XHR在JSP和Servlet下的请求和响应

1.Response Text

    1.1 JSP

    Client:

function JSP_Text(){   
    var url = server.jsp";
    if(window.ActiveXObject){        
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    }else if(window.XMLHttpRequest){     
        xmlHttp = new XMLHttpRequest();
    }
    xmlHttp.open("GET",url);
    xmlHttp.onreadystatechange = function(){
        if(xmlHttp.readyState==4){        
           if(xmlHttp.status==200){                alert(xmlHttp.responseText);
           }
        }
    };
    xmlHttp.send(null);
}

    Server:

<%@ page contentType="text/html; charset=gb2312" language="java"%>
<%
System.out.println("Server response");
out.println(request.getParameter("Hello!"));
%>

    1.2 Servlet 

    Client:

function Servlet_Text(){   
    var url = /server?";
    if(window.ActiveXObject){        
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    }else if(window.XMLHttpRequest){     
        xmlHttp = new XMLHttpRequest();
    }
    xmlHttp.open("GET",url);
    xmlHttp.onreadystatechange = function(){
        if(xmlHttp.readyState==4){        
           if(xmlHttp.status==200){  alert(xmlHttp.responseText);
           }
        }
    };
    xmlHttp.send(null);
}

    Server:

/** *//**
 * Get响应
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Document document = DocumentHelper.createDocument();  
Element map = document.addElement("map");
map.setText("This is a map");
try{              
            response.setContentType("text/html");          
            PrintWriter writer = response.getWriter();
            writer.write(obj.toString());
        }catch (IOException e) {
            // TODO 自动生成 catch 块
            e.printStackTrace();
        } 
           }

2. Response XML

    2.1 JSP
   
    Client:

function JSP_XML(){   
    var url = "server.jsp";
    if(window.ActiveXObject){        
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    }else if(window.XMLHttpRequest){     
        xmlHttp = new XMLHttpRequest();
    }
    xmlHttp.open("GET",url);
    xmlHttp.onreadystatechange = function(){
        if(xmlHttp.readyState==4){        
           if(xmlHttp.status==200){     
          listXmlNodes();    
           }
        }
    };
    xmlHttp.send(null);
}

function listXmlNodes(){
   var xmlDoc=xmlHttp.responseXML;
   var mapNode=xmlDoc.getElementsByTagName("map")[0];
   alert(mapNode.childNodes[0].nodeValue);
}

    Servlet:
    

<%
try{
Document document = DocumentHelper.createDocument();  
Element map = document.addElement("map");
map.setText("This is a map");
response.setContentType ("text/xml");
PrintWriter writer = response.getWriter();
//输出方法一
//document.writer(writer);
//输出方法二
OutputFormat format = OutputFormat.createPrettyPrint();
format.setEncoding("GBK");
XMLWriter output = new XMLWriter(writer,format);
output.write(document);
output.close();
}catch(Exception e){
  System.out.println(e);
}
%>

    2.2 Servlet
  
    Client:

function Servlet_XML(){   
    var url = "/server?";
    if(window.ActiveXObject){        
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    }else if(window.XMLHttpRequest){     
        xmlHttp = new XMLHttpRequest();
    }
    xmlHttp.open("GET",url);
    xmlHttp.onreadystatechange = function(){
        if(xmlHttp.readyState==4){        
           if(xmlHttp.status==200){     
          listXmlNodes();    
           }
        }
    };
    xmlHttp.send(null);
}

function listXmlNodes(){
   var xmlDoc=xmlHttp.responseXML;
   var mapNode=xmlDoc.getElementsByTagName("map")[0];
   alert(mapNode.childNodes[0].nodeValue);
}

    Server:

/** *//**
 * Get响应
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Document document = DocumentHelper.createDocument();  
Element map = document.addElement("map");
map.setText("This is a map");
try {
            response.setContentType("application/xml");           
            PrintWriter writer = response.getWriter();
            OutputFormat format = OutputFormat.createPrettyPrint();
            format.setEncoding("GBK");
            XMLWriter output = new XMLWriter(writer, format);
            output.write(doc);
            output.close();
        } catch (IOException e) {
            // TODO 自动生成 catch 块
            e.printStackTrace();
        }
           }

需要注意的是这里的ContentTyp要设定成"application/xml",否则客户端无法得到响应