Servlet - ServletResponse (MIME Types)

MIME types represent the type of response being sent to the end user.

Setting content type — 2 ways:

• By ServletResponse: resp.setContentType("text/html");
• By HttpServletResponse: resp.setHeader("content-type", "text/html");

Changing the MIME type to application/msword causes the browser to open the response as a Word document instead of rendering it as HTML.

<h1><table border=1>
<tr><th>NAME</th><th>RANK</th></tr>
<tr><td>SUNNY</td><td>1</td></tr>
<tr><td>MALLIKA</td><td>2</td></tr>
<tr><td>VEENA</td><td>3</td></tr>
<tr><td>MALLIKA ARORA</td><td>4</td></tr></h1>
      

Text Stream (PrintWriter):

Used to send text data as response. Obtained via resp.getWriter().

Binary Stream (ServletOutputStream):

Used to send binary data (images, video, audio). Obtained via resp.getOutputStream().

Note: Within a servlet, you can get either PrintWriter or ServletOutputStream, but not both. Trying to get both throws java.lang.IllegalStateException.

Folder structure: advapps1G/ → sunny.jpg, WEB-INF/ → classes/ → BinaryStreamDemoServlet.class

Folder structure: advapps1GA/ → dhoni.mp4, WEB-INF/ → classes/ → BinaryStreamDemoServlet.class

Sometimes we need to redirect an HTTP request to another URL. Use sendRedirect() from HttpServletResponse:

public void sendRedirect(String targetPath) throws IOException

Process of Redirection:

1. Browser sends a request to servlet-1
2. If servlet-1 is not responsible for the response, it updates the browser to contact servlet-2 by setting status code 302 and Location header with servlet-2's URL
3. By seeing 302 status code, the browser creates a new request and sends it to servlet-2
4. Servlet-2 provides the required response (200) to the browser

Note: After committing the response, redirection is not allowed (throws IllegalStateException). Redirection happens at the client side (browser side).

Real-world example: When you request google.com, the request is redirected to google.co.in.

Folder structure: advapps1H/ → WEB-INF/ → classes/ → FirstServlet.class, SecondServlet.class

<h1>Hi This is Second Servlet</h1>
      

A Cookie is a key-value pair used in session management.

Creating and adding a cookie:

Cookie c = new Cookie("durga", "java");
resp.addCookie(c);

To Set Response Headers:

• setHeader()
• addHeader()
• setIntHeader()
• addIntHeader()
• setDateHeader()
• addDateHeader()

To Set Content-Type:

resp.setContentType("text/html"); OR resp.setHeader("Content-Type", "text/html");

To Acquire Text Stream:

PrintWriter out = resp.getWriter();

To Acquire Binary Stream:

ServletOutputStream os = resp.getOutputStream();

To Redirect Request:

resp.sendRedirect("/advapps1A/test"); OR

resp.setStatus(302); resp.setHeader("Location", "/advapps1A/test");