day17 10.jdbc的crud操作

Posted 2020-09-07 绿茵好莱坞

每次都是注册驱动,获取连接,然后执行。每次都写很累,肯定能抽取出来一些东西。Java里面是这样的,相同的东西可以抽取做成一个方法。用的时候调这方法就OK了。这方法抽取到什么程度呢？

package cn.itcast.jdbc;

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

import org.junit.Test;

import cn.itcast.utils.JdbcUtils;

//jdbc的crud操作
public class JdbcDemo6 {

	@Test
	public void findByIdTest(){
    //1.定义sql
    String sql = "select * from user where id= 1";
    Connection con = null;
	   Statement st = null;
	   ResultSet rs = null;
	   
	   try {
		   
		//1.注册驱动  
		  
		   
		Class.forName("com.mysql.jdbc.Driver");
		
		//2.获取连接
		try {
			 con = DriverManager.getConnection("jdbc:mysql:///day17", "root", "");
		    
			//3.获取操作sql语句对象Statement
			 st =   con.createStatement();
		
		   //4.执行sql
		     rs = st.executeQuery(sql);
		   
		   //5.遍历结果集
		    while(rs.next()){
		    	int id = rs.getInt("id");
		    	//String id = rs.getString("id");//虽然用getString()行,但是用getInt()比较合适
		    	String username = rs.getString("username");
		    	String password = rs.getString("password");
		    	String email = rs.getString("email");
		    	System.out.println(id+"   "+username+"   "+password+"   "+email);
		    }
		
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	} catch (ClassNotFoundException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}finally{
		  //6.释放资源
		  try {
			  if(rs !=null ){
			rs.close();
			  }
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		  try {
			  if(st!=null){
			st.close();
			  }
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
       try {
     	  if(con!=null){
			con.close();
     	  }
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}	
	 }
}
	//添加操作
	@Test
	public void addTest(){
		//定义sql
		String sql = "insert into user values(null,\'张三\',\'123\',\'[e-mail]\')";
		Connection con = null;
		   Statement st = null;
		   ResultSet rs = null;
		   
		   try {
			   
			//1.注册驱动  
			  
			   
			Class.forName("com.mysql.jdbc.Driver");
			
			//2.获取连接
			try {
				 con = DriverManager.getConnection("jdbc:mysql:///day17", "root", "");
			    
				//3.获取操作sql语句对象Statement
				 st =   con.createStatement();
			
			   //4.执行sql
			     int row = st.executeUpdate(sql);
			     System.out.println(row);
			     if(row!=0){
			    	 System.out.println("添加成功");
			     }
			
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			  //6.释放资源
			  try {
				  if(rs !=null ){
				rs.close();
				  }
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			  try {
				  if(st!=null){
				st.close();
				  }
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
	       try {
	     	  if(con!=null){
				con.close();
	     	  }
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}	
		 }
	}
	
	//update操作
	@Test
	public void updateTest(){
		//将id=3的人的password修改为456
		String password = "456";
		String sql = "update user set password=\'"+password+"\' where id=3";
		
		//1.得到Connection
		Connection con = null;
		Statement st = null;
		try {
			con = JdbcUtils.getConnectin();
			
			//3.获取操作sql语句对象Statement
			 st =   con.createStatement();
		
		   //4.执行sql
		     int row = st.executeUpdate(sql);
		     System.out.println(row);
		     if(row!=0){
		    	 System.out.println("添加成功");
		     }
			
			
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
             //关闭资源
			  try {
				  if(st!=null){
				st.close();
				  }
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
	       try {
	     	  if(con!=null){
				con.close();
	     	  }
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}	
		}
		
	}
}
	

 

package cn.itcast.utils;

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

public class JdbcUtils {
   
	
    public static Connection getConnectin() throws ClassNotFoundException, SQLException{
      
    	Class.forName("com.mysql.jdbc.Driver");//在开发中用哪个Statement人家有选择的权利,你不能给它抽取
		
		//2.获取连接
	  Connection		 con = DriverManager.getConnection("jdbc:mysql:///day17", "root", "");
    return con;
}
}