/*
* Response.java February 2001
*
* Copyright (C) 2001, Niall Gallagher <niallg@users.sf.net>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
* implied. See the License for the specific language governing
* permissions and limitations under the License.
*/
package org.simpleframework.http;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
import java.nio.channels.WritableByteChannel;
/**
* This is used to represent the HTTP response. This provides methods that can
* be used to set various characteristics of the response. An
* <code>OutputStream</code> can be acquired via this interface which can be
* used to write the response body. A buffer size can be specified when
* acquiring the output stream which allows data to be buffered until it over
* flows or is flushed explicitly. This buffering allows a partially written
* response body to be reset.
* <p>
* This should never allow the message body be sent if it should not be sent
* with the headers as of RFC 2616 rules for the presence of a message body. A
* message body must not be included with a HEAD request or with a 304 or a 204
* response. A proper implementation of this will prevent a message body being
* sent if the response is to a HEAD request of if there is a 304 or 204
* response code.
* <p>
* It is important to note that the <code>Response</code> controls the
* processing of the HTTP pipeline. The next HTTP request is not processed until
* the response has been sent. To ensure that the response is sent the
* <code>close</code> method of the response or the output stream should be
* used. This will notify the server to dispatch the next request in the
* pipeline for processing.
*
* @author Niall Gallagher
*/
public interface Response extends ResponseHeader {
/**
* This should be used when the size of the message body is known. This
* ensures that Persistent HTTP (PHTTP) connections can be maintained for
* both HTTP/1.0 and HTTP/1.1 clients. If the length of the output is not
* known HTTP/1.0 clients will require a connection close, which reduces
* performance (see RFC 2616).
* <p>
* This removes any previous Content-Length headers from the message header.
* This will then set the appropriate Content-Length header with the correct
* length. If a the Connection header is set with the close token then the
* semantics of the connection are such that the server will close it once
* the output stream or request is closed.
*
* @param length
* this is the length of the HTTP message body
*/
void setContentLength(long length);
/**
* Used to write a message body with the <code>Response</code>. The
* semantics of this <code>OutputStream</code> will be determined by the
* HTTP version of the client, and whether or not the content length has
* been set, through the <code>setContentLength</code> method. If the length
* of the output is not known then the output is chunked for HTTP/1.1
* clients and closed for HTTP/1.0 clients.
*
* @return an output stream object with the specified semantics
*/
OutputStream getOutputStream() throws IOException;
/**
* Used to write a message body with the <code>Response</code>. The
* semantics of this <code>OutputStream</code> will be determined by the
* HTTP version of the client, and whether or not the content length has
* been set, through the <code>setContentLength</code> method. If the length
* of the output is not known then the output is chunked for HTTP/1.1
* clients and closed for HTTP/1.0 clients.
* <p>
* This will ensure that there is buffering done so that the output can be
* reset using the <code>reset</code> method. This will enable the specified
* number of bytes to be written without committing the response. This
* specified size is the minimum size that the response buffer must be.
*
* @return an output stream object with the specified semantics
*/
OutputStream getOutputStream(int size) throws IOException;
/**
* This method is provided for convenience so that the HTTP content can be
* written using the <code>print</code> methods provided by the
* <code>PrintStream</code>. This will basically wrap the
* <code>getOutputStream</code> with a buffer size of zero.
* <p>
* The retrieved <code>PrintStream</code> uses the charset used to describe
* the content, with the Content-Type header. This will check the charset
* parameter of the contents MIME type. So if the Content-Type was
* <code>text/plain; charset=UTF-8</code> the resulting
* <code>PrintStream</code> would encode the written data using the UTF-8
* encoding scheme. Care must be taken to ensure that bytes written to the
* stream are correctly encoded.
* <p>
* Implementations of the <code>Response</code> must guarantee that this can
* be invoked repeatedly without effecting any issued
* <code>OutputStream</code> or <code>PrintStream</code> object.
*
* @return a print stream that provides convenience writing
*/
PrintStream getPrintStream() throws IOException;
/**
* This method is provided for convenience so that the HTTP content can be
* written using the <code>print</code> methods provided by the
* <code>PrintStream</code>. This will basically wrap the
* <code>getOutputStream</code> with a specified buffer size.
