Package jakarta.servlet.http

Class HttpFilter

java.lang.Object

jakarta.servlet.GenericFilter

jakarta.servlet.http.HttpFilter

All Implemented Interfaces:

Filter, FilterConfig, Serializable

public abstract class HttpFilter
extends GenericFilter

Provides an abstract class to be subclassed to create an HTTP filter suitable for a Web site. A subclass of HttpFilter should override doFilter(jakarta.servlet.http.HttpServletRequest, jakarta.servlet.http.HttpServletResponse, jakarta.servlet.FilterChain).

Filters typically run on multithreaded servers, so be aware that a filter must handle concurrent requests and be careful to synchronize access to shared resources. Shared resources include in-memory data such as instance or class variables and external objects such as files, database connections, and network connections. See the Java Tutorial on Multithreaded Programming for more information on handling multiple threads in a Java program.

Since:

Servlet 4.0

See Also:

• Serialized Form

Constructor Summary

Constructors

Constructor	Description
HttpFilter()	Does nothing, because this is an abstract class.

Method Summary

Modifier and Type	Method	Description
void	doFilter(ServletRequest req, ServletResponse res, 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 jakarta.servlet.GenericFilter

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

Methods inherited from class java.lang.Object

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

Methods inherited from interface jakarta.servlet.Filter

destroy

Constructor Details

HttpFilter

public HttpFilter()

Does nothing, because this is an abstract class.

Since:

4.0

Method Details

doFilter

public void doFilter(ServletRequest req,
 ServletResponse res,
 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. There's no need to override this method.

The default implementation inspects the incoming req and res objects to determine if they are instances of HttpServletRequest and HttpServletResponse, respectively. If not, a ServletException is thrown. Otherwise, the protected doFilter(jakarta.servlet.http.HttpServletRequest, jakarta.servlet.http.HttpServletResponse, jakarta.servlet.FilterChain) method is called.

Parameters:

req - a ServletRequest object that contains the request the client has made of the filter

res - a ServletResponse object that contains the response the filter sends to the client

chain - the FilterChain for invoking the next filter or the resource

Throws:

IOException - if an input or output error is detected when the filter handles the request

ServletException - if the request for the could not be handled or either parameter is not an instance of the respective HttpServletRequest or HttpServletResponse.

Since:

Servlet 4.0

See Also:

• UnavailableException