GET

Let's say you have a URL with a parameter such as id=12345.

www.example.com?id=12345

The following markup uses JSTL, so lets add the following to the head of your JSP page.

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

The following will print the id (12345 in this example).

<c:out value="${param.id}" />

Or, you can use c:set to store the value in a variable. In this example, the ID is stored in a variable called "id".

<c:set var="id" value="${param.id}" />

You can then print the value using this markup.

${id}

POST to a JSP page

In this example the value in the form is associated with the "username" value are is POST to example.jsp.

<form method="post" action="example.jsp">
  <input type="text" name="username">
</form>

The following markup uses JSTL, so lets add the following to the head of your JSP page.

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

On example.jsp, use the following to display the username value.

<c:out value="${param.username}" />

Or, you can use c:set to store the value in a variable. In this example, the ID is stored in a variable called "username".

<c:set var="username" value="${param.username}" />

You can then print the value using this markup.

${username}

POST to a Servlet

Let's say you have a servlet that contains the following annotation.

@WebServlet("/foo")

In this example the value in the form is associated with the "username" value are is POST to the "foo" servlet.

<form method="post" action="foo">
  <input type="text" name="bar">
</form>

Since the form method is "post", we need to place markup inside of the doPost method in the servlet.

protected void doPost

This markup creates a variable called "bar" that will get the value that was put inside of the HTML form.

String bar = request.getParameter("bar");

We can then use the "bar" variable.

System.out.println(bar);