JSON-RPC（jsonrpc4j）使用demo

服务端开发，在很多情况下，需要使用到RPC框架，今天发现一款很轻量的RPC框架——JSON-RPC。json rpc 是一种以json为消息格式的远程调用服务，它是一套允许运行在不同操作系统、不同环境的程序实现基于Internet过程调用的规范和一系列的实现。这种远程过程调用可以使用http作为传输协议，也可以使用其它传输协议，传输的内容是json消息体。 
json rpc 和xmlrpc相比具有很多优点。首先xmlrpc是以xml作为消息格式，xml具有体积大，格式复杂，传输占用带宽。程序对xml的解析也比较复杂，并且耗费较多服务器资源。json相比xml体积小巧，并且解析相对容易很多。 
json-rpc是一种非常轻量级的跨语言远程调用协议，实现及使用简单。仅需几十行代码，即可实现一个远程调用的客户端，方便语言扩展客户端的实现。服务器端有php、java、python、ruby、.net等语言实现，是非常不错的及轻量级的远程调用协议。 
其官网地址是：http://www.jsonrpc.org/ 
其Wiki地址是：http://json-rpc.org/wiki/implementations 
可以看到，JSON-RPC有C，C++，C#，Javascipt，Erlang，Objective-C，Java等多种语言的实现，这里我简单介绍下Java使用JSON-RPC的示例，今天折腾了半天弄得。 
首先就是要下载jsonrpc4j的jar包以及其依赖的jar包，这里我直接搭建Maven项目，使用Maven来管理jar包，其pom文件如下：

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">    <modelVersion>4.0.0</modelVersion>    <groupId>com.hjc.demo</groupId>    <artifactId>jsonrpc_server</artifactId>    <packaging>war</packaging>    <version>0.0.1-SNAPSHOT</version>    <name>jsonrpc_server Maven Webapp</name>    <url>http://maven.apache.org</url>    <dependencies>        <!-- jsonrpc4j -->        <dependency>            <groupId>com.github.briandilley.jsonrpc4j</groupId>            <artifactId>jsonrpc4j</artifactId>            <version>1.0</version>        </dependency>        <!-- jsonrpc4j依赖的包 -->        <dependency>            <groupId>junit</groupId>            <artifactId>junit</artifactId>            <version>4.10</version>        </dependency>        <dependency>            <groupId>com.fasterxml.jackson.core</groupId>            <artifactId>jackson-core</artifactId>            <version>2.0.2</version>        </dependency>        <dependency>            <groupId>com.fasterxml.jackson.core</groupId>            <artifactId>jackson-databind</artifactId>            <version>2.0.2</version>        </dependency>        <dependency>            <groupId>com.fasterxml.jackson.core</groupId>            <artifactId>jackson-annotations</artifactId>            <version>2.0.2</version>        </dependency>        <dependency>            <groupId>javax.portlet</groupId>            <artifactId>portlet-api</artifactId>            <version>2.0</version>        </dependency>        <dependency>            <groupId>org.springframework</groupId>            <artifactId>spring-core</artifactId>            <version>3.1.2.RELEASE</version>        </dependency>        <dependency>            <groupId>org.springframework</groupId>            <artifactId>spring-context</artifactId>            <version>3.1.2.RELEASE</version>        </dependency>        <dependency>            <groupId>org.springframework</groupId>            <artifactId>spring-web</artifactId>            <version>3.1.2.RELEASE</version>        </dependency>        <dependency>            <groupId>org.springframework</groupId>            <artifactId>spring-test</artifactId>            <version>3.1.2.RELEASE</version>        </dependency>        <dependency>            <groupId>commons-codec</groupId>            <artifactId>commons-codec</artifactId>            <version>1.4</version>        </dependency>        <dependency>            <groupId>org.apache.httpcomponents</groupId>            <artifactId>httpcore-nio</artifactId>            <version>4.2.1</version>        </dependency>        <dependency>            <groupId>org.jmock</groupId>            <artifactId>jmock-junit4</artifactId>            <version>2.5.1</version>        </dependency>        <dependency>            <groupId>org.jmock</groupId>            <artifactId>jmock</artifactId>            <version>2.5.1</version>        </dependency>        <dependency>            <groupId>org.eclipse.jetty</groupId>            <artifactId>jetty-server</artifactId>            <version>9.0.0.RC0</version>        </dependency>        <dependency>            <groupId>org.eclipse.jetty</groupId>            <artifactId>jetty-servlet</artifactId>            <version>9.0.0.RC0</version>        </dependency>        <dependency>            <groupId>org.ow2.chameleon.fuchsia.base.json-rpc</groupId>            <artifactId>org.ow2.chameleon.fuchsia.base.json-rpc.json-rpc-bundle</artifactId>            <version>0.0.2</version>        </dependency>    </dependencies>    <build>        <finalName>jsonrpc_server</finalName>    </build></project>
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待以上jar包等环境部署好了之后，就可以进行开发了，我们先要部署一个Servlet，作为RPC调用的接口。（我的环境的Tomcat6，Tomcat7的朋友可以直接使用@WebServlet来部署Servlet，具体代码因环境而异）。

