spring虽然没有直接实现Bean校验这块JSR规范,但是从spring3.0开始,就提供了对Bean Valication的支持
。
BeanValidationPostProcessor
能够去校验Spring容器中的Bean,从而决定允不允许它初始化完成,若校验不通过,在违反约束的情况下就会抛出异常,阻止容器的正常启动。
public class BeanValidationPostProcessor implements BeanPostProcessor, InitializingBean {
@Nullable
private Validator validator;
private boolean afterInitialization = false;
@Override
public void afterPropertiesSet() throws Exception {
if (this.validator == null){
this.validator = Validation.buildDefaultValidatorFactory().getValidator();
}
}
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if (!this.afterInitialization){
doValidate(bean);
}
return bean;
}
protected void doValidate(Object bean) {
Assert.state(this.validator != null, "No Validator set");
Object objectToValidate = AopProxyUtils.getSingletonTarget(bean);
if (objectToValidate == null) {
objectToValidate = bean;
}
Set<ConstraintViolation<Object>> result = this.validator.validate(objectToValidate);
// 拼接错误消息最终抛出
if (!result.isEmpty()) {
StringBuilder sb = new StringBuilder("Bean state is invalid: ");
for (Iterator<ConstraintViolation<Object>> it = result.iterator(); it.hasNext();) {
ConstraintViolation<Object> violation = it.next();
sb.append(violation.getPropertyPath()).append(" - ").append(violation.getMessage());
if (it.hasNext()) {
sb.append("; ");
}
}
throw new BeanInitializationException(sb.toString());
}
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if (this.afterInitialization){
doValidate(bean);
}
return bean;
}
}
org.springframework.validation.Validator
应用程序特定对象的验证器,这时spring自己抽象的,区别于javax.validation.Validator
,这个接口完全脱离任何基础设施或上下文,也就说没有耦合到只验证web层、数据访问层或任何层中的对象,它支持应用于程序内的任何层。
// 注意:它可不是Spring3后才推出的 最初就有
public interface Validator {
// 此clazz是否可以被validate
boolean supports(Class<?> clazz);
// 执行校验,错误消息放在Errors 装着
// 可以参考ValidationUtils这个工具类,它能帮助你很多
void validate(Object target, Errors errors);
}
SmartValidator
这个子接口扩展增加了校验分组:hints
// @since 3.1 这个出现得比较晚
public interface SmartValidator extends Validator {
// 注意:这里的Hints最终都会被转化到JSR的分组里去~~
// 所以这个可变参数,传接口Class对象即可~
void validate(Object target, Errors errors, Object... validationHints);
// @since 5.1 简单的说,这个方法子类请复写 否则不能使用
default void validateValue(Class<?> targetType, String fieldName, @Nullable Object value, Errors errors, Object... validationHints) {
throw new IllegalArgumentException("Cannot validate individual value for " + targetType);
}
}
SpringValidatorAdapter:校验适配器
这个实现类Class是非常重要的,它是javax.valication.Validator
到spring的Validator
的适配,通过它就可以对接到JSR的校验器来完成校验工作,同时还公开了原始JSR-303 Validator接口本身。
// @since 3.0
public class SpringValidatorAdapter implements SmartValidator, javax.validation.Validator {
// 通用的三个约束注解都需要有的属性
private static final Set<String> internalAnnotationAttributes = new HashSet<>(4);
static {
internalAnnotationAttributes.add("message");
internalAnnotationAttributes.add("groups");
internalAnnotationAttributes.add("payload");
}
// 最终都是委托给它来完成校验的~~~
@Nullable
private javax.validation.Validator targetValidator;
public SpringValidatorAdapter(javax.validation.Validator targetValidator) {
Assert.notNull(targetValidator, "Target Validator must not be null");
this.targetValidator = targetValidator;
}
// 简单的说:默认支持校验所有的Bean类型~~~
@Override
public boolean supports(Class<?> clazz) {
return (this.targetValidator != null);
}
// processConstraintViolations做的事一句话解释:
// 把ConstraintViolations错误消息,全都适配放在Errors(BindingResult)里面存储着
@Override
public void validate(Object target, Errors errors) {
if (this.targetValidator != null) {
processConstraintViolations(this.targetValidator.validate(target), errors);
}
}
@Override
public void validate(Object target, Errors errors, Object... validationHints) {
if (this.targetValidator != null) {
processConstraintViolations(this.targetValidator.validate(target, asValidationGroups(validationHints)), errors);
}
}
@SuppressWarnings("unchecked")
@Override
public void validateValue(Class<?> targetType, String fieldName, @Nullable Object value, Errors errors, Object... validationHints) {
if (this.targetValidator != null) {
processConstraintViolations(this.targetValidator.validateValue(
(Class) targetType, fieldName, value, asValidationGroups(validationHints)), errors);
}
}
// 把validationHints都转换为group (支识别Class类型哦)
private Class<?>[] asValidationGroups(Object... validationHints) {
Set<Class<?>> groups = new LinkedHashSet<>(4);
for (Object hint : validationHints) {
if (hint instanceof Class) {
groups.add((Class<?>) hint);
}
}
return ClassUtils.toClassArray(groups);
}
// 关于Implementation of JSR-303 Validator interface 省略...
