Mybatis——传入POJO对象，动态SQL，多表关系，与Spring整合

传入POJO对象

QueryVo.java

public class QueryVo implements Serializable{

    private User user;

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }
}

SQL映射文件

	select * from user where id = #{user.id}

测试类

@Test
public void func9() throws IOException {

    // 1.加载配置文件
    InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
    // 2.创建sqlSessionFactory
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
    // 3.获取sqlsession
    SqlSession sqlSession = sqlSessionFactory.openSession();
    // -------------------------------------------

    // 4.SqlSEssion帮我生成一个实现类（给接口的字节码文件）
    UserDao mapper = sqlSession.getMapper(UserDao.class);

    // 创建一个POJO对象
    QueryVo vo = new QueryVo();
    User u = new User();
    u.setId(2);

    vo.setUser(u);

    User userByPOJO = mapper.findUserByPOJO(vo);

    System.out.println(userByPOJO);

    // -------------------------------------------

}

resultMap（手动指定字段）

数据库表

Order实体文件

public class Order {
	// 订单id
	private int id;
	// 用户id
	private Integer userId;
	// 订单号
	private String number;
	// 订单创建时间
	private Date createtime;
	// 备注
	private String note;
get/set。。。
}

SQL映射文件

由于实体和SQL中的userid字段不同，所以要使用resultMap

	




	select * from `order` where id = #{id}
	-- order是关键字，所以要用``包起来

OrderDao.java

public interface OrderDao {

    Order findOrderById(int i);

}

测试类

public void func() throws IOException {

    // 1.加载配置文件
    InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
    // 2.创建sqlSessionFactory
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
    // 3.获取sqlsession
    SqlSession sqlSession = sqlSessionFactory.openSession();
    // -------------------------------------------

    // 4.执行相应的SQL语句
    OrderDao mapper = sqlSession.getMapper(OrderDao.class);

    Order orderById = mapper.findOrderById(1);

    System.out.println(orderById);

    // -------------------------------------------
}

一.动态SQL

1）if标签&&where标签

	
		
			 and sex = #{sex} 
		
		
			 and username = #{username}
		
	
 

2）foreach标签

a.直接传入数组

UserDao.java

public interface UserDao {
    List selectUserByIds(int[] ids);
}

配置文件

	
	
		
		
			#{id}
		
	

测试类

@Test
public void func3() throws IOException {

    // 1.加载配置文件
    InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
    // 2.创建sqlSessionFactory
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
    // 3.获取sqlsession
    SqlSession sqlSession = sqlSessionFactory.openSession();
    // -------------------------------------------

    // 方法一：直接传入一个数组
    int[] ids = {1,2,3};

    UserDao mapper = sqlSession.getMapper(UserDao.class);

    List list = mapper.selectUserByIds(ids);

    System.out.println(list);

    // -------------------------------------------
}

b.直接传入集合

	
	
		
		
			#{id}
		
	

测试类

// 方法二：直接传入一个集合
List ids = new ArrayList<>();

ids.add(1);
ids.add(2);
ids.add(3);

UserDao mapper = sqlSession.getMapper(UserDao.class);

List list = mapper.selectUserByIds(ids);

System.out.println(list);

c.传入一个POJO，里面有集合或者数组

	
	
		
			#{id}
		
	

测试类

// 方法三：传入一个POJO
//List ids = new ArrayList<>();
//
//ids.add(1);
//ids.add(2);
//ids.add(3);
int[] ids = {1,2,3};
QueryVo vo = new QueryVo();
vo.setIds(ids);



UserDao mapper = sqlSession.getMapper(UserDao.class);

List list = mapper.selectUserByIds(vo);

System.out.println(list);

二.关联查询

1、一对一查询

1）在Order中添加一个user字段并提供get，set方法

 

2）书写接口

List findOrderList();

3）书写配置文件

	
	
	

	
	
		
		
	




	select
	o.id,o.user_id,o.number,o.createtime,u.username
	from `order` o
	left join
	user u
	on
	o.user_id=u.id

4）测试类

public void func4() throws IOException {

    // 1.加载配置文件
    InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
    // 2.创建sqlSessionFactory
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
    // 3.获取sqlsession
    SqlSession sqlSession = sqlSessionFactory.openSession();
    // -------------------------------------------

    OrderDao mapper = sqlSession.getMapper(OrderDao.class);

    List orderList = mapper.findOrderList();

    System.out.println(orderList);

    // -------------------------------------------
}

2、一对多查询

1）在User中添加一个集合，保存Order对象

2）书写接口

List findUserAllOrder();

3）SQL映射文件

	
	

	
	
		
		
		
		
	



	select
	o.id,o.user_id,o.number,o.createtime,u.username
	from user u
	left join
	`order` o
	on
	o.user_id=u.id

测试类

@Test
public void func5() throws IOException {

    // 1.加载配置文件
    InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
    // 2.创建sqlSessionFactory
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
    // 3.获取sqlsession
    SqlSession sqlSession = sqlSessionFactory.openSession();
    // -------------------------------------------

    OrderDao mapper = sqlSession.getMapper(OrderDao.class);

    List userAllOrderList = mapper.findUserAllOrder();

    System.out.println(userAllOrderList);

    // -------------------------------------------
}

三.与Spring整合

方式一：原始Dao方式

1）Spring配置文件

2）UserDao.java

// 继承SqlSessionDaoSupport，调用父类的getSqlSession方法
public class UserDaoImpl extends SqlSessionDaoSupport implements UserDao {

    public void main(String[] args) {
        super.getSqlSession().selectList("xxx.xxx","参数");
    }
}

方式二：mapper代理模式 

1）Spring配置文件

2）Mybatis主配置文件

3）SQL映射关系配置文件

	
	
	
	
		select * from user where id = #{id}
	
	

4）UserMapper接口

public interface UserMapper {
    User findUserById(Integer id);
}

5）测试类

public void func(){
    ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("spring-config.xml");
    UserMapper userMapper = (UserMapper) ac.getBean("userMapper");

    User userById = userMapper.findUserById(1);

    System.out.println(userById);
}

方式三：动态扫描

上面的会有一个弊端，如果Mapper太多，配置文件就变得很多。所以引入扫描

获取mapper方法

UserMapper userMapper = ac.getBean(UserMapper.class);

 

转载于:https://www.cnblogs.com/x54256/p/8538582.html