001 // Copyright 2005 The Apache Software Foundation
002 //
003 // Licensed under the Apache License, Version 2.0 (the "License");
004 // you may not use this file except in compliance with the License.
005 // You may obtain a copy of the License at
006 //
007 // http://www.apache.org/licenses/LICENSE-2.0
008 //
009 // Unless required by applicable law or agreed to in writing, software
010 // distributed under the License is distributed on an "AS IS" BASIS,
011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012 // See the License for the specific language governing permissions and
013 // limitations under the License.
014
015 package org.apache.tapestry.web;
016
017 import org.apache.tapestry.util.ContentType;
018
019 import java.io.IOException;
020 import java.io.OutputStream;
021 import java.io.PrintWriter;
022
023 /**
024 * Controls the response to the client, and specifically allows for creating the output stream (or
025 * print writer) to which content is sent. This is essentially a generic version of
026 * {@link javax.servlet.http.HttpServletResponse}. Some operations may be unsupported in some
027 * implementations (for example, the portlet implementation can't handle any of the setHeader
028 * methods).
029 *
030 * @author Howard M. Lewis Ship
031 * @since 4.0
032 */
033 public interface WebResponse
034 {
035 /**
036 * Returns a output stream to which output should be sent. This method should only be invoked
037 * once on a response.
038 *
039 * @param contentType
040 * The encoding type that this outputstream will write content as.
041 * @return the output stream, configured for the given type.
042 *
043 * @throws IOException On io error.
044 */
045
046 OutputStream getOutputStream(ContentType contentType)
047 throws IOException;
048
049 /**
050 * Returns a {@link PrintWriter} to which output should be sent. This method should be invoked
051 * once on a response. A second call is expected to be so that an exception page can be
052 * rendered, and the underlying request data is reset.
053 *
054 * @param contentType
055 * The type of content encoding the writer is for.
056 * @return A new {@link PrintWriter} instance.
057 *
058 * @throws IOException On io error.
059 */
060
061 PrintWriter getPrintWriter(ContentType contentType)
062 throws IOException;
063
064 /**
065 * Encodes a URL, which adds information to the URL needed to ensure that the request triggered
066 * by the URL will be associated with the current session (if any). In most cases, the string is
067 * returned unchanged.
068 *
069 * @param url
070 * The URL to encode.
071 * @return The url encoded.
072 */
073
074 String encodeURL(String url);
075
076 /**
077 * Resets any buffered content. This may be used after an error to radically change what the
078 * output will be.
079 */
080
081 void reset();
082
083 /**
084 * Sets the response content length header.
085 *
086 * @param contentLength
087 * The total content length this response will write.
088 */
089 void setContentLength(int contentLength);
090
091 /**
092 * Returns a value to be prefixed or suffixed with any client-side JavaScript elements
093 * (variables and function names) to ensure that they are unique with the context of the entire
094 * page. For servlets, this is the empty string.
095 *
096 * @return The namespace that this requests resources should be pre-pended with.
097 */
098
099 String getNamespace();
100
101 /**
102 * Sets a response header as a date.
103 *
104 * @param name
105 * the name of the header to set
106 * @param date
107 * the date value to set, in milliseconds since the epoch
108 */
109 void setDateHeader(String name, long date);
110
111 /**
112 * Sets a response header as a string.
113 *
114 * @param name
115 * the name of the header to set
116 * @param value
117 * the value for the named header
118 */
119
120 void setHeader(String name, String value);
121
122 /**
123 * Sets a response header with the given name and integer value.
124 *
125 * @param name
126 * the name of the header to set
127 * @param value
128 * the value for the named header
129 */
130 void setIntHeader(String name, int value);
131
132 /**
133 * Sets the status code for this response.
134 *
135 * @param status
136 * The HTTP status code to set on the return header.
137 */
138 void setStatus(int status);
139
140 /**
141 * Sends an error response.
142 *
143 * @param statusCode
144 * The error status code to set on the header.
145 * @param message
146 * The message to give as the reason for error.
147 *
148 * @throws IOException on io error.
149 */
150 void sendError(int statusCode, String message) throws IOException;
151 }