How to acquire a binary stream for the response ?

Method of ServletResponse interface

• ServletOutputStream getOutputStream()
  Returns ServletOutputStream for writing binary data in the response.
  
  Calling flush() on the ServletOutputStream commits the response.

How to acquire a text stream for the response ?

Method of ServletResponse interface

• PrintWriter getWriter()
  Returns a PrintWriter object that can send character text to the client
  
  Calling flush() on the PrintWriter commits the response.

How to set the content type of the response ?

Method of ServletResponse interface

• setContentType(String) 
• Sets the content type of the response being sent to the client 
• It may include character encoding as well. 
• Example : text/html; charset=ISO-8859-4

What will happen if headers are set after the response is committed ?

Headers must be set before the response is committed.

If headers are set after the response is committed, that will be ignored by the servlet container. 

How to set a HTTP response header ?

Methods of the HttpServletResponse interface

• setHeader : sets a header with a given name and value
  If header name already exists, it will replace all the n existing values with 1 new value
• addHeader : adds a header value to a given name
• setIntHeader : sets a int type header
• setDateHeader : sets a Date type header
• addIntHeader : adds a int type header
• addDateHeader : adds a Date type header

* Headers must be set before the response is committed.

How to retrieve HTTP request header information ?

Methods of HttpServletRequest interface

• getHeader : returns a header value by given header name
  If there are multiple headers with the same name, it returns the first head in the request.
  
• getHeaders : returns all the header values associated with the given header name (Enumeration of Strings)
  
• getHeaderNames : returns names of all the headers
  
• getIntHeader : returns header value (String) into int format
  If it cannot translate the header value to an int, a NumberFormatException is thrown.
  
• getDateHeader : returns header value (String) into Date format
  If it cannot translate the header to a Date object, an IllegalArgumentException is thrown.

How to retrieve a servlet initialization parameter ?

Methods of ServletConfig interface

• public String getInitParameter(String)returns a String containing the value of the named initialization parameter, or null if the parameter does not exist.
   
• public Enumeration getInitParameterNames()returns the names of the servlet’s initialization parameters as an Enumeration of String objects.