web.xml

<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd" ><web-app>  <display-name>Archetype Created Web Application</display-name>  <servlet>    <servlet-name>RpcServer</servlet-name>    <display-name>RpcServer</display-name>    <description></description>    <servlet-class>com.hjc.demo.RpcServer</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>RpcServer</servlet-name>    <url-pattern>/rpc</url-pattern>  </servlet-mapping></web-app>
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RpcServer.java

package com.hjc.demo;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.googlecode.jsonrpc4j.JsonRpcServer;public class RpcServer extends HttpServlet {    private static final long serialVersionUID = 1L;    private JsonRpcServer rpcServer = null;    public RpcServer() {        super();        rpcServer = new JsonRpcServer(new DemoServiceImply(), DemoService.class);    }    @Override    protected void service(HttpServletRequest request,            HttpServletResponse response) throws ServletException, IOException {        rpcServer.handle(request, response);    }}
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其中，DemoService是RPC调用的接口，DemoServiceImply是DemoService接口的实现，他们的代码分别如下：

DemoService.java

package com.hjc.demo;public interface DemoService {    public DemoBean getDemo(String code, String msg);    public Integer getInt(Integer code);    public String getString(String msg);    public void doSomething();}
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DemoServiceImply.java

package com.hjc.demo;public class DemoServiceImply implements DemoService {    public DemoBean getDemo(String code, String msg) {        DemoBean bean1 = new DemoBean();        bean1.setCode(Integer.parseInt(code));        bean1.setMsg(msg);        return bean1;    }    public Integer getInt(Integer code) {        return code;    }    public String getString(String msg) {        return msg;    }    public void doSomething() {        System.out.println("do something");    }}
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DemoBean是一个普通的JavaBean，其代码如下：

DemoBean.java

package com.hjc.demo;import java.io.Serializable;public class DemoBean implements Serializable{    private static final long serialVersionUID = -5141784402935371524L;    private int code;    private String msg;    public int getCode() {        return code;    }    public void setCode(int code) {        this.code = code;    }    public String getMsg() {        return msg;    }    public void setMsg(String msg) {        this.msg = msg;    }}
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以上代码即完成了服务端的代码，接下来写一个客户端的测试类：

