Java Servlet API 4.0.1 · javax.servlet.http.HttpFilter

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

Constructor Summary

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

Method Summary

Modifier and Type Method and Description

Modifier and Type	Method and Description
public void	doFilter(ServletRequest a `ServletRequest` object that contains the request the client has made of the filter req, ServletResponse a `ServletResponse` object that contains the response the filter sends to the client res, FilterChain the `FilterChain` for invoking the next filter or the resource chain) Implements javax.servlet.Filter.doFilter. 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.
protected void	doFilter(HttpServletRequest a `HttpServletRequest` object that contains the request the client has made of the filter req, HttpServletResponse a `HttpServletResponse` object that contains the response the filter sends to the client res, FilterChain the `FilterChain` for invoking the next filter or the resource 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.

public void

doFilter(ServletRequest

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

req, ServletResponse

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

res, FilterChain

the FilterChain for invoking the next filter or the resource

chain)

Implements javax.servlet.Filter.doFilter.

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.

protected void

doFilter(HttpServletRequest

a HttpServletRequest object that contains the request the client has made of the filter

req, HttpServletResponse

a HttpServletResponse object that contains the response the filter sends to the client

res, FilterChain

the FilterChain for invoking the next filter or the resource

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.

Inherited from javax.servlet.GenericFilter:: getFilterConfig getFilterName getInitParameter getInitParameterNames getServletContext init init

Constructor Detail

HttpFilter	back to summary
public HttpFilter() Does nothing, because this is an abstract class. Since 4.0

HttpFilter

back to summary

public HttpFilter()

Does nothing, because this is an abstract class.

Since: 4.0

Method Detail

doFilter back to summary

doFilter	back to summary
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException Implements javax.servlet.Filter.doFilter. 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(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, javax.servlet.FilterChain)` method is called. Parameters req:ServletRequest a `ServletRequest` object that contains the request the client has made of the filter res:ServletResponse a `ServletResponse` object that contains the response the filter sends to the client chain:FilterChain the `FilterChain` for invoking the next filter or the resource Annotations @Override Exceptions 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

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException

Implements javax.servlet.Filter.doFilter.

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(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, javax.servlet.FilterChain) method is called.

Parameters

req:ServletRequest: a ServletRequest object that contains the request the client has made of the filter
res:ServletResponse: a ServletResponse object that contains the response the filter sends to the client
chain:FilterChain: the FilterChain for invoking the next filter or the resource

Annotations

@Override

Exceptions

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