialization);
if (scopedProxy) {
continue;
}
if (ConfigurableBeanFactory.SCOPE_SINGLETON.equals(definition.getScope()) && defaultScope != null) {
definition.setScope(defaultScope);
}
if (!definition.isSingleton()) {
BeanDefinitionHolder proxyHolder = ScopedProxyUtils.createScopedProxy(holder, registry, true);
if (registry.containsBeanDefinition(proxyHolder.getBeanName())) {
registry.removeBeanDefinition(proxyHolder.getBeanName());
}
registry.registerBeanDefinition(proxyHolder.getBeanName(), proxyHolder.getBeanDefinition());
}
}
}
}
ClassPathBeanDefinitionScanner
扫描basePackage的Mapper,注册成BeanDefinition
public class ClassPathBeanDefinitionScanner extends ClassPathScanningCandidateComponentProvider {
public int scan(String... basePackages) {
int beanCountAtScanStart = this.registry.getBeanDefinitionCount();
doScan(basePackages);
// Register annotation config processors, if necessary.
if (this.includeAnnotationConfig) {
AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
}
return (this.registry.getBeanDefinitionCount() - beanCountAtScanStart);
}
/**
* Perform a scan within the specified base packages,
* returning the registered bean definitions.
* <p>This method does <i>not</i> register an annotation config processor
* but rather leaves this up to the caller.
* @param basePackages the packages to check for annotated classes
* @return set of beans registered if any for tooling registration purposes (never {@code null})
*/
protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
Assert.notEmpty(basePackages, "At least one base package must be specified");
Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
for (String basePackage : basePackages) {
Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
for (BeanDefinition candidate : candidates) {
ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
candidate.setScope(scopeMetadata.getScopeName());
String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
if (candidate instanceof AbstractBeanDefinition) {
postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
}
if (candidate instanceof AnnotatedBeanDefinition) {
AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
}
if (checkCandidate(beanName, candidate)) {
BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
definitionHolder =
AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
beanDefinitions.add(definitionHolder);
registerBeanDefinition(definitionHolder, this.registry);
}
}
}
return beanDefinitions;
}
}
MapperFactoryBean
获取Mapper的代理类
/**
* <p>
* MapperFactoryBean 是怎么注册到容器的:
* 1. ClassPathMapperScanner 将所有 Mapper 注册到 BeanDefinition 中,其中 beanClass 为 MapperFactotyBean,因此每一个 Mapper其实都是一个 MapperFactotyBean
* 2. Spring 容器在创建 Mapper Bean的时候,发现 Mapper Bean 是 FactoryBean,因此会调用 getObject 方法,给 Mapper 创建代理类对象
* 3. MapperFactoryBean 是如何将 SqlSessionTemplate 注入进来的??SqlSessionTemplate 又是怎样注册进容器的??初步猜想是 SqlSessionFactoty
* </p>
*/
/**
* BeanFactory that enables injection of MyBatis mapper interfaces. It can be set up with a SqlSessionFactory or a
* pre-configured SqlSessionTemplate.
* <p>
* Sample configuration:
*
* <pre class="code">
* {@code
* <bean id="baseMapper" class="org.mybatis.spring.mapper.MapperFactoryBean" abstract="true" lazy-init="true">
* <property name="sqlSessionFactory" ref="sqlSessionFactory" />
* </bean>
*
* <bean id="oneMapper" parent="baseMapper">
* <property name="mapperInterface" value="my.package.MyMapperInterface" />
* </bean>
*
* <bean id="anotherMapper" parent="baseMapper">
* <property name="mapperInterface" value="my.package.MyAnotherMapperInterface" />
* </bean>
* }
* </pre>
* <p>
* Note that this factory can only inject <em>interfaces</em>, not concrete classes.
