java - Spring Scheduler - 当存在循环依赖时，计划的方法不会在事务中启动

Question

我正在开发一个使用 Spring 3、Hibernate 和 JPA 的应用程序。我有两个类如下:

@Component
class Manager {
    @Autowired
    Util util;
}

和

@Component
class Util {
    @Autowired
    Manager manager;

    @Scheduled(fixedDelay = 1 * 60 * 1000)
    @Transactional(propagation = Propagation.REQUIRED)
    public void scheduledMethod(){
        // Need to update the database in a transaction
    }
}

应用上下文相关部分如下:

    <context:component-scan base-package="packageName" />
    <tx:annotation-driven />
    <bean id="entityManagerFactory"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
       <property name="persistenceUnitName" value="defaultPU" />
       <property name="dataSource" ref="dataSource" />
    </bean>
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
       <property name="entityManagerFactory" ref="entityManagerFactory" />
    </bean>
    <task:annotation-driven executor="executor" scheduler="scheduler"/>
    <task:executor id="executor"
       pool-size="10"
       queue-capacity="10000"
       rejection-policy="CALLER_RUNS"/>
    <task:scheduler id="scheduler" pool-size="10"/>

使用此配置，我得到以下异常

javax.persistence.TransactionRequiredException: no transaction is in progress
        at org.hibernate.ejb.AbstractEntityManagerImpl.flush(AbstractEntityManagerImpl.java:978)
        at sun.reflect.GeneratedMethodAccessor88.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:365)
        at com.sun.proxy.$Proxy43.flush(Unknown Source)
        at sun.reflect.GeneratedMethodAccessor88.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:240)
        at com.sun.proxy.$Proxy43.flush(Unknown Source)

如果我从 Util 类中删除 Manager 类的 Autowiring ，它就可以正常工作。此外，在调试时我发现即使应用程序上下文文件中存在一些错误，计划的方法也会开始执行。

由于某些遗留原因，我无法避免循环依赖。有人可以帮助解释为什么在循环依赖的情况下会出现此异常吗？

Answer 1

您可以使用@PostConstruct 实现这一点

@Component
class Manager {

    Util util;

    public void setUtil(Util util) {
        this.util =  util;
    }
}


@Component
class Util {
    @Autowired
    Manager manager;

    @PostConstruct
    public void init(){
        manager.setUtil(this);

    }

    @Scheduled(fixedDelay = 1 * 60 * 1000)
    @Transactional(propagation = Propagation.REQUIRED)
    public void scheduledMethod(){
        // Need to update the database in a transaction
    }
}