ajax利用servlet发送请求,不用form中的action=...
如果数据处理不改变数据模型的状态,理论上采用GET方法,获取数据时应用GET方法。如果因为存储、更新数据，或者发送电子邮件，操作改变了数据模型的状态，应该使用POST方法。
使用httpxmlrequest请求的话，将使用javascript创建查询串，来提交请求。使用GET发送请求send(null）。POST：send(...)。而不再用form的GET/POST，这样浏览器的url部分也不会出现。。?.....&....&...一连串的东西了。。。。
例子：getAndPostExample.html：
<html>
<head>
<title>Sending Request Data Using GET and POST</title>
<script type="text/javascript">
var xmlHttp;
function createXMLHttpRequest() {//创建xmlhttprequest对象。
if (window.ActiveXObject) {
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
else if (window.XMLHttpRequest) {
xmlHttp = new XMLHttpRequest();
}
}
function createQueryString() {//创建查询串
var firstName = document.getElementById("firstName").value;
var middleName = document.getElementById("middleName").value;
var birthday = document.getElementById("birthday").value;
var queryString = "firstName=" + firstName + "&middleName=" + middleName
+ "&birthday=" + birthday;
return queryString;
}
function doRequestUsingGET() {//Get的主js
createXMLHttpRequest();
var queryString = "GetAndPostExample?";
queryString = queryString + createQueryString()
+ "&timeStamp=" + new Date().getTime();
xmlHttp.onreadystatechange = handleStateChange;
xmlHttp.open("GET", queryString, true);
xmlHttp.send(null);
}
function doRequestUsingPOST() {//POST的主js
createXMLHttpRequest();
var url = "GetAndPostExample?timeStamp=" + new Date().getTime();
var queryString = createQueryString();
xmlHttp.open("POST", url, true);
xmlHttp.onreadystatechange = handleStateChange;
xmlHttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); //这句话不能去，否则得不到数据。确保服务器知道请求体中有参数。
xmlHttp.send(queryString);
}
function handleStateChange() {
if(xmlHttp.readyState == 4) {
if(xmlHttp.status == 200) {
parseResults();
}
}
}
function parseResults() {
var responseDiv = document.getElementById("serverResponse");
if(responseDiv.hasChildNodes()) {
responseDiv.removeChild(responseDiv.childNodes[0]);
}
var responseText = document.createTextNode(xmlHttp.responseText);
responseDiv.appendChild(responseText);
}
</script>
</head>
<body>
<h1>Enter your first name, middle name, and birthday:</h1>
<table>
<tbody>
<tr>
<td>First name:</td>
<td><input type="text" id="firstName"/>
</tr>
<tr>
<td>Middle name:</td>
<td><input type="text" id="middleName"/>
</tr>
<tr>
<td>Birthday:</td>
<td><input type="text" id="birthday"/>
</tr>
</tbody>
</table>
<form action="#">//这个时候向服务器发送请求就不用form action出马了，ajax自己能做了。
<input type="button" value="Send parameters using GET" onclick="doRequestUsingGET();"/>
<br/><br/>
<input type="button" value="Send parameters using POST" onclick="doRequestUsingPOST();"/>
</form> <br/>
<h2>Server Response:</h2>
<div id="serverResponse"></div>
</body>
</html>
处理请求的servlet：
package three;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class GetAndPostExample extends HttpServlet {
protected void processRequest(HttpServletRequest request,
HttpServletResponse response, String method)
throws ServletException, IOException {//自定义的一个方法，因为get与post都要用到。参数跟doPost\doGet差不多，抛出的异常也差不多
//Set content type of the response to text/xml
response.setContentType("text/xml");
//Get the user's input
String firstName = request.getParameter("firstName");
String middleName = request.getParameter("middleName");
String birthday = request.getParameter("birthday");
//Create the response text
String responseText = "Hello " + firstName + " " + middleName
+ ". Your birthday is " + birthday + "."
+ " [Method: " + method + "]";
//Write the response back to the browser
PrintWriter out = response.getWriter();
out.println(responseText);
//Close the writer
out.close();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//Process the request in method processRequest
processRequest(request, response, "GET");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//Process the request in method processRequest
processRequest(request, response, "POST");
}
}
web.xml：
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<servlet>
<servlet-name>GetAndPostExample</servlet-name>
<servlet-class>three.GetAndPostExample</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>GetAndPostExample</servlet-name>
<url-pattern>/three/GetAndPostExample</url-pattern>//注意，包名three要包含进去，因为你访问页面地址是：http://localhost:8080/ajaxfoundation/three/getAndPostExample.html，
</servlet-mapping>
</web-app>
运行结果是：(注意浏览器上方没有一连串的提交数据)
http://hi.baidu.com/sun1227/blog/item/41b46a4eb3cd1531aec3ab7c.html
