[Java知识库]Java的JDBC的练习三

Java的JDBC的select练习

先创个emp文件包，保存emp文件。这些属性都是要查询的表的属性

public class Emp {
    private int id;
    private String name;
    private int job_id;
    private double salary;


    @Override
    public String toString() {
        return "Emp{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", job_id=" + job_id +
                ", salary=" + salary +
                '}';
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public int getJob_id() {
        return job_id;
    }
    public void setJob_id(int job_id) {
        this.job_id = job_id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

}

然后主文件写代码

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

/*
练习：
查询emp表的数据将其封装成对象,然后装在集合,返回
 */
public class JDBC08 {
    /*
    查询所有emp对像
     */
    public static void main(String[] args) throws SQLException {
        List<Emp> list=new JDBC08().finfAll();
        System.out.println(list);
    }
        public List<Emp> finfAll () throws SQLException {
            Connection con = null;
            Statement s = null;
            ResultSet rs = null;
            List<Emp> list = null;
            try {
                //1.注册驱动
                Class.forName("com.mysql.cj.jdbc.Driver");
                //2.获取链接
                con = DriverManager.getConnection("jdbc:mysql:///hsp_db02", "root", "011012");
                //3.定义sql语句
                String sql = "select * from emp";
                //4.获取执行sql对象
                s = con.createStatement();
                //5.执行sql语句
                rs = s.executeQuery(sql);
                //6.遍历结果，封装对象，装在集合
                Emp emp = null;
                list = new ArrayList<Emp>();
                while (rs.next()) {
                    //获取数据
                    int id = rs.getInt("id");
                    String name = rs.getString("name");
                    int job_id = rs.getInt("job_id");
                    double salary = rs.getDouble("salary");
                    //创建emp对象,并赋值
                    emp = new Emp();
                    emp.setId(id);
                    emp.setJob_id(job_id);
                    emp.setName(name);
                    emp.setSalary(salary);

                    //装在集合
                    list.add(emp);
                }
            } catch (ClassNotFoundException | SQLException e) {
                e.printStackTrace();
            } finally {
                if (con != null) {
                    con.close();
                }
            }
            if (s != null) {
                s.close();
            }
            if (rs != null) {
                rs.close();
            }
            return null;
        }
    }