标准 mysql 数据库 jdbc 的两种写法 懒汉式 和 饿汉式

饿汉式写法如下：  建议使用

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

public class DataBaseConnection {
    private static final String DBDRIVER = "org.gjt.mm.mysql.Driver";
    private static final String DBURL = "jdbc:mysql://localhost:3306/test";
    private static final String DBUSER = "root";
    private static final String PASSWORD = "admin";
    public Connection conn;

    //饿汉式数据库连接
    public Connection getConnection() {
        try {
            if (conn == null && conn.isClosed())
                Class.forName(DBDRIVER);
            conn = DriverManager.getConnection(DBURL, DBUSER, PASSWORD);
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return conn;
    }
    public void close(){
        if(conn != null){
            try {
                this.conn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}

懒汉式

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

public class DatabaseConnection {
    private static final String DBDRIVER = "org.gjt.mm.mysql.Driver";
    private static final String DBURL = "jdbc:mysql://localhost:3306/test";
    private static final String DBUSER = "root";
    private static final String PASSWORD = "admin";
    private Connection conn = null;

    // 如果要实例化本类对象，实际上就是为了取得数据库连接，那么就把连接过程交给构造方法
    public DatabaseConnection() {
        try {
            Class.forName(DBDRIVER);
            this.conn = DriverManager.getConnection(DBURL, DBUSER, DBPASSWORD);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public Connection getConnection() {
        return this.conn;
    }

    public void close() {
        if (this.conn != null) {
            try { // 关闭时几乎不会有问题
                this.conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}