org.springframework.web.socket.sockjs.frame.AbstractSockJsMessageCodec Maven / Gradle / Ivy
/*
* Copyright 2002-2018 the original author or authors.
*
* 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
*
* https://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.springframework.web.socket.sockjs.frame;
import org.springframework.util.Assert;
/**
* An base class for SockJS message codec that provides an implementation of
* {@link #encode(String[])}.
*
* @author Rossen Stoyanchev
* @since 4.0
*/
public abstract class AbstractSockJsMessageCodec implements SockJsMessageCodec {
@Override
public String encode(String... messages) {
Assert.notNull(messages, "messages must not be null");
StringBuilder sb = new StringBuilder();
sb.append("a[");
for (int i = 0; i < messages.length; i++) {
sb.append('"');
char[] quotedChars = applyJsonQuoting(messages[i]);
sb.append(escapeSockJsSpecialChars(quotedChars));
sb.append('"');
if (i < messages.length - 1) {
sb.append(',');
}
}
sb.append(']');
return sb.toString();
}
/**
* Apply standard JSON string quoting (see https://www.json.org/).
*/
protected abstract char[] applyJsonQuoting(String content);
/**
* See "JSON Unicode Encoding" section of SockJS protocol.
*/
private String escapeSockJsSpecialChars(char[] characters) {
StringBuilder result = new StringBuilder();
for (char c : characters) {
if (isSockJsSpecialChar(c)) {
result.append('\\').append('u');
String hex = Integer.toHexString(c).toLowerCase();
for (int i = 0; i < (4 - hex.length()); i++) {
result.append('0');
}
result.append(hex);
}
else {
result.append(c);
}
}
return result.toString();
}
/**
* See `escapable_by_server` variable in the SockJS protocol test suite.
*/
private boolean isSockJsSpecialChar(char ch) {
return (ch <= '\u001F') || (ch >= '\u200C' && ch <= '\u200F') ||
(ch >= '\u2028' && ch <= '\u202F') || (ch >= '\u2060' && ch <= '\u206F') ||
(ch >= '\uFFF0') || (ch >= '\uD800' && ch <= '\uDFFF');
}
}