java - 为什么使用 Java 配置配置的 JPAPagingItemReader 的销毁方法 'close' 失败？

Question

我们正在尝试将 Spring-Batch 作业从 XML 配置转换为 Java 配置。我们正在使用 Spring 4.0.1.RELEASE 和 Spring Batch 2.2.1.RELEASE。

转换一项作业后，日志文件中开始出现以下警告:

15-Apr-2014 09:59:26.335 [Thread-2] WARN o.s.b.f.s.DisposableBeanAdapter - Invocation of destroy method 'close' failed on bean with name 'fileReader': org.springframework.batch.item.ItemStreamException: Error while closing item reader

完整的堆栈跟踪是:

org.springframework.batch.item.ItemStreamException: Error while closing item reader
    at org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader.close(AbstractItemCountingItemStreamItemReader.java:131) ~[spring-batch-infrastructure-2.2.1.RELEASE.jar:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.6.0_25]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) ~[na:1.6.0_25]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) ~[na:1.6.0_25]
    at java.lang.reflect.Method.invoke(Method.java:597) ~[na:1.6.0_25]
    at org.springframework.beans.factory.support.DisposableBeanAdapter.invokeCustomDestroyMethod(DisposableBeanAdapter.java:349) [spring-beans-4.0.1.RELEASE.jar:4.0.1.RELEASE]
    at org.springframework.beans.factory.support.DisposableBeanAdapter.destroy(DisposableBeanAdapter.java:272) [spring-beans-4.0.1.RELEASE.jar:4.0.1.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroyBean(DefaultSingletonBeanRegistry.java:540) [spring-beans-4.0.1.RELEASE.jar:4.0.1.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroySingleton(DefaultSingletonBeanRegistry.java:516) [spring-beans-4.0.1.RELEASE.jar:4.0.1.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.destroySingleton(DefaultListableBeanFactory.java:824) [spring-beans-4.0.1.RELEASE.jar:4.0.1.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.destroySingletons(DefaultSingletonBeanRegistry.java:485) [spring-beans-4.0.1.RELEASE.jar:4.0.1.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.destroyBeans(AbstractApplicationContext.java:921) [spring-context-4.0.1.RELEASE.jar:4.0.1.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.doClose(AbstractApplicationContext.java:895) [spring-context-4.0.1.RELEASE.jar:4.0.1.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext$1.run(AbstractApplicationContext.java:809) [spring-context-4.0.1.RELEASE.jar:4.0.1.RELEASE]
Caused by: java.lang.IllegalStateException: EntityManager is closed
    at org.hibernate.ejb.EntityManagerImpl.close(EntityManagerImpl.java:132) ~[hibernate-entitymanager-4.2.5.Final.jar:4.2.5.Final]
    at sun.reflect.GeneratedMethodAccessor14.invoke(Unknown Source) ~[na:na]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) ~[na:1.6.0_25]
    at java.lang.reflect.Method.invoke(Method.java:597) ~[na:1.6.0_25]
    at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:334) ~[spring-orm-4.0.1.RELEASE.jar:4.0.1.RELEASE]
    at $Proxy67.close(Unknown Source) ~[na:na]
    at org.springframework.batch.item.database.JpaPagingItemReader.doClose(JpaPagingItemReader.java:236) ~[spring-batch-infrastructure-2.2.1.RELEASE.jar:na]
    at org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader.close(AbstractItemCountingItemStreamItemReader.java:128) ~[spring-batch-infrastructure-2.2.1.RELEASE.jar:na]
    ... 13 common frames omitted

此错误仅在作业使用 Java 配置而非 XML 配置时出现。使用 XML 配置的步骤如下所示:

<batch:step id="createFile" next="insertFile">
    <batch:tasklet>
        <batch:chunk reader="fileReader" writer="fileWriter"
            commit-interval="#{jobProperties[commit_interval]}" />
    </batch:tasklet>
</batch:step>

<bean id="fileReader"
    class="org.springframework.batch.item.database.JpaPagingItemReader">
    <property name="entityManagerFactory" ref="entityManagerFactory" />
    <property name="queryString"
        value="select mt from MyTable mt where status in ('1','2','3')" />
    <property name="pageSize" value="1000" />
</bean>

Java 配置为:

@Bean
public Job fileProcessJob(JobBuilderFactory jobBuilders,
        Step loadConfig,
        Step createFile,
        Step insertFile
        ) {
    return jobBuilders.get(moduleName)
            .start(loadConfig)
            .next(createFile)
            .next(insertFile)
            .build()
            .build();
}

