JSON数据格式：
JSON(JavaScript Object Notation) 是一种轻量级的数据交换格式。 易于人阅读和编写。同时也易于机器解析和生成。 它基于的一个子集。 JSON采用完全独立于语言的文本格式，但是也使用了类似于C语言家族的习惯（包括C, C++, C#, Java, JavaScript, Perl, Python等）。 这些特性使JSON成为理想的数据交换语言。
JSON建构于两种结构：
（1）“名称/值”对的集合（A collection of name/value pairs）。不同的语言中，它被理解为对象（object），纪录（record），结构（struct），字典（dictionary），哈希表（hash table），有键列表（keyed list），或者关联数组 （associative array）。
（2）值的有序列表（An ordered list of values）。在大部分语言中，它被理解为数组（array）。
JSON具体的表现形式：
（1）对象是一个无序的“‘名称/值’对”集合。一个对象以“{”（左括号）开始，“}”（右括号）结束。每个“名称”后跟一个“:”（冒号）；“‘名称/值’ 对”之间使用“,”（逗号）分隔。
例：{“name”：“zhangsan”} //单属性 或者多个属性 {“name”：“lisi”，“sex”：“男” } // 具体对象
（2）数组是值（value）的有序集合。一个数组以“[”（左中括号）开始，“]”（右中括号）结束。值之间使用“,”（逗号）分隔。
例： ["value1","value2","value3"] //数组形式 [{“name”：“zhangsan1”},{“name”：“zhangsan2”},{“name”：“zhangsan3”}] //对象数组
Servlet与前端ajax的数据交互:
主要流程为 前端获取数据通过ajax的异步传输传至servlet，servlet处理数据后，通过response回传至前端页面。
注意： 一般在传输过程中会遇到两个比较常见的问题，第一就是传回前端时乱码问题，这个问题可以通过 在servlet处理方法中加入：response.setCharacterEncoding("UTF-8"）解决；第二就是传至前端后，不会触发ajax中的回调函数，原因是因为servlet传回的json数据格式不合法而没有触发ajax的success状态。
关于servlet返回的json数据处理方法：
（1）自己拼接json字符串（出错率较高），使其数据满足json格式
JSON对于servlet处理格式要求，键必须加双引号，值分为字符串和数字，数字可不加引号，字符串必须加引号
例： {“"name"："zhansan", "age"：13, "sex"："男" } // 这种为标准格式，字符串类型加引号，纯数字可不加
将一个独立对象转为以上的格式的字符串形式，才可以通过response.getWrite.append()传至前端 ajax 中，成功处罚回调函数
String result = "{"+"/"name/""+":"+"/""+name+"/""+","+"/"age/""+":"+"/""+age+"/""+","+"/"sex/""+":"+"/""+sex+"/""+"}";
（2）调用第三方封装好的 json 数据转换方法（个人使用的是Gson，链接地址：https://pan.baidu.com/s/1Yu91BYlqoJSXpzk37ZXZ6g）
建议使用这种方法，高效，简洁，适用于各种数据集合（list，map等）。详细使用可看下列实例（具体代码1）。
具体实例代码1（采用第一种字符串拼接方式）
前端html部分（含ajax）
1 <html> 2 <head> 3 <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 4 <title>Insert title here</title> 5 <script src="https://apps.bdimg.com/libs/jquery/2.1.4/jquery.min.js"></script> 6 </head> 7 <body> 8 ????<div class="box"> 9 ??????????<table>10 ????????????<tr>11 ??????????????<td>姓名</td>12 ??????????????<td><input name="username" type="text"></td>13 ????????????</tr>14 ????????????<tr>15 ??????????????<td>性别</td>16 ??????????????<td><input name="sex" type="text"></td>17 ????????????</tr> ?18 ????????????<tr>19 ??????????????<td>年龄</td>20 ??????????????<td><input name="age" type="text"></td>21 ????????????</tr> ?22 ????????????<tr>23 ??????????????<td>手机号</td>24 ??????????????<td><input name="phone" type="text"></td>25 ????????????</tr> ???26 ????????????<tr><td><button>提交</button></td></tr>27 ??????????</table> ??28 ????</div>29 ??????<div>30 ??????<table>31 ?????????????????????????????????信息返回32 ????????????<tr>33 ??????????????<td>姓名</td>34 ??????????????<td id="name"></td>35 ????????????</tr>36 ????????????<tr>37 ??????????????<td>性别</td>38 ??????????????<td id="sex"></td>39 ????????????</tr> ?40 ????????????<tr>41 ??????????????<td>年龄</td>42 ??????????????<td id="age"></td>43 ????????????</tr> ?44 ????????????<tr>45 ??????????????<td>手机号</td>46 ??????????????<td id="phone"></td>47 ????????????</tr> ???48 ??????????</table> ?49 ????</div> ?50 ????<script>51 ??????$(function(){52 ????????????$("button").click(function(){ ?53 ????????????????$.post("AjaxTest",54 ????????????????????????{‘username‘:$("input[name=username]").val(),55 ?????????????????????????‘sex‘:$("input[name=sex]").val(),56 ?????????????????????????‘age‘:$("input[name=age]").val(),57 ?????????????????????????‘phone‘:$("input[name=phone]").val()},58 ????????????????????????function(data,textStatus){59 ?????????????????????????????console.log(textStatus); 60 ?????????????????????????????console.log(data.username);61 ????????????????????????????$("#name").html(data.username);62 ????????????????????????????$("#sex").html(data.sex);63 ????????????????????????????$("#age").html(data.age);64 ????????????????????????????$("#phone").html(data.phone); 65 ????????????????????????},"json");66 ??????????});67 ?????????68 ???????})69 ????</script>70 </body>71 </html>后端servlet部分（字符串拼接）
