我编写了一个包含自动服务的自定义JsonDeserializer
,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;
}
}
当我第一次使用这个解串器时,我得到了NPE,因为personService没有自动装配。通过查看其他SO答案(特别是this one),似乎有两种方法可以使自动装配工作。
选项1是在自定义反序列化器的构造函数中使用SpringBeanAutowiringSupport
:
public PersonDeserializer() {
SpringBeanAutowiringSupport.processInjectionBasedOnCurrentContext(this);
}
选项2是使用HandlerInstantiator
并将其注册到我的ObjectMapper
bean:
@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;
}
}
我尝试了两种选择,但它们同样有效。显然,选项1更容易,因为它只有三行代码,但我的问题是:与SpringBeanAutowiringSupport
方法相比,使用HandlerInstantiator
有什么不利之处吗?我的应用程序将每分钟反序列化数百个对象,如果这有任何区别的话。
感谢任何建议/反馈。
答案 0 :(得分:4)
添加到Amir Jamak的答案中,您不必像Spring那样创建自定义HandlerInstantiator,它就是SpringHandlerInstantiator。
你需要做的是在Spring配置中将它连接到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;
}
答案 1 :(得分:0)
根据此comment中的建议并在此link上找到,您需要创建自定义HandlerInstantiator:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Component;
import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.KeyDeserializer;
import com.fasterxml.jackson.databind.SerializationConfig;
import com.fasterxml.jackson.databind.cfg.HandlerInstantiator;
import com.fasterxml.jackson.databind.cfg.MapperConfig;
import com.fasterxml.jackson.databind.introspect.Annotated;
import com.fasterxml.jackson.databind.jsontype.TypeIdResolver;
import com.fasterxml.jackson.databind.jsontype.TypeResolverBuilder;
@Component
public class SpringBeanHandlerInstantiator extends HandlerInstantiator {
private ApplicationContext applicationContext;
@Autowired
public SpringBeanHandlerInstantiator(ApplicationContext applicationContext) {
this.applicationContext = applicationContext;
}
@Override
public JsonDeserializer<?> deserializerInstance(DeserializationConfig config,
Annotated annotated,
Class<?> deserClass) {
try {
return (JsonDeserializer<?>) applicationContext.getBean(deserClass);
} catch (Exception e) {
// Return null and let the default behavior happen
}
return null;
}
@Override
public KeyDeserializer keyDeserializerInstance(DeserializationConfig config,
Annotated annotated,
Class<?> keyDeserClass) {
try {
return (KeyDeserializer) applicationContext.getBean(keyDeserClass);
} catch (Exception e) {
// Return null and let the default behavior happen
}
return null;
}
@Override
public JsonSerializer<?> serializerInstance(SerializationConfig config, Annotated annotated, Class<?> serClass) {
try {
return (JsonSerializer<?>) applicationContext.getBean(serClass);
} catch (Exception e) {
// Return null and let the default behavior happen
}
return null;
}
@Override
public TypeResolverBuilder<?> typeResolverBuilderInstance(MapperConfig<?> config, Annotated annotated,
Class<?> builderClass) {
try {
return (TypeResolverBuilder<?>) applicationContext.getBean(builderClass);
} catch (Exception e) {
// Return null and let the default behavior happen
}
return null;
}
@Override
public TypeIdResolver typeIdResolverInstance(MapperConfig<?> config, Annotated annotated, Class<?> resolverClass) {
try {
return (TypeIdResolver) applicationContext.getBean(resolverClass);
} catch (Exception e) {
// Return null and let the default behavior happen
}
return null;
}
}
自定义ObjectMapper:
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.cfg.HandlerInstantiator;
public class CustomObjectMapper extends ObjectMapper {
private static final long serialVersionUID = -8865944893878900100L;
@Autowired
ApplicationContext applicationContext;
public JamaxObjectMapper() {
// Problems serializing Hibernate lazily initialized collections? Fix here.
// HibernateModule hm = new HibernateModule();
// hm.configure(com.fasterxml.jackson.module.hibernate.HibernateModule.Feature.FORCE_LAZY_LOADING, true);
// this.registerModule(hm);
// Jackson confused by what to set or by extra properties? Fix it.
this.setSerializationInclusion(JsonInclude.Include.NON_NULL);
this.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
this.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
}
@Override
@Autowired
public Object setHandlerInstantiator(HandlerInstantiator hi) {
return super.setHandlerInstantiator(hi);
}
}
并注册您的自定义ObjectMapper:
<bean id="jacksonObjectMapper" class="com.acme.CustomObjectMapper" />
<bean id="jacksonMessageConverter" class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
<property name="prefixJson" value="false" />
<property name="supportedMediaTypes" value="application/json" />
<property name="objectMapper" ref="jacksonObjectMapper" />
</bean>
此时您可以使用:
@JsonDeserialize(contentUsing=PersonDeserializer.class)
public void setPerson(Person person) {
...
}
...而且personService不会为空。
答案 2 :(得分:0)
使用spring boot清理上面的答案,
@Bean
public HandlerInstantiator handlerInstantiator(ApplicationContext context) {
return new SpringHandlerInstantiator(context.getAutowireCapableBeanFactory());
}
@Bean
public ObjectMapper objectMapper(HandlerInstantiator handlerInstantiator) {
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
builder.handlerInstantiator(handlerInstantiator);
return builder.build();
}