JDBC工具類

抽取JDBC工具類

目的：方便代碼書寫

分析：

1. 註冊驅動
2. 抽取一個方法來獲取連接對象
3. 抽取一個方法來釋放資源

配置（properties）文件

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/city
user=root
password=root

類代碼

package jdbcutils;

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

public class JDBCUtil {

    private static String url;
    private static String user;
    private static String password;
    private static String driver;

    static {
        //Properties集合類
        Properties properties = new Properties();
        try {
            //獲取src下的文件的方式-->ClassLoader
            ClassLoader classLoader = JDBCUtil.class.getClassLoader();
            URL jdbcUrl = classLoader.getResource("jdbc.properties");
            String path = jdbcUrl.getPath();
            path = java.net.URLDecoder.decode(path, "utf-8");

            properties.load(new FileReader(path));
            url = properties.getProperty("url");
            user = properties.getProperty("user");
            password = properties.getProperty("password");
            driver = properties.getProperty("driver");
            Class.forName(driver);
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    /**
     * 獲取connection連接對象，無序傳遞參數
     * 使用配置文件的方式
     * @return Connection實例
     */
    public static Connection getConnection() {
        try {
            return DriverManager.getConnection(url, user, password);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * 釋放資源
     * @param statement
     * @param connection
     */
    public static void close(Statement statement, Connection connection) {
        if (statement != null) {
            close(statement);
        }
        if (connection != null) {
            close(connection);
        }
    }

    public static void close(Statement statement, Connection connection, ResultSet resultSet) {
        if (statement != null) {
            close(statement);
        }
        if (connection != null) {
            close(connection);
        }
        if (resultSet != null) {
            close(resultSet);
        }
    }

    public static void close(Statement statement) {
        try {
            statement.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static void close(Connection connection) {
        try {
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public static void close(ResultSet resultSet) {
        try {
            resultSet.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

}

工具類測試代碼

package jdbc;

import jdbcutils.JDBCUtil;

import java.sql.*;

public class JDBCDemo {
    public static void main(String[] args) {
        Connection connection = JDBCUtil.getConnection();
        Statement statement = null;
        ResultSet resultSet = null;
        try {
            statement = connection.createStatement();
            String querySQL = "SELECT * FROM student WHERE id = 1";
            resultSet = statement.executeQuery(querySQL);

            while(resultSet.next()) {
                int id = resultSet.getInt("id");
                String name = resultSet.getString("name");
                int age = resultSet.getInt("age");
                String sex = resultSet.getString("sex");
                String address = resultSet.getString("address");
                int math = resultSet.getInt("math");
                int english = resultSet.getInt("english");

                System.out.println(id + "  " + name + " " + age + "  " + sex + "  " + address + "  " + math + "  " + english);
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }

        JDBCUtil.close(statement, connection, resultSet);
    }
}

工具類測試（登陸）

import java.sql.*;
import java.util.Scanner;

public class JDBCDemo {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        Connection connection = JDBCUtil.getConnection();
        Statement statement = null;
        ResultSet resultSet = null;
        try {
            statement = connection.createStatement();

            String user, password;
            while(scanner.hasNext()) {
                user = scanner.next();
                password = scanner.next();

                String querySQL = "SELECT password FROM users WHERE name = " + "'" + user + "'";
                resultSet = statement.executeQuery(querySQL);
                if(!resultSet.next()) {
                    System.out.println("賬號不存在!");
                    continue;
                }

                if(password.trim().equals(resultSet.getString("password").trim())) {
                    System.out.println("登陸成功!");
                } else {
                    System.out.println("登陸失敗!");
                }
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }

        JDBCUtil.close(connection, statement, resultSet);
        scanner.close();
    }
}