Spring Boot学习（四）常用注解

一、注解对照表

二.注解用法示例

1.@Controller

用在类名

@Controller

@RequestMapping("/api/v1/user")

public class UserController {}

2.@RequestMapping

用在类名

@Controller

@RequestMapping("/api/v1/user")

public class UserController {}

用在方法名

@RequestMapping(value = "getuser", method = RequestMethod.POST)

public List<User> selectAll() {

    return userService.selectAll();

}

3.@ResponseBody

用在方法名上

将返回对象输出到客户端，如果是字符串，直接输出；如果不是，则默认用Jackson序列化成Json字符串输出。

@ResponseBody

public User addUser(@RequestBody User user) {}

该注解将返回类型转换为指定格式，格式由程序控制，格式包括json、text、xml和其他。若转为Json，需要依赖Json解析Jar包。

4. @RestController

用于返回json、text、xml和其他等格式的数据，但不能返回Jsp和HTML页面。

@RestController

@RequestMapping("/api/v1/user")

public class UserController {}

5.@RequestBody

过使用HandlerAdapter，配置的HttpMessageConverters来将请求内容，转为指定的对象。Spring boot 默认用Jackson来处理反序列化工作。 下面示例是将请求Json参数，利用@RequestBody直接注入到EnterpriseEntity中

@RequestMapping(value = "/enterprise/update", method = RequestMethod.PUT)

    public void updateEnterpriseInfo(@RequestBody EnterpriseEntity enterprise) {

    }

6.@Service

用在ServiceImpl实现类上,声明一个业务逻辑处理类。

@Service("userService")

public class UserServiceImpl implements UserService {}

7.@Repository

用在daoImpl实现类上，声明一个数据库访问类

@Repository

public class IocDao implements IIocDao{

    public void add(){

    }

}

8.@Component

如用在Mybatis的Mapper类上

@Component

@Mapper

public interface UserMapper {

    int deleteByPrimaryKey(Long userId);

}

9.@Configuration

@Configuration

@EnableCaching

public class RedisConfig {

    @Bean

    public CacheManager cacheManager(RedisTemplate redisTemplate) {

        RedisCacheManager cacheManager = new RedisCacheManager(redisTemplate);

        return cacheManager;

    }

}

10.@Bean

@Bean(name = "kafkaContainer")

public KafkaListenerContainerFactory<ConcurrentMessageListenerContainer<String, String>> kafkaListenerContainerFactory() {

    ConcurrentKafkaListenerContainerFactory<String, String> factory = new ConcurrentKafkaListenerContainerFactory<>();

    factory.setConsumerFactory(consumerFactory());

    factory.setConcurrency(1);

    factory.getContainerProperties().setPollTimeout(5000);

    return factory;

}

11.@Qualifier

先指定一个名字：@Qualifier(“primaryDataSource”)

@Autowired

@Qualifier("primaryDataSource")

private DataSource primaryDataSource;

再通过名字：@Qualifier(“primaryDataSource”)引用

@Bean(name = "primaryDataSource", initMethod = "init")

@Qualifier("primaryDataSource")

@ConfigurationProperties(prefix = "spring.datasource.primary")

@Primary

public DataSource primaryDataSource() {

    DataSource datasource = DruidDataSourceBuilder.create().build();

        return datasource;

    }

12.@Autowired

@Autowired

@Qualifier(value = "entityManagerFactoryPrimary")

LocalContainerEntityManagerFactoryBean entityManager;

13.@Resource

配置类：@Component标识这是一个需要注册为Bean的类，注册为Bean以后就可以在Spring容器中通过Resource注入

@Component("jpushConfig")

public class JpushConfig {

    @Value("${jpush.appKey}")

    private String appkey;

    @Value("${jpush.masterSecret}")

    private String masterSecret;

    @Value("${jpush.liveTime}")

    private String liveTime;

    public String getAppkey() {

        return appkey;

    }

    public String getMasterSecret() {

        return masterSecret;

    }

    public void setLiveTime(String liveTime) {

        this.liveTime = liveTime;

    }

}

使用配置：

@Resource

JpushConfig jpushConfig;

14.@Value

properities属性文件中创建键值对

spring.kafka.consumer.topic=test-topic

在Java中将properities属性文件中的值，注入到属性中。

@Value("${spring.kafka.consumer.topic}")

private String topic;

15.@PathVariable

@RequestMapping("/api/{type}")

public String getUser(@PathVariable int type) {}

{type}中的type需要跟参数名统一,若不统一，可用(value = "type")指定：

@RequestMapping("/api/{type}")

public String getUser(@PathVariable(value = "type") int myType) {}

请求示例： http://localhost:8080/User/getUser/123

16.@RequestParam

@Controller

@RequestMapping("/User")

public class HelloWorldController {

@RequestMapping("/getUser")

public String getUser(@RequestParam("uid")Integer id, Model model) {

    System.out.println("id:"+id);

    return "user";

}

}

请求示例： http://localhost:8080/User/getUser?uid=123