Apache Camel框架之Freemarker做数据转换

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在做系统集成的时候,必不可少的任务就是将数据从一种格式转换为另一种格式,再把转换后的格式发到目标系统,在此用实例介绍一下Camel中利用Freemarker做数据转换.

1,Freemarker的模板如下:

<?xml version="1.0" encoding="UTF-8"?><people  xmlns:h="http://www.w3.org/TR/html4/">    <#escape x as x?xml>    <#list body.peopleList as p>    <person id="000001" age="20">        <name>            <family>${p.fname}</family>            <given>${p.gname}</given>        </name>        <email>${p.email}</email>        <link manager="${p.manager}" />        <#if p.level == "L1">        <l1tag>xxx</l1tag>        </#if>    </person>    </#list>    </#escape></people>

2,与之对应的Java对象如下:每一个person节点对应一个ValueObject放在XMLTemplateParameter的peopleList里面.

public class XMLTemplateParameter {    private String fileName;        private List<ValueObject> peopleList = new ArrayList<ValueObject>();    public List<ValueObject> getPeopleList() {        return peopleList;    }    public void setPeopleList(List<ValueObject> peopleList) {        this.peopleList = peopleList;    }    public String getFileName() {        return fileName;    }    public void setFileName(String fileName) {        this.fileName = fileName;    }}public class ValueObject {    private String fname;    private String gname;    private String email;    private String manager;    private String level;

3,Route代码如下:

public class CamelFreemarkerRoute extends RouteBuilder {    public void configure() throws Exception {        from("quartz://report?cron=10 * * * * ?&stateful=true")        .beanRef("fmBean","prepareFMValues")         .to("freemarker:com/test/camel/freemarker/test.ftl")        .to("file:d:/temp/outbox?fileName=fm.xml");        }}

4,Route里用到的bean如下:xmlTemplateParameter做为顶级对象放在body里面,Freemarker里取数据的body.peopleList就对应于xmlTemplateParameter.peopleList

public class FmProcessorBean {        public void prepareFMValues(Exchange exchange){        XMLTemplateParameter xmlTemplateParameter = new XMLTemplateParameter();        ValueObject val = null;        for(int i=0;i<3;i++){            val = new ValueObject();                    val.setFname("Yao");            val.setGname("Yorker" +i);            val.setEmail("test@mail.com");            val.setManager("m&an<ager");            val.setLevel("L" + i);            xmlTemplateParameter.getPeopleList().add(val);                    }                exchange.getIn().setBody(xmlTemplateParameter);    }    }

5,Spring的配置文件如下:

<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:camel="http://camel.apache.org/schema/spring" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd" default-autowire="byName" default-init-method="init">    <bean id="fmBean" class="com.test.camel.freemarker.FmProcessorBean"/>    <camelContext id="testCamelContext" xmlns="http://camel.apache.org/schema/spring">        <package>com.test.camel.freemarker</package>    </camelContext>    </beans>

6,启动Spring,在D:\temp\outbox文件夹下,每隔10秒钟,会根据freemarker模板生成一个fm.xml文件.

        ApplicationContext ac = new ClassPathXmlApplicationContext("config/camelFreemarker.xml");
       while (true) {
           Thread.sleep(2000);
       }

对本例beanRef("fmBean","prepareFMValues")的解释:

其意思是调用fmBean的prepareFMValues方法,Camel会负责将message的body绑定到要调用方法的第一个参数上面,其中可能做相应的类型转换.(本例中的方法的第一个参数为Exchange,没有转换的过程 ),这里给一个如下示例图解释这个绑定转换的过程:Camel将Exchange的的input message(exchange.getIn())转换为String,绑定到mtd方法的name参数上.(图片来源于Camel in Action)

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