java – Spring Bean自定义范围JMS

我正在使用Spring Framework使用DefaultMessageListenerContainer并发消耗JMS队列中的消息.我希望能够为每个进入的消息创建自动装配的bean的新实例.我认为设置scope =“prototype”会起作用,但它似乎没有完成这项工作.有没有人知道自定义bean范围会为每个JMS消息创建新实例？就像“请求”范围对HTTP请求一样？

我意识到我可以创建com.sample.TestListener“BeanFactoryAware”,然后在我的onMessage中执行getBean(“foo”),但我想避免将Spring依赖项放入我的代码中.

在此先感谢您的帮助！

下面的示例,我想要一个新的“com.sample.Foo”实例,并在每次收到消息时注入所有bean.

<bean id="consumer"
    class="com.sample.TestListener">
    <constructor-arg ref="foo" />
</bean> 

<!--Configures the Spring Message Listen Container. Points to the Connection 
    Factory, Destination, and Consumer -->
<bean id="MessageListenerContainer"
    class="org.springframework.jms.listener.DefaultMessageListenerContainer">
    <property name="connectionFactory" ref="CachedConnectionFactory" />
    <property name="destination" ref="Topic" />
    <property name="messageListener" ref="consumer" />
    <property name="concurrency" value="10"/> 
</bean> 

<bean id="foo" class="com.sample.Foo">
    <property name="x" ref="xx" />
    <property name="y" ref="yy" /> 
    <property name="z" ref="zz" />
</bean>

解决方法:

编写自定义范围很容易做到这一点……

public class CustomScope implements Scope, BeanFactoryPostProcessor {

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
        String name = "myScope";

        beanFactory.registerScope(name, this);

        Assert.state(beanFactory instanceof BeanDefinitionRegistry,
                "BeanFactory was not a BeanDefinitionRegistry, so CustomScope cannot be used.");
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;

        for (String beanName : beanFactory.getBeanDefinitionNames()) {
            BeanDefinition definition = beanFactory.getBeanDefinition(beanName);
            if (name.equals(definition.getScope())) {
                BeanDefinitionHolder proxyHolder = ScopedProxyUtils.createScopedProxy(new BeanDefinitionHolder(definition, beanName), registry, false);
                registry.registerBeanDefinition(beanName, proxyHolder.getBeanDefinition());
            }
        }
    }

    @Override
    public Object get(String name, ObjectFactory<?> objectFactory) {
        return objectFactory.getObject(); // a new one every time
    }

    @Override
    public String getConversationId() {
        return null;
    }

    @Override
    public void registerDestructionCallback(String name, Runnable callback) {

    }

    @Override
    public Object remove(String name) {
        return null;
    }

    @Override
    public Object resolveContextualObject(String arg0) {
        return null;
    }

}


public class Foo implements MessageListener {

    private Bar bar;

    public void setBar(Bar bar) {
        this.bar = bar;
    }

    @Override
    public void onMessage(Message message) {
        System.out.println(bar.getId());
    }

}
@ContextConfiguration
@RunWith(SpringJUnit4ClassRunner.class)
public class FooTests {

    @Autowired
    private Foo foo;

    @Test
    public void test() {
        Message message = mock(Message.class);
        foo.onMessage(message);
        foo.onMessage(message);
    }

}

和一个样本背景……

<bean class="foo.CustomScope" />

<bean id="baz" class="foo.BazImpl" scope="myScope" />

<bean id="bar" class="foo.BarImpl" scope="myScope">
    <property name="baz" ref="baz" />
</bean>

<bean id="foo" class="foo.Foo">
    <property name="bar" ref="bar" />
</bean>

注意：使用这个简单的作用域,您必须将所有引用的bean放在作用域中(上面的bar和baz).您可以使所有引用的bean继承范围,但需要一些工作.这就是说 – 有一个例子说明如何在春季批次的StepScope中做到这一点.

注意#2这将为每个方法调用获取一个新实例.如果你调用多个方法,你将为每个调用获得一个新的bean.如果要将其范围限制为允许onMessage中的所有调用使用相同的实例,则需要添加更多技巧.

编辑：
以下是一些支持对onMessage()中实例的多次调用的更新…

private final ThreadLocal<Map<String, Object>> holder = new ThreadLocal<Map<String, Object>>();

...

@Override
public Object get(String name, ObjectFactory<?> objectFactory) {
    Map<String, Object> cache = this.holder.get();
    if (cache == null) {
        cache = new HashMap<String, Object>();
        this.holder.set(cache);
    }
    Object object = cache.get(name);
    if (object == null) {
        object = objectFactory.getObject();
        cache.put(name, object);
    }
    return object;
}

public void clearCache() {
    this.holder.remove();
}

现在,您必须清除缓存…

@Override
public void onMessage(Message message) {
    try {
        System.out.println(bar.getId());
        System.out.println(bar.getId());
    }
    finally {
        this.scope.clearCache();
    }
}

但即使这样也可以在AOP @After建议中完成,以保持听众完全清洁.

标签：java,scope,spring,spring-jms
来源： https://codeday.me/bug/20190629/1328372.html