项目结构
前端页面：
登录页面：login.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="css/style.css">
<title>登录页面</title>
<script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js"></script>
</head>
<body>
<div class="whole">
<p class="top">
请输入用户名和密码
</p>
<div class="input">
<div>
用户名
</div>
<input type="text" id="username">
</div>
<div class="input">
<div>
密码
</div>
<input type="password" id="password">
</div>
<div class="bottom">
<input type="submit" value="登录" onclick="login()">
</div>
</div>
</body>
<script>
function login(){
var username=$("#username").val();
var password=$("#password").val();
$.ajax({
url:"/WebNewLearn/LoginServlet",
data:{
"username":username,
"password":password
},
async:true,
type:"post",
success:function(data){
if(data.data.length>0){
location.href="/WebNewLearn/index.html";
}
else{
alert("用户名或密码错误！");
}
},
error(){
alert("登陆失败！");
}
})
}
</script>
</html>
style.css
*{
margin:0;
padding:0;
}
body{
background-image: url("../img/background.jpg");
background-position: center;
background-attachment: fixed;
background-size: cover;
background-repeat: no-repeat;
}
.whole{
width: 30%;
min-width: 300px;
margin: auto;
margin-top:150px ;
/* position: center; */
/* top: 30%; */
background-color: white;
opacity: 0.7;
padding-bottom: 2px;
}
.top{
height:40px;
margin:auto;
font-size:16px;
text-align: center;
line-height:40px;
background: linear-gradient(to left,red,blue);
}
.input{
margin: 10px;
}
.input div{
font-size: 16px;
color: rgb(112, 205, 241);
text-align: center;
line-height:20px;
}
.input input{
margin-top: 10px;
width:84%;
height: 32px;
/* (100-84)/2 */
margin-left: 8%;
border-width:1px;
border:1px solid black;
outline:none;
text-indent:10px;
color:rgb(17, 16, 16);
}
/* , */
.input input:hover{
box-shadow: 2px 2px 2px rgb(158, 154, 154);
}
.bottom{
width: 84%;
margin:30px auto;
/* margin-bottom: 40px; */
height: 40px;
text-align: center;
background: linear-gradient(to left,red,blue);
}
.bottom input{
display:block;
width:100%;
height:100%;
}
.bottom a:hover{
box-shadow:2px 2px wpx black;
}
页面效果
index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>主页面</title>
<script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js"></script>
<script src="layer/layer.js"></script>
<link rel="stylesheet" href="css/index.css">
<link rel="stylesheet" href="css/layui.css">
</head>
<body>
<button type="button" id="add" class="layui-btn layui-btn-lg layui-btn-radius layui-btn-normal">添加一条新闻</button>
<div class="top">
<h2>新闻查询</h2>
按照编号查询：
<input type="text" name="" id="id">
按照标题查询：
<input type="text" name="" id="title">
按照作者查询：
<input type="text" name="" id="author">
按照分类查询：
<select id="group" >
<option value="1">国际新闻</option>
<option value="2">娱乐新闻</option>
<option value="3">军事新闻</option>
<option value="4">头条新闻</option>
</select>
<button type="button" id="search" class="layui-btn">查询</button>
</div>
<div class="center">
<hr>
<div class="content">
<h1>新闻展示</h1>
<table border="1">
<tr>
<th>编号</th>
<th>标题</th>
<th>分类</th>
<th>作者</th>
<th>内容摘要</th>
<th>操作</th>
</tr>
<tbody class="t_content">
</tbody>
</table>
</div>
</div>
</body>
<script type="text/javascript">
function init(){
$.ajax({
url:"mainServlet",
async:true,
type:"post",
data:{
"action":"findAll"
},
success:function(data){
if(data.code==200){
data=data.data;
$(".t_content").empty();
for(var i = 0;i<data.length;i++){
$(".t_content").append("<tr><th>"+data[i][0]+"</th><th>"+data[i][1]+"</th><th>"+data[i][2]+"</th><th>"+data[i][3]+"</th><th>"+data[i][4]+"</th><th><button type='button' class='layui-btn del'>删除</button><button type='button' class='layui-btn update'>修改</button></th></tr>");
}
}
//JSON.parse();//把json字符串转成json对象,不转换之前一般就是字符串类型
//json数据类型string number boolean undefined null object function array 前五种是基本类型，后三种是复合类型
console.log(typeof data);
},
error(){
alert("请求失败！");
}
});
}
init();
</script>
<script>
$(document).on("click","#search",function (){
//两种方法都可以
var title=$("#title").val();//最后的括号如果不加会出现undefined的值
