MyBatis

准备

依赖

   
      junit
      junit
      4.12
      test
    
    
    
    
        mysql
        mysql-connector-java
        5.1.34
    
    
    
        
            org.mybatis
            mybatis
            3.2.7
        
    
    
        org.bgee.log4jdbc-log4j2
        log4jdbc-log4j2-jdbc4.1
        1.16
    
    
        org.slf4j
        slf4j-api
        1.7.13
    
    
        org.slf4j
        slf4j-log4j12
        1.7.5
    
    
        log4j
        log4j
        1.2.16
    
  

log4j.properties

# Global logging configuration
log4j.rootLogger=DEBUG, stdout
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

SqlMapConfig.xml

Mapper实现自增主键返回

        
        
            select last_insert_id();
        
        insert into user(username,birthday,sex,address) values(#{username},#{birthday},#{sex},#{address})

设置别名

Mappers映射器

MAVEN编译环境JDK版本插件

    
    
          
                org.apache.maven.plugins
                maven-compiler-plugin
                
                    1.8
                    1.8
                    UTF-8
                
            
    

动态SQL

IF

    
        select * 
        from user
         where  1 =1 
         
            and  id = #{id} 
         
         
            and address like '%${address}%'
         
    

WHERE

    select * from user
    
    
        
            #{id}   
        
    

SQL子句

    id,username,birthday,sex,address


    select  
    from user 
    where address like '%${user.address}%'

mybatis的关联查询

一：一对一关联查询

第一步，创建接口和映射文件

OrdersMapperQueryInterface接口定义

public interface OrdersMapperQueryInterface {
    List queryOrdersJoinUsers();
}

UserMppaerQueryInterface接口定义

public interface UserMppaerQueryInterface();

OrdersMapperQueryInterface.xml定义

UserMppaerQueryInterface.xml定义

第二步：配置包扫描路径（SqlMapConfig.xml中配置）

第三步：接口中定义查询方法

List queryOrdersJoinUsers();

第四步：在orders中添加user属性

第五步：定义sql语句查询

    
    
    
    
    
    
    
        
        
        
        
    
  
  
    SELECT * FROM orders myord LEFT JOIN user myuser ON myord.user_id = myuser.id
  

第六步：测试用例开发

@Test
public void testName() throws Exception {
    OrdersMapperQueryInterface mapper = sqlSession.getMapper(OrdersMapperQueryInterface.class);
    List queryOrdersJoinUsers = mapper.queryOrdersJoinUsers();
    for (Orders orders : queryOrdersJoinUsers) {
        System.out.println(orders.getUser().getAddress());
        System.out.println(orders.getUser().getUsername());
    }
}

二：一对多关联查询

第一步:定义pojo类中的对应关系

第二步：定义接口中的方法

第三步：定义sql语句及返回值

    
        
        
        
            
            
            
            
            
            
        
            
            
            
            
        
        
        
        
            select * from user left join orders on user.id = orders.user_id
        
    

Mapper代理形式开发dao

• 开发mapper接口
• 开发mapper文件
• 配置mapper代理

测试方法

public class UserMapperTest {

    private ApplicationContext applicationContext;
    @Before
    public void setUp() throws Exception {
        applicationContext = new ClassPathXmlApplicationContext("classpath:spring/applicationContext.xml");
    }

    @Test
    public void testGetUserById() {
        UserMapper userMapper = applicationContext.getBean(UserMapper.class);
        User user = userMapper.getUserById(1);
        System.out.println(user);
    }

}

扫描包形式配置mapper

每个mapper代理对象的id就是类名，首字母小写

动态代理

第一步：定义接口

public interface UserDao {
    public void eat();
}

第二步：定义实现类

public class UserDaoImpl implements UserDao {
    @Override
    public void eat() {
        System.out.println("我正在吃饭呢");
    }
}

第三步：定义代理类

public class UserProxy implements InvocationHandler{
    private UserDao userDao;
    public UserProxy(UserDao userDao){
        this.userDao = userDao;
    }
    public UserDao getUserDao(){
        UserDao dao = (UserDao) Proxy.newProxyInstance(userDao.getClass().getClassLoader(), userDao.getClass().getInterfaces(), this);
        return dao;
    }
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        if(method.getName().equals("eat")){
            System.out.println("我先睡一觉");
            return method.invoke(userDao, args);
        }
        return method.invoke(userDao, args);
    }
}

第四步：测试用例

public class UserMain {
    public static void main(String[] args) {
        UserDao dao  = new UserDaoImpl();
        UserProxy proxy = new UserProxy(dao);
        UserDao userDao = proxy.getUserDao();
        userDao.eat();
    }
}