ajax获取servlet发送的数据

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XMLHTTP中readState与status的状态值
0 (未初始化) 对象已建立,但是尚未初始化(尚未调用open方法
1 (初始化) 对象已建立,尚未调用send方法
2 (发送数据) send方法调用,但是当前的状态及http头未知
3 (数据传送中) 已接收部分数据,因为响应及http头不全,这时通过responseBody和responseText获取部分数据会出现错误
4 (完成) 数据接收完毕,此时可以通过通过responseBody和responseText获取完整的回应数据

当readState为4 status为200时说明成功

通过responseText获取servlet的文本

jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <script> function getContent() { var xmlHttp; xmlHttp = createXmlHttp(); alert("readyState:"+xmlHttp.readyState + "status:"+xmlHttp.status); xmlHttp.onreadystatechange=function (){ alert("readyState:"+xmlHttp.readyState + "status:"+xmlHttp.status); if (xmlHttp.readyState == 4 && xmlHttp.status == 200){ alert(xmlHttp.responseText); var text = document.getElementById("text"); text.value=xmlHttp.responseText; } }; xmlHttp.open("get","servlet",true); xmlHttp.send(null); } function createXmlHttp() { var xmlHttp; if(window.XMLHttpRequest) { xmlHttp = new XMLHttpRequest(); } //兼容IE else if(window.ActiveXObject) { xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); if(!xmlHttp) { xmlHttp = new ActiveXObject("Msxml2.XMLHTTP"); } } return xmlHttp; } </script>

  </head>

  <body>
    <input type="text" id="text">
    <button id="btn" onclick="getContent()">获取ajax数据</button>
  </body>
</html>

servlet

package com.cyh.test;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Servlet extends HttpServlet {

    public void doGet(HttpServletRequest request,HttpServletResponse response)
            throws ServletException,IOException {
        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");

        PrintWriter out = response.getWriter();
        out.println("后台发送的数据");
    }

    public void doPost(HttpServletRequest request,IOException {
    }

}

若servlet发送json格式

package com.cyh.test;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Servlet extends HttpServlet {

    public void doGet(HttpServletRequest request,IOException {
        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");

        //json格式{k : v,k : v}
        String content = "{\"name\":\"张三\",\"age\":\"18\"}"; 

        PrintWriter out = response.getWriter();
        out.println(content);
    }

    public void doPost(HttpServletRequest request,IOException {
        System.out.println("post");
    }

}

前台接受

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <script> function getContent() { var xmlHttp; xmlHttp = createXmlHttp(); xmlHttp.onreadystatechange=function (){ if (xmlHttp.readyState == 4 && xmlHttp.status == 200){ alert(xmlHttp.responseText); } }; xmlHttp.open("get",true); xmlHttp.send(null); } function createXmlHttp() { var xmlHttp; if(window.XMLHttpRequest) { xmlHttp = new XMLHttpRequest(); } //兼容IE else if(window.ActiveXObject) { xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); if(!xmlHttp) { xmlHttp = new ActiveXObject("Msxml2.XMLHTTP"); } } return xmlHttp; } </script>
  </head>

  <body>
    姓名<input type="text" id="name"><br>
    年龄<input type="text" id="age"><br>
    <button id="btn" onclick="getContent()">获取ajax数据</button>
  </body>
</html>

返回的形式是{“name”:”张三”,“age”:”18”}
通过 var obj = eval(“(“+xmlHttp.responseText+”)”);
返回的obj就是一对象, 可以输出key对应的值
alert(obj.name);
alert(obj.age);

导入json jar包

在servlet中可以这样设置 JSONObject content = new JSONObject(); content.put(“name”,“张三”); content.put(“age”,”19”);

原文链接:https://www.f2er.com/ajax/160955.html

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