var id=document.getElementById("id").value;
var author=$("#author").val();
var group=$("#group").val();
$.ajax({
url:"mainServlet",
async:true,
type:"post",
data:{
"action":"find",
"title":title,
"id":id,
"author":author,
"group":group
},
success:function(data){
if(data.code==200){
data=data.data;
if(data.length!=0){
$(".t_content").empty();
for(var i = 0;i<data.length;i++){
$(".t_content").append("<tr><th>"+data[i][0]+"</th><th>"+data[i][1]+"</th><th>"+data[i][2]+"</th><th>"+data[i][3]+"</th><th>"+data[i][4]+"</th><th><button type='button' class='layui-btn del'>删除</button><button type='button' class='layui-btn update'>修改</button></th></tr>");
}
}
else{
$(".t_content").html("<tr><th colspan='6'>暂无信息！</th></tr>");
}
}
//JSON.parse();//把json字符串转成json对象,不转换之前一般就是字符串类型
//json数据类型string number boolean undefined null object function array 前五种是基本类型，后三种是复合类型
console.log(typeof data);
},
error(){
alert("请求失败！");
}
});
})
//添加部分
var add_index=0;
$(document).on("click","#add",function (){
add_index=layer.open({
type: 1,
skin: 'layui-layer-rim', //加上边框
area: ['820px', '840px'], //宽高
content: "<div class=\"add\">\r\n" +
" <div class=\"add_content\">\r\n" +
" 请输入标题：<input type=\"text\" name=\"\" class=\"add_title\"><br>\r\n" +
" 请输入作者名字：<input type=\"text\" name=\"\" class=\"add_author\"><br>\r\n" +
" 请输入分类：\r\n" +
" <select name=\"\" class=\"add_group\">\r\n" +
" <option value=\"1\">国际新闻</option>\r\n" +
" <option value=\"2\">娱乐新闻</option>\r\n" +
" <option value=\"3\">军事新闻</option>\r\n" +
" <option value=\"4\">头条新闻</option>\r\n" +
" </select><br>\r\n" +
" 请输入主体内容：<textarea name=\"\" class=\"add_con\" cols=\"30\" rows=\"10\"></textarea>\r\n" +
" <button type=\"button\" id=\"add_button\" class=\"layui-btn\">确认添加</button>\r\n" +
" </div>\r\n" +
" </div>"
});
})
$(document).on("click","#add_button",function(){
var title=$(".add_title").val();//最后的括号如果不加会出现undefined的值
var author=$(".add_author").val();
var group=$(".add_group").val();
var content=$(".add_con").val();
if(title==""||author==""||content==""){
layer.msg("请确认信息输入完整！");
}else{
$.ajax({
url:"mainServlet",
async:true,
type:"post",
data:{
"action":"add",
"title":title,
"author":author,
"group":group,
"content":content
},
success:function(data){
if(data==1){
init();
layer.msg("添加成功！",{icon:1});
layer.close(add_index);
}else{
layer.msg("请确认数据是否输入完整！",{icon:2});
}
//JSON.parse();//把json字符串转成json对象,不转换之前一般就是字符串类型
//json数据类型string number boolean undefined null object function array 前五种是基本类型，后三种是复合类型
console.log(typeof data);
},
error(){
layer.alert("请求失败！",{icon:2});
}
});
}
})
//删除
$(document).on("click",".del",function (){
var id=$(this).parent().parent().children().first().text();
layer.confirm('您确认要删除吗？', {
btn: ['确认','取消'] //按钮
}, function(){
console.log(id);
$.ajax({
url:"mainServlet",
async:true,
type:"post",
data:{
"action":"delete",
"id":id
},
success:function(data){
if(data==1){
init();
layer.msg("删除成功！",{icon:1});
}else{
layer.alert("请确认数据是否输入完整！");
}
console.log(typeof data);
},
error(){
layer.alert("请求失败！");
}
});
}, function(){
layer.msg('撤销成功！', {
time: 2000
});
});
})
//修改
var update_index = 0;
$(document).on("click",".update",function(){
var id=$(this).parent().parent().children().eq(0).text();
var title=$(this).parent().parent().children().eq(1).text();//最后的括号如果不加会出现undefined的值
var group=$(this).parent().parent().children().eq(2).text();
var author=$(this).parent().parent().children().eq(3).text();
var content=$(this).parent().parent().children().eq(4).text();
console.log(id);
update_index=layer.open({
type: 1,
skin: 'layui-layer-rim', //加上边框
area: ['820px', '840px'], //宽高
content: "<div class=\"upd\">\r\n" +
" <div class=\"update_content\">\r\n" +
"<input type=\"text\" style=\"display:none\" class=\"update_id\">"+
" 请输入标题：<input type=\"text\" name=\"\" class=\"update_title\"><br>\r\n" +
" 请输入作者名字：<input type=\"text\" name=\"\" class=\"update_author\"><br>\r\n" +
" 请输入分类：\r\n" +
" <select name=\"\" class=\"update_group\">\r\n" +
" <option value=\"1\">国际新闻</option>\r\n" +
