談到JSON,簡單的說就是一種資料交換格式。近年來，其在伺服器之間交換資料的應用越來越廣，相比XML其格式更簡單、編解碼更容易、擴充套件性更好，所以深受開發人員的喜愛。
下面簡單的寫一下在專案中前後臺json傳值的一個小例子，供大家參考、查閱。
一：前臺傳後臺
1.前臺jsp頁面程式碼：
在index中將實體物件（自己建立即可）插入list中，再將list集合轉化成json陣列，利用post方式傳送AJAX請求，將這個json陣列傳送至後臺（servlet），再在後臺進行解析即可。
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屆全運會男單冠軍。");
Athlete athlete2 = new Athlete();//記錄2
athlete2.setAthlete_id(1004);
athlete2.setAthlete_name("鮑春來");
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年亞洲羽毛球錦標賽亞軍。");
List<Athlete> list1 = new ArrayList<Athlete>();
list1.add(athlete1);
list1.add(athlete2);
JsonConfig jsonConfig = new JsonConfig();//解決date型別的傳輸問題
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();
}
}
//回撥
function handleStateChange() {
if (xmlHttp.readyState == 4) {
if (xmlHttp.status == 200) {
parseResults();
}
}
}
//將後臺返回的資料顯示在層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以後可用來識別資料庫中的表
var str2=`<%=jsonarray%>`;
var url = "servlet/JsonServlet";
createXmlHttpRequest();
xmlHttp.open("POST", url, true);
xmlHttp.onreadystatechange = handleStateChange;//回撥
xmlHttp.setRequestHeader("Content-Type",
"application/x-www-form-urlencoded;text/xml;charset=utf-8"); //text/xml;charset=utf-8：解決漢字封裝json問題
xmlHttp.send("athletehead="+str1+"&athlete="+str2);//傳送了兩個物件
}
</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.後臺解析程式碼：
後臺接受前臺傳來的json物件，解析插入資料庫中，且反給前臺一個是否成功的訊息。具體插入資料庫的程式碼自己編寫一個即可。
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表的頭資料
String json2 = request.getParameter("athlete");//接收athlete表資料
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物件
JSONArray jsonArray2 = JSONArray.fromObject(json2);//生成JSON陣列
for(int i=0;i<jsonArray2.size();i++){
JSONObject resultObj = jsonArray2.optJSONObject(i);//根據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);//轉換成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);//對資料庫進行操作，具體程式碼未附
}
String result = "資料上傳成功！";
out.println("<response>");
out.println("<result>" + result + "</result>");
out.println("</response>");
out.close();
} else{
String result = "傳輸過程出錯，請重傳！";
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) 報錯："
+ e.getMessage());
}
}
public void init() throws ServletException {
}
}
3.解決傳遞日期的一個工具類
若沒有這個工具類，date型資料會被轉化成json陣列的格式，後臺解析起來會很複雜。
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：後臺傳前臺
後臺以list和map兩種形式封裝json，前臺注意json陣列和json物件解析時的差別即可。
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傳遞過來的paramater
System.out.println(str);
PrintWriter out = response.getWriter();
List list = new ArrayList();//傳遞List
//Map m=new HashMap();//傳遞Map
User u1=new User();
u1.setUsername("zah");
u1.setPassword("123");
User u2=new User();
u2.setUsername("ztf");
u2.setPassword("456");
list.add(u1); //新增User物件
list.add(u2); //新增User物件
//m.put("u1", u1);
//m.put("u2", u2);
JSONArray jsonArray2 = JSONArray.fromObject( list );//轉化成json物件
//JSONObject jo=JSONObject.fromObject(m);//轉化Map物件
out.print(jsonArray2);//返給ajax請求
System.out.println(jsonArray2);
//out.print(jo);//返給ajax請求
}
}
2.showjson.jsp
利用Jquery、AJAX非同步傳輸的方式接受後臺的傳送請求。
<%@ 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", //請求方式
url:"servlet/TestJson",//請求路徑
cache: false,
data:"name=zah", /傳參
dataType: `json`,//返回值型別
success:function(json){
alert(json[1].username+" "+ json[1].password);//彈出返回過來的List物件
}
});
}
</script>
</head>
<body>
<input type="button" name="b" value="測試"
</body>
</html>