JsonRpcTest.java

package com.hjc.test;import java.net.MalformedURLException;import java.net.URL;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import com.fasterxml.jackson.databind.node.ObjectNode;import com.googlecode.jsonrpc4j.JsonRpcHttpClient;import com.hjc.demo.DemoBean;public class JsonRpcTest {    static JsonRpcHttpClient client;    public JsonRpcTest() {    }    public static void main(String[] args) throws Throwable {        // 实例化请求地址，注意服务端web.xml中地址的配置        try {            client = new JsonRpcHttpClient(new URL(                    "http://127.0.0.1:8080/jsonrpc_server/rpc"));            // 请求头中添加的信息            Map<String, String> headers = new HashMap<String, String>();            headers.put("UserKey", "hjckey");            // 添加到请求头中去            client.setHeaders(headers);            JsonRpcTest test = new JsonRpcTest();            test.doSomething();            DemoBean demo = test.getDemo(1, "哈");            int code = test.getInt(2);            String msg = test.getString("哈哈哈");            // print            System.out.println("===========================javabean");            System.out.println(demo.getCode());            System.out.println(demo.getMsg());            System.out.println("===========================Integer");            System.out.println(code);            System.out.println("===========================String");            System.out.println(msg);            System.out.println("===========================end");        } catch (Exception e) {            e.printStackTrace();        }    }    public void doSomething() throws Throwable {        client.invoke("doSomething", null);    }    public DemoBean getDemo(int code, String msg) throws Throwable {        String[] params = new String[] { String.valueOf(code), msg };        DemoBean demo = null;        demo = client.invoke("getDemo", params, DemoBean.class);        return demo;    }    public int getInt(int code) throws Throwable {        Integer[] codes = new Integer[] { code };        return client.invoke("getInt", codes, Integer.class);    }    public String getString(String msg) throws Throwable {        String[] msgs = new String[] { msg };        return client.invoke("getString", msgs, String.class);    }}
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最后的打印结果如下：

服务端：

do something
1

客户端：

===========================javabean1哈===========================Integer2===========================String哈哈哈===========================end
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以上就完成了JSON-RPC全部的代码，值得说的是，这其中我也爬了很多坑，这里也提一下，JsonRpcHttpClient类的invoke方法，如果你要传递参数，必须是一个数组，这里我传的String[]和Integer[]，如果传递了别的类型会发生什么呢？你可以试一下这样调用：

client.invoke("getInt", 3, Integer.class);
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然后你就会发现服务端报错：

java.lang.IllegalArgumentException: Unknown params node type: 2    at com.googlecode.jsonrpc4j.JsonRpcServer.findBestMethodByParamsNode(JsonRpcServer.java:612)    at com.googlecode.jsonrpc4j.JsonRpcServer.handleObject(JsonRpcServer.java:373)    at com.googlecode.jsonrpc4j.JsonRpcServer.handleNode(JsonRpcServer.java:293)    at com.googlecode.jsonrpc4j.JsonRpcServer.handle(JsonRpcServer.java:230)    at com.googlecode.jsonrpc4j.JsonRpcServer.handle(JsonRpcServer.java:207)    at com.hjc.demo.RpcServer.service(RpcServer.java:24)        ...
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点进源码，你就全明白了，进入JsonRpcServer类查看findBestMethodByParamsNode方法，其代码如下：

/**     * Finds the {@link Method} from the supplied {@link Set} that     * best matches the rest of the arguments supplied and returns     * it as a {@link MethodAndArgs} class.     *     * @param methods the {@link Method}s     * @param paramsNode the {@link JsonNode} passed as the parameters     * @return the {@link MethodAndArgs}     */    private MethodAndArgs findBestMethodByParamsNode(Set<Method> methods, JsonNode paramsNode) {        // no parameters        if (paramsNode==null || paramsNode.isNull()) {            return findBestMethodUsingParamIndexes(methods, 0, null);        // array parameters        } else if (paramsNode.isArray()) {            return findBestMethodUsingParamIndexes(methods, paramsNode.size(), ArrayNode.class.cast(paramsNode));        // named parameters        } else if (paramsNode.isObject()) {            Set<String> fieldNames = new HashSet<String>();            Iterator<String> itr=paramsNode.fieldNames();            while (itr.hasNext()) {                fieldNames.add(itr.next());            }            return findBestMethodUsingParamNames(methods, fieldNames, ObjectNode.class.cast(paramsNode));        }        // unknown params node type        throw new IllegalArgumentException("Unknown params node type: "+paramsNode.toString());    }
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所以我就明白了，除了null（不传参数），Array，Object，其他的类都是“Unknown params node type”，当时我也很疑惑，Integer不也是Object嘛，断点一下，原来它认为这是IntNode类，所以不能识别，其他的参数我也试过一些，目前还是数组是最靠谱的，网上资料还比较少，希望有懂得给指点指点。 
这也是我今天花了半天时间弄得JSON-RPC，喜欢的朋友，源码地址在下面： 
https://github.com/hjcenry/json-rpc-demo