0. 準備工作

先要匯入mysql-connector的jar包，新增依賴關係。然後匯入jdbc.properties配置檔案

//jdbc 配置檔案內容
url=jdbc:mysql:///db1
user=root
password=root
driver=com.mysql.jdbc.Driver

1. JDBCUtils工具類程式碼實現

package util;

import java.io.FileReader;
import java.io.IOException;
import java.net.URL;
import java.sql.*;
import java.util.Properties;

/**
 * JDBC 工具類
 */
public class JDBCUtils {
    private static String url;
    private static String user;
    private static String password;
    private  static String driver;

    /**
     * 檔案讀取，只會執行一次，使用靜態程式碼塊
     */
    static {
        //讀取檔案，獲取值
        try {
            //1.建立Properties集合類
            Properties pro = new Properties();
            //獲取src路徑下的檔案--->ClassLoader類載入器
            ClassLoader classLoader = JDBCUtils.class.getClassLoader();
            URL resource = classLoader.getResource("jdbc.properties");;
            String path = resource.getPath();
            //2.載入檔案
            pro.load(new FileReader(path));
            //3獲取資料
            url = pro.getProperty("url");
            user = pro.getProperty("user");
            password = pro.getProperty("password");
            driver = pro.getProperty("driver");
            //4.註冊驅動
            Class.forName(driver);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    /**
     * 獲取連線
     * @return 連線物件
     */
    public static Connection getConnection() throws SQLException {
        Connection conn = DriverManager.getConnection(url, user, password);
        return conn;
    }

    /**
     * 釋放資源
     * @param rs
     * @param st
     * @param conn
     */
    public static void close(ResultSet rs, Statement st,Connection conn){
        if (rs != null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(st != null){
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

 

2. 把資料裡面建立的表格當作一個物件

如下面這個表：

建立一個數據庫表的類，程式碼如下：

package com.zk.demo02jdbcutils;

public class UserBean {
    private int id;
    private String username;
    private String password;
    public UserBean(int id, String username, String password){
        this.id = id;
        this.username = username;
        this.password = password;
    }

    @Override
    public String toString() {
        return "UserBean{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}
 

3.測試JDBCUtils工具類

package com.zk.demo02jdbcutils;

import util.JDBCUtils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class Demo01JDBCUtils {

public static void main(String[] args) {
    List<UserBean> list = findAll();
    System.out.println("list = " + list);
}

//定義一個方法，查詢user表的資料將其封裝為物件，然後裝載集合，返回。
public static List<UserBean> findAll(){
    Connection conn = null;
    Statement st = null;
    ResultSet rs = null;
    List<UserBean> list = null;
    try {
        conn = JDBCUtils.getConnection();
        //定義sql
        String sql = "SELECT * FROM user";
        //獲取執行sql的物件
        st = conn.createStatement();
        //執行sql
        rs = st.executeQuery(sql);
        UserBean bean = null;
        list = new ArrayList<UserBean>();
        while (rs.next()){
            int id = rs.getInt("id");
            String username = rs.getString("username");
            String password = rs.getString("password");
            bean = new UserBean(id,username,password);
            list.add(bean);
        }
    } catch (SQLException e) {
        e.printStackTrace();
    }finally {
        JDBCUtils.close(rs,st,conn);
    }
    return list;
}
}
 

執行結果如下圖