最近上班太忙，晚上抽空整理一下ajax请求中，后台返回json字符串和json数组的场景，以及前台的处理示例。
直接看代码。
json字符串的后台响应
package com.ajax;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/jsonStr")
public class JsonStr extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req,HttpServletResponse resp)
throws ServletException,IOException {
// 构造json对象
String resStr = "{" + "name:" + "\"zhangsan\"," + "id:" + "\"id001\"" + "}";
// 输出json对象到前台
PrintWriter out = resp.getWriter();
out.write(resStr);
out.flush();
out.close();
}
@Override
protected void doPost(HttpServletRequest req,IOException {
doGet(req,resp);
}
}
json数组的后台响应
package com.ajax;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/jsonArr")
public class JsonArr extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req,IOException {
// 构造json对象
String resStr1 = "{" + "name:" + "\"zhangsan\"," + "id:" + "\"id001\"" + "}";
String resStr2 = "{" + "name:" + "\"lisi\"," + "id:" + "\"id002\"" + "}";
String resStr3 = "{" + "name:" + "\"wangwu\"," + "id:" + "\"id003\"" + "}";
// 构造json数组
String jsonArr = "[" + resStr1 + "," + resStr2 + "," + resStr3 + "]";
// 输出json数组到前台
PrintWriter out = resp.getWriter();
out.write(jsonArr);
out.flush();
out.close();
}
@Override
protected void doPost(HttpServletRequest req,resp);
}
}
前台页面
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<Meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Json</title>
</head>
<body>
<br><br>
<input type="button" value="JsonStr" onclick="jsonStr()" />
<br><br>
<table>
<tr>
<td>username</td>
<td><input id="username"></td>
</tr>
<tr>
<td>id</td>
<td><input id="id"></td>
</tr>
</table>
<br><br><br>
<input type="button" value="JsonArr" onclick="jsonArr()" />
<br><br>
<table border="1" bordercolor="red">
<caption>Json Array</caption>
<thead>
<tr>
<th>Username</th>
<th>Id</th>
</tr>
</thead>
<tbody id="tb">
</tbody>
</table>
</body>
<script type="text/javascript">
// json字符串处理方法
function jsonStr() {
var xhr = new XMLHttpRequest();
xhr.open("get","jsonStr");
xhr.onreadystatechange = function(data) {
if (xhr.readyState == 4 && xhr.status == 200) {
// 将json字符串转换为json对象
var obj = eval("(" + data.target.responseText + ")");
document.getElementById("username").value = obj.name;
document.getElementById("id").value = obj.id;
}
};
xhr.send(null);
}
// json数组处理方法
function jsonArr() {
var xhr = new XMLHttpRequest();
xhr.open("get","jsonArr");
xhr.onreadystatechange = function(data) {
if (xhr.readyState == 4 && xhr.status == 200) {
// 将json字符串转换为json数组
var obj = eval("(" + data.target.responseText + ")");
// 创建代码片段，用于存放表格行
var oFragment = document.createDocumentFragment();
// 根据json数组长度，产生行数据
for (var i=0; i<obj.length; i++) {
var trObj = document.createElement("tr");
trObj.innerHTML = "<td>" + obj[i].name + "</td><td>" + obj[i].id + "</td>";
oFragment.appendChild(trObj);
}
// 将行数据添加在表格的tBody部分
document.getElementById("tb").appendChild(oFragment);
}
};
xhr.send(null);
}
</script>
</html>
页面效果图
点击 JsonStr 和 JsonArr 按钮后的效果
好了，整理完毕，示例仅供学习。
对了，有一点疑惑，之前回调函数中，获取响应数据的时候，都是直接通过data.responseText 来获取的，今天的代码中必须使用data.target.responseText，不知道为什么？有知道的朋友烦请告知一声，非常感谢。
