连接池

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

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;import javax.sql.DataSource;

public class ConnectionFactory {
   
    private static DataSource ds = null;
   
    private ConnectionFactory() {
       
    }
   
    static {       
        try {
            Context initCtx = new InitialContext();
            Context ctx = (Context) initCtx.lookup("java:comp/env");
            ds = (DataSource)ctx.lookup("jdbc/main");
        }catch(NamingException e) {
            e.printStackTrace();
        }       
    }
   
    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }
}

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class JdbcUtil {
   
    public static void close(ResultSet rs, Statement st, Connection con) {
        close(rs);
        close(st);
        close(con);
    }   
   
    public static void close(ResultSet rs) {
        if(rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * PreparedStatement, CallableStatement 都是 Statement 的子类，可以共用这个方法
     * @param st
     */   
    public static void close(Statement st) {
        if(st != null) {
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
   
    public static void close(Connection con) {
        if(con != null) {
            try {
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
   
    private JdbcUtil() {       
    }
}


调用时使用：

Java code

    public void updateBid(float topPrice, int aucIsSell, String aucId,            String buyerId) {        Connection con = null;        PreparedStatement ps = null;                try {                        String sql = "UPDATE 某表 SET PriceNum = PriceNum + 1, " +                    "TopPrice = ?, AucIsSell = ?, TopUserId = ? " +                    "WHERE Id = ?";            con = ConnectionFactory.getConnection();            ps = con.prepareStatement(sql);            ps.setFloat(1, topPrice);            ps.setInt(2, aucIsSell);            ps.setString(3, buyerId);            ps.setString(4, aucId);            ps.executeUpdate();        } catch (SQLException e) {            e.printStackTrace();        } finally {            JdbcUtil.close(null, ps, con);            // 或者使用：            // JdbcUtil.close(ps);            // JdbcUtil.close(con);        }    }