(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：

/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<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：

Servlet的创建：

/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", "-5-16 10:22:20", "/exclusive/-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", "-5-16 10:22:20", "/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?", "-5-16 10:22:20", "/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", "-5-16 10:22:20", "/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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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", "-5-16 10:22:20", ""); 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 } @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+"/"; %> <!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="/2001/XMLSchema-instance" xmlns="/xml/ns/javaee" xsi:schemaLocation="/xml/ns/javaee /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>

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：

/jaikydota163/article/details/51458880