数据库工具类（我老师写的 感觉很好用）

package cat.jdbc;

import java.sql.Connection;
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.Map;
import javax.sql.DataSource;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.MapHandler;
import org.apache.commons.dbutils.handlers.MapListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class DBUtil {
    private static DataSource dataSource = null;

    // 把构造函数私有化,可以防止别人new本类的实例
    private DBUtil() {
    }

    // 创建数据源
    static {
        dataSource = new ComboPooledDataSource("mysql");  //mysql是在配置文件中配置的
    }

    // 从C3P0数据源获取Connection对象(数据库连接对象)
    public static Connection getConn() {
        Connection conn = null;
        try {
            conn = dataSource.getConnection(); // 返回的是经过代理的对象,其close方法已经被重写
        } catch (SQLException e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }

        return conn;
    }

    // 关闭资源
    public static void close(ResultSet rs, Statement stm, Connection conn) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (stm != null) {
            try {
                stm.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close(); // 关连接的方法和过去一样,由于数据源返回的Connection对象是代理对象,所以close方法被处理
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    
    // 关闭资源
    public static void close(Connection conn) {
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    // 万能更新(可以进行添加,更新,删除三种操作)
    public static int update(String sql, Object... params) {
        int result = 0;
        QueryRunner qr = new QueryRunner(); // 是一个线程不安全的类
        Connection conn=getConn();
        try {
            result = qr.update(conn, sql, params);
        } catch (SQLException e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }finally{
            close(conn);
        }
        
        return result;
    }

    // 添加数据,并将生成的自增ID返回
    public static int addWithId(String sql, Object... params) {
        int autoId = 0;
        Connection conn = null;
        PreparedStatement stm = null;
        ResultSet rs = null;
        try {
            conn = getConn();
            stm = conn.prepareStatement(sql,
                    PreparedStatement.RETURN_GENERATED_KEYS);
            for (int i = 0; i < params.length; i++) {
                stm.setObject(i + 1, params[i]);
            }

            // 执行添加操作
            stm.executeUpdate();

            // 取出生成的自增ID
            ResultSet rsKey = stm.getGeneratedKeys();
            rsKey.next();
            autoId = rsKey.getInt(1);

        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        } finally {
            close(rs, stm, conn);
        }
        return autoId;
    }

    // 查询出一个单个的对象
    public static <T> T getSingleObj(String sql, Class<T> clazz,
            Object... params) {
        QueryRunner qr = new QueryRunner();
        T result = null;
        Connection conn=getConn();
        try {
            result = qr.query(conn, sql, new BeanHandler<T>(clazz),
                    params);
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }finally{
            close(conn);
        }

        return result;
    }

    // 查询出对象列表(以ArrayList的方式返回),注意,如果没有查询到数据,该方法返回一个空列表,而不是null
    public static <T> List<T> getList(String sql, Class<T> clazz,
            Object... params) {
        List<T> list = new ArrayList<T>();
        QueryRunner qr = new QueryRunner();
        Connection conn =getConn();
        
        try {
            list = qr.query(conn, sql, new BeanListHandler<T>(clazz), params);
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        } finally{
            close(conn);
        }

        return list;
    }

    // 返回Map集合(该方法只将一条数据返回为Map集合,key为字段名称,value为字段值)
    public static Map<String, Object> getMap(String sql, Object... params) {
        Map<String, Object> m = null;
        QueryRunner qr = new QueryRunner();
        Connection conn =getConn();
        
        try {
            m = qr.query(conn, sql, new MapHandler(), params);
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }finally{
            close(conn);
        }

        return m;
    }

    // 返回一个List集合,其中每条数据都被封装成了一个Map集合,
    public static List<Map<String, Object>> getMapList(String sql,
            Object... params) {
        List<Map<String, Object>> mapList = new ArrayList<Map<String, Object>>();
        QueryRunner qr = new QueryRunner();
        Connection conn =getConn();

        try {
            mapList = qr.query(conn, sql, new MapListHandler(),
                    params);

