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谈到JSON,简单的说就是一种数据交换格式。近年来，其在服务器之间交换数据的应用越来越广，相比XML其格式更简单、编解码更容易、扩展性更好，所以深受开发人员的喜爱。
下面简单的写一下在项目中前后台json传值的一个小例子，供大家参考、查阅。
一：前台传后台
1.前台jsp页面代码：
在index中将实体对象（自己创建即可）插入list中，再将list集合转化成json数组，利用post方式发送AJAX请求，将这个json数组发送至后台（servlet），再在后台进行解析即可。
index.jsp
<%@ page language="java" import="java.util.Date,com.badminton.utils.JsonDateValueProcessor,java.text.SimpleDateFormat,java.util.List,net.sf.json.JSONArray,net.sf.json.JSONObject,net.sf.json.JsonConfig,java.util.ArrayList,com.badminton.entity.Athlete,net.sf.json.JSONObject" pageEncoding="utf-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My first json page</title>
<%
SimpleDateFormat format1 = new SimpleDateFormat("yyyy-MM-dd");
Athlete athlete1 = new Athlete();
athlete1.setAthlete_id(1003);
athlete1.setAthlete_name("林丹");
athlete1.setAthlete_sex("男");
Date athlete_age1 = format1.parse("1983-10-14");//是java.util.date
athlete1.setAthlete_age(athlete_age1);
athlete1.setCoach_id(101);
athlete1.setEvent_id(1);
athlete1.setService_status("1");
athlete1.setExperience("2013年第12届全运会男单冠军。");
Athlete athlete2 = new Athlete();//记录2
athlete2.setAthlete_id(1004);
athlete2.setAthlete_name("鲍春来");
athlete2.setAthlete_sex("男");
Date athlete_age2 = format1.parse("1988-10-14");
athlete2.setAthlete_age(athlete_age2);
athlete2.setCoach_id(101);
athlete2.setEvent_id(1);
athlete2.setService_status("1");
athlete2.setExperience("2011年亚洲羽毛球锦标赛亚军。");
List<Athlete> list1 = new ArrayList<Athlete>();
list1.add(athlete1);
list1.add(athlete2);
JsonConfig jsonConfig = new JsonConfig();//解决date类型的传输问题
jsonConfig.registerJsonValueProcessor(Date.class , new JsonDateValueProcessor());
JSONArray jsonarray = JSONArray.fromObject(list1, jsonConfig);
%>
<script type="text/javascript" src="js/json2.js"></script>
<script type="text/javascript">
var xmlHttp;
function createXmlHttpRequest() {
if (window.ActiveXObject) {
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
} else if (window.XMLHttpRequest) {
xmlHttp = new XMLHttpRequest();
}
}
//回调
function handleStateChange() {
if (xmlHttp.readyState == 4) {
if (xmlHttp.status == 200) {
parseResults();
}
}
}
//将后台返回的数据显示在层serverResponse中
function parseResults() {
var result=xmlHttp.responseXML.getElementsByTagName("result")[0].firstChild.data;
alert(result);
}
function doJSON() {
var athletehead={athlete_id:1,tablename:"athlete"};
var myobj=eval(athletehead);
var str1=JSON.stringify(myobj);//str1以后可用来识别数据库中的表
var str2='<%=jsonarray%>';
var url = "servlet/JsonServlet";
createXmlHttpRequest();
xmlHttp.open("POST", url, true);
xmlHttp.onreadystatechange = handleStateChange;//回调
xmlHttp.setRequestHeader("Content-Type",
"application/x-www-form-urlencoded;text/xml;charset=utf-8"); //text/xml;charset=utf-8：解决汉字封装json问题
xmlHttp.send("athletehead="+str1+"&athlete="+str2);//传送了两个对象
}
</script>
</head>
<body>
<form id="form1">
<table>
<tr>
<td align="center"><input type="button" name="submit" value="提交" onClick="doJSON()"></td>
</tr>
</table>
</form>
</body>
</html>2.后台解析代码：
后台接受前台传来的json对象，解析插入数据库中，且反给前台一个是否成功的消息。具体插入数据库的代码自己编写一个即可。
JsonServlet.java
package com.badminton.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Date;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.badminton.app.AthleteAction;
import net.sf.json.JSONObject;
import net.sf.json.JSONArray;
public class JsonServlet extends HttpServlet {
public JsonServlet() {
super();
}
public void destroy() {
super.destroy();
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");
response.setCharacterEncoding("UTF-8");
PrintWriter out = response.getWriter();
AthleteAction athleteaction=new AthleteAction();
try {
String json1 = request.getParameter("athletehead");//接收athlete表的头数据
String json2 = request.getParameter("athlete");//接收athlete表数据
json1 = java.net.URLDecoder.decode(json1,"UTF-8");
json2 = java.net.URLDecoder.decode(json2, "UTF-8");
if ((json1 != "") && (json2 != "")) {
//System.out.println("json1:"+json1);
JSONObject jsonObject1 =JSONObject.fromObject(json1);//生成json对象
JSONArray jsonArray2 = JSONArray.fromObject(json2);//生成JSON数组
for(int i=0;i<jsonArray2.size();i++){