" <option value=\"2\">娱乐新闻</option>\r\n" +
" <option value=\"3\">军事新闻</option>\r\n" +
" <option value=\"4\">头条新闻</option>\r\n" +
" </select><br>\r\n" +
" 请输入主体内容：<textarea name=\"\" class=\"update_con\" cols=\"30\" rows=\"10\"></textarea>\r\n" +
" <button type=\"button\" class=\"layui-btn update_button\">确认修改</button>\r\n" +
" </div>\r\n" +
" </div>"
});
$(".update_id").val(id);
$(".update_title").val(title);
$(".update_author").val(author);
//给select赋值不是给select的value赋值
$(".update_group").attr("text", group);
$(".update_con").val(content);
})
$(document).on("click",".update_button",function(){
id=$(".update_id").val();
title=$(".update_title").val();//最后的括号如果不加会出现undefined的值
author=$(".update_author").val();
group=$(".update_group").val();
content=$(".update_con").val();
if(title==""||author==""||content==""){
layer.msg("请确认信息输入完整！");
}else{
$.ajax({
url:"mainServlet",
async:true,
type:"post",
data:{
"action":"update",
"id":id,
"title":title,
"author":author,
"group":group,
"content":content
},
success:function(data){
if(data==1){
init();
layer.msg("修改成功！",{icon:1});
layer.close(update_index);
}else{
layer.alert("请确认数据是否输入完整！",{icon:2});
}
document.getElementById("confirm").style.display="none";
document.getElementById("add").style.display="inline";
document.getElementById("search").style.display="inline";
},
error(){
layer.alert("请求失败！",{icon:2});
}
});
}
})
</script>
</html>
index.css:
select{
text-align: center;
text-align-last: center;
}
.top{
width: 50%;
margin: 0 auto;
text-align: center;
font-size: 18px;
}
.top input{
display: block;
margin: 10px auto;
width: 50%;
height: 20px;
text-indent: 10px;
}
#group{
display: block;
margin: 10px auto;
width: 30%;
height: 40px;
font-size:22px;
text-align:center
}
.top button{
display: block;
margin: 10px auto;
width: 30%;
height: 45px;
text-indent: 10px;
font-size: 20px;
}
.center{
width: 100%;
}
.content{
width: 60%;
margin: 0 auto;
text-align: center;
}
.content table{
margin: 0 auto;
width: 100%;
border-collapse: collapse;
border:1px solid black
}
.content table th{
height: 50px;
}
.content table th button{
display:inline;
margin:0 10px;
height: 40px;
width:60px;
}
body .add .add_content{
color:black;
text-align: center;
width:100%
}
.add_content input{
display: block;
margin: 10px auto;
width: 40%;
height: 20px;
text-indent: 10px;
}
.add_content select{
display: block;
margin: 10px auto;
width: 20%;
height: 30px;
text-indent: 10px;
}
.add_content textarea{
display: block;
margin: 10px auto;
width: 60%;
height: 300px;
text-indent: 10px;
font-size: 20px;
outline: none;
}
#add{
position: fixed;
top:40%;
left:10%
}
#add_button{
width:20%;
margin:20px;
}
body .upd .update_content{
color:black;
text-align: center;
width:100%
}
.update_content input{
display: block;
margin: 10px auto;
width: 40%;
height: 20px;
text-indent: 10px;
}
.update_content select{
display: block;
margin: 10px auto;
width: 20%;
height: 30px;
text-indent: 10px;
}
.update_content textarea{
display: block;
margin: 10px auto;
width: 60%;
height: 300px;
text-indent: 10px;
font-size: 20px;
outline: none;
}
#update_button{
width:20%;
margin:20px;
}
效果
servlet部分:
loginServlet:
package com.MyNewLearn.web;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.MyNewLearn.db.MysqlUtil;
/**
* Servlet implementation class LoginServlet
*/
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public LoginServlet() {
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.getWriter().append("Served at: ").append(request.getContextPath());
doPost(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
response.setContentType("text/json;charset=utf-8");
//如果是json是json格式，在前台不用把字符串转化成对象，如果是html，需要转化
String username =request.getParameter("username");
String password =request.getParameter("password");
String sql="select * from user where ";
String [] colums= {"username","password"};
String jsondata ="";
System.out.println(username);
System.out.println(password);
if (!username.equals("")) {