        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }finally{
            close(conn);
        }

        return mapList;
    }

    // 返回单行单个数据,该方法可以用来查询记录数(这时请使用Long型进行接收),单个字段值等数据
    public static <T> T getScalar(String sql, Object... obj) {
        T result = null;
        QueryRunner qr = new QueryRunner();
        Connection conn = getConn();
        try {
            result = qr.query(conn, sql, new ScalarHandler<T>(1), obj);
        } catch (Exception ex) {
            ex.printStackTrace();
            throw new RuntimeException(ex);
        } finally {
            close(conn);
        }

        return result;
    }
}

package cat.dao;
import java.util.List;
import java.util.Map;

import cat.beans.AdminInfo;
import cat.jdbc.DBUtil;

public class AdminDao {
    //测试添加  
    //2016-06-20　11:54 增加状态字段state
    public int addAdmin(AdminInfo admin){
        String sql="insert into adminInfo (adminName,password,note,state) values (?,?,?,?)";
        Object [] params={
                admin.getAdminName(),
                admin.getPassword(),
                admin.getNote(),
                admin.getState()
        };
        
        return DBUtil.update(sql, params);        
    }
    
    //测试查询单个对象
    public AdminInfo getAdminById(int id){
        String sql="select * from adminInfo where id=?";
        return DBUtil.getSingleObj(sql, AdminInfo.class, id);
    }
    
    //测试查询一组对象
    //2016-06-20　14:35 更改sql语句 添加 按照时间降序排序
    public List<AdminInfo> getAllAdmin(){
        String sql="select * from adminInfo order by editDate desc";
        return DBUtil.getList(sql, AdminInfo.class);
    }
    
    //测试返回id
    public int addAdminWidthId(AdminInfo admin){
        String sql="insert into adminInfo (adminName,password,note) values (?,?,?)";
        Object [] params={
                admin.getAdminName(),
                admin.getPassword(),
                admin.getNote()
        };
        
        int id=DBUtil.addWithId(sql, params);
        System.out.println("生成的id是"+id);
        return id;
        
    }
    
    //测试返回Map集合
    public Map<String,Object> getAdminMap(int id){
        String sql="select * from adminInfo where id=?";
        return DBUtil.getMap(sql, id);
    }
    
    //测试返回一组Map集合
    public List<Map<String,Object>> getAdminListMap(){
        String sql="select * from adminInfo";
        return DBUtil.getMapList(sql);
    }
    
    //测试返回行数(注意,对于查询行数,返回的默认是long型,所以要转成int型)
    public int getAdmminCount(){
        String sql="select count(*) from adminInfo";
        long count=DBUtil.getScalar(sql);
        return new Integer(count+"");
    }
    
    
    //测试删除
    public int delAdminById(int id){
        String sql="delete from adminInfo where id=?";
        return DBUtil.update(sql, id);    
    }
    
    public static void main(String[] args) {
        AdminDao dao=new AdminDao();
        
        
        AdminInfo admin=new AdminInfo();
        admin.setAdminName("张三");
        admin.setPassword("123");
        admin.setNote("这是备注信息");
        int result=dao.addAdmin(admin);
        
        System.out.println(1);
        
        /*
        AdminInfo admin=dao.getAdminById(22);
        System.out.println(admin); */
        
        /*
        List<AdminInfo> adminList=dao.getAllAdmin();
        for(AdminInfo admin:adminList){
            System.out.println(admin);
        }
        */
        
        /*
        AdminInfo admin=new AdminInfo();
        admin.setAdminName("张三");
        admin.setPassword("123");
        admin.setNote("这是备注信息");
        int id=dao.addAdminWidthId(admin); */
        
        /*
        Map<String ,Object> adminMap=dao.getAdminMap(23);
        for(Map.Entry<String, Object> item: adminMap.entrySet()){
            System.out.println(item.getKey() +"-"+item.getValue());
        }
        */
        
        /*List<Map<String,Object>> mapList=dao.getAdminListMap();
        for(Map<String,Object> m:mapList){
            for(Map.Entry<String, Object> item: m.entrySet()){
                System.out.print(item.getKey() +"-"+item.getValue()+"\t");
            }
            System.out.println();
        }*/
    
    /*    int count=dao.getAdmminCount();
        System.out.println(count);*/
        
        
//        int result=dao.delAdminById(25);
        System.out.println(result);
        
        
    }

    //根据用户名和密码,验证用户信息(用于登录页)
    public AdminInfo getLoginAdmin(String adminName, String password) {
        String sql="select * from adminInfo where adminName=? and password=?  and state =?";
        return DBUtil.getSingleObj(sql,AdminInfo.class, adminName,password,1);
    }
}