springboot（2.1.1.RELEASE）启用jdk动态代理（默认启用cglib）的方法

大前提：该类必须实现了某个接口，其他类使用注解引用该类时，必须基于其实现的接口类型注入，否则注入不成功。

• 方式1，启动类上注解如下设置

@SpringBootApplication(exclude = { AopAutoConfiguration.class})
@EnableTransactionManagement
           

• 方式2，配置文件如下设置

spring:
    aop:
      proxy-target-class: false
           

原因分析：

• AopAutoConfiguration.class源码

//作为配置类注入
@Configuration 
//当类路劲下存在以上这些类，继续向下判断
@ConditionalOnClass({ EnableAspectJAutoProxy.class, Aspect.class, Advice.class,
		AnnotatedElement.class })  
//当配置中存在以上配置信息，但不是必须要显式的配置，没有也可以
@ConditionalOnProperty(prefix = "spring.aop", name = "auto", havingValue = "true", matchIfMissing = true) 
public class AopAutoConfiguration {
     //作为配置类注入
	@Configuration 
     //开启动态代理（false时为jdk动态代理）
	@EnableAspectJAutoProxy(proxyTargetClass = false) 
     //当配置中存在以上配置信息，必须要显式的配置，没有不成立
	@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "false", matchIfMissing = false) 
	public static class JdkDynamicAutoProxyConfiguration {

	}
     //作为配置类注入
	@Configuration 
    //开启动态代理（true时为cglib动态代理）
	@EnableAspectJAutoProxy(proxyTargetClass = true) 
     //当配置中存在以上配置信息，但不是必须要显式的配置，没有也可以
	@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true", matchIfMissing = true)
	public static class CglibAutoProxyConfiguration {

	}

}
           

• EnableTransactionManagement注解源码
             

​//可注解的位置
@Target(ElementType.TYPE)
//生效的阶段
@Retention(RetentionPolicy.RUNTIME)
@Documented
//注入以下类
@Import(TransactionManagementConfigurationSelector.class)
public @interface EnableTransactionManagement {
    
    //默认false时jdk动态代理，设置为true时为cglib动态代理
	boolean proxyTargetClass() default false;
    //默认代理模式jdk本身自带的代理模式，可以选择为AspectJ
	AdviceMode mode() default AdviceMode.PROXY;
    //加载的顺序号
	int order() default Ordered.LOWEST_PRECEDENCE;

}

​
           

•  TransactionAutoConfiguration源码

@Configuration
@ConditionalOnClass(PlatformTransactionManager.class)
@AutoConfigureAfter({ JtaAutoConfiguration.class, HibernateJpaAutoConfiguration.class,
		DataSourceTransactionManagerAutoConfiguration.class,
		Neo4jDataAutoConfiguration.class })
@EnableConfigurationProperties(TransactionProperties.class)
public class TransactionAutoConfiguration {

	@Bean
	@ConditionalOnMissingBean
	public TransactionManagerCustomizers platformTransactionManagerCustomizers(
			ObjectProvider<PlatformTransactionManagerCustomizer<?>> customizers) {
		return new TransactionManagerCustomizers(
				customizers.orderedStream().collect(Collectors.toList()));
	}

	@Configuration
	@ConditionalOnSingleCandidate(PlatformTransactionManager.class)
	public static class TransactionTemplateConfiguration {

		private final PlatformTransactionManager transactionManager;

		public TransactionTemplateConfiguration(
				PlatformTransactionManager transactionManager) {
			this.transactionManager = transactionManager;
		}

		@Bean
		@ConditionalOnMissingBean
		public TransactionTemplate transactionTemplate() {
			return new TransactionTemplate(this.transactionManager);
		}

	}

	@Configuration
	@ConditionalOnBean(PlatformTransactionManager.class)
	@ConditionalOnMissingBean(AbstractTransactionManagementConfiguration.class)
	public static class EnableTransactionManagementConfiguration {

		@Configuration
		@EnableTransactionManagement(proxyTargetClass = false)
		@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "false", matchIfMissing = false)
		public static class JdkDynamicAutoProxyConfiguration {

		}

		@Configuration
		@EnableTransactionManagement(proxyTargetClass = true)
		@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true", matchIfMissing = true)
		public static class CglibAutoProxyConfiguration {

		}

	}

}
           

方式1去排除掉AopAutoConfiguration配置类不加载，同时显示的配置了EnableTransactionManagement注解，就能使aop动态代理设置成jdk动态代理模式。

方式2在配置文件中配置了动态代理的模式为jdk动态代理，整个项目的启动过程总会先加载AopAutoConfiguration配置类，之后才会加载TransactionAutoConfiguration配置类，这个是因为spring.factories这个配置文件中AopAutoConfiguration的出现顺序比TransactionAutoConfiguration早得多，这个是springboot的自动配置jar包下的一个文件，AopAutoConfiguration和TransactionAutoConfiguration这两个类都会因为配置文件中配置了满足设置aop方式为jdk动态代理的配置信息而分别先后设置aop动态代理模式为jdk动态代理，以致设置jdk动态代理生效。