javax.servlet

Interface Filter

public interface Filter

a request/response filter. Filters are classes that allow you to change the request and response that a target servlet receives.

Lifecycle

Developers must implement this interface for filtering code and then cause their Filters to be mapped to servlets or url-patterns (normally by using a webapp's deployment descriptor).

When the server loads the filter it causes the init() method to be called with the necessary config information (including init parameters, specified in the webapp's DD perhaps).

When the server recieves requests that match the filter conditions it calls the doFilter() method of the first matching filter. The remaining filters (and the target servlet) are passed in the FilterChain argument. The developer must call the FilterChain.doFilter() method to pass the request on to the next filter.

When the server has finished with the filter it calls the destory() method after the filter has been removed from use.

For more information see section 6 of the Servlet API 2.3 specification.

Since:

2.3

See Also:

for more information on how the chains work

Method Summary

Methods

Modifier and Type	Method and Description
void	destroy() destroy a filter.
void	doFilter(ServletRequest request, ServletResponse response, FilterChain chain) filter the request/response.
void	init(FilterConfig init) initialize a filter.

Method Detail

init

void init(FilterConfig init)
          throws ServletException

initialize a filter.

Parameters:

init - the filter's configuration information (including init params)

Throws:

ServletException

doFilter

void doFilter(ServletRequest request,
            ServletResponse response,
            FilterChain chain)
              throws ServletException,
                     java.io.IOException

filter the request/response.

Parameters:

request - the request to be filtered

response - the response to be filtered

chain - the remaining filters (and the target servlet) in the request chain

Throws:

ServletException

java.io.IOException

destroy

void destroy()

destroy a filter.