*
* @author Eduardo Macarron
*
* @see SqlSessionTemplate
*/
public class MapperFactoryBean<T> extends SqlSessionDaoSupport implements FactoryBean<T> {
private Class<T> mapperInterface;
private boolean addToConfig = true;
public MapperFactoryBean() {
// intentionally empty
}
public MapperFactoryBean(Class<T> mapperInterface) {
this.mapperInterface = mapperInterface;
}
/**
* {@inheritDoc}
*/
@Override
protected void checkDaoConfig() {
super.checkDaoConfig();
notNull(this.mapperInterface, "Property 'mapperInterface' is required");
Configuration configuration = getSqlSession().getConfiguration();
if (this.addToConfig && !configuration.hasMapper(this.mapperInterface)) {
try {
configuration.addMapper(this.mapperInterface);
} catch (Exception e) {
logger.error("Error while adding the mapper '" + this.mapperInterface + "' to configuration.", e);
throw new IllegalArgumentException(e);
} finally {
ErrorContext.instance().reset();
}
}
}
/**
* 创建 Mapper 的代理类
*/
@Override
public T getObject() throws Exception {
return getSqlSession().getMapper(this.mapperInterface);
}
/**
* {@inheritDoc}
*/
@Override
public Class<T> getObjectType() {
return this.mapperInterface;
}
/**
* {@inheritDoc}
*/
@Override
public boolean isSingleton() {
return true;
}
// ------------- mutators --------------
/**
* Sets the mapper interface of the MyBatis mapper
*
* @param mapperInterface
* class of the interface
*/
public void setMapperInterface(Class<T> mapperInterface) {
this.mapperInterface = mapperInterface;
}
/**
* Return the mapper interface of the MyBatis mapper
*
* @return class of the interface
*/
public Class<T> getMapperInterface() {
return mapperInterface;
}
/**
* If addToConfig is false the mapper will not be added to MyBatis. This means it must have been included in
* mybatis-config.xml.
* <p>
* If it is true, the mapper will be added to MyBatis in the case it is not already registered.
* <p>
* By default addToConfig is true.
*
* @param addToConfig
* a flag that whether add mapper to MyBatis or not
*/
public void setAddToConfig(boolean addToConfig) {
this.addToConfig = addToConfig;
}
/**
* Return the flag for addition into MyBatis config.
*
* @return true if the mapper will be added to MyBatis in the case it is not already registered.
*/
public boolean isAddToConfig() {
return addToConfig;
}
}
SqlSessionTemplate
线程安全,spring管理
public class SqlSessionTemplate implements SqlSession, DisposableBean {
private final SqlSession sqlSessionProxy;
@Override
public <T> T getMapper(Class<T> type) {
return getConfiguration().getMapper(type, this);
}
@Override
public Configuration getConfiguration() {
return this.sqlSessionFactory.getConfiguration();
}
@Override
public <E> List<E> selectList(String statement, Object parameter) {
return this.sqlSessionProxy.selectList(statement, parameter);
}
}
Configuration
包含了三大组件的创建方法,每个组件在创建前都会利用动态代理添加拦截器链,后续handller执行的时候拦截器会进行拦截
public class Configuration {
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
return mapperRegistry.getMapper(type, sqlSession);
}
public ParameterHandler newParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {
ParameterHandler parameterHandler = mappedStatement.getLang().createParameterHandler(mappedStatement, parameterObject, boundSql);
parameterHandler = (ParameterHandler) interceptorChain.pluginAll(parameterHandler);
return parameterHandler;
}
public ResultSetHandler newResultSetHandler(Executor executor, MappedStatement mappedStatement, RowBounds rowBounds, ParameterHandler parameterHandler,
ResultHandler resultHandler, BoundSql boundSql) {
ResultSetHandler resultSetHandler = new DefaultResultSetHandler(executor, mappedStatement, parameterHandler, resultHandler, boundSql, rowBounds);
resultSetHandler = (ResultSetHandler) interceptorChain.pluginAll(resultSetHandler);
return resultSetHandler;
}
public StatementHandler newStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
StatementHandler statementHandler = new RoutingStatementHandler(executor, mappedStatement, parameterObject, rowBounds, resultHandler, boundSql);
