1 package org.apache.turbine.pipeline; 2 3 4 /* 5 * Licensed to the Apache Software Foundation (ASF) under one 6 * or more contributor license agreements. See the NOTICE file 7 * distributed with this work for additional information 8 * regarding copyright ownership. The ASF licenses this file 9 * to you under the Apache License, Version 2.0 (the 10 * "License"); you may not use this file except in compliance 11 * with the License. You may obtain a copy of the License at 12 * 13 * http://www.apache.org/licenses/LICENSE-2.0 14 * 15 * Unless required by applicable law or agreed to in writing, 16 * software distributed under the License is distributed on an 17 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 18 * KIND, either express or implied. See the License for the 19 * specific language governing permissions and limitations 20 * under the License. 21 */ 22 23 24 import java.io.IOException; 25 26 import org.apache.turbine.util.TurbineException; 27 28 /** 29 * <p>A <b>Valve</b> is a request processing component. A series of 30 * Valves are generally associated with each other into a Pipeline. 31 * The detailed contract for a Valve is included in the description of 32 * the <code>invoke()</code> method below.</p> 33 * 34 * <b>HISTORICAL NOTE</b>: The "Valve" name was assigned to this concept 35 * because a valve is what you use in a real world pipeline to control and/or 36 * modify flows through it. 37 * 38 * @author Craig R. McClanahan 39 * @author Gunnar Rjnning 40 * @author Peter Donald 41 * @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a> 42 * 43 * @see #invoke(PipelineData, ValveContext) 44 */ 45 @FunctionalInterface 46 public interface Valve 47 { 48 /** 49 * <p>Perform request processing as required by this Valve.</p> 50 * 51 * <p>An individual Valve <b>MAY</b> perform the following actions, in 52 * the specified order:</p> 53 * <ul> 54 * <li>Examine and/or modify the properties of the specified Request and 55 * Response. 56 * <li>Examine the properties of the specified Request, completely generate 57 * the corresponding Response, and return control to the caller. 58 * <li>Examine the properties of the specified Request and Response, wrap 59 * either or both of these objects to supplement their functionality, 60 * and pass them on. 61 * <li>If the corresponding Response was not generated (and control was not 62 * returned, call the next Valve in the pipeline (if there is one) by 63 * executing <code>context.invokeNext()</code>. 64 * <li>Examine, but not modify, the properties of the resulting Response 65 * (which was created by a subsequently invoked Valve via a 66 * call to <code>context.invokeNext()</code>). 67 * </ul> 68 * 69 * <p>A Valve <b>MUST NOT</b> do any of the following things:</p> 70 * <ul> 71 * <li>Change request properties that have already been used to direct 72 * the flow of processing control for this request. 73 * <li>Create a completed Response <strong>AND</strong> pass this 74 * Request and Response on to the next Valve in the pipeline. 75 * <li>Consume bytes from the input stream associated with the Request, 76 * unless it is completely generating the response, or wrapping the 77 * request before passing it on. 78 * <li>Modify the HTTP headers included with the Response after the 79 * <code>invokeNext()</code> method has returned. 80 * <li>Perform any actions on the output stream associated with the 81 * specified Response after the <code>invokeNext()</code> method has 82 * returned. 83 * </ul> 84 * 85 * @param pipelineData The run-time information, including the servlet 86 * request and response we are processing. 87 * @param context The valve context used to invoke the next valve 88 * in the current processing pipeline 89 * 90 * @throws IOException Thrown by a subsequent Valve. 91 * @throws TurbineException Thrown by a subsequent Valve. 92 */ 93 void invoke(PipelineData pipelineData, ValveContext context) 94 throws IOException, TurbineException; 95 96 /** 97 * Initialize the valve before using in a pipeline. 98 * @throws Exception if initialization fails 99 */ 100 default void initialize() throws Exception 101 { 102 // empty 103 } 104 }