Comment Form Example using AJAX in Java

In this example, we are creating a form to post comment. The form data is saved in the database and a list of all posted comments are shown below the comment form.

Steps to create comment form example using AJAX in Java

You need to follow following steps:

Create table in database
load the org.json.jar file
Create comment form
Create server side page to save the form data and print all posted comments

Create table in database

In this example, we are using oracle 10g database. The table structure is given below:

The id field of "usercomment" table is auto incremented.

Load the org.json.jar file

download this example, we have included the org.json.jar file inside the WEB-INF/lib directory.

Create comment form

In this page, we have created a form that gets input from the user. When user clicks on the Post Comment button, postComment() function is called. We have written all the ajax code inside this function.

index.html

<!DOCTYPE html>
<html>
<head>
<script>
var request;
function postComment(){
var comment=document.commentform.comment.value;
var email=document.commentform.email.value;

var url="index.jsp?comment="+comment+"&email="+email;

if(window.XMLHttpRequest){
request=new XMLHttpRequest();
}
else if(window.ActiveXObject){
request=new ActiveXObject("Microsoft.XMLHTTP");
}

try{
request.onreadystatechange=function(){
if(request.readyState==4){
var val=request.responseText;
document.getElementById('mylocation').innerHTML=val;
}
}//end of function
request.open("GET",url,true);
request.send();
}catch(e){alert("Unable to connect to server");}
}
</script>
</head>
<body>
<h1>Comment Form</h1>
<form name="commentform">
Enter Comment:<br/>
<textarea name="comment" style="width:300px;height:100px" required>
</textarea><br/>
Enter Email:<br/>
<input type="text" name="email" required/><br/><br/>

<input type="button" value="Post Comment" onclick="postComment()">
</form>

<span id="mylocation"></span>
</body>
</html>

Create server side page to process the request

In this jsp page, we are writing the database code to save the comment and print all comments.

index.jsp

<!DOCTYPE html>
<html>
<head>
<style>
div.box{margin:2px;border:1px solid pink;padding:10px;background-color:#e3e3e3}
</style>
</head>
<body>

<%@ page import="java.sql.*" %>
<%
String comment=request.getParameter("comment");
String email=request.getParameter("email");
if(comment==null||email==null||comment.trim().equals("")||email.trim().equals("")){
out.print("<p>Please write comment</p>");
}else{

try{
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection con=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe","system","oracle");
PreparedStatement ps=con.prepareStatement("insert into usercomment(comment1,email) values(?,?)");
ps.setString(1,comment);
ps.setString(2,email);
int i=ps.executeUpdate();

PreparedStatement ps2=con.prepareStatement("select * from usercomment order by id desc");
ResultSet rs=ps2.executeQuery();

out.print("<hr/><h2>Comments:</h2>");
while(rs.next()){
out.print("<div class='box'>");
out.print("<p>"+rs.getString(2)+"</p>");
out.print("<p><strong>By: "+rs.getString(3)+"</strong></p>");
out.print("</div>");
}

con.close();
}catch(Exception e){out.print(e);}

}//end of else
%>
</body>
</html>

Download this ajax example