* <p>
* The retrieved <code>PrintStream</code> uses the charset used to describe
* the content, with the Content-Type header. This will check the charset
* parameter of the contents MIME type. So if the Content-Type was
* <code>text/plain; charset=UTF-8</code> the resulting
* <code>PrintStream</code> would encode the written data using the UTF-8
* encoding scheme. Care must be taken to ensure that bytes written to the
* stream are correctly encoded.
* <p>
* Implementations of the <code>Response</code> must guarantee that this can
* be invoked repeatedly without effecting any issued
* <code>OutputStream</code> or <code>PrintStream</code> object.
*
* @param size
* the minimum size that the response buffer must be
*
* @return a print stream that provides convenience writing
*/
PrintStream getPrintStream(int size) throws IOException;
/**
* Used to write a message body with the <code>Response</code>. The
* semantics of this <code>WritableByteChannel</code> are determined by the
* HTTP version of the client, and whether or not the content length has
* been set, through the <code>setContentLength</code> method. If the length
* of the output is not known then the output is chunked for HTTP/1.1
* clients and closed for HTTP/1.0 clients.
*
* @return a writable byte channel used to write the message body
*/
WritableByteChannel getByteChannel() throws IOException;
/**
* Used to write a message body with the <code>Response</code>. The
* semantics of this <code>WritableByteChannel</code> are determined by the
* HTTP version of the client, and whether or not the content length has
* been set, through the <code>setContentLength</code> method. If the length
* of the output is not known then the output is chunked for HTTP/1.1
* clients and closed for HTTP/1.0 clients.
* <p>
* This will ensure that there is buffering done so that the output can be
* reset using the <code>reset</code> method. This will enable the specified
* number of bytes to be written without committing the response. This
* specified size is the minimum size that the response buffer must be.
*
* @param size
* the minimum size that the response buffer must be
*
* @return a writable byte channel used to write the message body
*/
WritableByteChannel getByteChannel(int size) throws IOException;
/**
* This represents the time at which the response has fully written. Because
* the response is delivered asynchronously to the client this response time
* does not represent the time to last byte. It simply represents the time
* at which the response has been fully generated and written to the output
* buffer or queue. This returns zero if the response has not finished.
*
* @return this is the time taken to complete the response
*/
long getResponseTime();
/**
* This is used to determine if the HTTP response message is a keep alive
* message or if the underlying socket was closed. Even if the client
* requests a connection keep alive and supports persistent connections, the
* response can still be closed by the server. This can be explicitly
* indicated by the presence of the <code>Connection</code> HTTP header, it
* can also be implicitly indicated by using version HTTP/1.0.
*
* @return this returns true if the connection was closed
*/
boolean isKeepAlive();
/**
* This can be used to determine whether the <code>Response</code> has been
* committed. This is true if the <code>Response</code> was committed,
* either due to an explicit invocation of the <code>commit</code> method or
* due to the writing of content. If the <code>Response</code> has committed
* the <code>reset</code> method will not work in resetting content already
* written.
*
* @return true if the response headers have been committed
*/
boolean isCommitted();
/**
* This is used to write the headers that where given to the
* <code>Response</code>. Any further attempts to give headers to the
* <code>Response</code> will be futile as only the headers that were given
* at the time of the first commit will be used in the message header.
* <p>
* This also performs some final checks on the headers submitted. This is
* done to determine the optimal performance of the output. If no specific
* Connection header has been specified this will set the connection so that
* HTTP/1.0 closes by default.
*
* @exception IOException
* thrown if there was a problem writing
*/
void commit() throws IOException;
/**
* This can be used to determine whether the <code>Response</code> has been
* committed. This is true if the <code>Response</code> was committed,
* either due to an explicit invocation of the <code>commit</code> method or
* due to the writing of content. If the <code>Response</code> has committed
* the <code>reset</code> method will not work in resetting content already
* written.
*
* @throws IOException
* thrown if there is a problem resetting
*/
void reset() throws IOException;
/**
* This is used to close the connection and commit the request. This
* provides the same semantics as closing the output stream and ensures that
* the HTTP response is committed. This will throw an exception if the
* response can not be committed.
*
* @throws IOException
* thrown if there is a problem writing
*/
void close() throws IOException;
}