statementHandler = (StatementHandler) interceptorChain.pluginAll(statementHandler);
return statementHandler;
}
}
InterceptorChain
public class InterceptorChain {
private final List<Interceptor> interceptors = new ArrayList<>();
public Object pluginAll(Object target) {
for (Interceptor interceptor : interceptors) {
target = interceptor.plugin(target);
}
return target;
}
public void addInterceptor(Interceptor interceptor) {
interceptors.add(interceptor);
}
public List<Interceptor> getInterceptors() {
return Collections.unmodifiableList(interceptors);
}
}
Interceptor
public interface Interceptor {
Object intercept(Invocation invocation) throws Throwable;
default Object plugin(Object target) {
return Plugin.wrap(target, this);
}
default void setProperties(Properties properties) {
// NOP
}
}
Plugin
利用JDK动态代理对Handler进行增强,在执行handler的方法之前,先执行interceptor.intercept
重点关注getSignatureMap方法,解析 @Intercepts 注解,获取value属性,得知对哪个方法进行拦截
public class Plugin implements InvocationHandler {
private final Object target;
private final Interceptor interceptor;
private final Map<Class<?>, Set<Method>> signatureMap;
private Plugin(Object target, Interceptor interceptor, Map<Class<?>, Set<Method>> signatureMap) {
this.target = target;
this.interceptor = interceptor;
this.signatureMap = signatureMap;
}
public static Object wrap(Object target, Interceptor interceptor) {
Map<Class<?>, Set<Method>> signatureMap = getSignatureMap(interceptor);
Class<?> type = target.getClass();
Class<?>[] interfaces = getAllInterfaces(type, signatureMap);
if (interfaces.length > 0) {
return Proxy.newProxyInstance(
type.getClassLoader(),
interfaces,
new Plugin(target, interceptor, signatureMap));
}
return target;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
try {
Set<Method> methods = signatureMap.get(method.getDeclaringClass());
if (methods != null && methods.contains(method)) {
return interceptor.intercept(new Invocation(target, method, args));
}
// 在执行handler的方法之前,先执行interceptor.intercept
return method.invoke(target, args);
} catch (Exception e) {
throw ExceptionUtil.unwrapThrowable(e);
}
}
private static Map<Class<?>, Set<Method>> getSignatureMap(Interceptor interceptor) {
Intercepts interceptsAnnotation = interceptor.getClass().getAnnotation(Intercepts.class);
// issue #251
if (interceptsAnnotation == null) {
throw new PluginException("No @Intercepts annotation was found in interceptor " + interceptor.getClass().getName());
}
Signature[] sigs = interceptsAnnotation.value();
Map<Class<?>, Set<Method>> signatureMap = new HashMap<>();
for (Signature sig : sigs) {
Set<Method> methods = MapUtil.computeIfAbsent(signatureMap, sig.type(), k -> new HashSet<>());
try {
Method method = sig.type().getMethod(sig.method(), sig.args());
methods.add(method);
} catch (NoSuchMethodException e) {
throw new PluginException("Could not find method on " + sig.type() + " named " + sig.method() + ". Cause: " + e, e);
}
}
return signatureMap;
}
private static Class<?>[] getAllInterfaces(Class<?> type, Map<Class<?>, Set<Method>> signatureMap) {
Set<Class<?>> interfaces = new HashSet<>();
while (type != null) {
for (Class<?> c : type.getInterfaces()) {
if (signatureMap.containsKey(c)) {
interfaces.add(c);
}
}
type = type.getSuperclass();
}
return interfaces.toArray(new Class<?>[0]);
}
}
MapperRegistry
public class MapperRegistry {
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
if (mapperProxyFactory == null) {
throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
}
try {
return mapperProxyFactory.newInstance(sqlSession);
} catch (Exception e) {
throw new BindingException("Error getting mapper instance. Cause: " + e, e);
}
}
}
MapperProxyFactory
public class MapperProxyFactory<T> {
private final Class<T> mapperInterface;
private final Map<Method, MapperMethodInvoker> methodCache = new ConcurrentHashMap<>();
public MapperProxyFactory(Class<T> mapperInterface) {
this.mapperInterface = mapperInterface;
}
