Mapper系列六：类型处理器TypeHandler

古城微笑少年丶 2022-04-25 02:18 168阅读 0赞

简单类型和复杂类型  
![在这里插入图片描述][20190430142835490.png]  
通用 Mapper 默认情况下会忽略复杂类型，对复杂类型不进行“从类到表”的映射。  
1、创建table\_user表和数据

CREATE TABLE `table_user` (
    		`user_id` INT NOT NULL AUTO_INCREMENT,
    		`user_name` VARCHAR (100) NULL,
    		`address` VARCHAR (100) NULL,
    		`season` VARCHAR (100) NULL,
    		PRIMARY KEY (`user_id`)
    	);

![在这里插入图片描述][20190430143911941.png]  
2、自定义类型转换器  
![在这里插入图片描述][20190430144041479.png]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpemhpcWlhbmcxMjE3_size_16_color_FFFFFF_t_70]

public class AddressTypeHandler extends BaseTypeHandler<Address> {
    
    	@Override
    	public void setNonNullParameter(PreparedStatement ps, int i, Address address, JdbcType jdbcType)
    			throws SQLException {
    		//1.对address对象进行验证
    		if(address == null) {
    			return ;
    		}
    		//2.从address对象中取出具体数据
    		String province = address.getProvince();
    		String city = address.getCity();
    		String street = address.getStreet();
    		//3.拼装成一个字符串
    		//规则：各个值之间使用“,”分开
    		StringBuilder builder = new StringBuilder();
    		builder
    			.append(province)
    			.append(",")
    			.append(city)
    			.append(",")
    			.append(street);
    		String parameterValue = builder.toString();
    		//4.设置参数
    		ps.setString(i, parameterValue);
    	}
    
    	@Override
    	public Address getNullableResult(ResultSet rs, String columnName) throws SQLException {
    		//1.根据字段名从rs对象中获取字段值
    		String columnValue = rs.getString(columnName);
    		//2.验证columnValue是否有效
    		if(columnValue == null || columnValue.length() == 0 || !columnValue.contains(",")) {
    			return null;
    		}
    		//3.根据“,”对columnValue进行拆分
    		String[] split = columnValue.split(",");
    		//4.从拆分结果数组中获取Address需要的具体数据
    		String province = split[0];
    		String city = split[1];
    		String street = split[2];
    		//5.根据具体对象组装一个Address对象
    		Address address = new Address(province, city, street);
    		return address;
    	}
    
    	@Override
    	public Address getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
    		//1.根据字段名从rs对象中获取字段值
    		String columnValue = rs.getString(columnIndex);
    		//2.验证columnValue是否有效
    		if(columnValue == null || columnValue.length() == 0 || !columnValue.contains(",")) {
    			return null;
    		}
    		//3.根据“,”对columnValue进行拆分
    		String[] split = columnValue.split(",");
    		//4.从拆分结果数组中获取Address需要的具体数据
    		String province = split[0];
    		String city = split[1];
    		String street = split[2];
    		//5.根据具体对象组装一个Address对象
    		Address address = new Address(province, city, street);
    		return address;
    	}
    
    	@Override
    	public Address getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
    		//1.根据字段名从rs对象中获取字段值
    		String columnValue = cs.getString(columnIndex);
    		//2.验证columnValue是否有效
    		if(columnValue == null || columnValue.length() == 0 || !columnValue.contains(",")) {
    			return null;
    		}
    		//3.根据“,”对columnValue进行拆分
    		String[] split = columnValue.split(",");
    		//4.从拆分结果数组中获取Address需要的具体数据
    		String province = split[0];
    		String city = split[1];
    		String street = split[2];
    		//5.根据具体对象组装一个Address对象
    		Address address = new Address(province, city, street);
    		return address;
    	}
    }

3、注册自定义类型转换器  
 方式1：字段级别：@ColumnType 注解  
![在这里插入图片描述][20190430150913498.png]  
 方式2：全局级别：在 MyBatis 配置文件中配置 typeHandlers

4、枚举类型处理  
 方式1：让通用 Mapper 把枚举类型作为简单类型处理 。Spring 配置文件中添加通用 Mapper 的配置项 `enumAsSimpleType=true`。本质上使用了 `org.apache.ibatis.type.EnumTypeHandler<E>`

<bean class="tk.mybatis.spring.mapper.MapperScannerConfigurer">
    	<property name="basePackage" value="com.atguigu.mapper.mappers"/>
    	<property name="properties">
    		<value>
    			enumAsSimpleType=true
    		</value>
    	</property>
    </bean>

方式2：：为枚举类型配置对应的类型处理器  
![在这里插入图片描述][20190430150244182.png]  
5、枚举类型处理器 ：  
内置：  
 org.apache.ibatis.type.EnumTypeHandler  
   在数据库中存储枚举值本身  
 org.apache.ibatis.type.EnumOrdinalTypeHandler  
   在数据库中仅仅存储枚举值的索引  
自定义：和AddressTypeHandler操作一样  
6、内置枚举类型处理器注册  
 内置类型处理器不能使用@ColumnType 注解  
![在这里插入图片描述][20190430150852904.png]  
 在 MyBatis 配置文件中配置 typeHandlers

测试：

public class TypeHandlerTest {
    	
    	private UserService userService;
    	
    	{
    		userService = new ClassPathXmlApplicationContext("spring-context.xml").getBean(UserService.class);
    	}
    	
    	@Test
    	public void testQueryUser() {
    		Integer userId = 1;
    		User user = userService.getUserById(userId);
    		System.out.println(user);
    	}
    	
    	@Test
    	public void testSaveUser() {
    		User user = new User(null, "tom08", new Address("AAA", "BBB", "CCC"), SeasonEnum.AUTUMN);
    		userService.saveUser(user);
    	}
    }

Preparing: SELECT user_id,user_name,address,season FROM table_user WHERE user_id = ?   
    Parameters: 1(Integer)  
    Total: 1 
    User [userId=1, userName=justin, address=Address [province=aaa, city=bbb, street=ccc], season=summer @_@]

Preparing: INSERT INTO table_user ( user_id,user_name,address,season ) VALUES( ?,?,?,? )   
    Parameters: null, tom08(String), AAA,BBB,CCC(String), 2(Integer)  
    Updates: 1

[20190430142835490.png]: /images/20220210/4f14499ff24d4e69b42e37b6dd4f8f21.png
[20190430143911941.png]: /images/20220210/a91a6e94bae1478ebecf05aeea592bb3.png
[20190430144041479.png]: /images/20220210/cccff26c19cb4418adcd6cb972bb6a66.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpemhpcWlhbmcxMjE3_size_16_color_FFFFFF_t_70]: /images/20220210/f96a6efb0f15412a8b93a325f842654b.png
[20190430150913498.png]: /images/20220210/ca21fd3a139e4dbead2d0053e8f51239.png
[20190430150244182.png]: /images/20220210/348f827cd968443ca77d0afc8055ef95.png
[20190430150852904.png]: /images/20220210/a2d1a4dea53e45b78771b39cb969d58f.png