Jdbc封装工具

package jdbcutils;

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

//释放资源
public class JdbcUtils {
    private static String url;
    private static String user;
    private static String password;
    private static String driver;
    //文件的读取，只需要读取一次即可拿到这些值，使用静态代码块。
    static{
        try {
            //读取资源文件，获取值。
            //1.创建Properties集合
            Properties pro = new Properties();
            //2.加载文件
            //获取src路径下的文件的方式----》ClassLoader类加载器
            ClassLoader classLoader = JdbcUtils.class.getClassLoader();
            URL res = classLoader.getResource("Jdbc.properties");
            String path = res.getPath();
            System.out.println(path);
            pro.load(new FileReader(path));
//            pro.load(new FileReader("src/jdbcutils/jdbc.properties"));
            //获取数据，赋值
            url = pro.getProperty("url");
            user = pro.getProperty("user");
            password = pro.getProperty("password");
            driver = pro.getProperty("driver");
            //4.注册驱动
            try {
                Class.forName(driver);
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    //获取连接，返回连接对象。
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url,user,password);
    }
    public static void close(ResultSet rs,Statement stmt, Connection conn){
        if(rs != null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(stmt != null){
            try {
                stmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(conn!=null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

    }
}

---

url=jdbc:mysql:///test 
user=root
password=root
driver=com.mysql.jdbc.Driver

---

package jdbcutils;

import jdbcutils.JdbcUtils;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class JdbcEmp {
    public static void main(String[] args) {
        List<Emp1> all = new JdbcEmp().findAll();
        System.out.println(all);
        System.out.println(all.size());
    }
    public List<Emp1> findAll(){
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        List<Emp1> list = null;
        try {
            //1.注册驱动
//            try {
//                Class.forName("com.mysql.jdbc.Driver");
//            } catch (ClassNotFoundException e) {
//                e.printStackTrace();
//            }
//            //获取数据库连接对象
//            conn= DriverManager.getConnection("jdbc:mysql:///test", "root", "123456");
            conn = JdbcUtils.getConnection();
            //定义sql语句
            String sql = "select * from class";
            //获取执行sql对象
            stmt = conn.createStatement();
            //执行sql
            rs = stmt.executeQuery(sql);
            Emp1 emp = null;
            list = new ArrayList<Emp1>();
            while (rs.next()){
                int id = rs.getInt("id");
                String sname = rs.getString("sname");
                String company = rs.getString("company");
                double salary = rs.getDouble("salary");
                int fanbu = rs.getInt("fanbu");
                emp = new Emp1();
                emp.setId(id);
                emp.setSname(sname);
                emp.setCompany(company);
                emp.setSalary(salary);
                emp.setFanbu(fanbu);


                list.add(emp);

            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
//            if(rs!=null){
//                try {
//                    rs.close();
//                } catch (SQLException e) {
//                    e.printStackTrace();
//                }
//            }
//            if(stmt!=null){
//                try {
//                    stmt.close();
//                } catch (SQLException e) {
//                    e.printStackTrace();
//                }
//            }
//            if(conn!=null){
//                try {
//                    conn.close();
//                } catch (SQLException e) {
//                    e.printStackTrace();
//                }
//            }
            JdbcUtils.close(rs,stmt,conn);

        }
        return list;
    }
}