如何使用Spring Boot Java配置编写自定义Apache Camel组件/endpoint

Question

public class MyCustomComponent extends DefaultComponent {
    @Override
    protected Endpoint createEndpoint(String uri, String remaining, Map<String, Object> parameters) throws Exception {
        Endpoint endpoint = new MyCustomEndpoint(uri, this);
        setProperties(endpoint, parameters);
        return endpoint;
    }
}

注册的是resources/meta-inf/services/org/apache/camel/component/myscheme中的组件，其FQN为MyCustomComponent类。

public class MyCustomEndpoint extends DefaultEndpoint {

    public MyCustomEndpoint(String uri, MyCustomComponent component) {
        super(uri, component);
    }

    @Override
    public Producer createProducer() throws Exception {
        return new MyCustomProducer(this);
    }

    @Override
    public Consumer createConsumer(Processor processor) throws Exception {
        throw new UnsupportedOperationException("Not implemented yet: MyCustomEndpoint#createConsumer");
    }

    @Override
    public boolean isSingleton() {
        return false;
    }
}

public class MyCustomProducer extends DefaultProducer {

    public MyCustomProducer(Endpoint endpoint) {
        super(endpoint);
    }

    @Override
    public void process(Exchange exchange) throws Exception {
    }
}

Answer 1

经过大量搜索，我找到了一个基于Spring的BeanFactory的解决方案。主要障碍是循环依赖关系（组件->endpoint->组件endpoint->生产者->endpoint）。首先，我介绍了一个Spring配置类：

@Configuration
public class ComponentConfiguration {

    @Bean("myCustomEndpoint")
    @Scope("prototype")
    public MyCustomEndpoint myCustomEndpoint(String uri, MyCustomComponent component) {
        MyCustomEndpoint endpoint = new MyCustomEndpoint(uri, component);
        return endpoint;
    }

    @Bean("myCustomProducer")
    @Scope("prototype")
    public MyCustomProducer myCustomProducer(MyCustomEndpoint endpoint) {
        return new MyCustomProducer(endpoint);
    }
}

使自定义骆驼组件成为带有@component注释的Spring组件，这样我就可以插入BeanFactory来按需创建MyCustomEndpoint类的实例(Prototype作用域）。

@org.springframework.stereotype.Component
public class MyCustomComponent extends DefaultComponent {

    @Autowired
    private BeanFactory beanFactory;

    @Override
    protected Endpoint createEndpoint(String uri, String remaining, Map<String, Object> parameters) throws Exception {
        MyCustomEndpoint endpoint = (MyCustomEndpoint) beanFactory.getBean("myCustomEndpoint", uri, this);
        setProperties(endpoint, parameters);
        return endpoint;
    }
}

public class MyCustomEndpoint extends DefaultEndpoint {

    @Autowired
    private BeanFactory beanFactory;

    public MyCustomEndpoint(String uri, MyCustomComponent component) {
        super(uri, component);
    }

    @Override
    public Producer createProducer() throws Exception {
        MyCustomProducer producer = (MyCustomProducer) beanFactory.getBean("myCustomProducer",  this);
        return producer;
    }

    @Override
    public Consumer createConsumer(Processor processor) throws Exception {
        throw new UnsupportedOperationException("Not implemented yet: MyCustomEndpoint#createConsumer");
    }

    @Override
    public boolean isSingleton() {
        return true;
    }
}

public class MyCustomProducer extends DefaultProducer {

    // Now, I am able to inject some other Spring beans
    @Autowired
    private AnotherSpringBean bean;

    public MyCustomProducer(Endpoint endpoint) {
        super(endpoint);
    }

    @Override
    public void process(Exchange exchange) throws Exception {
    }
}

请注意，Camel组件MyCustomComponent已经注册在resources/META-INF/Services/org/apache/Camel/component/MyScheme中：

class=<fqn-of-MyCustomComponent>