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Tutorials > Servlet > Servlet Request and Response

Servlet Request and Response

Servlet Request and Response are important concepts in building web applications using Servlets. The Servlet Request represents an incoming HTTP request from a client, and the Servlet Response represents the outgoing HTTP response to the client.

Here's an example of how to use the Servlet Request and Response objects:

java
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public class MyServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // Get request parameters
        String name = request.getParameter("name");

        // Set response content type
        response.setContentType("text/html");

        // Write response
        PrintWriter out = response.getWriter();
        out.println("<html><body>");
        out.println("Hello, " + name + "!");
        out.println("</body></html>");
    }
}

In this example, the doGet() method of a Servlet handles an incoming HTTP GET request from a client. The HttpServletRequest object represents the incoming request, and the HttpServletResponse object represents the outgoing response.

The getParameter() method is used to retrieve the value of the "name" parameter from the request. The setContentType() method is used to set the content type of the response to "text/html". Finally, the getWriter() method is used to obtain a PrintWriter object, which is used to write the response output.

Here's another example that demonstrates how to set response headers and cookies:

java
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public class MyServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // Set response headers
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Pragma", "no-cache");
        response.setDateHeader("Expires", 0);

        // Set response cookie
        Cookie cookie = new Cookie("username", "john");
        cookie.setMaxAge(60 * 60 * 24 * 365); // 1 year
        response.addCookie(cookie);

        // Write response
        PrintWriter out = response.getWriter();
        out.println("<html><body>");
        out.println("Response headers and cookie have been set.");
        out.println("</body></html>");
    }
}

In this example, the doGet() method sets three response headers (Cache-Control, Pragma, and Expires) to prevent caching of the response. It also sets a cookie named "username" with a value of "john" that will expire in one year.

The addCookie() method is used to add the cookie to the response, and the getWriter() method is used to obtain a PrintWriter object to write the response output.

By using the Servlet Request and Response objects, you can handle incoming HTTP requests and generate appropriate responses to send back to the client. These examples demonstrate just a few of the many ways in which you can use the Servlet API to build powerful web applications.



Next: Servlet Annotations

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