AJAX编程实践之与服务器通信_AJAX教程

编辑Tag赚U币
教程Tag:暂无Tag,欢迎添加,赚取U币!

  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 " );
 }
}
  对get and post方法都用processRequest来处理。

  要向服务器发送相关复杂的查询串,可以将模型变化为XML发送到server 。

  client端:

function createXML() {
 var xml = "

" ;

 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 " " 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);
}
  createXML方法无非就是将内容以DOM的样式存到var xml(变量)里。有时也可能出现client直接将本地的一个XML文件直接以DOM(当然可以edit)的样式传送.(也放这个时个的Content-Type应该为text/xml了!)这时可能要用到ActiveXObject("MSXML2.DOMDocument.3.0")这样一个控件了。

  关于这个控件有个方法可以在各broswer中通用的JS代码:

// --------------------------------------------------------------------
// 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;
}

  然后直接用其load方法(本地)。

var xmlDoc = new ActiveXObject( " MSXML2.DOMDocument.3.0 " );
xmlDoc.load(local_XML_FileName);
  当然也可以直接从server取来(用get方法即可),然后以responseText的方法

xmlht.Open( " GET " ,server_XML_FileName, true );
xmlht.onreadystatechange = stateChange;
xmlht.Send( null );

function handleStateChange() {
 if (xmlHttp.readyState == 4 ) {
  if (xmlHttp.status == 200 ) {
   xmlDoc.loadXML(xmlht.responseText);
  }
 }
}
  实际上xmlDoc.loadXML(xmlht.responseText)所得到的就是一个于内存中的DOM了,而直接用responseXML的话就直接可以解析为一个DOM了!(注意load(FILE)与loadXML(DOM)是不同的)

  此时servert process :

import java.io. * ;
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;

public class PostingXMLExample extends HttpServlet {

protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

String xml = readXMLFromRequestBody(request);
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);
}

/**/ /* Note how the Java implementation of the W3C DOM has the same methods
* 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.setContentType( " text/xml " );
response.getWriter().print(responseText);
}

private String readXMLFromRequestBody(HttpServletRequest request) {
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();
}
}
  DOM,JDOM,JAXP随便你自己选好了!

来源:模板无忧//所属分类:AJAX教程/更新时间:2008-08-22
相关AJAX教程