jakarta.websocket.Decoder Maven / Gradle / Ivy
/*
* Copyright (c) 2018, 2020 Oracle and/or its affiliates and others.
* All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package jakarta.websocket;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.nio.ByteBuffer;
/**
* The Decoder interface holds member interfaces that define how a developer can provide the web socket container a way
* web socket messages into developer defined custom objects. The websocket implementation creates a new instance of the
* decoder per endpoint instance per connection. The lifecycle of the Decoder instance is governed by the container
* calls to the {@link Decoder#init(jakarta.websocket.EndpointConfig)} and {@link Decoder#destroy() } methods.
*
* @author dannycoward
*/
public interface Decoder {
/**
* This method is called with the endpoint configuration object of the endpoint this decoder is intended for when it
* is about to be brought into service.
*
* @implSpec The default implementation takes no action.
*
* @param config the endpoint configuration object when being brought into service
*/
default void init(EndpointConfig config) {
}
/**
* This method is called when the decoder is about to be removed from service in order that any resources the
* decoder used may be closed gracefully.
*
* @implSpec The default implementation takes no action.
*/
default void destroy() {
}
/**
* This interface defines how a custom object (of type T) is decoded from a web socket message in the form of a byte
* buffer.
*
* @param The type of the object that is decoded
*/
interface Binary extends Decoder {
/**
* Decode the given bytes into an object of type T.
*
* It is not safe for other threads to use the ByteBuffer until the decoding of the given bytes is complete. If
* the decoding completes successfully, the buffer's limit will be unchanged and the buffer's position
* will be equal to the limit. If the decoding does not complete successfully, the state of the buffer is
* undefined.
*
* @param bytes the bytes to be decoded.
* @return the decoded object.
*
* @throws DecodeException If the provided bytes cannot be decoded to type T
*/
T decode(ByteBuffer bytes) throws DecodeException;
/**
* Answer whether the given bytes can be decoded into an object of type T.
*
* It is not safe for other threads to use the ByteBuffer until this method completes. When the method
* completes, the buffer will be in the same state as it was at the start of the method call.
*
* @param bytes the bytes to be decoded.
* @return whether or not the bytes can be decoded by this decoder.
*/
boolean willDecode(ByteBuffer bytes);
}
/**
* This interface defines how a custom object is decoded from a web socket message in the form of a binary stream.
*
* @param The type of the object that is decoded
*/
interface BinaryStream extends Decoder {
/**
* Decode the given bytes read from the input stream into an object of type T.
*
* @param is the input stream carrying the bytes.
* @return the decoded object.
*
* @throws DecodeException If the provided input stream cannot be decoded to type T
* @throws IOException If an error occurs reading the input stream
*/
T decode(InputStream is) throws DecodeException, IOException;
}
/**
* This interface defines how a custom object is decoded from a web socket message in the form of a string.
*
* @param The type of the object that is decoded
*/
interface Text extends Decoder {
/**
* Decode the given String into an object of type T.
*
* @param s string to be decoded.
* @return the decoded message as an object of type T
*
* @throws DecodeException If the provided string cannot be decoded to type T
*/
T decode(String s) throws DecodeException;
/**
* Answer whether the given String can be decoded into an object of type T.
*
* @param s the string being tested for decodability.
* @return whether this decoder can decoded the supplied string.
*/
boolean willDecode(String s);
}
/**
* This interface defines how a custom object of type T is decoded from a web socket message in the form of a
* character stream.
*
* @param The type of the object that is decoded
*/
interface TextStream extends Decoder {
/**
* Reads the websocket message from the implementation provided Reader and decodes it into an instance of the
* supplied object type.
*
* @param reader the reader from which to read the web socket message.
* @return the instance of the object that is the decoded web socket message.
*
* @throws DecodeException If the data from the provided reader cannot be decoded to type T
* @throws IOException If an error occurs reading from the reader
*/
T decode(Reader reader) throws DecodeException, IOException;
}
}