}
CustomValidatorBean
可配置的Bean
public class CustomValidatorBean extends SpringValidatorAdapter implements Validator, InitializingBean {
@Nullable
private ValidatorFactory validatorFactory;
@Nullable
private MessageInterpolator messageInterpolator;
@Nullable
private TraversableResolver traversableResolver;
/**
* 提供配置校验器工厂的set方法
*
*/
public void setValidatorFactory(ValidatorFactory validatorFactory) {
this.validatorFactory = validatorFactory;
}
/**
* 指定用于此验证器的自定义MessageInterpolator。
*/
public void setMessageInterpolator(MessageInterpolator messageInterpolator) {
this.messageInterpolator = messageInterpolator;
}
/**
* 指定用于此验证器的自定义TraversableResolver
*/
public void setTraversableResolver(TraversableResolver traversableResolver) {
this.traversableResolver = traversableResolver;
}
/**
* 通过`javax.valication.Validator`获取实例
*/
@Override
public void afterPropertiesSet() {
if (this.validatorFactory == null) {
this.validatorFactory = Validation.buildDefaultValidatorFactory();
}
// 获取校验器上下文对象
ValidatorContext validatorContext = this.validatorFactory.usingContext();
// 获取插值器
MessageInterpolator targetInterpolator = this.messageInterpolator;
if (targetInterpolator == null) {
targetInterpolator = this.validatorFactory.getMessageInterpolator();
}
validatorContext.messageInterpolator(new LocaleContextMessageInterpolator(targetInterpolator));
if (this.traversableResolver != null) {
validatorContext.traversableResolver(this.traversableResolver);
}
// 把已经设置好的validator设置进去
setTargetValidator(validatorContext.getValidator());
}
}
LocalValidatorFactoryBean
CustomValidatorBean
平级,都是继承自SpringValidatorAdapter
,但是它提供的能力更加的强大,比如Spring处理校验这块最重要的处理器MethodValidationPostProcessor
就是依赖于它来给提供验证器~
// @since 3.0 这个类非常的丰富 实现了接口javax.validation.ValidatorFactory
// 实现了ApplicationContextAware拿到Spring上下文...
// 但其实,它的实际工作都是委托式,自己只提供了各式各样的配置~~~(主要是配置JSR)
public class LocalValidatorFactoryBean extends SpringValidatorAdapter implements ValidatorFactory, ApplicationContextAware, InitializingBean, DisposableBean {
... // 省略所有的配置属性
... // 省略所有的get/set
... // 省略afterPropertiesSet()进行的默认配置初始化 最终调用setTargetValidator(this.validatorFactory.getValidator());
// 备注:还记得上文吗?上文的validator校验器是从上下文拿的,这里是从工厂拿的
// 省略所有对ValidatorFactory接口的方法实现~
}
OptionalValidatorFactoryBean
它做的唯一一件事:让org.springframework.validation.Validator成为可选(即使没有初始化成功,也不会报错,相当于把异常吃了嘛~)
public class OptionalValidatorFactoryBean extends LocalValidatorFactoryBean {
@Override
public void afterPropertiesSet() {
try {
super.afterPropertiesSet();
}
catch (ValidationException ex) {
LogFactory.getLog(getClass()).debug("Failed to set up a Bean Validation provider", ex);
}
}
}
SpringConstraintValidatorFactory
将ConstraintValidator放入spring容器中,和spring整合。
public class SpringConstraintValidatorFactory implements ConstraintValidatorFactory {
private final AutowireCapableBeanFactory beanFactory;
public SpringConstraintValidatorFactory(AutowireCapableBeanFactory beanFactory) {
Assert.notNull(beanFactory, "BeanFactory must not be null");
this.beanFactory = beanFactory;
}
// 注意:此处是直接调用了create方法,放进容器
@Override
public <T extends ConstraintValidator<?, ?>> T getInstance(Class<T> key) {
return this.beanFactory.createBean(key);
}
// Bean Validation 1.1 releaseInstance method
public void releaseInstance(ConstraintValidator<?, ?> instance) {
this.beanFactory.destroyBean(instance);
}
}
MessageSourceResourceBundleLocator
扩展了Hibernate包的ResourceBundleLocator
国际化,而使用
Spring自己的国际化资源:org.springframework.context.MessageSource
public class MessageSourceResourceBundleLocator implements ResourceBundleLocator {
private final MessageSource messageSource;
public MessageSourceResourceBundleLocator(MessageSource messageSource) {
Assert.notNull(messageSource, "MessageSource must not be null");
this.messageSource = messageSource;
}
@Override
public ResourceBundle getResourceBundle(Locale locale) {
return new MessageSourceResourceBundle(this.messageSource, locale);
}
}
LocaleContextMessageInterpolator
它是个javax.validation.MessageInterpolator
插值器,Spring把它和自己的LocaleContext
结合起来了。
// @since 3.0
// org.springframework.context.i18n.LocaleContextHolder#getLocale()
public class LocaleContextMessageInterpolator implements MessageInterpolator {
private final MessageInterpolator targetInterpolator;
public LocaleContextMessageInterpolator(MessageInterpolator targetInterpolator) {
Assert.notNull(targetInterpolator, "Target MessageInterpolator must not be null");
this.targetInterpolator = targetInterpolator;
}
@Override
public String interpolate(String message, Context context) {
return this.targetInterpolator.interpolate(message, context, LocaleContextHolder.getLocale());
}
@Override
public String interpolate(String message, Context context, Locale locale) {
return this.targetInterpolator.interpolate(message, context, locale);
}
}