JSONObject resultObj = jsonArray2.optJSONObject(i);//根据JSONArray生成JSONObject
int athlete_id=resultObj.getInt("athlete_id");
String athlete_name=resultObj.getString("athlete_name");
String athlete_sex=resultObj.getString("athlete_sex");
String age=resultObj.getString("athlete_age");
Date athlete_age = Date.valueOf(age);//转换成java.sql.Date
//System.out.println(athlete_age);
int coach_id=resultObj.getInt("coach_id");
int event_id=resultObj.getInt("event_id");
System.out.println(athlete_name);
String service_status=resultObj.getString("service_status");
String experience=resultObj.getString("experience");
athleteaction.athleteAdd(athlete_id,athlete_name,athlete_sex,athlete_age,coach_id,event_id,service_status,experience);//对数据库进行操作，具体代码未附
}
String result = "数据上传成功！";
out.println("<response>");
out.println("<result>" + result + "</result>");
out.println("</response>");
out.close();
} else{
String result = "传输过程出错，请重传！";
out.println("<response>");
out.println("<result>" + result + "</result>");
out.println("</response>");
out.close();
}
} catch (Exception e) {
System.out
.println("JsonServlet doPost(HttpServletRequest request, HttpServletResponse response) 报错："
+ e.getMessage());
}
}
public void init() throws ServletException {
}
}3.解决传递日期的一个工具类
若没有这个工具类，date型数据会被转化成json数组的格式，后台解析起来会很复杂。
JsonDateValueProcessor.java
package com.badminton.utils;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import net.sf.json.JsonConfig;
import net.sf.json.processors.JsonValueProcessor;
public class JsonDateValueProcessor implements JsonValueProcessor{
/**
* datePattern
*/
private String datePattern = "yyyy-MM-dd";
/**
* JsonDateValueProcessor
*/
public JsonDateValueProcessor() {
super();
}
/**
* @param format
*/
public JsonDateValueProcessor(String format) {
super();
this.datePattern = format;
}
/**
* @param value
* @param jsonConfig
* @return Object
*/
public Object processArrayValue(Object value, JsonConfig jsonConfig) {
return process(value);
}
/**
* @param key
* @param value
* @param jsonConfig
* @return Object
*/
public Object processObjectValue(String key, Object value,
JsonConfig jsonConfig) {
return process(value);
}
/**
* process
* @param value
* @return
*/
private Object process(Object value) {
try {
if (value instanceof Date) {
SimpleDateFormat sdf = new SimpleDateFormat(datePattern,
Locale.UK);
return sdf.format((Date) value);
}
return value == null ? "" : value.toString();
} catch (Exception e) {
return "";
}
}
/**
* @return the datePattern
*/
public String getDatePattern() {
return datePattern;
}
/**
* @param pDatePattern the datePattern to set
*/
public void setDatePattern(String pDatePattern) {
datePattern = pDatePattern;
}
}二：后台传前台
后台以list和map两种形式封装json，前台注意json数组和json对象解析时的差别即可。
1.TestJson.java
package com.badminton.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
public class TestJson extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html");
String str= request.getParameter("name");//得到ajax传递过来的paramater
System.out.println(str);
PrintWriter out = response.getWriter();
List list = new ArrayList();//传递List
//Map m=new HashMap();//传递Map
User u1=new User();
u1.setUsername("zah");
u1.setPassword("123");
User u2=new User();
u2.setUsername("ztf");
u2.setPassword("456");
list.add(u1); //添加User对象
list.add(u2); //添加User对象
//m.put("u1", u1);
//m.put("u2", u2);
JSONArray jsonArray2 = JSONArray.fromObject( list );//转化成json对象
//JSONObject jo=JSONObject.fromObject(m);//转化Map对象
out.print(jsonArray2);//返给ajax请求
System.out.println(jsonArray2);
//out.print(jo);//返给ajax请求
}
}2.showjson.jsp
利用Jquery、AJAX异步传输的方式接受后台的发送请求。
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<script type="text/javascript" src="js/jquery-1.4.2.min.js"></script>
<script type="text/javascript">
function test(){
$.ajax({
type:"POST", //请求方式
url:"servlet/TestJson",//请求路径
cache: false,
data:"name=zah", /传参
dataType: 'json',//返回值类型
success:function(json){
alert(json[1].username+" "+ json[1].password);//弹出返回过来的List对象
}
});
}
</script>
</head>
<body>
<input type="button" name="b" value="测试"
</body>
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