Spring Boot 自动配置 : PersistenceExceptionTranslationAutoConfiguration

概述

自动配置类PersistenceExceptionTranslationAutoConfiguration的主要目的是启动Spring框架提供的持久化层异常向Spring标准异常的转换机制。

对该机制的启动PersistenceExceptionTranslationAutoConfiguration是通过向容器注册一个PersistenceExceptionTranslationPostProcessor来完成的。PersistenceExceptionTranslationAutoConfiguration向容器注册该组件的条件是:

• 此组件bean尚未注册;
• 配置选项spring.dao.exceptiontranslation.enabled未被明确设置为false;

而PersistenceExceptionTranslationPostProcessor是一个BeanPostProcessor。它将每个Repository组件bean包装成一个代理对象并为该代理对象添加一个PersistenceExceptionTranslationAdvisor。该PersistenceExceptionTranslationAdvisor会拦截Repository组件bean的方法调用产生的异常并将其转换成Spring框架标准异常。

源代码

源代码版本 : spring-boot-autoconfigure-2.1.3.RELEASE

package org.springframework.boot.autoconfigure.dao;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;
import org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor;


@Configuration
// 仅在类 PersistenceExceptionTranslationPostProcessor 存在于 classpath 上才生效
// PersistenceExceptionTranslationPostProcessor 由包 spring-tx 提供
@ConditionalOnClass(PersistenceExceptionTranslationPostProcessor.class)
public class PersistenceExceptionTranslationAutoConfiguration {

	@Bean
	@ConditionalOnMissingBean
	@ConditionalOnProperty(prefix = "spring.dao.exceptiontranslation", name = "enabled", 
		matchIfMissing = true)
	public static PersistenceExceptionTranslationPostProcessor 
			persistenceExceptionTranslationPostProcessor(Environment environment) {
		PersistenceExceptionTranslationPostProcessor postProcessor = 
			new PersistenceExceptionTranslationPostProcessor();
		boolean proxyTargetClass = environment.getProperty(
				"spring.aop.proxy-target-class", Boolean.class, Boolean.TRUE);
		postProcessor.setProxyTargetClass(proxyTargetClass);
		return postProcessor;
	}

}

参考文章

• Spring BeanPostProcessor – PersistenceExceptionTranslationPostProcessor