学步园

继上次Camel如何在做项目集成类型的项目中用于从FTP取文件和传文件之后,我们在系统集成中经常遇到的另一个应用就是将数据通过JMS传到消息中间件的queue里,或者从消息中间件的queue里取消息.

本文简单的介绍和示例一个用Camel实现这样的需求:监听某一个文件夹是否有文件,取到文件后发送到另外一个系统监听的queue.(图片来源于Camel in Action)

1,因为要用JMS,这里介绍一个open source的activeMQ,可以从http://activemq.apache.org/download.html 下载,下载后解压,bin目录有一个activemq.bat文件,在命令行里运行activemq 启动activeMQ,如果能从从浏览器里访问 http://localhost:8161/admin/则activeMQ成功启动了.

2,在Camel里实现上图所示的路由:JAVA项目里需要将activeMQ的jar包配置到classpath下,Java代码如下:

    private static String user = ActiveMQConnection.DEFAULT_USER;
    private static String password = ActiveMQConnection.DEFAULT_PASSWORD;
    private static String url = ActiveMQConnection.DEFAULT_BROKER_URL;
    
    public static void main(String args[]) throws Exception {        
        CamelContext context = new DefaultCamelContext();        
        ConnectionFactory connectionFactory = 
            new ActiveMQConnectionFactory(user, password, url);
        context.addComponent("jms",
            JmsComponent.jmsComponentAutoAcknowledge(connectionFactory));
        System.out.println(url + " " + user + password);        
        context.addRoutes(new RouteBuilder() {
            public void configure() {                
                from("file:d:/temp/inbox").to(
                "jms:queue:TOOL.DEFAULT");
            }
        });
        context.start();
        boolean loop = true;
        while (loop) {
            Thread.sleep(25000);
        }

        context.stop();
    }

Camel会在路由的时候将文件的内容以binary message发到activeMQ的名为'TOOL.DEFAULT'的queue .

当然也可以用如下的方式发送textmessage:from("file:d:/temp/inbox").convertBodyTo(String.class).to("jms:queue:TOOL.DEFAULT");

用下面的代码可以从Camel发送的queue里取到消息.

    private static String user = ActiveMQConnection.DEFAULT_USER;
    private static String password = ActiveMQConnection.DEFAULT_PASSWORD;
    private static String url = ActiveMQConnection.DEFAULT_BROKER_URL;
    private static boolean transacted;
    private static int ackMode = Session.AUTO_ACKNOWLEDGE;

    public static void main(String[] args) throws Exception {
        ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory(user, password, url);
        Connection connection = connectionFactory.createConnection();
        connection.start();
        Session session = connection.createSession(transacted, ackMode);
        Destination destination = session.createQueue("TOOL.DEFAULT");
        MessageConsumer consumer = session.createConsumer(destination);
        Message message = consumer.receive(1000);
        if (message instanceof TextMessage) {
            TextMessage txtMsg = (TextMessage) message;
            System.out.println("Received Text message : " + txtMsg.getText());
        } else if(message != null){
            BytesMessage bytesMsg = (BytesMessage) message;
            byte[] bytes = new byte[(int) bytesMsg.getBodyLength()];
            bytesMsg.readBytes(bytes);
            System.out.println("Received byte message: " + new String(bytes));
        }
        consumer.close();
        session.close();
        connection.close();
    }

同样,上面的路由也可以通过Spring配置实现:

    <bean id="jms" class="org.apache.camel.component.jms.JmsComponent">
        <property name="connectionFactory">
            <bean class="org.apache.activemq.ActiveMQConnectionFactory">
                <property name="brokerURL" value="failover://tcp://localhost:61616"/>
            </bean>
        </property>
    </bean>    
    <camelContext xmlns="http://camel.apache.org/schema/spring">
        <route>
            <from uri="file:d:/temp/inbox"/>
            <to uri="jms:queue:TOOL.DEFAULT"/>
        </route>
    </camelContext>