databaseidgenerator.java

这是一本描述JDBC数据库的书籍

/*
 * DatabaseIDGenerator.java
 *
 * Created on 2005年6月9日, 下午7:28
 *
 * To change this template, choose Tools | Options and locate the template under
 * the Source Creation and Management node. Right-click the template and choose
 * Open. You can then make changes to the template in the Source Editor.
 */

package oid;

import java.sql.*;
import common.*;
/**
 *
 * @author kevin
 */
public class DatabaseIDGenerator {
    public final static long ID_TYPE_PERSON = 1;
    public final static long ID_TYPE_STUDENT = 11;
    public final static long ID_TYPE_EMPLOYEE = 12;
    
    public final static long ID_TYPE_MASTER = 111;
    public final static long ID_TYPE_BACHELOR = 112;
    
    public final static long ID_TYPE_MANAGER = 121;
    public final static long ID_TYPE_ENGINEER = 122;
    
    public static synchronized long nextPersonID(){
        return nextID(ID_TYPE_PERSON);
    }
    
    public static synchronized long nextStudentID(){
        return nextID(ID_TYPE_STUDENT);
    }
    
    public static synchronized long nextEmployeeID(){
        return nextID(ID_TYPE_EMPLOYEE);
    }
    
    public static synchronized long nextMasterID(){
        return nextID(ID_TYPE_MASTER);
    }
    
    public static synchronized long nextBachelorID(){
        return nextID(ID_TYPE_BACHELOR);
    }
    
    public static synchronized long nextManagerID(){
        return nextID(ID_TYPE_MANAGER);
    }
    
    public static synchronized long nextEngineerID(){
        return nextID(ID_TYPE_ENGINEER);
    }
    
    private static long nextID(long type){
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        long nextID = 0;
        try{
            ConnectionFactory factory = ConnectionFactory.getConnectionFactory();
            conn = factory.getConnection();
            
            String sql = "select nextval from oid_tbl where type=" + type;
            stmt = conn.createStatement();
            
            rs = stmt.executeQuery(sql);
            rs.next();
            nextID = rs.getLong("nextval");
            
            String updateSql = "update oid_tbl set nextval = nextval + 1 where type = " + type;
            stmt.execute(updateSql);
        }catch(Exception e){
            e.printStackTrace();
        }finally{
            DBUtils.close(rs, stmt, conn);
        }
        return nextID;
    }
    
}