(017)java后台开发之客户端通过HTTP获取接口Json数据
通过前面的文章，我们能了解javaWeb工程的基本知识。然后最激动的东西来了！我们建立了JsonTest工程，部署到了tomcat，本地浏览器访问了我们的JsonTest工程的index.jsp页面。
- 那我们怎么进行客户端和服务器后台交互尼？
跟着一个例子实现：
http://blog.csdn.net/jaikydota163/article/details/51458880
在之前建好的JsonTest工程，创建我们需要的文件。
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ID
private 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 rows; //新闻列表
public NewTotal() {
}
public NewTotal(int total, List rows) {
this.total = total;
this.rows = rows;
}
public int getTotal() {
return total;
}
public void setTotal(int total) {
this.total = total;
}
public List getRows() {
return rows;
}
public void setRows(List 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：
Servlet的创建：
http://blog.csdn.net/gaohuanjie/article/details/36377425
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;
@Override
protected 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 newslist = new ArrayList();
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
}
@Override
protected 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+"/";
%>
<html>
<head>
<base href="<%=basePath%>">
<title>Test Jsontitle>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8>
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">
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：
<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>JsonTestdisplay-name>
<welcome-file-list>
<welcome-file>index.jspwelcome-file>
welcome-file-list>
<servlet>
<servlet-name>JsonServletservlet-name>
<servlet-class>com.test.json.JsonServletservlet-class>
servlet>
<servlet-mapping>
<servlet-name>JsonServletservlet-name>
<url-pattern>/getJsonurl-pattern>
servlet-mapping>
web-app> 步骤三：添加项目到Tomcat容器，运行服务器
运行服务器，在地址栏输入地址：
http://localhost:8080/JsonTest/getJson?page=0，
⚠️这里可能会出现乱码。解决办法：
只需要把网页编码切换一下就可以了,设置下编码为utf-8。客户端编码设置为utf8，这样保证交互过程中，编码一致。OK了！
效果如图：
一个简单的http请求已经返回就完成了！
例子参考：
http://blog.csdn.net/jaikydota163/article/details/51458880