首先看下看下相對簡單些的——向服務器發送一個包含有名/值對的簡單查詢串，在這種情況下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/值對的參數形式了（如name=LiLin&age=23），在調用OPEN方法中，當請求方法是用POST的時候為了確保服務器知道請求體中有請求參數，需要調用setRequestHeader，將Content-Type值設置為application/x-www-form-urlencoded.當然也可不放在請求體中（那就不要用POST啦！）
此時server處理：
對get and post方法都用processRequest來處理。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 " );
}
}
要向服務器發送相關復雜的查詢串，可以將模型變化為XML發送到server 。
clIEnt端：
function createXML() {
var XML = " <pets> " ;var options = document.getElementById( " petTypes " ).childNodes;
var option = null ;
for ( var i = 0 ; i < options.length; i ++ ) {
option = options[i];
if (option.selected) {
xml = XML + " <type> " + option.value + " <\/type> " ;
}
}xml = XML + " <\/pets> " ;
return XML;
}function sendPetTypes() {
createXMLHttpRequest();var xml = createXML();
var url = " PostingXMLExample?timeStamp= " + new Date().getTime();XMLHttp.open( " POST " , url, true );
XMLHttp.onreadystatechange = handleStateChange;
XMLHttp.setRequestHeader( " Content-Type " ," application/x-www-form-urlencoded " );
xmlHttp.send(XML);
}
關於這個控件有個方法可以在各broswer中通用的JS代碼：
// ------------------------------------------------
// Function: CreateXMLDOM
//
// Purpose: Creates a new XML DOM.
//
// Parameters: None
//
// Returns: XMLDOM object OR null
// -------------------------------------------------
function CreateXMLDOM()
{
var oXML = new ActiveXObject(GetXMLParserProgID());
try
{
oXML.setProperty( " AllowXsltScript " , true );
}
catch (err) {}
oXML.async = false ;
oXML.validateOnParse = false ;
oXML.resolveExternals = false ;
oXML.setProperty( " SelectionLanguage " , " XPath " );
try {oXML.setProperty( " NewParser " , true );} catch (e) {}
return oXML;
}
// -------------------------------------------------
// Function: GetXMLParserProgID
//
// Purpose:
// Gets the ProgID of the highest available version of the
// Microsoft XML parser.
//
// Parameters: None
//
// Returns: String (i.e. "MsXML2.DOMDocument.4.0")
//
// -------------------------------------------------
function GetXMLParserProgID()
{
var MAX_MAJOR_PARSER_VERSION = 10 ;
var MIN_MAJOR_PARSER_VERSION = 0 ;
var MAX_MINOR_PARSER_VERSION = 9 ;
var MIN_MINOR_PARSER_VERSION = 0 ;
var sProgID = g_sXMLParserProgID;
var bFound = false ;
if ( ! sProgID)
{
// Iterate through possible versions
for ( var nMajor = MAX_MAJOR_PARSER_VERSION;
nMajor >= MIN_MAJOR_PARSER_VERSION; nMajor -- )
{
for ( var nMinor = MAX_MINOR_PARSER_VERSION;
nMinor >= MIN_MINOR_PARSER_VERSION; nMinor -- )
{
// Set up the classname for the version that
we're trying to instantiate
sProgID = " MsXML2.DOMDocument. " + nMajor + " . " + nMinor;
try
{
if ( new ActiveXObject(sProgID))
{
bFound = true ;
break ;
}
}
catch (e)
{}
}
if (bFound)
{
// store in a global variable to
speedup subsequent calls
g_sXMLParserProgID = sProgID;
break ;
}
}
}
return sProgID;
}然後直接用其load方法（本地）。
var xmlDoc = new ActiveXObject( " MSXML2.DOMDocument.3.0 " );
xmlDoc.load(local_XML_FileName);
當然也可以直接從server取來（用get方法即可），然後以responseText的方法。
xmlht.Open( " GET " ,server_XML_FileName, true ); function handleStateChange() { 實際上xmlDoc.loadXML(xmlht.responseText)所得到的就是一個於內存中的DOM了，而直接用responseXML的話就直接可以解析為一個DOM了！(注意load（FILE）與loadXML（DOM）是不同的) 此時servert process ： import Java.io. * ; public class PostingXMLExample extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) String xml = readXMLFromRequestBody(request); /**/ /* Note how the Java implementation of the W3C DOM has the same methods response.setContentType( " text/XML " ); private String readXMLFromRequestBody(HttpServletRequest request) {
XMLht.onreadystatechange = stateChange;
XMLht.Send( null );
if (XMLHttp.readyState == 4 ) {
if (XMLHttp.status == 200 ) {
xmlDoc.loadXML(XMLht.responseText);
}
}
}
import Javax.servlet. * ;
import Javax.servlet.http. * ;
import Javax.XML.parsers.DocumentBuilderFactory;
import Javax.XML.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.XML.sax.SAXException;
throws ServletException, IOException {
Document XMLDoc = null ;
try {
XMLDoc =
DocumentBuilderFactory.newInstance().newDocumentBuilder()
.parse( new ByteArrayInputStream(XML.getBytes()));
}
catch (ParserConfigurationException e) {
System.out.println( " ParserConfigurationException: " + e);
}
catch (SAXException e) {
System.out.println( " SAXException: " + e);
}
* as the JavaScript implementation, such as getElementsByTagName and
* getNodeValue.
*/
NodeList selectedPetTypes = XMLDoc.getElementsByTagName( " type " );
String type = null ;
String responseText = " Selected Pets: " ;
for ( int i = 0 ; i < selectedPetTypes.getLength(); i ++ ) {
type = selectedPetTypes.item(i).getFirstChild().getNodeValue();
responseText = responseText + " " + type;
}
response.getWriter().print(responseText);
}
StringBuffer XML = new StringBuffer();
String line = null ;
try {
BufferedReader reader = request.getReader();
while ((line = reader.readLine()) != null ) {
XML.append(line);
}
}
catch (Exception e) {
System.out.println( " Error reading XML: " + e.toString());
}
return XML.toString();
}
}