sessionId产生方法参考

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Hibernate JVM Tomcat J#

tomcat

java 代码

protected synchronized String generateSessionId() {
byte random[] = new byte[16];
// Render the result as a String of hexadecimal digits
StringBuffer result = new StringBuffer();
int resultLenBytes = 0;
while (resultLenBytes < this.sessionIdLength) {
getRandomBytes(random);
random = getDigest().digest(random);
for (int j = 0;
j < random.length && resultLenBytes < this.sessionIdLength;
j++) {
byte b1 = (byte) ((random[j] & 0xf0) >> 4);
byte b2 = (byte) (random[j] & 0x0f);
if (b1 < 10)
result.append((char) ('0' + b1));
else
result.append((char) ('A' + (b1 - 10)));
if (b2 < 10)
result.append((char) ('0' + b2));
else
result.append((char) ('A' + (b2 - 10)));
resultLenBytes++;
}
}
return (result.toString());
}

hibernate uuid：

java 代码

public abstract class AbstractUUIDGenerator implements IdentifierGenerator {
private static final int IP;
static {
int ipadd;
try {
ipadd = BytesHelper.toInt( InetAddress.getLocalHost().getAddress() );
}
catch (Exception e) {
ipadd = 0;
}
IP = ipadd;
}
private static short counter = (short) 0;
private static final int JVM = (int) ( System.currentTimeMillis() >>> 8 );
public AbstractUUIDGenerator() {
}
/**
* Unique across JVMs on this machine (unless they load this class
* in the same quater second - very unlikely)
*/
protected int getJVM() {
return JVM;
}
/**
* Unique in a millisecond for this JVM instance (unless there
* are > Short.MAX_VALUE instances created in a millisecond)
*/
protected short getCount() {
synchronized(AbstractUUIDGenerator.class) {
if (counter<0) counter=0;
return counter++;
}
}
/**
* Unique in a local network
*/
protected int getIP() {
return IP;
}
/**
* Unique down to millisecond
*/
protected short getHiTime() {
return (short) ( System.currentTimeMillis() >>> 32 );
}
protected int getLoTime() {
return (int) System.currentTimeMillis();
}
}
public class UUIDHexGenerator extends AbstractUUIDGenerator implements Configurable {
private String sep = "";
protected String format(int intval) {
String formatted = Integer.toHexString(intval);
StringBuffer buf = new StringBuffer("00000000");
buf.replace( 8-formatted.length(), 8, formatted );
return buf.toString();
}
protected String format(short shortval) {
String formatted = Integer.toHexString(shortval);
StringBuffer buf = new StringBuffer("0000");
buf.replace( 4-formatted.length(), 4, formatted );
return buf.toString();
}
public Serializable generate(SessionImplementor session, Object obj) {
return new StringBuffer(36)
.append( format( getIP() ) ).append(sep)
.append( format( getJVM() ) ).append(sep)
.append( format( getHiTime() ) ).append(sep)
.append( format( getLoTime() ) ).append(sep)
.append( format( getCount() ) )
.toString();
}
public void configure(Type type, Properties params, Dialect d) {
sep = PropertiesHelper.getString("separator", params, "");
}
public static void main( String[] args ) throws Exception {
Properties props = new Properties();
props.setProperty("separator", "/");
IdentifierGenerator gen = new UUIDHexGenerator();
( (Configurable) gen ).configure(Hibernate.STRING, props, null);
IdentifierGenerator gen2 = new UUIDHexGenerator();
( (Configurable) gen2 ).configure(Hibernate.STRING, props, null);
for ( int i=0; i<10; i++) {
String id = (String) gen.generate(null, null);
System.out.println(id);
String id2 = (String) gen2.generate(null, null);
System.out.println(id2);
}
}
}