Servlet URL call in JSP using AJAX

Question

Appreciate if someone could assist me on this. i have a servlet coded already (Its a http url). I would need to access the servlet in JSP to get the data using ajax. can someone tel me how to obtain this?

url link below is given for sample.

$.ajax({
                type: 'GET',
                data : {  },
                success: function(data) {
                    console.log(data);     
                     });

Answer 1

Parlad highlights an important common practice in AJAX design is that XML has been replaced by JSON (therefore do we now implement AJAJ?).

But for your question you probably need to focus a little higher. If this is truly an AJAX request then you probably don't wan't to implement the service as a JSP. JSP is a templated frame work for dynamic web pages. Even though for a simple hello world connection test it is easy to write a scriptlet to return static content.

Rather your best implementation is true servlet.

Spend some time reading here:

• Servlets and JSP Pages Best Practices
• What is the difference between JSF, Servlet and JSP?

Here is a sample servlet that is useful for understanding how to process the request.

package com.reallysimpleservice.web;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import java.util.Map;
import java.util.concurrent.*;

import javax.naming.Context;
import javax.naming.InitialContext; 
import javax.naming.NamingException;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class servAjax
*/
//@WebServlet(name = "ServAjax", urlPatterns = { "/write/*", "/read/*" })
public class SimplyServed extends HttpServlet {
private ServletContext servContext;
private ServletConfig config;

/**
 * @see HttpServlet#HttpServlet()
 */
public SimplyServed() {
    super();
}

public void init()  throws ServletException
{
}

/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    doPost(request,response);
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

response.setContentType("text/html; charset=UTF-8");
response.setCharacterEncoding("UTF-8");
PrintWriter responseOut = response.getWriter();

System.out.println("SimplyServed");

this.servContext = this.getServletContext();

 System.out.println("<Begin>");

 System.out.println("request.getParameter(\"whom\") = "+request.getParameter("whom")+"<br>");        

 System.out.println("servContext.getInitParameter(\"jdbcURL\") = "+servContext.getInitParameter("jdbcURL")+"<br>");
 System.out.println("servContext.getInitParameter(\"dataService\") = "+servContext.getInitParameter("dataService")+"<br>");
 System.out.println("request.getAttributeNames().hasMoreElements() = "+request.getAttributeNames().hasMoreElements()+"<br>");
 if(request.getAttributeNames().hasMoreElements()) {
     System.out.println("request.getAttributeNames().nextElement() = "+request.getAttributeNames().nextElement()+"<br>");
 }
 System.out.println("request.getHeaderNames().hasMoreElements() = "+request.getHeaderNames().hasMoreElements()+"<br>");
 Enumeration<String> hnames = request.getHeaderNames();
 String hname = "";
 while(hnames.hasMoreElements()) {
        hname = (String) hnames.nextElement();
        System.out.println("request.getHeaderNames().nextElement() = "+hname+"<br>");
        System.out.println("request.getHeader("+hname+") = "+request.getHeader(hname)+"<br>");
 }   
 System.out.println("request.getAuthType() = "+request.getAuthType()+"<br>");
 System.out.println("request.getCharacterEncoding() = "+request.getCharacterEncoding()+"<br>");
 System.out.println("request.getContentLength() = "+request.getContentLength()+"<br>");
 System.out.println("request.getContentType() = "+request.getContentType()+"<br>");
 System.out.println("request.getContextPath() = "+request.getContextPath()+"<br>");
 System.out.println("request.getRequestedSessionId() = "+request.getRequestedSessionId()+"<br>");
 System.out.println("request.getRequestURI() = "+request.getRequestURI()+"<br>");
 System.out.println("request.getLocalAddr() = "+request.getLocalAddr()+"<br>");
 System.out.println("request.getLocalName() = "+request.getLocalName()+"<br>");
 System.out.println("request.getLocalPort() = "+request.getLocalPort()+"<br>");
 System.out.println("request.getMethod() = "+request.getMethod()+"<br>");
 try {
    System.out.println("request.getPart() = "+request.getPart("mime-type")+"<br>");
} catch (IllegalStateException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
} catch (ServletException e) {
    e.printStackTrace();
}
 System.out.println("request.getPathTranslated() = "+request.getPathTranslated()+"<br>");
 System.out.println("request.getPathInfo() = "+request.getPathInfo() +"<br>");
 System.out.println("request.getProtocol() = "+request.getProtocol()+"<br>");
 System.out.println("request.getQueryString() = "+request.getQueryString()+"<br>");
 System.out.println("request.getRequestedSessionId() = "+request.getRequestedSessionId()+"<br>");
 System.out.println("request.getServletPath() = "+request.getServletPath()+"<br>");
 System.out.println("request.isRequestedSessionIdFromCookie() = "+request.isRequestedSessionIdFromCookie()+"<br>");
 System.out.println("request.isRequestedSessionIdFromURL() = "+request.isRequestedSessionIdFromURL()+"<br>");
 System.out.println("request.isRequestedSessionIdValid() = "+request.isRequestedSessionIdValid()+"<br>");
 System.out.println("request.isSecure() = "+request.isSecure()+"<br>");
 System.out.println("request.getSession() = "+request.getSession()+"<br>");
 System.out.println("request.getUserPrincipal() = "+request.getUserPrincipal()+"<br>");
 System.out.println("request.isAsyncStarted() = "+request.isAsyncStarted()+"<br>");
 System.out.println("request.isAsyncSupported() = "+request.isAsyncSupported()+"<br>");
 System.out.println("</End>");


