JDBC 使用和配置

Posted 2020-10-04 清泉＊＊＊

/**
 * 数据库工具类,封装数据库操作中多次使用的数据库操作代码
 * @author Administrator
 *
 */
public class DBUtils {
	
	public static Connection getConnection() {

		Connection connection = null;
		try {

			Class.forName("com.mysql.jdbc.Driver");

			String databaseName = "jdbc_test";
			String url = "jdbc:mysql://localhost:3306/" + databaseName;
			String user = "root";
			String password = "111";

			connection = DriverManager.getConnection(url, user, password);

		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return connection;

	}

}

*Connection connection = DBUtils.getConnection();　

*PreparedStatement preparedStatement = connection.prepareStatement(sql);

*ResultSet resultSet = preparedStatement.executeQuery();

以上三个流都需要进行关闭  也都可以用try - with - resource 进行关闭  (自动关闭  不需要手动)

 *   jdbc.properties

url=jdbc:mysql://localhost:3306/test104
user=root
password=123456

 

package com.zhiyou100.util;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public enum DBUtils {

	/*
	 * 单例通过枚举实现，枚举最后一个单词后以 ; 结尾
	 * 构造方法都是 private 修饰，不让通过 new 构造方法创建对象
	 * static 方法中只能使用 static 变量，不能使用类的实例变量（属性，全局变量）
	 */
	INSTANCE;
	
	private String url;
	
	private String user;
	
	private String password;
	
	private DBUtil() {
		try {
			InputStream inputStream = DBUtils.class.getClassLoader().getResourceAsStream("jdbc.properties");

			Properties properties = new Properties();
			
			properties.load(inputStream);
			
			url = properties.getProperty("url");

			user = properties.getProperty("user");

			password = properties.getProperty("password");
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public Connection getConnection() {

		Connection conn = null;

		try {

			Class.forName("com.mysql.jdbc.Driver");

			// 读取编译后的 class 文件夹下的某一个文件
			conn = DriverManager.getConnection(url, user, password);

		} catch (ClassNotFoundException e) {

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

			e.printStackTrace();
		} 

		return conn;
	}
}