JDBC的练习

1.所需要用到的db3中emp表

2.创建JDBC的Emp类
这里一定要重写toString方法 否则写出来的值为地址值

package cn.itcast.domain;

import java.util.Date;

public class Emp {
    private int id;
    private String ename;
    private int job_id;
    private int mgr;
    private Date joindate;
    private double salary;
    private int dept_id;
    private double bonus;

    public double getBonus() {
        return bonus;
    }

    public void setBonus(double bonus) {
        this.bonus = bonus;
    }

    public int getId() {
        return id;
    }

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

    public String getEname() {
        return ename;
    }

    public void setEname(String ename) {
        this.ename = ename;
    }

    public int getJob_id() {
        return job_id;
    }

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

    public int getMgr() {
        return mgr;
    }

    public void setMgr(int mgr) {
        this.mgr = mgr;
    }

    public Date getJoindate() {
        return joindate;
    }

    @Override
    public String toString() {
        return "Emp{" +
                "id=" + id +
                ", ename='" + ename + '\'' +
                ", job_id=" + job_id +
                ", mgr=" + mgr +
                ", joindate=" + joindate +
                ", salary=" + salary +
                ", dept_id=" + dept_id +
                ", bonus=" + bonus +
                '}';
    }

    public void setJoindate(Date joindate) {
        this.joindate = joindate;
    }

    public double getSalary() {
        return salary;
    }

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

    public int getDept_id() {
        return dept_id;
    }

    public void setDept_id(int dept_id) {
        this.dept_id = dept_id;
    }
}

3.创建JDBC练习类

package cn.itcast.jdbc;

import cn.itcast.domain.Emp;

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

public class JDBCDemo8 {
    public static void main(String[] args) {
        List<Emp> list = new JDBCDemo8().findAll();
        System.out.println(list);
        System.out.println(list.size());

    }
    public List<Emp> findAll() {
        Statement stmt = null;
        Connection conn = null;
        ResultSet rs = null;
        List<Emp> list = null;
        try {
            //1.注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2.获取连接
            conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "123456");
            //3.定义sql
            String sql = "select * from emp";
            //4.获取执行sql的对象
            stmt = conn.createStatement();
            //5.执行sql
            rs = stmt.executeQuery(sql);
            //6.遍历结果集
            Emp emp = null;
            list = new ArrayList<Emp>();
            while (rs.next()) {
                int id = rs.getInt("id");
                String ename = rs.getString("ename");
                int job_id = rs.getInt("job_id");
                int mgr = rs.getInt("mgr");
                Date joindate = rs.getDate("joindate");
                double salary = rs.getDouble("salary");
                int dept_id = rs.getInt("dept_id");
                double bonus = rs.getDouble("bonus");

                //创建emp对象
                emp = new Emp();
                emp.setId(id);
                emp.setEname(ename);
                emp.setJob_id(job_id);
                emp.setMgr(mgr);
                emp.setJoindate(joindate);
                emp.setSalary(salary);
                emp.setBonus(bonus);
                emp.setDept_id(dept_id);

                //转载集合
                list.add(emp);
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            //stmt.close();
            //释放资源
            //避免空指针异常
            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();
            }
        }
        return list;
    }
}

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