2019-06-12 学习日记 day33 JDBC

JDBC

JAVA Database Connectivity 

java数据库

sun公司提供的一种数据库访问规则，规范，由于数据库种类较多，并且java语言使用比较广泛，sun就通过了一种规范，让其他的数据库提供商去实现的访问规则

JDBC的基本步骤

1.注册驱动

2.建立连接

3.创建statement

4.执行sql，得到ResultSet

5.遍历结果集

6.释放资源

package tan.jung.test;

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

import tan.jung.JDBCUtil;

public class MianTest {

    public static void main(String[] args) {
        
        Connection conn = null;
        Statement st = null;
        ResultSet rs =null;
        try {
        //注册驱动
        DriverManager.registerDriver(new com.mysql.jdbc.Driver());
        //建立连接
        conn = DriverManager.getConnection("jdbc:mysql://localhost/student", "root", "root");
        //创建statement
        st= conn.createStatement();
        
        //得到结果集
        String sql="select * from tab_belong";
        rs = st.executeQuery(sql);
        //遍历查询每一条记录
        while(rs.next()){
            int id = rs.getInt("id");
            String belong = rs.getString("belong");
            System.out.println("id="+id+",belong="+belong);
        }
        
        } catch (SQLException e) {
            e.printStackTrace();
        }
        finally {
            JDBCUtil.release(conn, st, rs);            
        }
    }

}

//第二个包
package tan.jung;

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

public class JDBCUtil {
    
    public static void release(Connection conn,Statement st,ResultSet rs){
        closers(rs);
        closest(st);
        closeconn(conn);
        
    }
    private static void closers(ResultSet rs){
        try {
            if(rs !=null){
            rs.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();    
    }finally {
        rs=null;
    }
    }
    
    private static void closest(Statement st){
        try {
            if(st !=null){
            st.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();    
    }finally {
        st=null;
    }
    }
    
    private static void closeconn(Connection conn){
        try {
            if(conn !=null){
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();    
    }finally {
        conn=null;
    }
    }
}

JDBC　工具类构建

1.资源释放工作的整合

2.驱动防二次注册

 Class.forName("com.mysql.jdbc.Driver");

3.使用properties配置文件

package tan.jung.test;

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

import tan.jung.JDBCUtil;

public class MianTest {

    public static void main(String[] args) {
        
        Connection conn = null;
        Statement st = null;
        ResultSet rs =null;
        try {
        
            conn =JDBCUtil.getConn();
        //创建statement
        st= conn.createStatement();
        
        //得到结果集
        String sql="select * from tab_belong";
        rs = st.executeQuery(sql);
        //遍历查询每一条记录
        while(rs.next()){
            int id = rs.getInt("id");
            String belong = rs.getString("belong");
            System.out.println("id="+id+",belong="+belong);
        }
        
        } catch (Exception e) {
            e.printStackTrace();
        }
        finally {
            JDBCUtil.release(conn, st, rs);            
        }
    }

}



//第二个包

package tan.jung;

import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JDBCUtil {
    static    String driverClass = null;
    static    String url=null;
    static    String name=null;
    static    String password=null;
    
    static{
        try {
            //1.创建一个属性配置对象
            Properties properties = new Properties();
            //InputStream is =new FileInputStream("jdbc.properties");
            InputStream is =JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties"); 
            //导入输出流
            properties.load(is);
            
            //读取属性
            driverClass=properties.getProperty("driverClass");
            url=properties.getProperty("url");
            name=properties.getProperty("name");
            password=properties.getProperty("password");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static Connection getConn(){
        
        Connection conn =null;
        try {
            Class.forName(driverClass);
            
        //建立连接
        conn = DriverManager.getConnection(url, name, password);    
        } catch (Exception e) {
            
            e.printStackTrace();
        }
        
        
        
        return conn;
        
    }
    
    
    public static void release(Connection conn,Statement st,ResultSet rs){
        closers(rs);
        closest(st);
        closeconn(conn);
        
    }
    private static void closers(ResultSet rs){
        try {
            if(rs !=null){
            rs.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();    
    }finally {
        rs=null;
    }
    }
    
    private static void closest(Statement st){
        try {
            if(st !=null){
            st.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();    
    }finally {
        st=null;
    }
    }
    
    private static void closeconn(Connection conn){
        try {
            if(conn !=null){
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();    
    }finally {
        conn=null;
    }
    }
}

创建jdbc.properties文件

driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1/student
name=root
password=root