JDBC02

带配置文件的工具类

public class DBUtil {
	//声明成成员变量 方便使用
	private static Connection connection;
	private static String driverClass;
	private static String url;
	private static String username;
	private static String password;
static {
	readFile();
	//注册驱动
	try {
		Class.forName(driverClass);
	} catch (ClassNotFoundException e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}
	
}

//读文件的方法 
public static void readFile() {
	//读文件
		//类加载器 直接获取bin文件夹下的该文件
	InputStream inputStream = DBUtil.class.getClassLoader().getResourceAsStream("db.properties");
	Properties properties=new Properties();
	try {
		properties.load(inputStream);
		driverClass= properties.getProperty("driverClass");
		url= properties.getProperty("url");
		username= properties.getProperty("username");
		password= properties.getProperty("password");
	} catch (IOException e) {
		e.printStackTrace();
	
	}
	
}
//获取连接方法
public static Connection getConnection()  {
	try {
		connection=DriverManager.getConnection(url, username, password);
	} catch (SQLException e) {
		e.printStackTrace();
		throw new RuntimeException("获取连接失败");
	}
	return connection;
}
}

DBUtil 第三方类库

数据库的工具类

简化数据库操作的代码和jdbc连接的代码

操作数据库的三个核心类

1.DBUtil 关闭数据库

closeQuietly 不会抛出SQLException异常

2.QueryRunner 查询对象

update(Connection conn, String sql, Object... params)

传入的sql语句可以只用占位符?

通过参数3 把替换?的值传进去

3.ResultSetHandle 查询结果的返回集

接口需要使用它的实现类(8个)

插入一条数据:

        QueryRunner qr=new QueryRunner();
	String sql ="insert into goods values(null,?,?,?)";
	Object[] params = {"糖",4,"好吃不贵"};
	int row = qr.update(DBUtil.getConnection(), sql, params);
	System.out.println(row);
	DbUtils.closeQuietly(DBUtil.getConnection());

使用arrayhandle

                QueryRunner qr=new QueryRunner();
		String sql="select * from goods";
		Object[] query = qr.query(DBUtil.getConnection(), sql, new ArrayHandler());
		使用arrayhandle类 会返回数据库中的一条记录  并且会把该记录的字段放入object数组中
		for (Object object : query) {
			System.out.println(object);
		}

测试ArrayListHandel

                QueryRunner qr=new QueryRunner();
		String sql="select * from goods";
		集合中每一个object[] 就是数据库中的一条记录
		List<Object[]> query = qr.query(DBUtil.getConnection(), sql, new ArrayListHandler());
		for (Object[] objects : query) {
			for (Object object : objects) {
				System.out.print(object);
			}
			System.out.println();
		}

测试beanhandle

                可以将查询结果放入实体对象中
		QueryRunner qr=new QueryRunner();
		String sql="select * from goods";
		参数是放入对象的实体类的.class文件类型
		Goods query = qr.query(DBUtil.getConnection(), sql, new BeanHandler<Goods>(Goods.class));
		System.out.println(query);

测试beanlisthandle

                QueryRunner qr = new QueryRunner();
		String sql = "select * from goods";
		 List<Goods> query = qr.query(DBUtil.getConnection(), sql, new BeanListHandler<>(Goods.class));
		 for (Goods goods : query) {
		System.out.println(goods);
		}

测试columnlisthandle

                可以将查询结果放入实体对象中
		QueryRunner qr = new QueryRunner();
		String sql = "select * from goods";
		数据库中一列数据放入集合中返回
		List<Object> query = qr.query(DBUtil.getConnection(), sql, new ColumnListHandler<>("sname"));
		for (Object object : query) {
			System.out.println(object);
		}

测试scalarhandler

                QueryRunner qr = new QueryRunner();
		String sql = "select count(*) from goods";
		该方法返回类型是long	
		Long query = qr.query(DBUtil.getConnection(), sql, new ScalarHandler<Long>());
		System.out.println(query);

测试maphandler

                QueryRunner qr = new QueryRunner();
		String sql = "select * from goods";
		Map<String, Object> query = qr.query(DBUtil.getConnection(), sql, new MapHandler());
		for (String key : query.keySet()) {
			System.out.println(key+" "+query.get(key));
		}

测试maplisthandler

        QueryRunner qr = new QueryRunner();
        String sql = "select * from goods";
	List<Map<String,Object>> query = qr.query(DBUtil.getConnection(), sql, new MapListHandler());
	for (Map<String, Object> map : query) {
	for (String key : map.keySet()) {
		System.out.print(key+" "+map.get(key));
	}
	System.out.println();
	}

datasourse数据源

数据库连接池中保存了许多的连接(connection)

在操作数据库时最耗费资源的是创建连接和销毁连接

当用户查询数据库时从连接池取出一个使用用完后重新放入连接池

java为连接池准备了一套规范(接口)

javax.sql扩展包

这套规范也是由数据库厂商实现该类也提供获取连接的方法

常用的数据库连接池:

DBCP C3P0

                利用数据库连接池获取连接
		BasicDataSource dataSource=new BasicDataSource();
		基础设置
		dataSource.setDriverClassName("com.mysql.jdbc.Driver");
		dataSource.setUrl("jdbc:mysql://localhost:3306/myjdbc01");
		dataSource.setUsername("root");
		dataSource.setPassword("123456");
		获取连接
		Connection connection = dataSource.getConnection();
		System.out.println(connection);

测试向queryrunner中传入数据源

                传入数据源后 就不用考虑连接的事 直接调用查询
		QueryRunner qr=new QueryRunner(DatasourseUitl.getDataSourse());
		String sql="select * from goods";
		List<Goods> query = qr.query(sql, new BeanListHandler<>(Goods.class));
		for (Goods goods : query) {
			System.out.println(goods);
		}

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