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JSR 356: Java API for WebSocket
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright (c) 2012-2013 Oracle and/or its affiliates. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License"). You
* may not use this file except in compliance with the License. You can
* obtain a copy of the License at
* http://glassfish.java.net/public/CDDL+GPL_1_1.html
* or packager/legal/LICENSE.txt. See the License for the specific
* language governing permissions and limitations under the License.
*
* When distributing the software, include this License Header Notice in each
* file and include the License file at packager/legal/LICENSE.txt.
*
* GPL Classpath Exception:
* Oracle designates this particular file as subject to the "Classpath"
* exception as provided by Oracle in the GPL Version 2 section of the License
* file that accompanied this code.
*
* Modifications:
* If applicable, add the following below the License Header, with the fields
* enclosed by brackets [] replaced by your own identifying information:
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* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
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*/
package javax.websocket;
import java.io.IOException;
import java.io.OutputStream;
import java.io.Writer;
import java.nio.ByteBuffer;
/**
* The Encoder interface defines how developers can provide a way to convert
* their custom objects into web socket messages. The Encoder interface contains
* subinterfaces that allow encoding algorithms to encode custom objects to: text,
* binary data, character stream and write to an output stream.
* The websocket implementation creates a new instance of the encoder per
* endpoint instance per connection. This means that each encoder instance has
* at most one calling thread at a time.
* The lifecycle of the Encoder instance is governed by the container calls to the
* {@link Encoder#init(javax.websocket.EndpointConfig)} and {@link Encoder#destroy() }
* methods. Developers may subclass the {@link Encoder.Adapter} class to avoid
* having to implement these lifecycle methods if they wish.
*
* @author dannycoward
*/
public interface Encoder {
/**
* This method is called with the endpoint configuration object of the
* endpoint this encoder is intended for when
* it is about to be brought into service.
*
* @param config the endpoint configuration object when being brought into
* service
*/
void init(EndpointConfig config);
/**
* This method is called when the encoder is about to be removed
* from service in order that any resources the encoder used may
* be closed gracefully.
*/
void destroy();
/**
* A convenience class for developers who do not wish to provide any
* special behavior in the init() or destroy() methods.
*/
abstract class Adapter implements Encoder {
/**
* Constructs an adapter.
*/
public Adapter() {
}
/**
* This method does nothing and may be overridden.
*
* @param config the endpoint configuration object when being brought into
* service
*/
@Override
public void init(EndpointConfig config) {}
/**
* This method does nothing and may be overridden.
*
*/
@Override
public void destroy() {}
}
/**
* This interface defines how to provide a way to convert a custom
* object into a text message.
*
* @param The type of the custom developer object that this Encoder can encode into a String.
*/
interface Text extends Encoder {
/**
* Encode the given object into a String.
*
* @param object the object being encoded.
* @return the encoded object as a string.
*/
String encode(T object) throws EncodeException;
}
/**
* This interface may be implemented by encoding algorithms
* that want to write the encoded object to a character stream.
*
* @param the type of the object this encoder can encode to a CharacterStream.
*/
interface TextStream extends Encoder {
/**
* Encode the given object to a character stream writing it
* to the supplied Writer. Implementations of this method may use the EncodeException
* to indicate a failure to convert the supplied object to an encoded form, and may
* use the IOException to indicate a failure to write the data to the supplied
* stream.
*
* @param object the object to be encoded.
* @param writer the writer provided by the web socket runtime to write the encoded data.
* @throws EncodeException if there was an error encoding the object due to its state.
* @throws IOException if there was an exception writing to the writer.
*/
void encode(T object, Writer writer) throws EncodeException, IOException;
}
/**
* This interface defines how to provide a way to convert a custom
* object into a binary message.
*
* @param The type of the custom object that this Encoder can encoder to a ByteBuffer.
*/
interface Binary extends Encoder {
/**
* Encode the given object into a byte array.
*
* @param object the object being encoded.
* @return the binary data.
*/
ByteBuffer encode(T object) throws EncodeException;
}
/**
* This interface may be implemented by encoding algorithms
* that want to write the encoded object to a binary stream.
*
* @param the type of the object this encoder can encode.
*/
interface BinaryStream extends Encoder {
/**
* Encode the given object into a binary stream written to the
* implementation provided OutputStream.
*
* @param object the object being encoded.
* @param os the output stream where the encoded data is written.
*/
void encode(T object, OutputStream os) throws EncodeException, IOException;
}
}