Cannot set property 'innerHTML' of null. Issue with AJAX (java)
Question
So I want to learn AJAX and I wanted to make identical app like the one in here and I pretty much copied it but it doesn't work. I don't know why, I was trying to solve it on my own but can't find any solution.
My .js file is :
function ajaxAsyncRequest(reqURL) {
var xmlhttp;
xmlhttp = new XMLHttpRequest();
xmlhttp.open("GET", reqURL, true);
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4) {
if (xmlhttp.status == 200) {
// How to get message
alert('It\'s K');
document.getElementById("message").innerHTML = xmlhttp.responseText;
alert(xmlhttp.responseText);
} else {
alert('Something is wrong !');
}
}
};
xmlhttp.send(null);
}
The index .jsp is:
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<script type="text/javascript" src="javascript.js"></script>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<input type="button" value="Show Server Time" onclick='ajaxAsyncRequest("getTime")' />
</body>
</html>
and my servlet code is:
import java.io.IOException;
import java.io.PrintWriter;
import java.time.LocalDate;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/getTime")
public class GetTimeServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public GetTimeServlet() {
super();
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
public void doGet (HttpServletRequest request,HttpServletResponse response)
throws ServletException, IOException
{
response.setHeader("Cache-Control", "no-cache");
response.setHeader("Pragma", "no-cache");
PrintWriter out = response.getWriter();
LocalDate currentTime= LocalDate.now();
String message = "Currently time is "+currentTime.toString();
out.write(message);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
}
But when I click on the button I get the message which I pointed in the title in the line document.getElementById("message").innerHTML = xmlhttp.responseText; in .js file. I'm running it through http://localhost:8080/HelloAjax/ , so no local, It loads later than the page, so I have no idea what can it be.
1 answers
solution1
2 2014-07-09 13:17:20
document.getElementById("message") is null because there is no element with id 'message' in the DOM. Try changing your HTML:
<body>
<div id="message"></div>
<input type="button" value="Show Server Time" onclick='ajaxAsyncRequest("getTime")' />
</body>
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