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a fast small database connection pool and a active record flavor mini framework
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package com.bixuebihui.sequence;

import com.bixuebihui.jdbc.IDbHelper;
import com.bixuebihui.util.DbUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.sql.Connection;
import java.sql.SQLException;

/**
 * Created by IntelliJ IDEA.

 * User: leizhimin

 * Date: 2008-4-2 15:24:52

 * Note: Sequence载体 DROP TABLE IF EXISTS t_sequence; CREATE TABLE
 * t_sequence( KEYNAME varchar(24) NOT NULL ,--COMMENT 'Sequence名称', KEYVALUE
 * numeric(20) DEFAULT 10000,-- COMMENT 'Sequence最大值', PRIMARY KEY (KEYNAME) ) ;
 *
 * @author xingwx
 * @version $Id: $Id
 */
public class KeyInfo {
    /**
     * Constant SEQUENCE_TABLE="t_sequence"
     */
    public static final String SEQUENCE_TABLE = "t_sequence";
    /** Constant SEQUENCE_DBHELPER_NAME="sequenceDbHelper" */
    public static final String SEQUENCE_DBHELPER_NAME = "sequenceDbHelper";
    /** 当前Sequence载体的最大值 */
	private long maxKey;
    /** 当前Sequence载体的最小值 */
	private long minKey;
    /** 下一个Sequence值 */
	private long nextKey;
    /** Sequence值缓存大小 */
	private int poolSize;
    /** Sequence的名称 */
	private String keyName;
	private static final String SQL_UPDATE = "UPDATE " + SEQUENCE_TABLE
			+ " SET KEYVALUE = KEYVALUE + ? WHERE KEYNAME = ? and KEYVALUE=?";
	private static final String MOVE_TO_MAX = "UPDATE " + SEQUENCE_TABLE
			+ " SET KEYVALUE =  ? WHERE KEYNAME = ? ";
	private static final String SQL_QUERY = "SELECT KEYVALUE FROM "
			+ SEQUENCE_TABLE + " WHERE KEYNAME = ?";
	static final String[] INSTALL ={
			"CREATE TABLE  IF NOT EXISTS  t_sequence ( KEYNAME varchar(24) NOT NULL PRIMARY KEY ,"+
							" KEYVALUE INT default 10000"+
								"  );"
	};

	private IDbHelper dbHelper;

	protected Logger LOG = LoggerFactory.getLogger(KeyInfo.class);

    private void init(String keyName, int poolSize, IDbHelper dbHelper) throws SQLException{
        this.dbHelper = dbHelper;

        this.poolSize = poolSize;
        this.keyName = keyName;

        retrieveFromDB();
    }

    /**
     * Constructor for KeyInfo.
     *
     * @param keyName a {@link java.lang.String} object.
     * @param poolSize a int.
     * @param dbHelper a {@link IDbHelper} object.
     * @throws java.sql.SQLException if any.
     */
    public KeyInfo(String keyName, int poolSize, IDbHelper dbHelper) throws SQLException {
        init(keyName, poolSize, dbHelper);
    }


    /**
     * Getter for the field keyName.
     *
     * @return a {@link java.lang.String} object.
     */
    public String getKeyName() {
        return keyName;
    }

    /**
     * Getter for the field maxKey.
     *
     * @return a long.
     */
    public long getMaxKey() {
        return maxKey;
    }

    /**
     * Getter for the field minKey.
     *
     * @return a long.
     */
    public long getMinKey() {
        return minKey;
    }

    /**
     * Getter for the field poolSize.
     *
     * @return a int.
     */
    public int getPoolSize() {
        return poolSize;
    }

	/**
	 * 获取下一个Sequence值
     *
	 * @return 下一个Sequence值
     * @throws java.sql.SQLException 数据库出错
     */
	public long getNextKey() throws SQLException {
		if (nextKey > maxKey) {
			int maxTries=10;
			int i=0;
			int res=0;
			while(imoveTo.
     *
     * @param max a {@link java.lang.Long} object.
     * @throws java.sql.SQLException if any.
     */
    public void moveTo(Long max) throws SQLException {
        dbHelper.executeNoQuery(MOVE_TO_MAX, new Object[] {
                max, keyName });
        nextKey = max;
    }
}