01: /*
02: * Licensed to the Apache Software Foundation (ASF) under one or more
03: * contributor license agreements. See the NOTICE file distributed with
04: * this work for additional information regarding copyright ownership.
05: * The ASF licenses this file to You under the Apache License, Version 2.0
06: * (the "License"); you may not use this file except in compliance with
07: * the License. You may obtain a copy of the License at
08: *
09: * http://www.apache.org/licenses/LICENSE-2.0
10: *
11: * Unless required by applicable law or agreed to in writing, software
12: * distributed under the License is distributed on an "AS IS" BASIS,
13: * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14: * See the License for the specific language governing permissions and
15: * limitations under the License.
16: */
17:
18: package org.apache.catalina;
19:
20: import java.io.IOException;
21:
22: import javax.servlet.Filter;
23: import javax.servlet.ServletException;
24:
25: /**
26: * A Comet filter, similar to regular filters, performs filtering tasks on either
27: * the request to a resource (a Comet servlet), or on the response from a resource, or both.
28: * <br><br>
29: * Filters perform filtering in the <code>doFilterEvent</code> method. Every Filter has access to
30: * a FilterConfig object from which it can obtain its initialization parameters, a
31: * reference to the ServletContext which it can use, for example, to load resources
32: * needed for filtering tasks.
33: * <p>
34: * Filters are configured in the deployment descriptor of a web application
35: * <p>
36: * Examples that have been identified for this design are<br>
37: * 1) Authentication Filters <br>
38: * 2) Logging and Auditing Filters <br>
39: * 3) Image conversion Filters <br>
40: * 4) Data compression Filters <br>
41: * 5) Encryption Filters <br>
42: * 6) Tokenizing Filters <br>
43: * 7) Filters that trigger resource access events <br>
44: * 8) XSL/T filters <br>
45: * 9) Mime-type chain Filter <br>
46: * <br>
47: *
48: * @author Remy Maucherat
49: * @author Filip Hanik
50: */
51: public interface CometFilter extends Filter {
52:
53: /**
54: * The <code>doFilterEvent</code> method of the CometFilter is called by the container
55: * each time a request/response pair is passed through the chain due
56: * to a client event for a resource at the end of the chain. The CometFilterChain passed in to this
57: * method allows the Filter to pass on the event to the next entity in the
58: * chain.<p>
59: * A typical implementation of this method would follow the following pattern:- <br>
60: * 1. Examine the request<br>
61: * 2. Optionally wrap the request object contained in the event with a custom implementation to
62: * filter content or headers for input filtering and pass a CometEvent instance containing
63: * the wrapped request to the next filter<br>
64: * 3. Optionally wrap the response object contained in the event with a custom implementation to
65: * filter content or headers for output filtering and pass a CometEvent instance containing
66: * the wrapped request to the next filter<br>
67: * 4. a) <strong>Either</strong> invoke the next entity in the chain using the CometFilterChain object (<code>chain.doFilterEvent()</code>), <br>
68: * 4. b) <strong>or</strong> not pass on the request/response pair to the next entity in the filter chain to block the event processing<br>
69: * 5. Directly set fields on the response after invocation of the next entity in the filter chain.
70: *
71: * @param event the event that is being processed. Another event may be passed along the chain.
72: * @param chain
73: * @throws IOException
74: * @throws ServletException
75: */
76: public void doFilterEvent(CometEvent event, CometFilterChain chain)
77: throws IOException, ServletException;
78:
79: }
|