为什么我的 Spring 数据的 Page 对象的自定义 json 序列化程序没有被调用

Question

这是我的对象映射器配置。我提供了我自己的对象映射器，以便覆盖 Spring boot 2.0 包含的对象映射器。尽管如此，我还包含了 JsonComponentModule()，以便我可以使用@JsonComponent注释来选取自定义序列化程序。

public class ObjectMapperConfigurer {
public static ObjectMapper configureObjectMapper(ObjectMapper objectMapper) {
return objectMapper.registerModules(
// First three modules can be found here. https://github.com/FasterXML/jackson-modules-java8
new Jdk8Module(), // support for other new Java 8 datatypes outside of date/time: most notably Optional, OptionalLong, OptionalDouble
new JavaTimeModule(), // support for Java 8 date/time types (specified in JSR-310 specification)
new ParameterNamesModule(), // Support for detecting constructor and factory method ("creator") parameters without having to use @JsonProperty annotation
// These two modules are provided by spring
new JsonComponentModule(), // Enables https://docs.spring.io/spring-boot/docs/2.1.0.RELEASE/reference/htmlsingle/#boot-features-json-components
new GeoModule(), // Enables marshalling of GeoResult<T>, GeoResults<T>, and GeoPage<T>
new Hibernate5Module().enable(Hibernate5Module.Feature.FORCE_LAZY_LOADING) // Allows jackson to gracefully handle Hibernate lazy loading,
)
.setSerializationInclusion(JsonInclude.Include.NON_NULL)
// Turn on/off some features. https://github.com/FasterXML/jackson-databind/wiki/JacksonFeatures
.enable(DeserializationFeature.FAIL_ON_NUMBERS_FOR_ENUMS)
.enable(DeserializationFeature.FAIL_ON_READING_DUP_TREE_KEY)
.enable(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS)
.enable(SerializationFeature.INDENT_OUTPUT)
.enable(SerializationFeature.WRITE_DATE_KEYS_AS_TIMESTAMPS)
.disable(DeserializationFeature.READ_DATE_TIMESTAMPS_AS_NANOSECONDS)
.disable(SerializationFeature.WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS)
.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
.disable(MapperFeature.DEFAULT_VIEW_INCLUSION)
.setFilterProvider(new SimpleFilterProvider().addFilter(FilteringAnnotationInspector.DEFAULT_FILTER, new DepthFilter()))
.setAnnotationIntrospector(new FilteringAnnotationInspector());
}
public static ObjectMapper configureObjectMapper() {
return configureObjectMapper(new ObjectMapper());
}
}

这是我的自定义序列化程序。如果序列化的实现是错误的也没关系，我的核心问题是它没有被调用。

@JsonComponent
public class PageJsonSerializer extends JsonSerializer<Page> {
@Override
public void serialize(Page page, JsonGenerator jsonGen, SerializerProvider serializerProvider) throws IOException {
System.out.println("serializing using pagejsonserializer");
ObjectMapper om = new ObjectMapper()
.disable(MapperFeature.DEFAULT_VIEW_INCLUSION)
.setSerializationInclusion(JsonInclude.Include.NON_EMPTY);
jsonGen.writeStartObject();
jsonGen.writeFieldName("size");
jsonGen.writeNumber(page.getSize());
jsonGen.writeFieldName("number");
jsonGen.writeNumber(page.getNumber());
jsonGen.writeFieldName("totalElements");
jsonGen.writeNumber(page.getTotalElements());
jsonGen.writeFieldName("last");
jsonGen.writeBoolean(page.isLast());
jsonGen.writeFieldName("totalPages");
jsonGen.writeNumber(page.getTotalPages());
jsonGen.writeObjectField("sort", page.getSort());
jsonGen.writeFieldName("first");
jsonGen.writeBoolean(page.isFirst());
jsonGen.writeFieldName("numberOfElements");
jsonGen.writeNumber(page.getNumberOfElements());
jsonGen.writeFieldName("content");
jsonGen.writeRawValue(om.writerWithView(serializerProvider.getActiveView()).writeValueAsString(page.getContent()));
jsonGen.writeEndObject();
}
}

下面是返回 Page(d) 对象的控制器。

@GetMapping(JobController.uri.path)
@PreAuthorize("hasAuthority('" + SpringSecurityConfig.Authority.LIST_JOBS + "')")
public Page<Job> listJobs(Pageable pageable) {
return jobRepository.findAllByCandidates(currentUserHolder.getUser(), pageable);
}

我希望上述内容会导致调用PageJsonSerializer类。我可以看到该类已成功注册到JsonComponentModule()。我还尝试了类声明的许多不同变体。像下面这样，但没有一个有任何影响。

public class PageJsonSerializer extends JsonSerializer<Page<?>> {
public class PageJsonSerializer extends JsonSerializer<PageImpl> {

我不确定接下来要检查什么。我也在努力查看 Jackson 在调试来自 JobController 的返回行程时，它将要用序列化程序序列化的对象排在哪里。

最后，我认为这不是问题，我正在使用一些RestControllerAdvice扩展AbstractMappingJacksonResponseBodyAdvice，该根据当前用户的角色选择我想使用的 jsonView。

编辑：我刚刚注释掉了控制器建议，它仍然没有调用我的自定义反序列化程序。

@RestControllerAdvice
@Slf4j
class SecurityJsonViewControllerAdvice extends AbstractMappingJacksonResponseBodyAdvice {

@Override
protected void beforeBodyWriteInternal(
@NotNull MappingJacksonValue bodyContainer,
@NotNull MediaType contentType,
@NotNull MethodParameter returnType,
@NotNull ServerHttpRequest request,
@NotNull ServerHttpResponse response) {
if (SecurityContextHolder.getContext().getAuthentication() != null && SecurityContextHolder.getContext().getAuthentication().getAuthorities() != null) {
Collection<? extends GrantedAuthority> authorities = SecurityContextHolder.getContext().getAuthentication().getAuthorities();
Class<?> viewClass = User.Role.jsonViewFrom(authorities);
if (true || log.isDebugEnabled()) {
log.debug("Deserializing using view {}", viewClass.getSimpleName());
}
bodyContainer.setSerializationView(viewClass);
}
}
}

Answer 1

就我而言，我必须手动配置消息转换器。我将其添加到WebMvcConfigurer的实现中：

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
builder.serializerByType(PageImpl.class, new PageJsonSerializer());
converters.add(new MappingJackson2HttpMessageConverter(builder.build()));
}

Answer 2

我能够通过做两件事来解决我的问题。

@Component
public class PageJsonSerializer extends StdSerializer<Page> {

扩展StdSerializer而不是JsonSerializer我实际上不知道这是否是解决方案的一部分。

我认为真正的帮助来自手动注册序列化程序而不是依赖@JsonComponent。

所以我的ObjectMapperConfigurer现在看起来像这样。

public class ObjectMapperConfigurer {
public static ObjectMapper configureObjectMapper(ObjectMapper objectMapper) {
return objectMapper.registerModules(
// First three modules can be found here. https://github.com/FasterXML/jackson-modules-java8
new Jdk8Module(), // support for other new Java 8 datatypes outside of date/time: most notably Optional, OptionalLong, OptionalDouble
new JavaTimeModule(), // support for Java 8 date/time types (specified in JSR-310 specification)
new ParameterNamesModule(), // Support for detecting constructor and factory method ("creator") parameters without having to use @JsonProperty annotation
// Manually registering my serializer. 
new SimpleModule().addSerializer(Page.class, pageJsonSerializer),
... all the same
}

我还从我的ObjectMapper中删除了JsonComponentModule，因为它似乎被破坏了。