/*
* Copyright (c) 2002-2012 Alibaba Group Holding Limited.
* All rights reserved.
*
* 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.alibaba.citrus.service.requestcontext.session.idgen.random.impl;
import static com.alibaba.citrus.util.Assert.*;
import static com.alibaba.citrus.util.ObjectUtil.*;
import java.security.SecureRandom;
import java.util.Random;
import com.alibaba.citrus.service.requestcontext.session.SessionIDGenerator;
import com.alibaba.citrus.springext.support.BeanSupport;
import com.alibaba.citrus.util.ToStringBuilder;
import org.apache.commons.codec.binary.Base64;
/**
* 用随机数生成session ID的机制。
*
* @author Michael Zhou
*/
public class RandomIDGenerator extends BeanSupport implements SessionIDGenerator {
private Integer length;
private Random rnd;
public int getLength() {
return length;
}
public void setLength(int length) {
this.length = length;
}
@Override
protected void init() {
length = defaultIfNull(length, SESSION_ID_LENGTH_DEFAULT);
try {
rnd = new SecureRandom();
} catch (Throwable e) {
rnd = new Random();
}
}
public String generateSessionID() {
assertInitialized();
byte[] bytes = new byte[(length + 3) / 4 * 3];
rnd.nextBytes(bytes);
byte[] b64Encoded = Base64.encodeBase64(bytes);
StringBuilder buf = new StringBuilder(length);
for (int i = 0; i < length; i++) {
char ch = (char) b64Encoded[i];
// 替换掉/和+，因为这两个字符在url中有特殊用处。
switch (ch) {
case '/':
ch = '$';
break;
case '+':
ch = '-';
break;
case '=':
unreachableCode();
}
buf.append(ch);
}
return buf.toString();
}
@Override
public String toString() {
return new ToStringBuilder().append("RandomSessionIDGenerator[length=").append(length).append("]").toString();
}
}