javax.servlet.http.HttpFilter Maven / Gradle / Ivy
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package javax.servlet.http;
import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.GenericFilter;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
/**
*
* Provides an abstract class to be subclassed to create
* an HTTP filter suitable for a Web site. A subclass of
* HttpFilter should override {@link #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.
*
* @author Various
*
* @since Servlet 4.0
*/
public abstract class HttpFilter extends GenericFilter
{
/**
*
Does nothing, because this is an abstract class.
*
* @since 4.0
*/
public HttpFilter() { }
/**
*
* 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 {@code req} and {@code res}
* objects to determine if they are instances of {@link HttpServletRequest}
* and {@link HttpServletResponse}, respectively. If not, a {@link ServletException} is thrown.
* Otherwise, the protected {@link #doFilter(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, javax.servlet.FilterChain)}
* method is called.
*
* @param req a {@link ServletRequest} object that
* contains the request the client has made
* of the filter
*
* @param res a {@link ServletResponse} object that
* contains the response the filter sends
* to the client
*
* @param 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
*
* @throws ServletException if the request for the could not be handled or
* either parameter is not an instance of the respective {@link HttpServletRequest}
* or {@link HttpServletResponse}.
*
* @since Servlet 4.0
*/
@Override
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
if (!(req instanceof HttpServletRequest &&
res instanceof HttpServletResponse)) {
throw new ServletException("non-HTTP request or response");
}
this.doFilter((HttpServletRequest)req, (HttpServletResponse)res, 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.
* The FilterChain passed in to this method allows the Filter to pass
* on the request and response to the next entity in the chain.
*
* The default implementation simply calls {@link FilterChain#doFilter}
*
* @param req a {@link HttpServletRequest} object that
* contains the request the client has made
* of the filter
*
* @param res a {@link HttpServletResponse} object that
* contains the response the filter sends
* to the client
*
* @param 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
*
* @throws ServletException if the request for the could not be handled
*
* @since Servlet 4.0
*/
protected void doFilter(HttpServletRequest req, HttpServletResponse res, FilterChain chain) throws IOException, ServletException {
chain.doFilter(req, res);
}
}