ID Generator
ID的生成策略参见：生成方法
简单的实现了其思想中的方法。
package dataSource.idGenerator;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.apache.log4j.Logger;
import dataBasePool.DataBasePool;
/*
* ID Generator
* You need two SQL server
* Their config should be like the following:
* Server 1:
auto-increment-increment = 2
auto-increment-offset = 1
Server 2:
auto-increment-increment = 2
auto-increment-offset = 2
*
*/
public class IDGenerator {
public static Logger log = Logger.getLogger(IDGenerator.class);
private Connection[] conns;
public IDGenerator(){
try {
conns[0] = DataBasePool.getPools().get("id_server_1").getConnection();
conns[1] = DataBasePool.getPools().get("id_server_2").getConnection();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public long getPrimaryKey(){
//default id
long id = 1;
PreparedStatement pstmt = null;
String sql = "";
//use the system time to keep loading balancing
long current_time = System.currentTimeMillis()/1000;
Connection conn = null;
if(current_time % 2 == 0){
try {
conn = conns[0];
conn.setAutoCommit(false);
sql = "replace into id_sequence (stub) values('a')";
pstmt = conn.prepareStatement(sql);
pstmt.execute();
sql = "select last_insert_id()";
pstmt = conn.prepareStatement(sql);
ResultSet rs = pstmt.executeQuery();
if(rs.next()){
id = rs.getLong("last_insert_id()");
}
conn.commit();
log.info("Get ID: "+id);
} catch (SQLException e) {
e.printStackTrace();
}
}else{
try {
conn = conns[1];
sql = "replace into id_sequence (stub) values('a')";
pstmt = conn.prepareStatement(sql);
pstmt.execute();
sql = "select last_insert_id()";
pstmt = conn.prepareStatement(sql);
ResultSet rs = pstmt.executeQuery();
if(rs.next()){
id = rs.getLong("last_insert_id()");
}
log.info("Get ID: "+id);
} catch (SQLException e) {
e.printStackTrace();
}
}
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return id;
}
public static void main(String[] args){
IDGenerator id_generator = new IDGenerator();
System.out.println(id_generator.getPrimaryKey());
System.out.println(id_generator.getPrimaryKey());
}
}