idgenerator.java

JDBC连数据库,这是一门很基初的技术,一定要好好研究

package com.allanlxf.jdbc.orm.id;

public class IdGenerator
{
    private static Object lock = new Object();
    private static int currentId;
    
    public static int nextId(int type)
    {
        if(type == 1)
        {
            return getIdFromMemory();
        }
    }
    
    private static int getIdFromMemory()
    {
        synchronized(lock)
        {
            return ++currentId;
        }
    }
    
    private static int getIdFromTable()
    {
        synchronized(lock)
        {
            int id = -1;
            Statement st = con.createStatement();
            ResultSet rs = st.executeQuery("select currentId from id_holder");
            rs.next();
            int = rs.getInt(1);
            rs.close();
            st.executeUpdate("update id_holder set currentId = currentId + 1");
            st.close();
            return id;
        }
    }
    
    private static int getIdFromSequence()
    {
        int id = -1;
        Statement st = con.createStatement();
        ResultSet rs = st.executeQuery("select acc_seq.nextval from dual");
        rs.next();
        int = rs.getInt(1);
        rs.close();
        st.close();
        return id;
    }
}