public Class<T> getMapperInterface() {
return mapperInterface;
}
public Map<Method, MapperMethodInvoker> getMethodCache() {
return methodCache;
}
@SuppressWarnings("unchecked")
protected T newInstance(MapperProxy<T> mapperProxy) {
return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
}
public T newInstance(SqlSession sqlSession) {
final MapperProxy<T> mapperProxy = new MapperProxy<>(sqlSession, mapperInterface, methodCache);
return newInstance(mapperProxy);
}
}
MapperProxy
public class MapperProxy<T> implements InvocationHandler, Serializable {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
try {
if (Object.class.equals(method.getDeclaringClass())) {
return method.invoke(this, args);
} else {
return cachedInvoker(method).invoke(proxy, method, args, sqlSession);
}
} catch (Throwable t) {
throw ExceptionUtil.unwrapThrowable(t);
}
}
private MapperMethodInvoker cachedInvoker(Method method) throws Throwable {
try {
return MapUtil.computeIfAbsent(methodCache, method, m -> {
if (m.isDefault()) {
try {
if (privateLookupInMethod == null) {
return new DefaultMethodInvoker(getMethodHandleJava8(method));
} else {
return new DefaultMethodInvoker(getMethodHandleJava9(method));
}
} catch (IllegalAccessException | InstantiationException | InvocationTargetException
| NoSuchMethodException e) {
throw new RuntimeException(e);
}
} else {
return new PlainMethodInvoker(new MapperMethod(mapperInterface, method, sqlSession.getConfiguration()));
}
});
} catch (RuntimeException re) {
Throwable cause = re.getCause();
throw cause == null ? re : cause;
}
}
interface MapperMethodInvoker {
Object invoke(Object proxy, Method method, Object[] args, SqlSession sqlSession) throws Throwable;
}
private static class PlainMethodInvoker implements MapperMethodInvoker {
private final MapperMethod mapperMethod;
public PlainMethodInvoker(MapperMethod mapperMethod) {
super();
this.mapperMethod = mapperMethod;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args, SqlSession sqlSession) throws Throwable {
return mapperMethod.execute(sqlSession, args);
}
}
private static class DefaultMethodInvoker implements MapperMethodInvoker {
private final MethodHandle methodHandle;
public DefaultMethodInvoker(MethodHandle methodHandle) {
super();
this.methodHandle = methodHandle;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args, SqlSession sqlSession) throws Throwable {
return methodHandle.bindTo(proxy).invokeWithArguments(args);
}
}
}
MapperMethod
public class MapperMethod {
public Object execute(SqlSession sqlSession, Object[] args) {
Object result;
switch (command.getType()) {
case INSERT: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.insert(command.getName(), param));
break;
}
case UPDATE: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.update(command.getName(), param));
break;
}
case DELETE: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.delete(command.getName(), param));
break;
}
case SELECT:
if (method.returnsVoid() && method.hasResultHandler()) {
executeWithResultHandler(sqlSession, args);
result = null;
} else if (method.returnsMany()) {
result = executeForMany(sqlSession, args);
} else if (method.returnsMap()) {
result = executeForMap(sqlSession, args);
} else if (method.returnsCursor()) {
result = executeForCursor(sqlSession, args);
} else {
Object param = method.convertArgsToSqlCommandParam(args);
result = sqlSession.selectOne(command.getName(), param);
if (method.returnsOptional()
&& (result == null || !method.getReturnType().equals(result.getClass()))) {
result = Optional.ofNullable(result);
}
}
break;
case FLUSH:
result = sqlSession.flushStatements();
break;
default:
throw new BindingException("Unknown execution method for: " + command.getName());
}
if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
throw new BindingException("Mapper method '" + command.getName()
+ "' attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
}
return result;
}
private <E> Object executeForMany(SqlSession sqlSession, Object[] args) {