sql+="username = \""+username+"\" and password = \""+password+"\"";
MysqlUtil mysqlUtil=new MysqlUtil();
jsondata =MysqlUtil.getJsonBySql(sql, colums);
}
response.getWriter().append(jsondata);
}
}
mainServlet：
package com.MyNewLearn.web;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.MyNewLearn.db.MysqlUtil;
/**
* Servlet implementation class mainServlet
*/
@WebServlet("/mainServlet")
public class mainServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public mainServlet() {
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.getWriter().append("Served at: ").append(request.getContextPath());
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
response.setContentType("text/json;charset=utf-8");
//如果是json是json格式，在前台不用把字符串转化成对象，如果是html，需要转化
String id =request.getParameter("id");
String title =request.getParameter("title");
String author =request.getParameter("author");
String group =request.getParameter("group");
String content=request.getParameter("content");
String action=request.getParameter("action");
String sql="";
String sql1="";
String [] colums= {"id","title","group_name","author","content"};
MysqlUtil mysqlUtil=new MysqlUtil();
String jsondata="";
int result = 0;
int result1 = 0;
//查询部分
if (action.equals("findAll")) {
sql+="select * from news n,news_con nc where n.group_id=nc.id group by n.id";
}
if (action.equals("find")) {
sql+="select * from news n,news_con nc where n.group_id=nc.id ";
if (!title.equals("")) {
sql+=" and n.name like \"%"+title+"%\"";
}
if (!id.equals("")) {
sql+=" and n.id = \""+id+"\"";
}
if (!author.equals("")) {
sql+=" and n.age = \""+author+"\"";
}
if (!group.equals("")) {
sql+=" and n.group_id = \""+group+"\"";
}
sql+="group by n.id";
}
//添加部分
if (action.equals("add")) {
sql+="insert into news (title,author,group_id,content) values(\""+title+"\",\""+author+"\",\""+group+"\",\""+content+"\")";
}
//删除部分
if(action.equals("delete")&&!id.equals("")) {
if(!id.equals("")) {
sql+="delete from news where id = \""+id+"\"";
}
}
//更新部分
if(action.equals("update")) {
sql+="UPDATE news n SET n.title = \""+title+"\" ";
sql+=", n.author = \""+author+"\" ";
sql+=", n.group_id = \""+group+"\" ";
sql+=", n.content = \""+content+"\" ";
sql+=" WHERE n.id = \""+id+"\"";
}
if (action.equals("findAll")||action.equals("find")) {
jsondata =MysqlUtil.getJsonBySql(sql, colums);
System.out.println(jsondata);
response.getWriter().append(jsondata);
}
else {
result = MysqlUtil.update(sql);
response.getWriter().print(result);
}
}
}
后台连接数据库部分：
DBConnection.java
package com.MyNewLearn.db;
import java.sql.Connection;
import java.sql.DriverManager;
public class DBConnection {
public static void main(String[] args) {
}
String driver = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://49.232.18.90:3306/myTest?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC&useSSL=false";
String user = "root";
String password = "wxw123456789";
public Connection conn;
public DBConnection() {
try {
Class.forName(driver);
conn = (Connection) DriverManager.getConnection(url, user, password);//
// if(!conn.isClosed())
// System.out.println("Succeeded connecting to the Database!");
} catch (Exception e) {
e.printStackTrace();
}
}
public void close() {
try {
this.conn.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
MysqlUtil部分
package com.MyNewLearn.db;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class MysqlUtil {
public static void main(String[] args) {
// TODO Auto-generated method stub
//String sql = "insert into userinfo (id,`name`,age,otherinfo) values (1500,'吴强3',20,'很英俊，十分帅气')";
//add(sql);
//String sqldel = "delete from userinfo where id = 1500";
//del(sqldel);
String[] col = {"id","name","age"};
String sql = "select * from test order by id asc limit 10";
String strJson = MysqlUtil.getJsonBySql(sql, col);
System.out.println(strJson);
// ArrayList< String[] > data = MysqlUtil.showUtil(sql, col);
// System.out.println( data.get(3)[2] );
//
// String str = MysqlUtil.show(sql, col);
//
// System.out.println( str );
