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>4.0.0modelVersion>
<groupId>com.hjc.demogroupId>
<artifactId>jsonrpc_serverartifactId>
<packaging>warpackaging>
<version>0.0.1-SNAPSHOTversion>
<name>jsonrpc_server Maven Webappname>
<url>http://maven.apache.orgurl>
<dependencies>
<dependency>
<groupId>com.github.briandilley.jsonrpc4jgroupId>
<artifactId>jsonrpc4jartifactId>
<version>1.0version>
dependency>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.10version>
dependency>
<dependency>
<groupId>com.fasterxml.jackson.coregroupId>
<artifactId>jackson-coreartifactId>
<version>2.0.2version>
dependency>
<dependency>
<groupId>com.fasterxml.jackson.coregroupId>
<artifactId>jackson-databindartifactId>
<version>2.0.2version>
dependency>
<dependency>
<groupId>com.fasterxml.jackson.coregroupId>
<artifactId>jackson-annotationsartifactId>
<version>2.0.2version>
dependency>
<dependency>
<groupId>javax.portletgroupId>
<artifactId>portlet-apiartifactId>
<version>2.0version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-coreartifactId>
<version>3.1.2.RELEASEversion>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-contextartifactId>
<version>3.1.2.RELEASEversion>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-webartifactId>
<version>3.1.2.RELEASEversion>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-testartifactId>
<version>3.1.2.RELEASEversion>
dependency>
<dependency>
<groupId>commons-codecgroupId>
<artifactId>commons-codecartifactId>
<version>1.4version>
dependency>
<dependency>
<groupId>org.apache.httpcomponentsgroupId>
<artifactId>httpcore-nioartifactId>
<version>4.2.1version>
dependency>
<dependency>
<groupId>org.jmockgroupId>
<artifactId>jmock-junit4artifactId>
<version>2.5.1version>
dependency>
<dependency>
<groupId>org.jmockgroupId>
<artifactId>jmockartifactId>
<version>2.5.1version>
dependency>
<dependency>
<groupId>org.eclipse.jettygroupId>
<artifactId>jetty-serverartifactId>
<version>9.0.0.RC0version>
dependency>
<dependency>
<groupId>org.eclipse.jettygroupId>
<artifactId>jetty-servletartifactId>
<version>9.0.0.RC0version>
dependency>
<dependency>
<groupId>org.ow2.chameleon.fuchsia.base.json-rpcgroupId>
<artifactId>org.ow2.chameleon.fuchsia.base.json-rpc.json-rpc-bundleartifactId>
<version>0.0.2version>
dependency>
dependencies>
<build>
<finalName>jsonrpc_serverfinalName>
build>
project>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
<web-app>
<display-name>Archetype Created Web Applicationdisplay-name>
<servlet>
<servlet-name>RpcServerservlet-name>
<display-name>RpcServerdisplay-name>
<description>description>
<servlet-class>com.hjc.demo.RpcServerservlet-class>
servlet>
<servlet-mapping>
<servlet-name>RpcServerservlet-name>
<url-pattern>/rpcurl-pattern>
servlet-mapping>
web-app>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);
}
}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();
}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");
}
}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;
}
}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 headers = new HashMap();
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);
}
} 最后的打印结果如下：
服务端：
do something客户端：
===========================javabean
1
哈
===========================Integer
2
===========================String
哈哈哈
===========================end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);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)
...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 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 fieldNames = new HashSet();
Iterator 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());
} 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