java笔记2-spring

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JAVA EE

JDBC

上手参考：https://www.zybuluo.com/wuxin1994/note/1430332

DAO: Data Access Object 数据访问对象

作用：

(1).隔离业务逻辑代码和数据访问代码,位于业务逻辑和持久化数据之间，实现对持久化数据的访问。
(2).隔离不同数据库的实现。

组成部分：

(1).DAO接口
(2).DAO实现类
(3).实体类
(4).数据库连接和关闭工具类

直接上代码

(1).DAO接口

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package jdbc;public interface DAO {    void findeAll();}

(2).DAO实现类(实体类略去)

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package jdbc;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
/**
 * @Author: wufan
 */
public class UerDao implements DAO {
    @Override
    public void findeAll() {
        Connection conn = null;
        Statement st = null;
        ResultSet rs = null;
        try {
            //1. 获取连接对象
            conn = JDBCUtil.getConnection();
            //2. 创建statement对象
            st = conn.createStatement();
            String sql = "select * from user";
            rs = st.executeQuery(sql);
            while(rs.next()){
                String phone = rs.getString("phone");
                int id = rs.getInt("uid");
                System.out.print(id+"\t"+phone);
                System.out.println("");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            JDBCUtil.release(conn, st, rs);
        }
    }
    public static void main(String[] args) {
        UerDao ud = new UerDao();
        ud.findeAll();
    }
}

(4).数据库连接和关闭工具类

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package jdbc;
import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
/**
 * @Author: wufan
 */
public class JDBCUtil {
    private static String driverClass;
    private static String url;
    private static String username;
    private static String password;
    static{
        try {
            Properties properties = new Properties();
            //InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("JDBC.properties");
            InputStream is = new FileInputStream("P:\\Java\\Database\\src\\JDBC.properties"); //对应文件位于工程根目录
            properties.load(is);
            driverClass = properties.getProperty("driverClass");
            url = properties.getProperty("url");
            username = properties.getProperty("username");
            password = properties.getProperty("password");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //获取连接
    public static Connection getConnection() {
        Connection conn = null;
        try {
            Class.forName(driverClass);
            conn = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return conn;
    }
    //释放资源
    public static void release(Connection conn, Statement pstmt, ResultSet rs) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (pstmt != null) {
            try {
                pstmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

spring上手

# 挖坑中….新的坑，新的挑战