JAVA学习笔记(五十一)- DBUtil 封装数据库工具类

数据库工具类

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/*
 * 数据库工具类
 */
public class DBUtil {

    // 获取数据库连接
    public static Connection getConnection() {
        String driverClassName = "com.mysql.jdbc.Driver";
        String url = "jdbc:mysql://localhost:3306/test";
        String user = "root";
        String password = "123456";
        Connection conn = null;
        try {
            Class.forName(driverClassName);
            conn = DriverManager.getConnection(url, user, password);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }

    // 关闭所有
    public static void closeAll(ResultSet rs, Statement stmt, Connection conn) {
        try {
            if (rs != null)
                rs.close();
            if (stmt != null)
                stmt.close();
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            rs = null;
            stmt = null;
            conn = null;
        }
    }
}

JDBC 数据库连接实例

登录

import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JTextField;
import javax.swing.JLabel;
import java.awt.FlowLayout;
import javax.swing.JButton;

public class Login extends JFrame {

    private JPanel contentPane;
    private JTextField textField;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Login frame = new Login();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public Login() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 450, 300);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(0, 0));
        setContentPane(contentPane);

        JPanel panel = new JPanel();
        contentPane.add(panel, BorderLayout.CENTER);
        panel.setLayout(new FlowLayout(FlowLayout.CENTER, 5, 5));

        JLabel label = new JLabel("用户名");
        panel.add(label);

        textField = new JTextField();
        panel.add(textField);
        textField.setColumns(20);

        JButton btnNewButton = new JButton("登陆");
        panel.add(btnNewButton);
    }

}

查询相关信息

import java.sql.Connection;
import java.sql.Date;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.List;

public class Test04 {
    Connection conn = null;
    PreparedStatement pstmt = null;
    ResultSet rs = null;

    // 根据编号查询用户信息
    public User getUserById(int id) {
        User user = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(
                    "jdbc:mysql://localhost:3306/test", "root", "123456");
            /*
             * stmt = conn.createStatement(); String sql =
             * "select * from user where id=" + id;
             */
            String sql = "select * from user where id=?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, id);
            rs = pstmt.executeQuery();
            if (rs.next()) {
                user = new User(rs.getInt("id"), rs.getString("name"),
                        rs.getString("password"), rs.getInt("age"),
                        rs.getDate("birthday"));
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                rs.close();
                pstmt.close();
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                rs = null;
                pstmt = null;
                conn = null;
            }
        }
        return user;
    }

    // 检查用户登陆，即判断用户名或密码是否正确
    public boolean checkLogin(User user) {
        boolean flag = false;
        /*String sql = "select *  from user where name=‘" + user.getName()
                + "‘ and password=‘" + user.getPassword() + "‘";*/
        String sql="select * from user where name=? and password=?";

        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(
                    "jdbc:mysql://localhost:3306/test", "root", "123456");
            pstmt=conn.prepareStatement(sql);
            pstmt.setString(1, user.getName());
            pstmt.setString(2, user.getPassword());
            rs=pstmt.executeQuery();
            if(rs.next()){
                flag=true;
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            try {
                rs.close();
                pstmt.close();
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return flag;
    }

    //查询所有用户信息
    public List<User> getAllUser(){
        List<User> users=new ArrayList<User>();
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection(
                    "jdbc:mysql://localhost:3306/test", "root", "123456");
            String sql = "select * from user";
            pstmt = conn.prepareStatement(sql);
            rs = pstmt.executeQuery();
            while(rs.next()) {
                users.add(new User(rs.getInt("id"), rs.getString("name"),
                        rs.getString("password"), rs.getInt("age"),
                        rs.getDate("birthday")));
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                rs.close();
                pstmt.close();
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                rs = null;
                pstmt = null;
                conn = null;
            }
        }
        return users;
    }

    //用户注册，即添加用户
    public void addUser(User user){
        String sql="insert into user values (null,?,?,?,?)";

        //调用工具类，获取连接Connection
        conn=DBUtil.getConnection();
        try {
            pstmt=conn.prepareStatement(sql);
            pstmt.setString(1, user.getName());
            pstmt.setString(2,user.getPassword());
            pstmt.setInt(3, user.getAge());
            pstmt.setDate(4, new Date(user.getBirthday().getTime()));//将java.util.Date转换为java.sql.Date
            pstmt.executeUpdate();
            System.out.println("添加用户成功！");
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            DBUtil.closeAll(rs, pstmt, conn);
        }
    }

    //根据编号删除用户信息
    public void deleteUserById(int id){

    }

    //更新用户信息
    public void updateUser(User user){

    }

    //根据编号范围和姓名模糊查询
    public List<User> getUserByCondition(int sid,int eid,String name){

        return null;
    }

    public static void main(String[] args) {
        Test04 test = new Test04();
        User user = test.getUserById(2);
        System.out.println(user);

        User user=new User("赵超","222222");
        boolean flag=test.checkLogin(user);
        System.out.println("是否登陆成功？"+flag);

        List<User> users=test.getAllUser();
        System.out.println(users);
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
        java.util.Date birthday=null;
        try {
            birthday = sdf.parse("2014-2-14");
        } catch (ParseException e) {
            e.printStackTrace();
        }
        test.addUser(new User("余书石", "123456", 18, birthday));
    }
}

用户类,实体类

import java.util.Date;

/*
 * 用户类,实体类
 */
public class User {
    private int id;
    private String name;
    private String password;
    private int age;
    private Date birthday;

    public User(int id, String name, String password, int age, Date birthday) {
        super();
        this.id = id;
        this.name = name;
        this.password = password;
        this.age = age;
        this.birthday = birthday;
    }

    public User() {
    }

    public User(String name, String password, int age, Date birthday) {
        super();
        this.name = name;
        this.password = password;
        this.age = age;
        this.birthday = birthday;
    }

    public User(String name, String password) {
        super();
        this.name = name;
        this.password = password;
    }

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String toString() {
        return "User[id=" + id + ",name=" + name + ",age=" + age + ",birthday="
                + birthday + "]";
    }

}

创建数据库语句

create table user
(
    id int primary key auto_increment,
    name varchar(20) not null,
    password varchar(20),
    age int,
    birthday date
);