一起艳恶学习打造一个通用的JDBC

前言：jdbc写的繁琐，mybatis要映射，hiberante配置太烦，好吧，就简单写个增删改查的jdbcUtil，以供学习，可以学到类的加载顺序，ResourceBundle加载资源文件，数据库三大核心接口，类的反射，泛型（特别是泛型方法），可变形参的使用，以及集合中的List,ArrayList等。当然还有很多不足，比如每次程序拿连接都要new,这样就给系统加大了负担，没有事务，没有dataSource等等，望大神补充。。。

util类的代码如下：

package com.yanhui.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import java.util.ResourceBundle;


/**
 * 数据库连接
 * @author colorbin
 *
 */
public class _jdbcUtil {
    private static String url = null;
    private static String user = null;
    private static String password = null;
    private static Connection conn;

    public static void main(String[] args) throws Exception {
        System.out.println(getConnection());
    }

    private _jdbcUtil(){}

    static {
        try{
            ResourceBundle res = ResourceBundle.getBundle("config");  
            Class.forName(res.getString("driverName"));
            url = res.getString("url");
            user = res.getString("user");
            password = res.getString("password");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() {
        if(null == conn) {
            try {
                conn = DriverManager.getConnection(url, user, password);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return conn;
    }

    public static void closeResource(ResultSet rs, Statement st, Connection conn){
        if(null != rs) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
                throw new RuntimeException(e);
            } finally {
                if(null != st) {
                    try {
                        st.close();
                    } catch (SQLException e) {
                        e.printStackTrace();
                        throw new RuntimeException(e);
                    } finally {
                        if(null != conn) {
                            try {
                                conn.close();
                            } catch (SQLException e) {
                                e.printStackTrace();
                                throw new RuntimeException(e);
                            }
                        }
                    }
                }
            }
        }
    }



    /**
     * 从数据库取得一个
     *
     * @param sql 执行的sql语句
     * @param row 对象赋值方法
     * @param params 填充sql中的？
     * @return
     */
    public static Object getOne(String sql, RowMapper row, Object... params){
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        Object obj = null;
        try {
            conn = _jdbcUtil.getConnection();
            ps = conn.prepareStatement(sql);
            if(params != null){
                for (int i = 1; i <= params.length; i++) {
                    ps.setObject(i, params[i - 1]);
                }
            }
            rs = ps.executeQuery();
            if (rs.next()) {
                obj = row.mapRow(rs);
            }
            return obj;
        } catch (SQLException e) {
            throw new RuntimeException(e.getMessage(), e);
        } finally {
            _jdbcUtil.closeResource(rs, ps, conn);
        }
    }



    /**
     * 取出所有sql语句查询的结果
     *
     * @param sql sql语句
     * @param row 对象赋值方法
     * @param params 用来填充sql中的？
     * @return
     */
    @SuppressWarnings("unchecked")
    public static <T> List<T> getSome(String sql, RowMapper row, Object... params){
        List<T> arrays = null;
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        T obj = null;
        try {
            conn = _jdbcUtil.getConnection();
            ps = conn.prepareStatement(sql);
            if(params != null){
                for (int i = 1; i <= params.length; i++) {
                    ps.setObject(i, params[i - 1]);
                }
            }
            rs = ps.executeQuery();
            arrays = new ArrayList<T>();
            while (rs.next()) {
                obj = (T) row.mapRow(rs);
                arrays.add(obj);
            }
        } catch (SQLException e) {
            throw new RuntimeException(e.getMessage(), e);
        } finally {
            _jdbcUtil.closeResource(rs, ps, conn);
        }
        return arrays;
    }


    /**
     * 执行更新操作
     * @param sql 执行的sql语句
     * @param params 用来填充sql语句中的？(若没有参数需要给null)
     */
    public static void update(String sql, Object... params){
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            conn = _jdbcUtil.getConnection();
            conn.setAutoCommit(false);
            ps = conn.prepareStatement(sql);
            if(params != null){
                for (int i = 1; i <= params.length; i++) {
                    ps.setObject(i, params[i - 1]);
                }
            }
            ps.executeUpdate();
            conn.commit();
        } catch (SQLException e) {
            try {
                conn.rollback();
            } catch (SQLException e1) {
                throw new RuntimeException(e1.getMessage(), e1);
            }
            throw new RuntimeException(e.getMessage(), e);
        } finally {
            _jdbcUtil.closeResource(rs, ps, conn);
        }
    }



}