JDBC优化之路-2（添加工具类DBUtil）

2.两个实例对象

users数据表：

admin数据表：

项目目录：

dao层：IUserDao.java

package com.hpe.dao;

import java.util.List;

import com.hpe.pojo.User;

public interface IUserDao {
	User login(User user);
	List<User> selectAll();
	int add(User user);
}

dao层：IAdminDao.java

package com.hpe.dao;

import com.hpe.pojo.Admin;

public interface IAdminDao {
	Admin login(Admin admin);
}

dao实现层：UserDaoImpl.java

package com.hpe.dao.impl;

import java.util.List;

import com.hpe.dao.IUserDao;
import com.hpe.pojo.User;
import com.hpe.util.DBUtil;

public class UserDaoImpl implements IUserDao {
	@Override
	public User login(User user) {	
		String sql = "select * from users where name=? and pwd=?";
		Object[] params = {user.getName(),user.getPwd()};		
		User resUser =DBUtil.selectObject(sql, params, User.class);
		return resUser;
	}
	@Override
	public List<User> selectAll() {		
		String sql = "select * from users ";
		List<User>list=DBUtil.select(sql, null,User.class);
		return list;
	}
	@Override
	public int add(User user) {
		String sql = "insert into users (name,pwd) values(?,?)";
		Object[] params = {user.getName(),user.getPwd()};
		int res = DBUtil.update(sql, params);
		return res;
	}	
}

dao实现层：AdminDaoImpl.java

package com.hpe.dao.impl;

import com.hpe.dao.IAdminDao;
import com.hpe.pojo.Admin;
import com.hpe.util.DBUtil;

public class AdminDaoImpl implements IAdminDao {
		
		@Override
		public Admin login(Admin admin) {	
			String sql = "select * from admin where adminname=? and adminpassword=?";
			Object[] params = {admin.getAdminname(),admin.getAdminpassword()};		
			Admin resAdmin = DBUtil.selectObject(sql, params,Admin.class);
			return resAdmin;
		}
	
}

实体类：User.java

package com.hpe.pojo;

public class User {
	private int id;
	private String name;
	private String pwd;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	
	public String getPwd() {
		return pwd;
	}
	public void setPwd(String pwd) {
		this.pwd = pwd;
	}
	@Override
	public String toString() {
		return "User [id=" + id + ", name=" + name + ", pwd=" + pwd + "]";
	}
	
}

实体类：Admin.java

package com.hpe.pojo;

public class Admin {
	private int adminid;
	private String adminname;
	private String adminpassword;
	public int getAdminid() {
		return adminid;
	}
	public void setAdminid(int adminid) {
		this.adminid = adminid;
	}
	public String getAdminname() {
		return adminname;
	}
	public void setAdminname(String adminname) {
		this.adminname = adminname;
	}
	public String getAdminpassword() {
		return adminpassword;
	}
	public void setAdminpassword(String adminpassword) {
		this.adminpassword = adminpassword;
	}
	@Override
	public String toString() {
		return "Admin [adminid=" + adminid + ", adminname=" + adminname + ", adminpassword=" + adminpassword + "]";
	}
	
}

工具类：DBUtil.java

package com.hpe.util;

import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class DBUtil {
	/*
	 * 获取数据库连接
	 */
	public static Connection getConn() throws ClassNotFoundException, SQLException{
		Class.forName("com.mysql.jdbc.Driver");
		
