实现效果

实现原因

目前主流的CS结构，数据都是通过RESTful风格接口形式呈现，不管是桌面级应用程序还是手机端，接口是我们获取数据的大多数选择，主流数据接口呈现形式主要是Json和Xml，后者目前基本渐行渐远。Json的轻量级和可读型成为了大多数公司及个人开发者的第一选择。

主流公司在编写数据接口时大多通过框架实现，如RESTEasy、Retrofit等，在这里通过简单的java web代码写一个简单的接口项目例子供大家参考，后附项目源代码。

实现步骤

在Eclipse中新建项目JsonTest项目，项目结构如下，

此处主要用到的类只有几个，其他类为Json测试用类，此处可以忽略。

在lib下导入或在maven中引用gson-2.6.2.jar包和servlet-api.jar包。

gson此处用于将持久化对象解析为Json，或将Json序列化为对象。

servlet-api用于servlet相关类创建及API运用。

关于gson，是Google开源项目下的一个Java Json解析工具包，具体使用及详细信息可以看这篇文章：Gson简要使用

步骤一：新建测试用Model类

新建新闻测试类News，主要用于数据模型测试显示，Json转换测试等，代码如下：

import java.util.Date;public class News {private int nId; // 新闻IDprivate String title; // 新闻标题private String content; // 新闻内容private String date; // 新闻发布日期private String url; //新闻地址private Date nDate; // 新闻日期，Date类型public News(int nId, String title, String content, String date, String url) {this.nId = nId;this.title = title;this.content = content;this.date = date;this.url = url;}public News() {}public News(int nId, String title, String content, Date nDate, String url) {this.nId = nId;this.title = title;this.content = content;this.nDate = nDate;this.url = url;}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}public Date getnDate() {return nDate;}public void setnDate(Date nDate) {this.nDate = nDate;}public int getnId() {return nId;}public void setnId(int nId) {this.nId = nId;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getContent() {return content;}public void setContent(String content) {this.content = content;}public String getDate() {return date;}public void setDate(String date) {this.date = date;}}

新建分页测试类NewTotal，主要用于Json分页显示，代码如下：

import java.util.List;public class NewTotal {private int total; //新闻数量private List<News> rows; //新闻列表public NewTotal() {}public NewTotal(int total, List<News> rows) {this.total = total;this.rows = rows;}public int getTotal() {return total;}public void setTotal(int total) {this.total = total;}public List<News> getRows() {return rows;}public void setRows(List<News> rows) {this.rows = rows;}}

步骤二：添加测试用Action和JSP界面

新建JsonServlet，继承自HttpServlet，具体代码详解已经在代码中注释：

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import com.google.gson.Gson;
import com.test.model.NewTotal;
import com.test.model.News;public class JsonServlet extends HttpServlet {private static final long serialVersionUID = 1L;@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 创建多个新闻类，模拟从数据库获取数据，可将此处改为用JDBC从数据库读取数据News new1 = new News(110, "日本地震", "日本福田发生了7级地震", "2016-5-16 10:22:20","http://world.huanqiu.com/exclusive/2016-05/8974294.html");News new2 = new News(111, "Apple库克第八次访华", "近日库克第八次访华，与滴滴高层会谈", "2016-5-16 10:22:20","http://mobile.163.com/16/0523/09/BNO7SG2B001168BQ.html");News new3 = new News(113, "Google I/O大会开幕", "Google开发者大会即将举办，是否推出Android7.0?", "2016-5-16 10:22:20","http://www.ithome.com/html/android/227647.htm");News new4 = new News(114, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20","http://news.mydrivers.com/1/484/484072.htm");News new5 = new News(115, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new6 = new News(116, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new7 = new News(117, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new8 = new News(118, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new9 = new News(119, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new10 = new News(120, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new11 = new News(121, "获取新数据！！！！！！", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new12 = new News(122, "获取新数据！！！！！！", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new13 = new News(123, "获取新数据！！！！！！", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new14 = new News(124, "获取新数据！！！！！！", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new15 = new News(125, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new16 = new News(126, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new17 = new News(127, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new18 = new News(128, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new19 = new News(129, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");News new20 = new News(130, "格力营收下滑400亿", "格里营收下滑400亿，董明珠说我活得好的很", "2016-5-16 10:22:20", "www.baidu.com");String page = req.getParameter("page");// 将数据添加到数组List<News> newslist = new ArrayList<News>();if (page == null || page.equals("0")) {newslist.add(new1);newslist.add(new2);newslist.add(new3);newslist.add(new4);newslist.add(new5);newslist.add(new6);newslist.add(new7);newslist.add(new8);newslist.add(new9);newslist.add(new10);}else {newslist.add(new11);newslist.add(new12);newslist.add(new13);newslist.add(new14);newslist.add(new15);newslist.add(new16);newslist.add(new17);newslist.add(new18);newslist.add(new19);newslist.add(new20);}// 将数据封装到新闻总计类NewTotal nt = new NewTotal(newslist.size(), newslist);// 调用GSON jar工具包封装好的toJson方法，可直接生成JSON字符串Gson gson = new Gson();String json = gson.toJson(nt);// 输出到界面System.out.println(json);resp.setContentType("text/plain");resp.setCharacterEncoding("gb2312");PrintWriter out = new PrintWriter(resp.getOutputStream());out.print(json);out.flush();// 更多Json转换使用请看JsonTest类}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doGet(req, resp);}}

修改项目index.jsp页面如下：

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head><base href="<%=basePath%>"><title>Test Json</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8><meta http-equiv="pragma" content="no-cache"><meta http-equiv="cache-control" content="no-cache"><meta http-equiv="expires" content="0">    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"><meta http-equiv="description" content="This is my page"><!--<link rel="stylesheet" type="text/css" href="styles.css">--></head><body><form action="getJson" method="get"><input type="submit" value="点击获取新闻JSON数据"/></form></body>
</html>

在项目中配置web.xml，注册JsonServlet映射，配置如下：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"><display-name>JsonTest</display-name><welcome-file-list><welcome-file>index.jsp</welcome-file></welcome-file-list><servlet><servlet-name>JsonServlet</servlet-name><servlet-class>com.test.json.JsonServlet</servlet-class></servlet><servlet-mapping><servlet-name>JsonServlet</servlet-name><url-pattern>/getJson</url-pattern></servlet-mapping>
</web-app>