}
/**
* 用于插入数据
* @param sql insert语句
* @return
*/
public static int add(String sql) {
// System.out.println("sql语句是：" + sql);
int i=0;
//数据库连接
DBConnection db = new DBConnection();
try {
PreparedStatement preStmt = (PreparedStatement) db.conn.prepareStatement(sql);
preStmt.executeUpdate();
preStmt.close();
db.close();//关闭连接
i = 1;
// System.out.println("数据插入成功，sql语句是：" + sql);
} catch (Exception e) {
e.printStackTrace();
}
return i;//返回影响的行数，1为执行成功;
}
//
public static ArrayList<String[]> showUtil( String sql, String[] colums){
ArrayList<String[]> result = new ArrayList<String[]>();
DBConnection db = new DBConnection();
try {
Statement stmt = (Statement) db.conn.createStatement();
ResultSet rs = (ResultSet) stmt.executeQuery(sql);
while(rs.next()){
String[] dataRow = new String[colums.length];
for( int i = 0; i < dataRow.length; i++ ) {
dataRow[i] = rs.getString( colums[i] );
}
result.add(dataRow);
}
rs.close();
db.close();//
} catch (SQLException e) {
e.printStackTrace();
}
return result;
}
public static String getJsonBySql( String sql, String[] colums){
System.err.println("标红信息展示sql:" + sql);
ArrayList<String[]> result = new ArrayList<String[]>();
DBConnection db = new DBConnection();
try {
Statement stmt = (Statement) db.conn.createStatement();
ResultSet rs = (ResultSet) stmt.executeQuery(sql);
while(rs.next()){
String[] dataRow = new String[colums.length];
for( int i = 0; i < dataRow.length; i++ ) {
dataRow[i] = rs.getString( colums[i] );
}
result.add(dataRow);
}
rs.close();
db.close();//
} catch (SQLException e) {
e.printStackTrace();
}
return listToJson(result);
}
public static int update(String sql) {
int i =0;
DBConnection db = new DBConnection();
try {
PreparedStatement preStmt = (PreparedStatement) db.conn.prepareStatement(sql);
preStmt.executeUpdate();
preStmt.close();
db.close();
i = 1;
System.out.println("数据更新成功，sql语句是：" + sql);
} catch (SQLException e) {
e.printStackTrace();
}
return i;
}
/**
* 查询数据
* @param sql select * from 表
* @param params [id,name,sex,age] 我们要查询的列名的一个字符串数组
* @return
*/
public static String show(String sql, String[] params){
List< Map<String,String> > listmap = new ArrayList<>();
DBConnection db = new DBConnection();
ResultSet rs = null;
try {
Statement stmt = (Statement) db.conn.createStatement();
rs = (ResultSet) stmt.executeQuery(sql);
while(rs.next()){
Map<String,String> map = new HashMap<String,String>();
for(int i = 0; i < params.length; i++) {
map.put(params[i], rs.getString(params[i]));
}
listmap.add(map);
}
rs.close();
db.close();
} catch (SQLException e) {
e.printStackTrace();
}
return mapToJson(listmap);
}
public static int del(String delstr) {
int i=0;
DBConnection db = new DBConnection();
try {
PreparedStatement preStmt = (PreparedStatement) db.conn.prepareStatement(delstr);
preStmt.executeUpdate();
preStmt.close();
db.close();
i = 1;
System.out.println("数据删除成功，sql语句是：" + delstr);
} catch (SQLException e){
e.printStackTrace();
}
return i;
}
/**
* map转化为json数据字符串
* @param maplist
* @return
*/
public static String mapToJson( List<Map<String,String>> maplist ) {
String jsonData = "{ \"data\":[";
for(int i = 0; i < maplist.size(); i++) {
String outstr = "[\"" ;
int size = 0;
for(String value : maplist.get(i).values()){
size += 1;
outstr += value;
if( size < maplist.get(i).values().size() ) {
outstr += "\",\"";
}
}
outstr += "\"]";
if(i < maplist.size() -1) {
outstr += ",";
}
jsonData += outstr;
}
jsonData += "]}";
return jsonData;
}
public static String listToJson( ArrayList<String[]> list) {
String jsonStr = "{\"code\":200,\"message\":\"成功了\",\"data\":[";
for(int i = 0; i < list.size(); i++) {
String arr = "[";
for( int j = 0; j < list.get(0).length; j++) {
if( list.get(i)[j] == null || "NULL".equals(list.get(i)[j])) {
arr += "\"\"";
}else {
arr += "\"" + list.get(i)[j].replace("\"", "\\\"") + "\"";
}
if( j < list.get(0).length - 1 ) {
arr += ",";
}
}
arr += "]";
if( i < list.size() - 1 ) {
arr += ",";
}
jsonStr += arr;
}
jsonStr += "]}";
return jsonStr;
}
}
