YourAboutMeIsBlank Madan Sapko

初始化数据库常量

创建常量属性数据库用户名、密码、URL和驱动程序、轮询限制等。

// init database constants
// com.mysql.jdbc.Driver
private static final String DATABASE_DRIVER = "com.mysql.cj.jdbc.Driver";
private static final String DATABASE_URL = "jdbc:mysql://localhost:3306/database_name";
private static final String USERNAME = "root";
private static final String PASSWORD = "";
private static final String MAX_POOL = "250"; // set your own limit

初始化连接和属性

建立连接后,最好存储以供重用。

// init connection object
private Connection connection;
// init properties object
private Properties properties;

创建属性

properties对象保存连接信息,检查它是否已设置。

// create properties
private Properties getProperties() {
    if (properties == null) {
        properties = new Properties();
        properties.setProperty("user", USERNAME);
        properties.setProperty("password", PASSWORD);
        properties.setProperty("MaxPooledStatements", MAX_POOL);
    }
    return properties;
}

连接数据库

现在使用初始化的常量和属性连接到数据库。

// connect database
public Connection connect() {
    if (connection == null) {
        try {
            Class.forName(DATABASE_DRIVER);
            connection = DriverManager.getConnection(DATABASE_URL, getProperties());
        } catch (ClassNotFoundException | SQLException e) {
            // Java 7+
            e.printStackTrace();
        }
    }
    return connection;
}

断开数据库连接

完成数据库操作后,请关闭连接。

// disconnect database
public void disconnect() {
    if (connection != null) {
        try {
            connection.close();
            connection = null;
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

一切都在一起

使用这个类 MysqlConnect 直接更改数据库名称、用户名和密码等。

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

public class MysqlConnect {
    // init database constants
    private static final String DATABASE_DRIVER = "com.mysql.cj.jdbc.Driver";
    private static final String DATABASE_URL = "jdbc:mysql://localhost:3306/database_name";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "";
    private static final String MAX_POOL = "250";

    // init connection object
    private Connection connection;
    // init properties object
    private Properties properties;

    // create properties
    private Properties getProperties() {
        if (properties == null) {
            properties = new Properties();
            properties.setProperty("user", USERNAME);
            properties.setProperty("password", PASSWORD);
            properties.setProperty("MaxPooledStatements", MAX_POOL);
        }
        return properties;
    }

    // connect database
    public Connection connect() {
        if (connection == null) {
            try {
                Class.forName(DATABASE_DRIVER);
                connection = DriverManager.getConnection(DATABASE_URL, getProperties());
            } catch (ClassNotFoundException | SQLException e) {
                e.printStackTrace();
            }
        }
        return connection;
    }

    // disconnect database
    public void disconnect() {
        if (connection != null) {
            try {
                connection.close();
                connection = null;
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

如何使用?

初始化数据库类。

// !_ note _! this is just init
// it will not create a connection
MysqlConnect mysqlConnect = new MysqlConnect();

在你代码的其他地方。。。

String sql = "SELECT * FROM `stackoverflow`";
try {
    PreparedStatement statement = mysqlConnect.connect().prepareStatement(sql);
    ... go on ...
    ... go on ...
    ... DONE ....
} catch (SQLException e) {
    e.printStackTrace();
} finally {
    mysqlConnect.disconnect();
}

就这些 :) 如果有什么要改进的话就编辑吧!希望这对你有帮助。