List<E> result;
Object param = method.convertArgsToSqlCommandParam(args);
if (method.hasRowBounds()) {
RowBounds rowBounds = method.extractRowBounds(args);
result = sqlSession.selectList(command.getName(), param, rowBounds);
} else {
result = sqlSession.selectList(command.getName(), param);
}
// issue #510 Collections & arrays support
if (!method.getReturnType().isAssignableFrom(result.getClass())) {
if (method.getReturnType().isArray()) {
return convertToArray(result);
} else {
return convertToDeclaredCollection(sqlSession.getConfiguration(), result);
}
}
return result;
}
}
DefaultSqlSession
public class DefaultSqlSession implements SqlSession {
@Override
public <E> List<E> selectList(String statement, Object parameter) {
return this.selectList(statement, parameter, RowBounds.DEFAULT);
}
@Override
public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) {
return selectList(statement, parameter, rowBounds, Executor.NO_RESULT_HANDLER);
}
private <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler) {
try {
MappedStatement ms = configuration.getMappedStatement(statement);
return executor.query(ms, wrapCollection(parameter), rowBounds, handler);
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error querying database. Cause: " + e, e);
} finally {
ErrorContext.instance().reset();
}
}
}
Executor
public interface Executor {
ResultHandler NO_RESULT_HANDLER = null;
int update(MappedStatement ms, Object parameter) throws SQLException;
<E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey cacheKey, BoundSql boundSql) throws SQLException;
<E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException;
<E> Cursor<E> queryCursor(MappedStatement ms, Object parameter, RowBounds rowBounds) throws SQLException;
List<BatchResult> flushStatements() throws SQLException;
void commit(boolean required) throws SQLException;
void rollback(boolean required) throws SQLException;
CacheKey createCacheKey(MappedStatement ms, Object parameterObject, RowBounds rowBounds, BoundSql boundSql);
boolean isCached(MappedStatement ms, CacheKey key);
void clearLocalCache();
void deferLoad(MappedStatement ms, MetaObject resultObject, String property, CacheKey key, Class<?> targetType);
Transaction getTransaction();
void close(boolean forceRollback);
boolean isClosed();
void setExecutorWrapper(Executor executor);
}
CachingExecutor
public class CachingExecutor implements Executor {
@Override
public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {
BoundSql boundSql = ms.getBoundSql(parameterObject);
CacheKey key = createCacheKey(ms, parameterObject, rowBounds, boundSql);
return query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}
@Override
public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql)
throws SQLException {
Cache cache = ms.getCache();
if (cache != null) {
flushCacheIfRequired(ms);
if (ms.isUseCache() && resultHandler == null) {
ensureNoOutParams(ms, boundSql);
@SuppressWarnings("unchecked")
List<E> list = (List<E>) tcm.getObject(cache, key);
if (list == null) {
list = delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
tcm.putObject(cache, key, list); // issue #578 and #116
}
return list;
}
}
return delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}
}
BaseExecutor
public abstract class BaseExecutor implements Executor {
@Override
public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
ErrorContext.instance().resource(ms.getResource()).activity("executing a query").object(ms.getId());
if (closed) {
throw new ExecutorException("Executor was closed.");
}
if (queryStack == 0 && ms.isFlushCacheRequired()) {
clearLocalCache();
}
List<E> list;
try {
queryStack++;
list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;
if (list != null) {
handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
} else {
list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);
}
} finally {
queryStack--;
}
if (queryStack == 0) {
for (DeferredLoad deferredLoad : deferredLoads) {
