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首先看下看下相对简单些的--向服务器发送一个包含有名/值对的简单查询串,在这种情况下XHP即可以用GET也可以用POST。

GET

function doRequestUsingGET() {
 createXMLHttpRequest();

 var queryString = " GetAndPostExample? " ;
 queryString = queryString + createQueryString()+ " &timeStamp= " + new Date().getTime();
 xmlHttp.onreadystatechange = handleStateChange;
 xmlHttp.open( " GET " , queryString, true );
 xmlHttp.send( null );
}

POST

function doRequestUsingPOST() {
 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 " );
 xmlHttp.send(queryString);
}

  queryString就是名/值对的参数形式了(如name=LiLin&age=23),在调用OPEN方法中,当请求方法是用POST的时候为了确保服务器知道请求体中有请求参数,需要调用setRequestHeader,将Content-Type值设置为application/x-www-form-urlencoded.当然也可不放在请求体中(那就不要用POST啦!)

  此时server处理:

import java.io. * ;
import java.net. * ;
import javax.servlet. * ;
import javax.servlet.http. * ;

public class GetAndPostExample extends HttpServlet {

 protected void processRequest(HttpServletRequest request, HttpServletResponse response, String method)
throws ServletException, IOException {

  // 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 " );

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