JsonDeserializer中的自动装配：SpringBeanAutowiringSupport与HandlerInstantiator

Question

我写了一个JsonDeserializer包含自动连线服务的自定义，如下所示：

public class PersonDeserializer extends JsonDeserializer<Person> {

    @Autowired
    PersonService personService;

    @Override
    public Person deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException, JsonProcessingException {

        // deserialization occurs here which makes use of personService

        return person;
    }
}

当我第一次使用此反序列化器时，我得到的是NPE，因为personService没有自动接线。从其他SO答案（特别是这个答案）来看，似乎有两种方法可以使自动布线起作用。

选项1是SpringBeanAutowiringSupport在自定义反序列化器的构造函数中使用：

public PersonDeserializer() { 

    SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this); 
}

选项2是使用A HandlerInstantiator并将其注册到我的ObjectMapperbean中：

@Component
public class SpringBeanHandlerInstantiator extends HandlerInstantiator {

    @Autowired
    private ApplicationContext applicationContext;

    @Override
    public JsonDeserializer<?> deserializerInstance(DeserializationConfig config, Annotated annotated, Class<? extends JsonDeserializer<?>> deserClass) {

        try {

            return (JsonDeserializer<?>) applicationContext.getBean(deserClass);

        } catch (Exception e) {

            // Return null and let the default behavior happen
            return null;
        }
    }
}

@Configuration  
public class JacksonConfiguration {

    @Autowired
    SpringBeanHandlerInstantiator springBeanHandlerInstantiator;

    @Bean
    public ObjectMapper objectMapper() {

        Jackson2ObjectMapperFactoryBean jackson2ObjectMapperFactoryBean = new Jackson2ObjectMapperFactoryBean();
        jackson2ObjectMapperFactoryBean.afterPropertiesSet();

        ObjectMapper objectMapper = jackson2ObjectMapperFactoryBean.getObject();

        // add the custom handler instantiator
        objectMapper.setHandlerInstantiator(springBeanHandlerInstantiator);

        return objectMapper;
    }
}

我已经尝试了这两种选择，并且它们同样工作良好。显然，选项1更容易，因为它只有三行代码，但是我的问题是：SpringBeanAutowiringSupport与该HandlerInstantiator方法相比，使用它有什么缺点吗？我的应用程序每分钟将反序列化数百个对象，如果有什么不同的话。

任何建议/反馈表示赞赏。

Answer 1

添加到Amir Jamak的答案中，你不必创建自定义HandlerInstantiator，因为Spring已经有了它，即SpringHandlerInstantiator。

你需要做的是将其连接到Spring配置中的Jackson2ObjectMapperBuilder。

@Bean
public HandlerInstantiator handlerInstantiator(ApplicationContext applicationContext) {
    return new SpringHandlerInstantiator(applicationContext.getAutowireCapableBeanFactory());
}

@Bean
public Jackson2ObjectMapperBuilder objectMapperBuilder(HandlerInstantiator handlerInstantiator) {
    Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
    builder.handlerInstantiator(handlerInstantiator);
    return builder;
}