概述
mybatis 使用
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
这几行的加载流程
其中最重要的就是第4步，从xml中解析获取configuration对象，configruration对象在mybatis中基本贯穿整个框架；
今天单独说一下configuratin这个对象
configuration主要组成部分
从上图我们可以知道 mybatis中一个配置文件和mapper文件或者是注解，我们开发中一般是用mapper xml文件方式，所以源码分析以xml为主
组件的构建过程
源码分析
org.apache.ibatis.session.SqlSessionFactoryBuilder#build(java.io.InputStream, java.lang.String, java.util.Properties)
XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
return build(parser.parse());
XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
这一行代码主要是进行对象的创建
private XMLConfigBuilder(XPathParser parser, String environment, Properties props) {
super(new Configuration());
ErrorContext.instance().resource("SQL Mapper Configuration");
this.configuration.setVariables(props);
this.parsed = false;
this.environment = environment;
this.parser = parser;
}
public BaseBuilder(Configuration configuration) {
this.configuration = configuration;
this.typeAliasRegistry = this.configuration.getTypeAliasRegistry();
this.typeHandlerRegistry = this.configuration.getTypeHandlerRegistry();
}完成configuration ， typeAliasRegistry 和 typeHandlerRegistry 的初始化，没有多少内容
parser.parse()
public Configuration parse() {
if (parsed) {
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
parsed = true;
parseConfiguration(parser.evalNode("/configuration"));
return configuration;
}
// mybatis-config.xml 配置文件的解析
private void parseConfiguration(XNode root) {
try {
// issue #117 read properties first
propertiesElement(root.evalNode("properties"));
Properties settings = settingsAsProperties(root.evalNode("settings"));
loadCustomVfs(settings);
loadCustomLogImpl(settings);
typeAliasesElement(root.evalNode("typeAliases"));
pluginElement(root.evalNode("plugins"));
objectFactoryElement(root.evalNode("objectFactory"));
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
reflectorFactoryElement(root.evalNode("reflectorFactory"));
//设置setting 值，获取不到的使用默认值
settingsElement(settings);
// read it after objectFactory and objectWrapperFactory issue #631
environmentsElement(root.evalNode("environments"));
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
typeHandlerElement(root.evalNode("typeHandlers"));
//mapper文件解析
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}上面的代码就不太多的深入分析了，比较简单，都是从xml中获取配置信息进行赋值操作
mapperElement(root.evalNode(“mappers”)); mapper配置的解析
<mappers>
<package name="com.wfg"/>
<mapper resource="ActivityMapper.xml" class="com.wfg.ActivityEntity" url=""/>
</mappers>
private void mapperElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
if ("package".equals(child.getName())) { //mapper文件按照包进行配置的
String mapperPackage = child.getStringAttribute("name");
configuration.addMappers(mapperPackage);
} else { //mapper 获取三个属性 并且三者只能有其一
String resource = child.getStringAttribute("resource");
String url = child.getStringAttribute("url");
String mapperClass = child.getStringAttribute("class");
if (resource != null && url == null && mapperClass == null) {
ErrorContext.instance().resource(resource);
try(InputStream inputStream = Resources.getResourceAsStream(resource)) {
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
mapperParser.parse();
}
} else if (resource == null && url != null && mapperClass == null) {
ErrorContext.instance().resource(url);
try(InputStream inputStream = Resources.getUrlAsStream(url)){
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments());
mapperParser.parse();
}
} else if (resource == null && url == null && mapperClass != null) {
Class<?> mapperInterface = Resources.classForName(mapperClass);
configuration.addMapper(mapperInterface);
} else {
throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");
}
}
}
}
}我们按照resource 方式进行分析
try(InputStream inputStream = Resources.getResourceAsStream(resource)) {
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
mapperParser.parse();
}try（资源流）{
}
这种语法避免了 finally 关闭操作，会进行自动关闭操作
通用获取XMLMapperBuilder
private XMLMapperBuilder(XPathParser parser, Configuration configuration, String resource, Map<String, XNode> sqlFragments) {
super(configuration);
this.builderAssistant = new MapperBuilderAssistant(configuration, resource);
this.parser = parser;
this.sqlFragments = sqlFragments;
this.resource = resource;
}mapperParser.parse(); mapper.xml 进行解析
public void parse() {
if (!configuration.isResourceLoaded(resource)) {
configurationElement(parser.evalNode("/mapper"));
configuration.addLoadedResource(resource);
bindMapperForNamespace();
}
parsePendingResultMaps();
parsePendingCacheRefs();
parsePendingStatements();
}private void configurationElement(XNode context) {
try {
String namespace = context.getStringAttribute("namespace");
if (namespace == null || namespace.isEmpty()) {
throw new BuilderException("Mapper's namespace cannot be empty");
}
builderAssistant.setCurrentNamespace(namespace);
cacheRefElement(context.evalNode("cache-ref"));
cacheElement(context.evalNode("cache"));
parameterMapElement(context.evalNodes("/mapper/parameterMap"));
resultMapElements(context.evalNodes("/mapper/resultMap"));
sqlElement(context.evalNodes("/mapper/sql"));
buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
} catch (Exception e) {
throw new BuilderException("Error parsing Mapper XML. The XML location is '" + resource + "'. Cause: " + e, e);
}
}buildStatementFromContext(context.evalNodes(“select|insert|update|delete”));
这个就是原来分析等sql元素解析
MappedStatement 构建过程
xml方式
注解解析