String resourceServlet = "";
String resourcePath = "";
String whom="";

resourceServlet = request.getServletPath();
resourcePath = request.getPathInfo();
whom=request.getParameter("whom");

responseOut.print("Hello "+whom);

   }

}

And the Java Script to call it. Uses a global event handler - so alternative example for processing the response.

<script type="text/javascript" src="ScriptLibrary/jquery-1.10.2.js"></script>
<script type="text/javascript" src="ScriptLibrary/jquery.json-2.4.min.js"></script>

<script>
var objCounter;

function ajaxReq(ajaxQuery, mimeType, serv, path){
  // confirm("ajaxQuery"+ajaxQuery);
  // confirm("mimeType"+mimeType);
  // confirm("serv"+serv);
  //  confirm("path"+path);
var slash = "/";
if (typeof serv == "undefined"){serv="";path="";slash="";}
if (typeof path == "undefined"){path="";slash="";}
if (serv == ""){path="";slash="";}
if (path == ""){slash="";}
var ajaxHREF = serv+slash+path;

$.ajax({
    url: ajaxHREF,
    type: "post",
    data: ajaxQuery,         
    beforeSend: function ( xhr ) {
        xhr.overrideMimeType(mimeType);
        },
    success: function(response, textStatus, jqXHR){ 
        },         
    error: function(jqXHR, textStatus, errorThrown){             
        console.log("JSQL ajax error: " + textStatus + ", " + errorThrown);
        console.log(jqXHR.responseText);
        }, 
    complete: function(){
        }
    });     
}


function getGreeting() {
    //var mimeType = "application/xml";
      //var mimeType = "text/html";
    //var mimeType = "application/json";
    //var mimeType = "image/svg+xml";
      var ajaxQuery =  'whom='+$('#helloWhom').find('.whom').val();
  ajaxReq(ajaxQuery, mimeType, 'simply', 'served');
}

$(document).ajaxSuccess(function(event, xhr, settings) {
if (typeof settings.data == 'undefined') {return false;}
if (typeof settings.mimeType == 'undefined') {return false;}
    var query = settings.data;
    var mimeType = settings.mimeType;
    if (query.match(/whom/)){
        if(mimeType.match(/application\/xml/)){
        }
        if(mimeType.match(/text\/html/)){
            $('#divGreeting').text(xhr.responseText);
            }
        if(mimeType.match(/application\/json/)){
            }
        if(mimeType.match(/image\/svg\+xml/)){
            }
    }
});
</script>

Answer 2

Here is little information about ajax and how to use it.

Here is sample ajax request code with json file ,

$.ajax({
            url : 'your_servlet_url',
            type : 'POST',
            dataType : 'json',// 
            data : {
                var yourVariable : jsonData // jsonData is jsonFormated data
            },
            contentType : 'application/json',
            complete : function(response) {
                 console.log(response);  
                }

            }
        });

In servlet , get json data like

JSONObject jObj = new JSONObject(request.getParameter("yourVariable"));
String myIndividualData = jObj.get("myIndividualDataFromJsp").toString().trim();

And you can retrieve the json data like this.

ObjectMapper mapper = new ObjectMapper();
String jsonString = mapper.writeValueAsString(dataYouWantToSend);
resp.getWriter().write(jsonString);

what goes in data :{} is the data you want to send to the servlet. This is how you can work ajax with json, there could be many different ways, since you don't specify which data time and don't forget to add the json jar, Here is the link.