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JSON主要创建如下两种数据对象：

  • 由JSON格式字符串创建，转换成JavaScript的Object对象；
  • 由JSON格式字符串创建，转换成JavaScript的List或数组链表对象。

更多关于JSON的信息，请参考：JSON概述及其在JavaScript与Java中的应用（整理）

1. JSP页面中将对象转换为JSON字符串提交

1.1 创建JSP文件（convertObject2Json.jsp）

<%@ page language="java" import="java.util.*" pageEncoding="utf-8" %> 
 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 
<html> 
    <head> 
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 
        <script type="text/javascript" src="../../js/json2.js"> 
        </script> 
        <script type="text/javascript"> 
            function ajaxTransferText(){ 
                var BigText = document.getElementById("BigText").value; 
                var ajaxTransferObjectRef = new ajaxTransferObject("张三", "密码11", 10, BigText); 
                var JSONString = JSON.stringify(ajaxTransferObjectRef); 
                 
                if (window.ActiveXObject) { 
                    myAjaxObject = new ActiveXObject("Microsoft.XMLHTTP"); 
                } 
                else { 
                    myAjaxObject = new XMLHttpRequest(); 
                } 
                 
                var urlString = "jsonString=" + JSONString; 
                 
                alert(urlString); 
                myAjaxObject.open("POST", "postJson.action"+"?timestamp=" + new Date().getTime(), true); 
                myAjaxObject.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); 
                 
                myAjaxObject.send(urlString); 
            } 
             
            function ajaxTransferObject(username, password, age, BigText){ 
                this.username = username; 
                this.password = password; 
                this.age = age; 
                this.BigText = BigText; 
            } 
        </script> 
    </head> 
    <body> 
        <textarea name="textarea" id="BigText" cols="45" rows="5">需要提交的信息主体...</textarea> 
        <br/> 
        <input type="button" value="提交试试" onclick="ajaxTransferText()"/> 
    </body> 
</html>

1.2 创建后台处理Action类

package com.clzhang.ssh.demo6; 
 
import net.sf.json.JSONObject; 
 
import com.opensymphony.xwork2.ActionSupport; 
 
/** 
 * 获取前台提交的JSON数据 
 * @author Administrator 
 * 
 */ 
public class PostJSONAction extends ActionSupport { 
    public static final long serialVersionUID = 1; 
 
    private String jsonString; 
 
    public String getJsonString() { 
        return jsonString; 
    } 
 
    public void setJsonString(String jsonString) { 
        this.jsonString = jsonString; 
    } 
 
    public String execute() { 
        System.out.println(jsonString); 
         
        JSONObject json = JSONObject.fromObject(jsonString); 
        System.out.println("username=" + json.get("username")); 
        System.out.println("username=" + json.get("password")); 
        System.out.println("username=" + json.get("age")); 
        System.out.println("username=" + json.get("BigText")); 
 
        return null; 
    } 
}

1.3 修改配置文件struts.xml

        <action name="postJson" class="com.clzhang.ssh.demo6.PostJSONAction"> 
        </action>

1.4 测试

打开IE，输入地址：http://127.0.0.1:8080/st/ssh/demo6/convertObject2Json.jsp

结果如下：

确定后，后台显示：

2. JSP页面获取后台Response返回的JSON对象

2.1 创建JSP文件（getJsonFromResp.jsp）

<%@ page language="java" import="java.util.*" pageEncoding="utf-8" %> 
 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 
<html> 
    <head> 
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 
        <script type="text/javascript" src="../../js/json2.js"> 
        </script> 
        <script type="text/javascript"> 
            var myAjaxObject; 
            //在List中存字符串 
            function getListString(){ 
                if (window.ActiveXObject) { 
                    myAjaxObject = new ActiveXObject("Microsoft.XMLHTTP"); 
                } 
                else { 
                    myAjaxObject = new XMLHttpRequest(); 
                } 
                 
                myAjaxObject.open("GET", "getJson!listString.action?date=" + new Date().getTime(), true); 
                myAjaxObject.onreadystatechange = retrunListString; 
                myAjaxObject.send(); 
            } 
             
            function retrunListString(){ 
                if (myAjaxObject.readyState == 4) { 
                    if (myAjaxObject.status == 200) { 
                        var returnJSONString = myAjaxObject.responseText; 
                        var returnJSON = JSON.parse(returnJSONString); 
                        var showString = ""; 
                        for (var i = 0; i < returnJSON.length; i++) { 
                            showString = showString + returnJSON[i] + " "; 
                        } 
                        alert(showString); 
                    } 
                } 
            } 
             
