Repository 接口为什么不用写实现:代理与 SimpleJpaRepository

repo.getClass() = jdk.proxy2.$Proxy107;AopUtils.isJdkDynamicProxy = true
实现的接口:[UserRepo, Repository, TransactionalProxy, Advised, DecoratingProxy]
代理的目标对象(Advised.getTargetSource().getTarget()):org.springframework.data.jpa.repository.support.SimpleJpaRepository
BeanDefinition 的类:org.springframework.data.jpa.repository.support.JpaRepositoryFactoryBean
容器里 UserRepo 类型的 Bean 个数:1;FactoryBean 的 Bean:[&userRepo]

  …data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor
  …dao.support.PersistenceExceptionTranslationInterceptor
  …transaction.interceptor.TransactionInterceptor
  …data.projection.DefaultMethodInvokingMethodInterceptor
  …data.repository.core.support.QueryExecutorMethodInterceptor
  …data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor
  …dao.support.PersistenceExceptionTranslationInterceptor

  findAll()(继承自 CrudRepository):
    SQL 发出时:[select] 事务激活=true,只读=true
    调用栈里的关键帧(从里到外):[SimpleJpaRepository.findAll, RepositoryMethodInvoker$RepositoryFragmentMethodInvoker.lambda$new$0, RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke, QueryExecutorMethodInterceptor.invoke, DefaultMethodInvokingMethodInterceptor.invoke, TransactionInterceptor$1.proceedWithInvocation, TransactionInterceptor.invoke, JdkDynamicAopProxy.invoke, $Proxy107.findAll]
  findById(1L):
    SQL 发出时:[select] 事务激活=true,只读=true
    调用栈里的关键帧(从里到外):[$Proxy98.find, SimpleJpaRepository.findById, RepositoryMethodInvoker$RepositoryFragmentMethodInvoker.lambda$new$0, RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke, QueryExecutorMethodInterceptor.invoke, DefaultMethodInvokingMethodInterceptor.invoke, TransactionInterceptor$1.proceedWithInvocation, TransactionInterceptor.invoke, JdkDynamicAopProxy.invoke, $Proxy107.findById]
  save(new User):
    SQL 发出时:[insert] 事务激活=true,只读=false
    调用栈里的关键帧(从里到外):[$Proxy98.persist, SimpleJpaRepository.save, RepositoryMethodInvoker$RepositoryFragmentMethodInvoker.lambda$new$0, RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke, QueryExecutorMethodInterceptor.invoke, DefaultMethodInvokingMethodInterceptor.invoke, TransactionInterceptor$1.proceedWithInvocation, TransactionInterceptor.invoke, JdkDynamicAopProxy.invoke, $Proxy107.save]
  findByName("a")(派生查询):
    SQL 发出时:[select] 事务激活=false,只读=false
    调用栈里的关键帧(从里到外):[$Proxy111.getResultList, AbstractJpaQuery.execute, QueryExecutorMethodInterceptor.invoke, DefaultMethodInvokingMethodInterceptor.invoke, TransactionInterceptor$1.proceedWithInvocation, TransactionInterceptor.invoke, JdkDynamicAopProxy.invoke, $Proxy107.findByName]
  count():
    SQL 发出时:[select] 事务激活=true,只读=true
    调用栈里的关键帧(从里到外):[SimpleJpaRepository.count, RepositoryMethodInvoker$RepositoryFragmentMethodInvoker.lambda$new$0, RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke, QueryExecutorMethodInterceptor.invoke, DefaultMethodInvokingMethodInterceptor.invoke, TransactionInterceptor$1.proceedWithInvocation, TransactionInterceptor.invoke, JdkDynamicAopProxy.invoke, $Proxy107.count]
  custom()(自定义片段 UserRepoCustomImpl) → 返回 来自 UserRepoCustomImpl:
    没有发出 SQL
    自定义方法体里的事务状态:custom → 事务激活=false,只读=false
  hello()(接口 default 方法,里面调 count()) → 返回 default 方法:3:
    SQL 发出时:[select] 事务激活=true,只读=true
    调用栈里的关键帧(从里到外):[SimpleJpaRepository.count, RepositoryMethodInvoker$RepositoryFragmentMethodInvoker.lambda$new$0, RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke, QueryExecutorMethodInterceptor.invoke, DefaultMethodInvokingMethodInterceptor.invoke, TransactionInterceptor$1.proceedWithInvocation, TransactionInterceptor.invoke, JdkDynamicAopProxy.invoke, $Proxy107.count, $Proxy107.hello]

  外面(调用方)当前:事务激活=false,只读=false