@Bean
public ItemReader<MyTable> cetFileReader(EntityManagerFactory entityManagerFactory) {
    JpaPagingItemReader<MyTable> itemReader = new JpaPagingItemReader<MyTable>();
    itemReader.setEntityManagerFactory(entityManagerFactory);
    itemReader.setQueryString("select mt from MyTable mt where status in ('1','2','3')");
    itemReader.setPageSize(1000);
    return itemReader;
}

为什么在使用 Java 配置而不是 XML 配置时，日志中会出现此警告？

Answer 1

TLDR；

Spring 尝试在使用 Java 配置时自动推断 destroyMethod(但在使用 XML 配置时不会这样做)。要禁用此自动推理，请使用:

@Bean(destroyMethod="")

---

答案在@Bean注解的JavaDoc中；特别是关于 org.springframework.context.annotation.Bean.destroyMethod() 方法(强调我的):

The optional name of a method to call on the bean instance upon closing the application context, for example a close() method on a JDBC DataSource implementation, or a Hibernate SessionFactory object. The method must have no arguments but may throw any exception.

As a convenience to the user, the container will attempt to infer a destroy method against an object returned from the @Bean method. For example, given a @Bean method returning an Apache Commons DBCP BasicDataSource, the container will notice the close() method available on that object and automatically register it as the destroyMethod. This 'destroy method inference' is currently limited to detecting only public, no-arg methods named 'close'. The method may be declared at any level of the inheritance hierarchy and will be detected regardless of the return type of the @Bean method (i.e., detection occurs reflectively against the bean instance itself at creation time).

To disable destroy method inference for a particular @Bean, specify an empty string as the value, e.g. @Bean(destroyMethod=""). Note that the org.springframework.beans.factory.DisposableBean and the java.io.Closeable/java.lang.AutoCloseable interfaces will nevertheless get detected and the corresponding destroy/close method invoked.

Note: Only invoked on beans whose lifecycle is under the full control of the factory, which is always the case for singletons but not guaranteed for any other scope.

将Java配置更改为:

@Bean(destroyMethod="")
public ItemReader<MyTable> cetFileReader(EntityManagerFactory entityManagerFactory) {
    JpaPagingItemReader<MyTable> itemReader = new JpaPagingItemReader<MyTable>();
    itemReader.setEntityManagerFactory(entityManagerFactory);
    itemReader.setQueryString("select mt from MyTable mt where status in ('1','2','3')");
    itemReader.setPageSize(1000);
    return itemReader;
}

警告不再出现。我可以通过在 org.springframework.beans.factory.support.DisposableBeanAdapter.destroy() 方法上放置一个断点并启动 XML 配置的作业和 Java 配置的作业来确认这一点。

对于 XML 配置:

• DisposableBeanAdapter.invokeDisposableBean = false
• DisposableBeanAdapter.destroyMethod = null
• DisposableBeanAdapter.destroyMethodName = null

对于 Java 配置(未设置 destroyMethod=""):

• DisposableBeanAdapter.invokeDisposableBean = false
• DisposableBeanAdapter.destroyMethod = public void org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader.close() 抛出 org.springframework.batch.item.ItemStreamException
• DisposableBeanAdapter.destroyMethodName = 关闭

对于 Java 配置(带有 destroyMethod="" 集):

• DisposableBeanAdapter.invokeDisposableBean = false
• DisposableBeanAdapter.destroyMethod = null
• DisposableBeanAdapter.destroyMethodName = null

基于这些观察，我得出结论，容器在通过 XML 配置时不会尝试推断销毁方法；但它在通过 Java 配置时确实如此。这就是为什么会针对 Java 配置而不是 XML 配置显示警告的原因。

另外，容器推断的方法destroyMethod似乎来自org.springframework.batch.item.ItemStreamSupport.close()。因此，这可能发生在任何实现通过 @Bean 注释配置的 ItemStreamSupport 接口(interface)的 bean 上。

---

注释已添加到 Spring Framework Reference material for @Bean描述这种行为:

By default, beans defined using Java config that have a public close or shutdown method are automatically enlisted with a destruction callback. If you have a public close or shutdown method and you do not wish for it to be called when the container shuts down, simply add @Bean(destroyMethod="") to your bean definition to disable the default (inferred) mode.