servlet部分@WebServlet("/AjaxTest")public class AjaxTest extends HttpServlet { ???private static final long serialVersionUID = 1L; ??????????/** ????* @see HttpServlet#HttpServlet() ????*/ ???public AjaxTest() { ???????super(); ???????// TODO Auto-generated constructor stub ???} ???/** ????* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) ????*/ ???protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ???????// TODO Auto-generated method stub ???????String name = request.getParameter("username"); ???????String sex = request.getParameter("sex"); ???????String age = request.getParameter("age"); ???????String phone = request.getParameter("phone"); ????????response.setCharacterEncoding("UTF-8"); ??????????response.setContentType("application/json"); ?????????????????????????User one = new User(name,sex,age,phone); ???????String result = one.toString(); ???????System.out.println(result); ???????response.getWriter().append(result); ???} ???/** ????* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) ????*/ ???protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ???????// TODO Auto-generated method stub ???????doGet(request, response); ???}User类public class User ?{ ?private String username; ?private String sex; ?private String age; ?private String phone; ?public User(String username, String sex, String age, String phone) { ???this.username = username; ???this.sex = sex; ???this.age = age; ???this.phone = phone;} ?public String getUsername() { ???return username;}public void setUsername(String username) { ???this.username = username;}public String getSex() { ???return sex;}public void setSex(String sex) { ???this.sex = sex;}public String getAge() { ???return age;}public void setAge(String age) { ???this.age = age;}public String getPhone() { ???return phone;}public void setPhone(String phone) { ???this.phone = phone;}@Overridepublic String toString() { ???return "{" + ?"\"username\"" + ‘:‘ + "\""+ username +"\"" + ","+ "\"sex\""+‘:‘ +"\"" +sex +"\""+‘,‘+ "\"age\""+‘:‘ + "\"" + age + "\"" +‘,‘+"\"phone\""+‘:‘ + "\""+phone+"\"" + "}";}}具体实例代码2（采用gson转换json方式处理）
前端代码（含ajax）
1 <html> 2 <head> 3 ?4 <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 5 <title>Insert title here</title> 6 <script src="https://apps.bdimg.com/libs/jquery/2.1.4/jquery.min.js"></script> 7 </head> 8 <body> 9 <input type="text" name="cc" ?/ >10 <input type="submit" />11 <div>12 ?????姓名：<span id="name"></span> <br/>13 ?????性别：<span id="sex"></span><br/>14 ?????年龄： <span id="age"></span> ?????15 </div>16 </form>17 ??<script type="text/javascript">18 ???????$(function(){19 ???????????$("input[type=submit]").click(function(){20 ???????????????$.post("ajax",21 ???????????????????{"cc":$("input[name=cc]").val()},22 ?????????????????function(data,textStatus){23 ??????????????????????console.log(data.name); 24 ??????????????????????$("#name").html(data.name);25 ??????????????????????$("#sex").html(data.sex);26 ??????????????????????$("#age").html(data.age);27 ???????????????????},28 ?????????????????"json" ??29 ???????????????);30 ????????????});31 ???????????32 ???????})33 ??</script>34 </body>35 </html>servlet部分（调用gson方法）
servlet部分@WebServlet("/ajax")public class ajax extends HttpServlet { ???private static final long serialVersionUID = 1L; ??????????/** ????* @see HttpServlet#HttpServlet() ????*/ ???public ajax() { ???????super(); ???????// TODO Auto-generated constructor stub ???} ???/** ????* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) ????*/ ???protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ???????// TODO Auto-generated method stub ???????response.setCharacterEncoding("utf-8"); ???????String c = request.getParameter("cc"); ???????System.out.println(c); ???????User one = new User(c, "男", 13); ???????Gson gson = new Gson(); ???????String result = gson.toJson(one); ???????response.getWriter().append(result); ???????????