java - 空指针异常 Spring Integration 消息传递

Question

我正在开始使用 Spring 集成......以下代码产生了空指针异常。

Spring context.xml(Spring配置)

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:int="http://www.springframework.org/schema/integration"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/integration
    http://www.springframework.org/schema/integration/spring-integration-2.1.xsd
    http://www.springframework.org/schema/context 
    http://www.springframework.org/schema/context/spring-context-3.0.xsd">
    <context:component-scan base-package="co.in" />

    <int:channel id="input" />
    <int:channel id="output">
        <int:queue capacity="10" />
    </int:channel>
    <int:service-activator input-channel="input"
        output-channel="output" ref="messageHandler" />
</beans>

app.java(主类)

package co.in;

import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.integration.Message;
import org.springframework.integration.MessageChannel;
import org.springframework.integration.core.PollableChannel;
import org.springframework.integration.support.MessageBuilder;

public class app {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                "classpath:resources/spring-context.xml");
        context.start();

        MessageChannel input = (MessageChannel) context.getBean("input",
                MessageChannel.class);
        PollableChannel output = (PollableChannel) context.getBean("output",
                PollableChannel.class);
        input.send(MessageBuilder.withPayload("Pro Spring Integration Example")
                .build());

        Message<?> reply = output.receive();
        System.out.println("received: " + reply);

    }
}

MessageHandler.java(服务激活器 bean 定义)

package co.in;

import org.springframework.integration.annotation.ServiceActivator;

@Component
public class MessageHandler {

    @ServiceActivator
    public String handleMessage(String message) {
        System.out.println("Received message: " + message);
        return "MESSAGE:" + message;
    }
} 

错误堆栈

Exception in thread "main" org.springframework.beans.factory.BeanDefinitionStoreException: Unexpected exception parsing XML document from class path resource [resources/spring-context.xml]; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:420)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:342)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:310)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:143)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:178)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:149)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:212)
    at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:113)
    at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:80)
    at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:123)
    at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:422)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:352)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
    at co.in.app.main(app.java:11)
Caused by: java.lang.NullPointerException
    at org.springframework.beans.factory.support.BeanDefinitionReaderUtils.generateBeanName(BeanDefinitionReaderUtils.java:115)
    at org.springframework.beans.factory.support.BeanDefinitionReaderUtils.generateBeanName(BeanDefinitionReaderUtils.java:159)
    at org.springframework.beans.factory.support.DefaultBeanNameGenerator.generateBeanName(DefaultBeanNameGenerator.java:31)
    at org.springframework.beans.factory.xml.XmlReaderContext.generateBeanName(XmlReaderContext.java:77)
    at org.springframework.beans.factory.xml.AbstractBeanDefinitionParser.resolveId(AbstractBeanDefinitionParser.java:102)
    at org.springframework.beans.factory.xml.AbstractBeanDefinitionParser.parse(AbstractBeanDefinitionParser.java:59)
    at org.springframework.beans.factory.xml.NamespaceHandlerSupport.parse(NamespaceHandlerSupport.java:69)
    at org.springframework.integration.config.xml.AbstractIntegrationNamespaceHandler.parse(AbstractIntegrationNamespaceHandler.java:57)
    at org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.parseCustomElement(BeanDefinitionParserDelegate.java:1297)
    at org.springframework.beans.factory.xml.BeanDefinitionParserDelegate.parseCustomElement(BeanDefinitionParserDelegate.java:1287)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.parseBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:135)
    at org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader.registerBeanDefinitions(DefaultBeanDefinitionDocumentReader.java:92)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.registerBeanDefinitions(XmlBeanDefinitionReader.java:507)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:398)
    ... 14 more

Answer 1

根据堆栈跟踪，您似乎正在使用 Spring Integration 2.0.x。

您使用的是哪个版本的 Spring？

我建议您使用当前版本(2.1.3.RELEASE)。