deferredLoad.load();
}
// issue #601
deferredLoads.clear();
if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {
// issue #482
clearLocalCache();
}
}
return list;
}
private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
List<E> list;
localCache.putObject(key, EXECUTION_PLACEHOLDER);
try {
list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
} finally {
localCache.removeObject(key);
}
localCache.putObject(key, list);
if (ms.getStatementType() == StatementType.CALLABLE) {
localOutputParameterCache.putObject(key, parameter);
}
return list;
}
protected abstract <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql)
throws SQLException;
}
SimpleExecutor
public class SimpleExecutor extends BaseExecutor {
@Override
public <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
Statement stmt = null;
try {
Configuration configuration = ms.getConfiguration();
StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
stmt = prepareStatement(handler, ms.getStatementLog());
return handler.query(stmt, resultHandler);
} finally {
closeStatement(stmt);
}
}
private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException {
Statement stmt;
Connection connection = getConnection(statementLog);
stmt = handler.prepare(connection, transaction.getTimeout());
handler.parameterize(stmt);
return stmt;
}
}
这里需要关注两点:
- StatementHandler 的创建
StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
StatementHandler 是 Mybatis 的三大组件(ParameterHandler, StatementHandler, ResultSetHandler)之一,在创建这些组件之前,Mybatis会用拦截器链将Handler包装起来,具体可见 Configuration
- Statement 的获取
stmt = prepareStatement(handler, ms.getStatementLog());
Statement 获取的过程中需要处理参数,用到了另外一个组件 ParameterHandler,具体可见PreparedStatementHandler.parameterize
StatementHandler
public interface StatementHandler {
Statement prepare(Connection connection, Integer transactionTimeout)
throws SQLException;
void parameterize(Statement statement)
throws SQLException;
void batch(Statement statement)
throws SQLException;
int update(Statement statement)
throws SQLException;
<E> List<E> query(Statement statement, ResultHandler resultHandler)
throws SQLException;
<E> Cursor<E> queryCursor(Statement statement)
throws SQLException;
BoundSql getBoundSql();
ParameterHandler getParameterHandler();
}
BaseStatementHandler
public abstract class BaseStatementHandler implements StatementHandler {
@Override
public Statement prepare(Connection connection, Integer transactionTimeout) throws SQLException {
ErrorContext.instance().sql(boundSql.getSql());
Statement statement = null;
try {
statement = instantiateStatement(connection);
setStatementTimeout(statement, transactionTimeout);
setFetchSize(statement);
return statement;
} catch (SQLException e) {
closeStatement(statement);
throw e;
} catch (Exception e) {
closeStatement(statement);
throw new ExecutorException("Error preparing statement. Cause: " + e, e);
}
}
protected void setStatementTimeout(Statement stmt, Integer transactionTimeout) throws SQLException {
Integer queryTimeout = null;
if (mappedStatement.getTimeout() != null) {
queryTimeout = mappedStatement.getTimeout();
} else if (configuration.getDefaultStatementTimeout() != null) {
queryTimeout = configuration.getDefaultStatementTimeout();
}
if (queryTimeout != null) {
stmt.setQueryTimeout(queryTimeout);
}
StatementUtil.applyTransactionTimeout(stmt, queryTimeout, transactionTimeout);
}
protected void setFetchSize(Statement stmt) throws SQLException {
Integer fetchSize = mappedStatement.getFetchSize();
if (fetchSize != null) {
stmt.setFetchSize(fetchSize);
return;
}
Integer defaultFetchSize = configuration.getDefaultFetchSize();
if (defaultFetchSize != null) {
stmt.setFetchSize(defaultFetchSize);
}
}
}
PreparedStatementHandler
public class PreparedStatementHandler extends BaseStatementHandler {
@Override
protected Statement instantiateStatement(Connection connection) throws SQLException {
String sql = boundSql.getSql();
if (mappedStatement.getKeyGenerator() instanceof Jdbc3KeyGenerator) {
