September 11, 2021
example java server servlets post librariesThis example uses an the Apache Commons Text library to escape user input. Learn more in the java server libraries tutorial.
index.html contains an HTML form:
<!DOCTYPE html>
<html>
<head>
<title>Form</title>
</head>
<body>
<h1>Enter some input:</h1>
<form action="/user-input-escaped/form" method="POST">
<input type="text" name="data" value="<h1>oh no</h1>">
<br><br>
<input type="submit" value="Submit">
</form>
</body>
</html>
FormServlet.java handles the POST
request by escaping the user’s content and outputting it in the response:
package io.happycoding.servlets;
import java.io.IOException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.apache.commons.text.StringEscapeUtils;
@WebServlet("/form")
public class FormServlet extends HttpServlet {
@Override
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws IOException {
String userInput = request.getParameter("data");
String escapedUserInput = StringEscapeUtils.escapeHtml4(userInput);
response.setContentType("text/html");
response.getWriter().println("You entered: " + escapedUserInput);
}
}
Because the servlet escapes the data, the HTML is rendered as text in the output:
See the server libraries tutorial and the sanitizing user input tutorial for more information.
Happy Coding is a community of folks just like you learning about coding.
Do you have a comment or question? Post it here!
Comments are powered by the Happy Coding forum. This page has a corresponding forum post, and replies to that post show up as comments here. Click the button above to go to the forum to post a comment!