camel开源框架简介

camel是实现企业应用集成的开源免费框架，网址：

http://camel.apache.org/

用camel可以很容易实现自动的消息路由和消息转换。基于camel可以将原来复杂和需求经常变化的应用，分解为多个消息生产者和消息消费者程序，这样每个程序更小，更容易设计和部署，需求的改动也不影响其他程序。

 

以下是一个最简单的示例。

这个示例可以特别简单。需要的准备依赖的类库（包括activemq），用maven的配置如下：

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-jms</artifactId>
    <version>1.6.0</version>
</dependency>
<dependency>
    <groupId>org.apache.activemq</groupId>
    <artifactId>activemq-core</artifactId>
    <version>5.2.0</version>
</dependency>

安装基于web管理的activemq，参见tomcat下部署activemq。

编写代码：

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-->import javax.jms.ConnectionFactory;

import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.camel.CamelContext;
import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.component.jms.JmsComponent;
import org.apache.camel.impl.DefaultCamelContext;

public class Helloworld {
    public static void main(String[] args) throws Exception {
        CamelContext context = new DefaultCamelContext();
        context.addRoutes(new RouteBuilder() {

            public void configure() {
                from("jms:test.a").to("file://e:/jms.test");
            }
        });

        ConnectionFactory connectionFactory = new ActiveMQConnectionFactory(
                "tcp://localhost:61616");
        context.addComponent("jms", JmsComponent.jmsComponentAutoAcknowledge(connectionFactory)); 

        context.start();
    }
}

这样只要在test.a队列中发送消息，就会被此程序（守护线程）复制该消息到e盘的jms.test目录。因为注册转换器，所以会有警告：

2009-7-18 12:06:10 org.apache.camel.impl.converter.DefaultTypeConverter addTypeConverter
警告: Overriding type converter from: InstanceMethodTypeConverter: public java.lang.String org.apache.camel.converter.jaxp.XmlConverter.toString(javax.xml.transform.Source) throws javax.xml.transform.TransformerException to: StaticMethodTypeConverter: public static java.lang.String org.apache.camel.converter.IOConverter.toString(javax.xml.transform.Source) throws javax.xml.transform.TransformerException,java.io.IOException

如果想将该消息转发到另外的队列，并作一些处理，可以这样：

<!--

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-->import javax.jms.ConnectionFactory;

import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.camel.CamelContext;
import org.apache.camel.Exchange;
import org.apache.camel.Processor;
import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.component.jms.JmsComponent;
import org.apache.camel.impl.DefaultCamelContext;

public class Helloworld {
    public static void main(String[] args) throws Exception {
        CamelContext context = new DefaultCamelContext();
        context.addRoutes(new RouteBuilder() {

            public void configure() {
                from("jms:test.a").to("jms:test.b");

                from("jms:test.b").process(new Processor() {
                    public void process(Exchange e) {
                        System.out.println("Received exchange: " + e.getIn());
                    }
                });
            }
        });

        ConnectionFactory connectionFactory = new ActiveMQConnectionFactory(
                "tcp://localhost:61616");
        context.addComponent("jms", JmsComponent.jmsComponentAutoAcknowledge(connectionFactory)); 

        context.start();
    }
}