} ???/** ????* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) ????*/ ???protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ???????// TODO Auto-generated method stub ???????doGet(request, response); ???}}User类部分public class User { ?private String name; ?private String sex; ?private int age;public User(String name, String sex, int age) { ???this.name = name; ???this.sex = sex; ???this.age = age;}public String getName() { ???return name;}public void setName(String name) { ???this.name = name;}public String getSex() { ???return sex;}public void setSex(String sex) { ???this.sex = sex;}public int getAge() { ???return age;}public void setAge(int age) { ???this.age = age;} ?}具体实例代码3（多组数据传至ajax）
前端代码（含ajax）
1 <html> 2 <head> 3 ?4 <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 5 <title>Insert title here</title> 6 <script src="https://apps.bdimg.com/libs/jquery/2.1.4/jquery.min.js"></script> 7 </head> 8 <body> 9 <input type="text" name="ceshi">10 <input type="submit" value="获取名单"/>11 <table id="table">12 13 </table>14 </form>15 ??<script type="text/javascript">16 ???????$(function(){17 ???????????$("input[type=submit]").click(function(){18 ???????????????$.post("ajax",19 ???????????????????{"ceshi":$("input[name=ceshi]").val()},20 ?????????????????function(data,textStatus){21 ??????????????????????console.log(data); 22 ??????????????????????for(var i = 0;i<data.length; i++)23 ????????????????????????{24 ?????????????????????????$("#table").append( $("<tr></tr>")25 ?????????????????????????????????.append($("<td></td>").html(data[i].name))26 ?????????????????????????????????.append($("<td></td>").html(data[i].sex))27 ?????????????????????????????????.append($("<td></td>").html(data[i].age)));28 ????????????????????????}29 ???????????????????},30 ?????????????????"json" ??31 ???????????????);32 ????????????});33 ???????????34 ???????})35 ??</script>36 </body>37 </html>servlet部分（调用gson方法处理数据）
1 servlet部分 2 @WebServlet("/ajax") 3 public class ajax extends HttpServlet { 4 ????private static final long serialVersionUID = 1L; 5 ????????6 ????/** 7 ?????* @see HttpServlet#HttpServlet() 8 ?????*/ 9 ????public ajax() {10 ????????super();11 ????????// TODO Auto-generated constructor stub12 ????}13 ????/**14 ?????* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)15 ?????*/16 ????protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {17 ????????// TODO Auto-generated method stub18 ????????response.setCharacterEncoding("utf-8");19 ????????String string = request.getParameter("ceshi");20 ????????Gson gson = new Gson();21 ????????List list = new ArrayList();22 ????????User one = new User("张三", "男", 13);23 ????????User two = new User("李四","男", 15);24 ????????User three = new User("王五","男", 20);25 ????????list.add(one);26 ????????list.add(two);27 ????????list.add(three);28 ????????29 ????????String result = gson.toJson(list); ???30 ????????response.getWriter().append(result);31 ????}32 ????/**33 ?????* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)34 ?????*/35 ????protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {36 ????????// TODO Auto-generated method stub37 ????????doGet(request, response);38 ????}39 40 }41 42 User类43 44 45 public class User {46 ??private String name;47 ??private String sex;48 ??private int age;49 public User(String name, String sex, int age) {50 ????this.name = name;51 ????this.sex = sex;52 ????this.age = age;53 }54 public String getName() {55 ????return name;56 }57 public void setName(String name) {58 ????this.name = name;59 }60 public String getSex() {61 ????return sex;62 }63 public void setSex(String sex) {64 ????this.sex = sex;65 }66 public int getAge() {67 ????return age;68 }69 public void setAge(int age) {70 ????this.age = age;71 }72 ??73 }servlet与ajax数据交换（json格式）
原文地址：https://www.cnblogs.com/TheGCC/p/8891251.html