		String url = "jdbc:mysql://localhost:3306/work?useUnicode=true&characterEncoding=utf-8";
		String username="root";
		String password="root";
	    Connection conn=DriverManager.getConnection(url, username, password);
	    return conn;
	}
	/*
	 * 关闭数据库资源
	 */
	public static void close(ResultSet rs,PreparedStatement ps,Connection conn){
		try {
			if(rs!=null){
				rs.close();
			}		
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		try {
			if(ps!=null){
				ps.close();
			}		
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		try {
			if(conn!=null){
				conn.close();
			}		
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	/*
	 * Class<T> type创建什么类型的对象
	 * T用来保存一个参数类型
	 */
	public static <T> List<T> select(String sql,Object[] params,Class<T> type){
		Connection conn=null;
		PreparedStatement ps=null;
		ResultSet rs=null;
		List<T>list =new ArrayList<>();
		try {
			conn=getConn();		
			ps=conn.prepareStatement(sql);
			if(params != null){
				for(int i=0;i<params.length;i++){
					ps.setObject(i+1, params[i]);
				}
			}	
			rs  = ps.executeQuery();
			ResultSetMetaData metaData = rs.getMetaData();//
			int colCount = metaData.getColumnCount();//获取列的数量
			while(rs.next()){			
				/*
				 * 把数据库查询出来的通过内省丢给Object
				 */
				T obj = type.newInstance();
				BeanInfo beanInfo = Introspector.getBeanInfo(type);//obj的属性
				PropertyDescriptor[] properties = beanInfo.getPropertyDescriptors();//属性信息的数组
				
				for (int i = 0; i < colCount; i++) {
					String cloName = metaData.getColumnName(i+1);	//获取到列名	
					Object value = rs.getObject(i+1);//列的值
					
					/*
					 * 遍历properties数组，找到一个名字和cloName一样的属性
					 */
					for(int j=0;j<properties.length;j++){
						PropertyDescriptor property = properties[j];
						String propertyName = property.getName();//属性名字
						Method method = property.getWriteMethod();//写方法
						
						if(propertyName.equals(cloName)){
							//属性名与数据表的列名一样，将值传给obj
							method.invoke(obj, value);
						}
					}
				
				}
				list.add(obj);
			}		
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			System.out.println("请正确配置驱动程序");
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IntrospectionException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally {
			close(rs, ps, conn);
		}
		return list;
	}
	public static <T> T  selectObject(String sql,Object[] params,Class<T> type){
		List<T> list = select(sql, params,type);
		T resObj = null;
		if(list.size()>0){
			resObj=list.get(0);
		} 
		return resObj;
	}
	
	/*
	 * UPdate方法, 支持增,删,改
	 */
	public static int update(String sql, Object[] params){
		
		Connection conn = null;
		PreparedStatement ps = null;		
		int res = 0;
		
		try {
			conn = getConn();		
			ps = conn.prepareStatement(sql);	
			
			if (params != null){
				for (int i=0; i<params.length; i++){
					ps.setObject(i+1, params[i]);
				}
			}			
			res = ps.executeUpdate();			
		} catch (SQLException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally {
			close(null, ps, conn);
		}	
		return res;
	}
}

测试类：MainTest.java

package com.hpe.test;

import java.util.List;

import org.junit.Test;

import com.hpe.dao.IAdminDao;
import com.hpe.dao.IUserDao;
import com.hpe.dao.impl.AdminDaoImpl;
import com.hpe.dao.impl.UserDaoImpl;
import com.hpe.pojo.Admin;
import com.hpe.pojo.User;

public class MainTest {
	@Test
	public void user_login(){
		IUserDao iUserDao = new UserDaoImpl();
		
		User user = new User();
		user.setName("admin");
		user.setPwd("123");
		User resUser = iUserDao.login(user);
		
		if (resUser != null){
			System.out.println("登录成功");
			System.out.println(resUser);
		}
		else{
			System.out.println("登录失败");
		}
	}
	
	@Test
	public void selectAll(){
		IUserDao iUserDao = new UserDaoImpl();
		List<User> list = iUserDao.selectAll();
		
		for (User user : list) {
		System.out.println(user);	
		}
	}
	
	@Test
	public void user_add(){
		IUserDao iUserDao = new UserDaoImpl();
		User user = new User();
		user.setName("mq");
		user.setPwd("111");
		int res = iUserDao.add(user);
		if(res == 1){
			System.out.println("添加成功");
		}
		else{
			System.out.println("添加失败");
		}
	}
	
	@Test
	public void admin_login(){
		IAdminDao iAdminDao = new AdminDaoImpl();
		Admin admin = new Admin();
		admin.setAdminname("admin");
		admin.setAdminpassword("123");
		Admin resAdmin = iAdminDao.login(admin);
		if(resAdmin !=null){
			System.out.println("管理员登录成功");
			System.out.println(resAdmin);
		}
		else {
			System.out.println("管理员登录失败");
		}
	}
}