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java Bean工厂 Dao层设计初级

有勇气的牛排 1080 Java 2021-08-26 21:57:34

1 util 工具类

package net920vip.util;

import java.sql.*;

public class DBUtil {
    Connection con;
    PreparedStatement pstm;
    ResultSet rs;

    public Connection getCon() {

        try {
            Class.forName("com.mysql.jdbc.Driver");
            String username = "root";
            String password = "root";
            String datebase = "student";
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/" + datebase + "?useUnicode=true&characterEncoding=utf-8", username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return con;
    }

    public void closeAll() {
        try {
            // 做非空判断
            if (rs != null) {
                rs.close();
            }
            if (pstm != null) {
                pstm.close();
            }
            if (con != null) {
                con.close();
            }

//            con.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

2 Bean工厂

package net920vip.Bean;

public class Student {
    private int id;
    private String username;
    private String passoword;

    // 无参构造
    public Student() {
    }

    // 带参构造 两个参数
    public Student(String username, String passoword) {
        this.username = username;
        this.passoword = passoword;
    }

    // 带参构造 三个参数
    public Student(int id, String username, String passoword) {
        this.id = id;
        this.username = username;
        this.passoword = passoword;
    }

    public int getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassoword() {
        return passoword;
    }

    public void setPassoword(String passoword) {
        this.passoword = passoword;
    }

    @Override
    public String toString() {
        return "net920vip.Bean.Student{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", passoword='" + passoword + '\'' +
                '}';
    }
}

3 Dao层设计

  • Dao 数据库和java的连接

  • 专门对Student表的插入方法

如果按照下面这种方法设计，每个表都要写个Dao文件，就会特别麻烦，下篇文章，会对Dao层抽象设计，分离通用代码

package net920vip.Dao;


import net920vip.Bean.Student;
import net920vip.util.DBUtil;

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

/**
 * Dao 数据库和java的连接
 * 专门对Student表的插入方法
 */
public class StudentDao {

    /**
     * 新增学生
     * 返回值：
     * 1：修改成功
     */
    public int insert(Student s) throws SQLException {

        DBUtil db = new DBUtil();
        Connection con = db.getCon();

        String sql = "insert into Student(username,password) values(?,?)";
        PreparedStatement pstm = con.prepareStatement(sql);

        pstm.setString(1, s.getUsername());
        pstm.setString(2, s.getPassoword());
        int i = pstm.executeUpdate();

        return i;
    }

    /**
     * 修改学生
     * 返回值：
     * 1：修改成功
     */
    public int update(Student s) throws SQLException {
        DBUtil db = new DBUtil();
        Connection con = db.getCon();
        String sql = "update Student set username = ?, password = ? where id = ?";
        PreparedStatement pstm = con.prepareStatement(sql);

        pstm.setString(1, s.getUsername());
        pstm.setString(2, s.getPassoword());
        pstm.setInt(3, s.getId());

        int i = pstm.executeUpdate();
        db.closeAll();

        return i;
    }

    /**
     * 根据id删除学生
     * 返回值：
     * 1：删除成功
     * 0：失败，（数据可能不存在）
     */
    public int del(int id) throws SQLException {
        DBUtil db = new DBUtil();
        Connection con = db.getCon();
        String sql = "delete from Student where id = ?";
        PreparedStatement pstm = con.prepareStatement(sql);

        pstm.setInt(1, id);

        int i = pstm.executeUpdate();
        db.closeAll();

        return i;
    }

    /**
     * 根据用户名模糊查询
     * 返回值：
     * 1：删除成功
     * 0：失败，（数据可能不存在）
     */
    public List queryByName(String inputName) throws SQLException {
        ArrayList<Student> list = new ArrayList<Student>();

        DBUtil db = new DBUtil();
        Connection con = db.getCon();
        String sql = "select * from Student where username like ?";
        PreparedStatement pstm = con.prepareStatement(sql);

        pstm.setString(1, "%" + inputName + "%");

        ResultSet rs = pstm.executeQuery();

        while (rs.next()) {
            // 取出每一行中的每一列的数据
            int id = rs.getInt(1);
            String username = rs.getString(2);
            String password = rs.getString(3);

            // 将数据封装到Studnet对象里
            Student s = new Student(id, username, password);

            // 分别将每一个studnet对象，添加到list集合中
            list.add(s);
        }


        db.closeAll();

        return list;
    }

    /**
     * 查询所有学生信息
     * 返回值：list
     */
    public List queryAll() throws SQLException {

        ArrayList<Student> list = new ArrayList<Student>();

        DBUtil db = new DBUtil();
        Connection con = db.getCon();
        String sql = "select * from Student";
        PreparedStatement pstm = con.prepareStatement(sql);

        ResultSet rs = pstm.executeQuery();

        while (rs.next()) {
            // 取出每一行中的每一列的数据
            int id = rs.getInt(1);
            String username = rs.getString(2);
            String password = rs.getString(3);

            // 将数据封装到Studnet对象里
            Student s = new Student(id, username, password);

            // 分别将每一个studnet对象，添加到list集合中
            list.add(s);
        }

        db.closeAll();

        return list;
    }

}

4 测试

import net920vip.Bean.Student;
import net920vip.Dao.StudentDao;

import java.sql.SQLException;

public class SDaoTest {
    public static void main(String[] args) throws SQLException {

        // 插入数据
        StudentDao dao = new StudentDao();
        Student s = new Student("tom", "abc");
        dao.insert(s);

        // 更新数据
//        StudnetDao dao = new StudnetDao();
//        Student s = new Student(1, "tom", "CC1");
//        int i = dao.update(s);
//        System.out.println(i);

        // 删除数据
//        StudnetDao dao = new StudnetDao();
//        int i = dao.del(4);
//        System.out.println(i);

        // 查询所有用户信息
//        StudnetDao dao = new StudnetDao();
//        List<Student> list = dao.queryAll();
//
//        if (list != null) {
//            for (int i = 0; i < list.size(); i++) {
//                Student s = list.get(i);
//                System.out.println("索引：" + (i + 1) + "用户名：" + s.getUsername() + "密码：" + s.getPassoword());
//            }
//        }

        // 模糊查询
//        System.out.println("请输入要查询的用户名");
//        String inputName = "admin";
//
//        StudnetDao1 dao = new StudnetDao1();
//        List<Student> list = dao.queryByName(inputName);
//
//        if (list != null) {
//            for (int i = 0; i < list.size(); i++) {
//                Student s = list.get(i);
//                System.out.println("索引：" + (i + 1) + "用户名：" + s.getUsername() + "密码：" + s.getPassoword());
//            }
//        }

    }
}

上篇文章：java jdbc连接数据库

下篇文章：java Dao层抽象化设计

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