| 最近上班太忙，晚上抽空整理一下ajax请求中，后台返回json字符串和json数组的场景，以及前台的处理示例。 直接看代码。 json字符串的后台响应 package com.ajax;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;@WebServlet("/jsonStr")public class JsonStr extends HttpServlet { /** * */ private static final long serialVersionUID = 1L; @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // 构造json对象 String resStr = "{" + "name:" + "/"zhangsan/"," + "id:" + "/"id001/"" + "}"; // 输出json对象到前台 PrintWriter out = resp.getWriter(); out.write(resStr); out.flush(); out.close(); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); }}
json数组的后台响应
package com.ajax;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;@WebServlet("/jsonArr")public class JsonArr extends HttpServlet { /** * */ private static final long serialVersionUID = 1L; @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // 构造json对象 String resStr1 = "{" + "name:" + "/"zhangsan/"," + "id:" + "/"id001/"" + "}"; String resStr2 = "{" + "name:" + "/"lisi/"," + "id:" + "/"id002/"" + "}"; String resStr3 = "{" + "name:" + "/"wangwu/"," + "id:" + "/"id003/"" + "}"; // 构造json数组 String jsonArr = "[" + resStr1 + "," + resStr2 + "," + resStr3 + "]"; // 输出json数组到前台 PrintWriter out = resp.getWriter(); out.write(jsonArr); out.flush(); out.close(); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); }}前台页面 <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Json</title></head><body> <br><br> <input type="button" value="JsonStr" onclick="jsonStr()" /> <br><br> <table> <tr> <td>username</td> <td><input id="username"></td> </tr> <tr> <td>id</td> <td><input id="id"></td> </tr> </table> <br><br><br> <input type="button" value="JsonArr" onclick="jsonArr()" /> <br><br> <table border="1" bordercolor="red"> <caption>Json Array</caption> <thead> <tr> <th>Username</th> <th>Id</th> </tr> </thead> <tbody id="tb"> </tbody> </table></body><script type="text/javascript"> // json字符串处理方法 function jsonStr() { var xhr = new XMLHttpRequest(); xhr.open("get", "jsonStr"); xhr.onreadystatechange = function(data) { if (xhr.readyState == 4 && xhr.status == 200) { // 将json字符串转换为json对象 var obj = eval("(" + data.target.responseText + ")"); document.getElementById("username").value = obj.name; document.getElementById("id").value = obj.id; } }; xhr.send(null); } // json数组处理方法 function jsonArr() { var xhr = new XMLHttpRequest(); xhr.open("get", "jsonArr"); xhr.onreadystatechange = function(data) { if (xhr.readyState == 4 && xhr.status == 200) { // 将json字符串转换为json数组 var obj = eval("(" + data.target.responseText + ")"); // 创建代码片段，用于存放表格行 var oFragment = document.createDocumentFragment(); // 根据json数组长度，产生行数据 for (var i=0; i<obj.length; i++) { var trObj = document.createElement("tr"); trObj.innerHTML = "<td>" + obj[i].name + "</td><td>" + obj[i].id + "</td>"; oFragment.appendChild(trObj); } // 将行数据添加在表格的tBody部分 document.getElementById("tb").appendChild(oFragment); } }; xhr.send(null); }</script></html>页面效果图 
点击 JsonStr 和 JsonArr 按钮后的效果 
好了，整理完毕，示例仅供学习。 对了，有一点疑惑，之前回调函数中，获取响应数据的时候，都是直接通过data.responseText 来获取的，今天的代码中必须使用data.target.responseText，不知道为什么？有知道的朋友烦请告知一声，非常感谢。
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