Java实现数据库连接的五种方法

清疚 2024-04-01 09:36 70阅读 0赞

## 数据库连接方式 ##

### 方式一 ###

直接使用com.mysql.jdbc.Driver(),属于静态加载，灵活性差，依赖性强  
推出方式2

public void connect01() throws SQLException {
        
          //创建dirver对象
           Driver driver =new Driver();
    
           String  url = "jdbc:mysql://localhost:3306/studb";
           //用户名与密码放入properties对象
           Properties properties = new Properties();
           properties.setProperty("user","root");
           properties.setProperty("password","123456");
           //建立连接
           Connection connection = driver.connect(url,properties);
           System.out.println(connection);
       }

### 方式二 ###

利用反射加载Driver类，动态加载，更加灵活

public void connect02() throws ClassNotFoundException, InstantiationException, IllegalAccessException, SQLException {
        
            Class<?> aClass = Class.forName("com.mysql.cj.jdbc.Driver");
            Driver driver = (Driver) aClass.newInstance();
    
            String  url = "jdbc:mysql://localhost:3306/studb";
            //用户名与密码放入properties对象
            Properties properties = new Properties();
            properties.setProperty("user","root");
            properties.setProperty("password","123456");
            //建立连接
            Connection connection = driver.connect(url,properties);
            System.out.println(connection);
    
        }

### 方式三 ###

用DriverManager替代Driver进行统一管理,具有更好的扩展性

public void connect03() throws ClassNotFoundException, InstantiationException, IllegalAccessException, SQLException {
        
            //利用反射加载Driver
            Class<?> aClass = Class.forName("com.mysql.cj.jdbc.Driver");
            Driver driver = (Driver) aClass.newInstance();
            //创建url和user和password
            String  url = "jdbc:mysql://localhost:3306/studb";
            String user = "root";
            String password = "123456";
    //      注册Driver驱动
            DriverManager.registerDriver(driver);
            Connection connection = DriverManager.getConnection(url, user, password);
            System.out.println(connection);
        }

### 方式四 ###

使用Class.forName 自动完成注册驱动，简化代码  
是使用最多的

public void connect04() throws ClassNotFoundException, SQLException {
        
            //利用反射加载Driver类
            //在加载Driver类时，完成注册
            /*源码
            1.静态代码块，在类加载时，会执行一次
            2.DriverManager.registerDriver(new Driver));
            static {
            try {
                DriverManager.registerDriver(new Driver());
            } catch (SQLException var1) {
                throw new RuntimeException("Can't register driver!");
            }
        }
    }
             */
            Class.forName("com.mysql.cj.jdbc.Driver");
    
            //创建url，user，password
            String  url = "jdbc:mysql://localhost:3306/studb";
            String user = "root";
            String password = "123456";
            Connection connection = DriverManager.getConnection(url,user,password);
    
            System.out.println(connection);
        }

### 方式五 ###

实际开发中比较好的，在方式4上改进，使用配置文件，连接数据库更加灵活

public void connect05() throws IOException, ClassNotFoundException, SQLException {
        
            //通过properties对象获取文件信息
            Properties properties = new Properties();
            properties.load(new FileInputStream("src\\Jdbc\\myjdbc\\mysql.properities"));
            //获取相关的值
            String user = properties.getProperty("user");
            String url = properties.getProperty("url");
            String driver = properties.getProperty("driver");
            String password = properties.getProperty("password");
    
            Class.forName(driver);
            Connection connection = DriverManager.getConnection(url,user,password);
            System.out.println(connection);
        }