Java手写Ajax

一、客户端发出请求

1.Gets the browser specific XmlHttpRequest Objects

function getXmlHttpRequestObject() {
 if (window.XMLHttpRequest) {
  return new XMLHttpRequest();
 } else if(window.ActiveXObject) {
  return new ActiveXObject("Microsoft.XMLHTTP");
 } else {
  alert("Your Browser Sucks!/nIt's about time to upgrade don't you think?");
 }
}
2.Create Ajax Object
function createAjaxObj(){
  var httprequest=false
  if (window.XMLHttpRequest)
  {
    httprequest=new XMLHttpRequest()
    if (httprequest.overrideMimeType)
      httprequest.overrideMimeType('text/xml')
   }
   else if (window.ActiveXObject)
   {
     try {
       httprequest=new ActiveXObject("Msxml2.XMLHTTP");
     }
     catch (e){
       try{
          httprequest=new ActiveXObject("Microsoft.XMLHTTP");
       }
       catch (e){}
     }
   }
   return httprequest
}
var searchReq = createAjaxObj();

//Called from keyup on the search textbox.
//Starts the AJAX request.
function searchSuggest() {
 if (searchReq.readyState == 4 || searchReq.readyState == 0) {
  var str = escape(document.getElementById('txtSearch').value);
  searchReq.open("GET", 'search?search=' + str, true);
  searchReq.onreadystatechange = handleSearchSuggest;
  searchReq.send(null);
 }  
}

//Called when the AJAX response is returned.
function handleSearchSuggest() {
 if (searchReq.readyState == 4) {
  var ss = document.getElementById('search_suggest')
  ss.innerHTML = '';
  var str = searchReq.responseText.split("/n");
  for(i=0; i < str.length - 1; i++) {
   //Build our element string.  This is cleaner using the DOM, but
   //IE doesn't support dynamically added attributes.
   var suggest = '<div onmouseover="javascript:suggestOver(this);" ';
   suggest += 'onmouseout="javascript:suggestOut(this);" ';
   suggest += 'onclick="javascript:setSearch(this.innerHTML);" ';
   suggest += 'class="suggest_link">' + str[i] + '</div>';
   ss.innerHTML += suggest;
  }
 }
}

//Mouse over function
function suggestOver(div_value) {
 div_value.className = 'suggest_link_over';
}
//Mouse out function
function suggestOut(div_value) {
 div_value.className = 'suggest_link';
}
//Click function
function setSearch(value) {
 document.getElementById('txtSearch').value = value;
 document.getElementById('search_suggest').innerHTML = '';
}

二、服务器，接受到数据后，把客户端需要的信息返回给客户端

java.io.PrintWriter out = response.getWriter();

StringBuffer buf = new StringBuffer();

 out.print(buf.toString());
   out.flush();

   out.close();