JDBC（14）—对DAO进行改进修改

结构：

DAO2_7< T >（接口）—>DAOTestImpl< T >（实现类）—>CustomerDAO（继承的子类）—>CustomerDAOTest（继承的测试类）

代码：

• 接口：

package JDBC;

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

/**
 * 访问数据的接口
 *其中定义了访问数据表的各种方法
 *@param T：DAO处理的实体类的类型
 *版本：2.0
 *
 */
public interface DAO2_7<T> {

    /**
     * 1.功能：insert、update、delete
     * @param conn：链接数据库
     * @param sql：SQL语句
     * @param objects：占位符的可变参数
     * @throws SQLException
     */
    void update(Connection conn, String sql, Object ... objects ) throws SQLException;
    /**
     * 2.功能：返回一个T类型对象
     * @param conn
     * @param sql
     * @param objects
     * @return
     * @throws SQLException
     */
    T get(Connection conn, String sql, Object ...objects) throws SQLException;
    /**
     * 3.功能：返回一个T类型的对象的集合
     * @param conn
     * @param sql
     * @param objects
     * @return
     * @throws SQLException
     */
    List<T> getForList(Connection conn, String sql, Object ...objects) throws SQLException;
    /**
     * 4.返回具体的一个值，例如：总人数、平均数，某个人的名字。
     * @param conn
     * @param sql
     * @param objects
     * @return
     * @throws SQLException
     */
    <E> E getForValue(Connection conn, String sql, Object ...objects) throws SQLException;
    /**
     * 5.批量处理的方法
     * @param conn
     * @param sql
     * @param objects：填充占位符的Object[]类型的可变参数
     * @throws SQLException
     */
    void batch(Connection conn, String sql, Object[] ...objects) throws SQLException;
}

• 实现类

package JDBC;

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 反射机制.ReflectionUtils;

public class DAOTestImpl<T> implements DAO2_7<T> {

    private QueryRunner queryRunner = null;
    private Class <T> type;
    //构造器
    public DAOTestImpl(){
        queryRunner = new QueryRunner();
        type = ReflectionUtils.getSuperGenericType(getClass());
    }
    //更新数据
    @Override
    public void update(Connection conn, String sql, Object... objects) throws SQLException {
        queryRunner.update(conn, sql, objects);
    }
    //查询数据
    @Override
    public T get(Connection conn, String sql, Object... objects) throws SQLException {
        return queryRunner.query(conn, sql, new BeanHandler<>(type), objects);
    }
    //获取多条记录
    @Override
    public List<T> getForList(Connection conn, String sql, Object... objects) throws SQLException {
        return queryRunner.query(conn, sql, new BeanListHandler<>(type), objects);
    }
    //获取某一列值，或计算总数
    @Override
    public <E> E getForValue(Connection conn, String sql, Object... objects) throws SQLException {
        return (E)queryRunner.query(conn, sql, new ScalarHandler(), objects);
    }
    //批量操作
    @Override
    public void batch(Connection conn, String sql, Object[]... objects) throws SQLException {
        queryRunner.batch(conn, sql, objects);
    }

}

• 继承的子类

package JDBC;

import JDBCTest.Customers;

public class CustomerDAO extends DAOTestImpl<Customers> {

}

• 继承子类的测试类

package JDBC;

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

import org.junit.Test;

import JDBCTest.Customers;
import JDBCTest.TestTools;

public class CustomerDAOTest extends CustomerDAO {

    Connection conn = null;
    CustomerDAO customerDao = new CustomerDAO();
    //构造器
    public CustomerDAOTest() throws Exception{
        conn = TestTools.getConnection();
    }
    @Test
    public void testUpdate() {
        try {
            String sql = "INSERT INTO customers(id,name,age,birth,address) VALUES(?, ?, ?, ?, ?)";
            customerDao.update(conn, sql, 1, "张力", "32", new Date(new java.util.Date().getTime()), "上海市" );
            System.out.println("OK");
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            TestTools.release(null, conn);
        }
    }

    @Test
    public void testGet() {
        try {

            String sql = "select id, name, age, birth from customers where id = ?";
            Customers customer = customerDao.get(conn, sql, 15);
            System.out.println(customer);
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            TestTools.release(null, conn);
        }
    }

    @Test
    public void testGetForList() {
        try {
                String sql = "select id, name, age, birth from customers where id > ?";
                List<Customers> customers = customerDao.getForList(conn, sql, 15);
                System.out.println(customers);
            } catch (Exception e) {
                e.printStackTrace();
            }finally{
                TestTools.release(null, conn);
            }
    }

    @Test
    public void testGetForValue() {
        try {
            String sql = "select count(id) from customers";
            Object result = customerDao.getForValue(conn, sql, null);
            System.out.println(result);
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            TestTools.release(null, conn);
        }
    }

    @Test
    public void testBatch() {
        try {
            String sql = "INSERT INTO customers(name, age, birth, address) VALUES(?, ?, ?, ?)";
            Object objects[][] = new Object[1000][4];
            for(int i = 0; i < 1000; i++){
                objects[i][0] = "name_"+i;
                objects[i][1] = "20";
                objects[i][2] = (new Date(new java.util.Date().getTime()));
                objects[i][3] = "河南省";
            }

            customerDao.batch(conn, sql, objects);
            System.out.println("OK");
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            TestTools.release(null, conn);
        }
    }

}