            //在List中存Bean             
            function getListBean(){ 
                if (window.ActiveXObject) { 
                    myAjaxObject = new ActiveXObject("Microsoft.XMLHTTP"); 
                } 
                else { 
                    myAjaxObject = new XMLHttpRequest(); 
                } 
                 
                myAjaxObject.open("GET", "getJson!listBean.action?date=" + new Date().getTime(), true); 
                myAjaxObject.onreadystatechange = retrunListBean; 
                myAjaxObject.send(); 
            } 
             
            function retrunListBean(){ 
                if (myAjaxObject.readyState == 4) { 
                    if (myAjaxObject.status == 200) { 
                        var returnJSONString = myAjaxObject.responseText; 
                        var returnJSON = JSON.parse(returnJSONString); 
                        var showString = ""; 
                        for (var i = 0; i < returnJSON.length; i++) { 
                            showString = showString + returnJSON[i].username + " " + returnJSON[i].password + " " + returnJSON[i].age + " " + returnJSON[i].createDate + "\n"; 
                        } 
                        alert(showString); 
                    } 
                } 
            } 
             
            //在Map中存字符串             
            function getMapString(){ 
                if (window.ActiveXObject) { 
                    myAjaxObject = new ActiveXObject("Microsoft.XMLHTTP"); 
                } 
                else { 
                    myAjaxObject = new XMLHttpRequest(); 
                } 
                 
                myAjaxObject.open("GET", "getJson!mapString.action?date=" + new Date().getTime(), true); 
                myAjaxObject.onreadystatechange = retrunMapString; 
                myAjaxObject.send(); 
            } 
             
            function retrunMapString(){ 
                if (myAjaxObject.readyState == 4) { 
                    if (myAjaxObject.status == 200) { 
                        var returnJSONString = myAjaxObject.responseText; 
                        var returnJSON = JSON.parse(returnJSONString); 
                        var showString = ""; 
                        for (var i in returnJSON[0]) { 
                            showString = showString + "key=" + i + " value=" + returnJSON[0][i] + "\n"; 
                        } 
                        alert(showString); 
                    } 
                } 
            } 
             
            //在Map中存Bean             
            function getMapBean(){ 
                if (window.ActiveXObject) { 
                    myAjaxObject = new ActiveXObject("Microsoft.XMLHTTP"); 
                } 
                else { 
                    myAjaxObject = new XMLHttpRequest(); 
                } 
                 
                myAjaxObject.open("GET", "getJson!mapBean.action?date=" + new Date().getTime(), true); 
                myAjaxObject.onreadystatechange = retrunMapBean; 
                myAjaxObject.send(); 
            } 
             
            function retrunMapBean(){ 
                if (myAjaxObject.readyState == 4) { 
                    if (myAjaxObject.status == 200) { 
                        var returnJSONString = myAjaxObject.responseText; 
                        var returnJSON = JSON.parse(returnJSONString); 
                        var showString = ""; 
                        for (var i in returnJSON[0]) { 
                            showString = showString + "key=" + i + " username=" + returnJSON[0][i].username + " password=" + returnJSON[0][i].password + " age=" + returnJSON[0][i].age + " createDate=" + returnJSON[0][i].createDate + "\n"; 
                        } 
                        alert(showString); 
                    } 
                } 
            } 
        </script> 
    </head> 
    <body> 
        <input type="button" value="返回List中存String类型的JSON" onclick="getListString()"/> 
        <br/> 
        <br/> 
        <input type="button" value="返回List中存Bean类型的JSON" onclick="getListBean()"/> 
        <br/> 
        <br/> 
        <input type="button" value="返回Map中存String类型的JSON" onclick="getMapString()"/> 
        <br/> 
        <br/> 
        <input type="button" value="返回Map中存Bean类型的JSON" onclick="getMapBean()"/> 
        <br/> 
    </body> 
</html>

2.2 创建后台处理Action类

package com.clzhang.ssh.demo6; 
 
import java.io.IOException; 
import java.text.SimpleDateFormat; 
import java.util.*; 
 
import net.sf.json.JSONArray; 
import org.apache.struts2.ServletActionContext; 
import com.opensymphony.xwork2.ActionSupport; 
 
