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WebSocket client implementation in Java.
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/*
* Copyright (C) 2015-2016 Neo Visionaries Inc.
*
* 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 com.neovisionaries.ws.client;
import java.util.LinkedHashMap;
import java.util.Map;
/**
* A class to hold the name and the parameters of
* a WebSocket extension.
*/
public class WebSocketExtension
{
/**
* The name of permessage-deflate extension that is
* defined in 7. The "permessage-deflate" Extension in RFC 7692.
*
* @since 1.17
*/
public static final String PERMESSAGE_DEFLATE = "permessage-deflate";
private final String mName;
private final Map mParameters;
/**
* Constructor with an extension name.
*
* @param name
* The extension name.
*
* @throws IllegalArgumentException
* The given name is not a valid token.
*/
public WebSocketExtension(String name)
{
// Check the validity of the name.
if (Token.isValid(name) == false)
{
// The name is not a valid token.
throw new IllegalArgumentException("'name' is not a valid token.");
}
mName = name;
mParameters = new LinkedHashMap();
}
/**
* Copy constructor.
*
* @param source
* A source extension. Must not be {@code null}.
*
* @throws IllegalArgumentException
* The given argument is {@code null}.
*
* @since 1.6
*/
public WebSocketExtension(WebSocketExtension source)
{
if (source == null)
{
// If the given instance is null.
throw new IllegalArgumentException("'source' is null.");
}
mName = source.getName();
mParameters = new LinkedHashMap(source.getParameters());
}
/**
* Get the extension name.
*
* @return
* The extension name.
*/
public String getName()
{
return mName;
}
/**
* Get the parameters.
*
* @return
* The parameters.
*/
public Map getParameters()
{
return mParameters;
}
/**
* Check if the parameter identified by the key is contained.
*
* @param key
* The name of the parameter.
*
* @return
* {@code true} if the parameter is contained.
*/
public boolean containsParameter(String key)
{
return mParameters.containsKey(key);
}
/**
* Get the value of the specified parameter.
*
* @param key
* The name of the parameter.
*
* @return
* The value of the parameter. {@code null} may be returned.
*/
public String getParameter(String key)
{
return mParameters.get(key);
}
/**
* Set a value to the specified parameter.
*
* @param key
* The name of the parameter.
*
* @param value
* The value of the parameter. If not {@code null}, it must be
* a valid token. Note that RFC 6455 says "When using the quoted-string syntax
* variant, the value after quoted-string unescaping MUST
* conform to the 'token' ABNF."
*
* @return
* {@code this} object.
*
* @throws IllegalArgumentException
*
* - The key is not a valid token.
*
- The value is not {@code null} and it is not a valid token.
*
*/
public WebSocketExtension setParameter(String key, String value)
{
// Check the validity of the key.
if (Token.isValid(key) == false)
{
// The key is not a valid token.
throw new IllegalArgumentException("'key' is not a valid token.");
}
// If the value is not null.
if (value != null)
{
// Check the validity of the value.
if (Token.isValid(value) == false)
{
// The value is not a valid token.
throw new IllegalArgumentException("'value' is not a valid token.");
}
}
mParameters.put(key, value);
return this;
}
/**
* Stringify this object into the format "{name}[; {key}[={value}]]*".
*/
@Override
public String toString()
{
StringBuilder builder = new StringBuilder(mName);
for (Map.Entry entry : mParameters.entrySet())
{
// "; {key}"
builder.append("; ").append(entry.getKey());
String value = entry.getValue();
if (value != null && value.length() != 0)
{
// "={value}"
builder.append("=").append(value);
}
}
return builder.toString();
}
/**
* Validate this instance. This method is expected to be overridden.
*/
void validate() throws WebSocketException
{
}
/**
* Parse a string as a {@link WebSocketExtension}. The input string
* should comply with the format described in 9.1. Negotiating
* Extensions in RFC 6455.
*
* @param string
* A string that represents a WebSocket extension.
*
* @return
* A new {@link WebSocketExtension} instance that represents
* the given string. If the input string does not comply with
* RFC 6455, {@code null} is returned.
*/
public static WebSocketExtension parse(String string)
{
if (string == null)
{
return null;
}
// Split the string by semi-colons.
String[] elements = string.trim().split("\\s*;\\s*");
if (elements.length == 0)
{
// Even an extension name is not included.
return null;
}
// The first element is the extension name.
String name = elements[0];
if (Token.isValid(name) == false)
{
// The extension name is not a valid token.
return null;
}
// Create an instance for the extension name.
WebSocketExtension extension = createInstance(name);
// For each "{key}[={value}]".
for (int i = 1; i < elements.length; ++i)
{
// Split by '=' to get the key and the value.
String[] pair = elements[i].split("\\s*=\\s*", 2);
// If {key} is not contained.
if (pair.length == 0 || pair[0].length() == 0)
{
// Ignore.
continue;
}
// The name of the parameter.
String key = pair[0];
if (Token.isValid(key) == false)
{
// The parameter name is not a valid token.
// Ignore this parameter.
continue;
}
// The value of the parameter.
String value = extractValue(pair);
if (value != null)
{
if (Token.isValid(value) == false)
{
// The parameter value is not a valid token.
// Ignore this parameter.
continue;
}
}
// Add the pair of the key and the value.
extension.setParameter(key, value);
}
return extension;
}
private static String extractValue(String[] pair)
{
if (pair.length != 2)
{
return null;
}
return Token.unquote(pair[1]);
}
private static WebSocketExtension createInstance(String name)
{
if (PERMESSAGE_DEFLATE.equals(name))
{
return new PerMessageDeflateExtension(name);
}
return new WebSocketExtension(name);
}
}