jdbc连接mysql的标准写法

经常会忘记jdbc原生态写法，故此写下来以备后用~

JDBC的步骤无非就简单的四步：

一、创建连接；

二、创建Statement对象；

三、执行查询；

四、关闭连接。

饿汉式

<span style="font-size:18px;">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);
            <span style="white-space:pre">	</span>conn = DriverManager.getConnection(DBURL, DBUSER, PASSWORD);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }
    public void close(){
        if(conn != null){
            try {
                this.conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }</span>

<span style="font-size:18px;">}</span>

懒汉式

<span style="font-size:18px;">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();
            }
        }
    }
}</span>