/** 
 * 返回给前台JSON数据，以四种方式  
 * @author Administrator 
 * 
 */ 
public class ReturnJSONAction extends ActionSupport { 
    public static final long serialVersionUID = 1; 
     
    private List<String> lstString = new ArrayList<String>(); 
     
    public ReturnJSONAction() { 
        lstString.add("你今天吃了吗？"); 
        lstString.add("吃了多吃点"); 
        lstString.add("没吃回家吃去"); 
        lstString.add("好好学习"); 
        lstString.add("天天向上"); 
    } 
 
    public String listString() throws IOException { 
        JSONArray json = JSONArray.fromObject(lstString); 
        System.out.println(json.toString()); 
 
        ServletActionContext.getResponse().setContentType("text/html"); 
        ServletActionContext.getResponse().setCharacterEncoding("utf-8"); 
        ServletActionContext.getResponse().getWriter().printf(json.toString()); 
        ServletActionContext.getResponse().getWriter().flush(); 
        ServletActionContext.getResponse().getWriter().close(); 
 
        return null; 
    } 
 
    public String listBean() throws IOException { 
        List<UserInfo> listBean = new ArrayList<UserInfo>(); 
         
        for(String str: lstString) { 
            UserInfo userInfo1 = new UserInfo(); 
            userInfo1.setUsername(str); 
            userInfo1.setPassword("P" + Math.random()); 
            userInfo1.setAge((int)(Math.random()*10)); 
            userInfo1.setCreateDate(new SimpleDateFormat("yyyy-MM-dd hh-mm-ss") 
                    .format(new Date())); 
 
            listBean.add(userInfo1); 
        } 
 
        JSONArray json = JSONArray.fromObject(listBean); 
        System.out.println(json.toString()); 
 
        ServletActionContext.getResponse().setContentType("text/html"); 
        ServletActionContext.getResponse().setCharacterEncoding("utf-8"); 
        ServletActionContext.getResponse().getWriter().printf(json.toString()); 
        ServletActionContext.getResponse().getWriter().flush(); 
        ServletActionContext.getResponse().getWriter().close(); 
 
        return null; 
    } 
 
    public String mapString() throws Exception { 
        LinkedHashMap<String, String> mapString = new LinkedHashMap<String, String>(); 
        int count = 1; 
        for(String str: lstString) { 
            mapString.put(""+count++, str+count); 
        } 
 
        JSONArray json = JSONArray.fromObject(mapString); 
        System.out.println(json.toString()); 
 
        ServletActionContext.getResponse().setContentType("text/html"); 
        ServletActionContext.getResponse().setCharacterEncoding("utf-8"); 
        ServletActionContext.getResponse().getWriter().printf(json.toString()); 
        ServletActionContext.getResponse().getWriter().flush(); 
        ServletActionContext.getResponse().getWriter().close(); 
 
        return null; 
    } 
 
    public String mapBean() throws Exception { 
        LinkedHashMap<String, UserInfo> mapString = new LinkedHashMap<String, UserInfo>(); 
 
        int count = 1; 
        for(String str: lstString) { 
            UserInfo userInfo1 = new UserInfo(); 
            userInfo1.setUsername(str); 
            userInfo1.setPassword("P" + Math.random()); 
            userInfo1.setAge((int)(Math.random()*10)); 
            userInfo1.setCreateDate(new SimpleDateFormat("yyyy-MM-dd hh-mm-ss") 
                    .format(new Date())); 
 
            mapString.put(""+count++, userInfo1); 
        } 
 
        JSONArray json = JSONArray.fromObject(mapString); 
        System.out.println(json.toString()); 
 
        ServletActionContext.getResponse().setContentType("text/html"); 
        ServletActionContext.getResponse().setCharacterEncoding("utf-8"); 
        ServletActionContext.getResponse().getWriter().printf(json.toString()); 
        ServletActionContext.getResponse().getWriter().flush(); 
        ServletActionContext.getResponse().getWriter().close(); 
 
        return null; 
    } 
 
    public String execute() throws IOException { 
        return null; 
    } 
}

2.3 修改配置文件struts.xml

        <action name="getJson" class="com.clzhang.ssh.demo6.ReturnJSONAction"> 
        </action>

2.4 测试

打开IE，输入地址：http://127.0.0.1:8080/st/ssh/demo6/getJsonFromResp.jsp

2.4.1 按下“返回List中存String类型的JSON”按钮

2.4.2 按下“返回List中存Bean类型的JSON”按钮

2.4.3 按下“返回Map中存String类型的JSON”按钮

2.4.4 按下“返回Map中存Bean类型的JSON”按钮

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