JDBC连接数据库之编写通用的Dao（7）

Dao.java:

package com.atguigu.common;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

/**
 * 访问数据的 DAO 接口. 
 * 里边定义好访问数据表的各种方法
 * @param T: DAO 处理的实体类的类型. 
 */
public interface DAO {

	/**
	 * 批量处理的方法
	 * @param connection
	 * @param sql
	 * @param args: 填充占位符的 Object [] 类型的可变参数.
	 * @throws SQLException 
	 */  
	void batch(Connection connection, 
			String sql, Object [] ... args) throws SQLException;
	
	/**
	 * 返回具体的一个值, 例如总人数, 平均工资, 某一个人的 email 等.
	 * @param connection
	 * @param sql
	 * @param args
	 * @return
	 * @throws SQLException 
	 */
	 E getForValue(Connection connection,
			String sql, Object ... args) throws SQLException;
	
	/**
	 * 返回 T 的一个集合
	 * @param connection
	 * @param sql
	 * @param args
	 * @return
	 * @throws SQLException 
	 */
	List getForList(Connection connection,
			String sql, Object ... args) throws SQLException;
	
	/**
	 * 返回一个 T 的对象
	 * @param connection
	 * @param sql
	 * @param args
	 * @return
	 * @throws SQLException 
	 */
	T get(Connection connection, String sql, 
			Object ... args) throws SQLException;
	
	/**
	 * INSRET, UPDATE, DELETE
	 * @param connection: 数据库连接
	 * @param sql: SQL 语句
	 * @param args: 填充占位符的可变参数.
	 * @throws SQLException 
	 */
	void update(Connection connection, String sql, 
			Object ... args) throws SQLException;

}

JdbcDaoImpl.java

package com.atguigu.common;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

import com.atguigu.jdbc.ReflectionUtils;

/**
 * 使用 QueryRunner 提供其具体的实现
 * @param : 子类需传入的泛型类型. 
 */
public class JdbcDaoImpl implements DAO {

	private QueryRunner queryRunner = null;
	private Class type;
	
	public JdbcDaoImpl() {
		queryRunner = new QueryRunner();
		type = ReflectionUtils.getSuperGenericType(getClass());
	}
	
	@Override
	public void batch(Connection connection, String sql, Object[]... args) throws SQLException {
		queryRunner.batch(connection, sql, args);
	}

	@Override
	public  E getForValue(Connection connection, String sql, Object... args) throws SQLException {
		return (E) queryRunner.query(connection, sql, new ScalarHandler(), args);
	}

	@Override 
	public List getForList(Connection connection, String sql, Object... args) 
			throws SQLException {
		return queryRunner.query(connection, sql, 
				new BeanListHandler(type), args);
	}

	@Override
	public T get(Connection connection, String sql, Object... args) throws SQLException { 
		return queryRunner.query(connection, sql, 
				new BeanHandler(type), args);
	}

	@Override
	public void update(Connection connection, String sql, Object... args) throws SQLException {
		queryRunner.update(connection, sql, args);
	}
	
}

package com.atguigu.common;

import com.atguigu.jdbc.Customer;

public class CustomerDao 
	extends JdbcDaoImpl{
	
}