String[] keyColumnNames = mappedStatement.getKeyColumns();
if (keyColumnNames == null) {
return connection.prepareStatement(sql, PreparedStatement.RETURN_GENERATED_KEYS);
} else {
return connection.prepareStatement(sql, keyColumnNames);
}
} else if (mappedStatement.getResultSetType() == ResultSetType.DEFAULT) {
return connection.prepareStatement(sql);
} else {
return connection.prepareStatement(sql, mappedStatement.getResultSetType().getValue(), ResultSet.CONCUR_READ_ONLY);
}
}
@Override
public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
PreparedStatement ps = (PreparedStatement) statement;
ps.execute();
return resultSetHandler.handleResultSets(ps);
}
@Override
public void parameterize(Statement statement) throws SQLException {
parameterHandler.setParameters((PreparedStatement) statement);
}
}
ParameterHandler
public interface ParameterHandler {
Object getParameterObject();
void setParameters(PreparedStatement ps) throws SQLException;
}
DefaultParameterHandler
public class DefaultParameterHandler implements ParameterHandler {
@Override
public void setParameters(PreparedStatement ps) {
ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());
List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
if (parameterMappings != null) {
for (int i = 0; i < parameterMappings.size(); i++) {
ParameterMapping parameterMapping = parameterMappings.get(i);
if (parameterMapping.getMode() != ParameterMode.OUT) {
Object value;
String propertyName = parameterMapping.getProperty();
if (boundSql.hasAdditionalParameter(propertyName)) { // issue #448 ask first for additional params
value = boundSql.getAdditionalParameter(propertyName);
} else if (parameterObject == null) {
value = null;
} else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
value = parameterObject;
} else {
MetaObject metaObject = configuration.newMetaObject(parameterObject);
value = metaObject.getValue(propertyName);
}
TypeHandler typeHandler = parameterMapping.getTypeHandler();
JdbcType jdbcType = parameterMapping.getJdbcType();
if (value == null && jdbcType == null) {
jdbcType = configuration.getJdbcTypeForNull();
}
try {
typeHandler.setParameter(ps, i + 1, value, jdbcType);
} catch (TypeException | SQLException e) {
throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + e, e);
}
}
}
}
}
}
ResultSetHandler
Mybatis 三大组件之一,对结果集进行处理,只有一个默认实现类DefaultResultSetHandler
public interface ResultSetHandler {
<E> List<E> handleResultSets(Statement stmt) throws SQLException;
<E> Cursor<E> handleCursorResultSets(Statement stmt) throws SQLException;
void handleOutputParameters(CallableStatement cs) throws SQLException;
}
DefaultResultSetHandler
public class DefaultResultSetHandler implements ResultSetHandler {
@Override
public List<Object> handleResultSets(Statement stmt) throws SQLException {
ErrorContext.instance().activity("handling results").object(mappedStatement.getId());
final List<Object> multipleResults = new ArrayList<>();
int resultSetCount = 0;
ResultSetWrapper rsw = getFirstResultSet(stmt);
List<ResultMap> resultMaps = mappedStatement.getResultMaps();
int resultMapCount = resultMaps.size();
validateResultMapsCount(rsw, resultMapCount);
while (rsw != null && resultMapCount > resultSetCount) {
ResultMap resultMap = resultMaps.get(resultSetCount);
handleResultSet(rsw, resultMap, multipleResults, null);
rsw = getNextResultSet(stmt);
cleanUpAfterHandlingResultSet();
resultSetCount++;
}
String[] resultSets = mappedStatement.getResultSets();
if (resultSets != null) {
while (rsw != null && resultSetCount < resultSets.length) {
ResultMapping parentMapping = nextResultMaps.get(resultSets[resultSetCount]);
if (parentMapping != null) {
String nestedResultMapId = parentMapping.getNestedResultMapId();
ResultMap resultMap = configuration.getResultMap(nestedResultMapId);
handleResultSet(rsw, resultMap, null, parentMapping);
}
rsw = getNextResultSet(stmt);
cleanUpAfterHandlingResultSet();
resultSetCount++;
}
}
return collapseSingleResultList(multipleResults);
}
}