JDBC优化之路-1

1.原始JDBC使用

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();
}

dao实现层：UserDaoImpl.java

package com.hpe.dao.impl;

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

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

public class UserDaoImpl implements IUserDao {
	
	@Override
	public User login(User user) {
		// 使用原生JDBC
		/*
		 * 1.加载驱动
		 * 2.创建连接对象
		 * 3.创建执行对象
		 * 4.操作数据库
		 * 5.关闭资源
		 */
		Connection conn=null;
		PreparedStatement ps=null;
		ResultSet rs=null;
		User resUser=null;
		try {
			Class.forName("com.mysql.jdbc.Driver");
			
			String url = "jdbc:mysql://localhost:3306/work?useUnicode=true&characterEncoding=utf-8";
			String username="root";
			String password="root";
		        conn=DriverManager.getConnection(url, username, password);
			
			String sql = "select * from users where name=? and pwd=?";
			ps=conn.prepareStatement(sql);
			
			ps.setString(1, user.getName());//下标从1开始
			ps.setString(2, user.getPwd());
			
			rs  = ps.executeQuery();
			
			if(rs.next()){
				int id = rs.getInt("id");//也可以使用1（下标从1开始），习惯用表的列名
				String name = rs.getString("name");
				String pwd = rs.getString("pwd");
				
				resUser = new User();
				resUser.setId(id);
				resUser.setName(name);
				resUser.setPwd(pwd);
			}		
		} 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();
		}finally {
			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();
			}
		}
		return resUser;
	}
	@Override
	public List<User> selectAll() {
		Connection conn=null;
		PreparedStatement ps=null;
		ResultSet rs=null;
		List<User>list=new ArrayList<>();
		try {
			Class.forName("com.mysql.jdbc.Driver");
			
			String url = "jdbc:mysql://localhost:3306/work?useUnicode=true&characterEncoding=utf-8";
			String username="root";
			String password="root";
		        conn=DriverManager.getConnection(url, username, password);
			
			String sql = "select * from users ";
			ps=conn.prepareStatement(sql);
			
			rs  = ps.executeQuery();
			
			while(rs.next()){
				int id = rs.getInt("id");//也可以使用1（下标从1开始），习惯用表的列名
				String name = rs.getString("name");
				String pwd = rs.getString("pwd");
				
				User resUser = new User();
				resUser.setId(id);
				resUser.setName(name);
				resUser.setPwd(pwd);
				
				list.add(resUser);
			}		
		} 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();
		}finally {
			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();
			}
		}
		return list;
	}	
}

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 + "]";
	}
	
}

测试类：MainTest.java

package com.hpe.test;

import java.util.List;

import org.junit.Test;

import com.hpe.dao.IUserDao;
import com.hpe.dao.impl.UserDaoImpl;
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);	
		}
	}
}

大量重复代码使程序很繁琐，接下来进行优化。

第一步优化:

dao实现层：UserDaoImpl.java:

package com.hpe.dao.impl;

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

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

public class UserDaoImpl implements IUserDao {
	private 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;
	}
	private 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();
		}
	}
	@Override
	public User login(User user) {
		// 使用原生JDBC
		/*
		 * 1.加载驱动
		 * 2.创建连接对象
		 * 3.创建执行对象
		 * 4.操作数据库
		 * 5.关闭资源
		 */
		Connection conn=null;
		PreparedStatement ps=null;
		ResultSet rs=null;
		User resUser=null;
		try {
			
			conn=getConn();
			String sql = "select * from users where name=? and pwd=?";
			ps=conn.prepareStatement(sql);
			
			ps.setString(1, user.getName());//下标从1开始
			ps.setString(2, user.getPwd());
			
			rs  = ps.executeQuery();
			
			if(rs.next()){
				int id = rs.getInt("id");//也可以使用1（下标从1开始），习惯用表的列名
				String name = rs.getString("name");
				String pwd = rs.getString("pwd");
				
				resUser = new User();
				resUser.setId(id);
				resUser.setName(name);
				resUser.setPwd(pwd);
			}		
		} 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();
		}finally {
			close(rs, ps, conn);
		}
		return resUser;
	}
	@Override
	public List<User> selectAll() {
		Connection conn=null;
		PreparedStatement ps=null;
		ResultSet rs=null;
		List<User>list=new ArrayList<>();
		try {
			
		    conn=getConn();
			
			String sql = "select * from users ";
			ps=conn.prepareStatement(sql);
			
			rs  = ps.executeQuery();
			
			while(rs.next()){
				int id = rs.getInt("id");//也可以使用1（下标从1开始），习惯用表的列名
				String name = rs.getString("name");
				String pwd = rs.getString("pwd");
				
				User resUser = new User();
				resUser.setId(id);
				resUser.setName(name);
				resUser.setPwd(pwd);
				
				list.add(resUser);
			}		
		} 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();
		}finally {
		close(rs, ps, conn);
		}
		return list;
	}	
}

第二步优化:

dao实现层：UserDaoImpl.java:

package com.hpe.dao.impl;

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

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

public class UserDaoImpl implements IUserDao {
	private 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;
	}
	private 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();
		}
	}
	private List<User> select(String sql,Object[] params){
		Connection conn=null;
		PreparedStatement ps=null;
		ResultSet rs=null;
		List<User>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();			
			while(rs.next()){
				int id = rs.getInt("id");//也可以使用1（下标从1开始），习惯用表的列名
				String name = rs.getString("name");
				String pwd = rs.getString("pwd");
				
				User resUser = new User();
				resUser.setId(id);
				resUser.setName(name);
				resUser.setPwd(pwd);
				
				list.add(resUser);
			}		
		} 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();
		}finally {
			close(rs, ps, conn);
		}
		return list;
	}
	private User selectObject(String sql,Object[] params){
		List<User> list = select(sql, params);
		User resUser = null;
		if(list.size()>0){
		    resUser=list.get(0);
		} 
		return resUser;
	}
	@Override
	public User login(User user) {	
		String sql = "select * from users where name=? and pwd=?";
		Object[] params = {user.getName(),user.getPwd()};		
		User resUser = selectObject(sql, params);
		return resUser;
	}
	@Override
	public List<User> selectAll() {		
		String sql = "select * from users ";
		List<User>list=select(sql, null);
		return list;
	}	
}