Package javax.servlet.http

Class HttpFilter

java.lang.Object

javax.servlet.GenericFilter

javax.servlet.http.HttpFilter

All Implemented Interfaces:

Serializable, Filter, FilterConfig

public abstract class HttpFilter
extends GenericFilter

Provides a base class that implements the Filter interface and ensures that the Request and Response are of type HttpServletRequest and HttpServletResponse respectively.

See Also:

• Serialized Form

Constructor Summary

Constructors

Constructor	Description
HttpFilter()

Method Summary

Modifier and Type	Method	Description
protected void	doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain)	The doFilter method of the Filter is called by the container each time a request/response pair is passed through the chain due to a client request for a resource at the end of the chain.
void	doFilter(ServletRequest request, ServletResponse response, FilterChain chain)	The doFilter method of the Filter is called by the container each time a request/response pair is passed through the chain due to a client request for a resource at the end of the chain.

Methods inherited from class javax.servlet.GenericFilter

getFilterConfig, getFilterName, getInitParameter, getInitParameterNames, getServletContext, init, init

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface javax.servlet.Filter

destroy

Constructor Details

HttpFilter

public HttpFilter()

Method Details

doFilter

public void doFilter(ServletRequest request,
 ServletResponse response,
 FilterChain chain)
              throws IOException,
ServletException

The doFilter method of the Filter is called by the container each time a request/response pair is passed through the chain due to a client request for a resource at the end of the chain. The FilterChain passed in to this method allows the Filter to pass on the request and response to the next entity in the chain.

A typical implementation of this method would follow the following pattern:-
1. Examine the request
2. Optionally wrap the request object with a custom implementation to filter content or headers for input filtering
3. Optionally wrap the response object with a custom implementation to filter content or headers for output filtering
4. a) Either invoke the next entity in the chain using the FilterChain object (chain.doFilter()),
4. b) or not pass on the request/response pair to the next entity in the filter chain to block the request processing
5. Directly set headers on the response after invocation of the next entity in the filter chain. This implementation tests the request and response to see if they are instances of HttpServletRequest and HttpServletResponse respectively. If they are then they are passed to doFilter(HttpServletRequest, HttpServletResponse, FilterChain). If not, a ServletException is thrown.

Parameters:

request - The request to process

response - The response associated with the request

chain - Provides access to the next filter in the chain for this filter to pass the request and response to for further processing

Throws:

ServletException - If either the request or response are not of the expected types or any other error occurs

IOException - if an I/O error occurs during this filter's processing of the request

doFilter

protected void doFilter(HttpServletRequest request,
 HttpServletResponse response,
 FilterChain chain)
                 throws IOException,
ServletException

The doFilter method of the Filter is called by the container each time a request/response pair is passed through the chain due to a client request for a resource at the end of the chain. The FilterChain passed in to this method allows the Filter to pass on the request and response to the next entity in the chain.

A typical implementation of this method would follow the following pattern:-
1. Examine the request
2. Optionally wrap the request object with a custom implementation to filter content or headers for input filtering
3. Optionally wrap the response object with a custom implementation to filter content or headers for output filtering
4. a) Either invoke the next entity in the chain using the FilterChain object (chain.doFilter()),
4. b) or not pass on the request/response pair to the next entity in the filter chain to block the request processing
5. Directly set headers on the response after invocation of the next entity in the filter chain. This default implementation simply calls the next filter in the filter chain.

Parameters:

request - The request to process

response - The response associated with the request

chain - Provides access to the next filter in the chain for this filter to pass the request and response to for further processing

Throws:

IOException - if an I/O error occurs during this filter's processing of the request

ServletException - if the processing fails for any other reason