spring.jackson.default-property-inclusion 无效问题分析

转x33g5p2x  于9个月前 转载在 Spring  
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spring.jackson.default-property-inclusion 不生效问题分析

背景

项目里每个返回体里都有 @JsonInclude(JsonInclude.Include.NON_NULL) 这个注解，也就是不返回 null 字段

想有没有办法全局配置一下，这样就不用每个类都加这个注解了

  1. spring:
  2.   jackson:
  3.     default-property-inclusion: non_null

看网上说加上这个配置项就可以了，于是加上之后，发现不生效，后来又查到不生效的原因是因为项目里手动注入了 WebMvcConfigurationSupport 这个类

看我们的项目里确实是这样的，配置如下：

  1. @Configuration
  2. @Import(WebMvcAutoConfiguration.EnableWebMvcConfiguration.class)
  3. public class WebConfig implements WebMvcConfigurer, WebMvcRegistrations {
  4. }

导入了 EnableWebMvcConfiguration 这个类，这个类继承了 DelegatingWebMvcConfiguration , DelegatingWebMvcConfiguration 这个类实现了 WebMvcConfigurationSupport

那就一起来看下不生效的原因以及解决办法

例子

  1. web配置
  2. @Configuration
  3. @Import(WebMvcAutoConfiguration.EnableWebMvcConfiguration.class)
  4. public class WebConfig implements WebMvcConfigurer, WebMvcRegistrations {
  5. }
  7. controller
  8. @RestController
  9. @RequestMapping("/api/jackson")
  10. public class JacksonTestController {
  12.     @GetMapping("/data")
  13.     public Object getData() {
  14.         return new Result();
  15.     }
  17.     @Data
  18.     public static class Result {
  19.         private String string1 = "hello";
  20.         private String string2;
  21.     }
  22. }
  24. application.yml
  25. spring:
  26.   jackson:
  27.     default-property-inclusion: non_null
  29. 启动类
  30. @SpringBootApplication
  31. public class MyApplication {
  32.     public static void main(String[] args) {
  33.         SpringApplication.run(MyApplication.class, args);
  34.     }
  35. }
  1. 访问 http://127.0.0.1:8080/api/jackson/data
  2. 返回
  3. {
  4.   "string1": "hello",
  5.   "string2": null
  6. }

可以看出确实是不生效的

先看一下比较明显的方案：

  1. 方法一
  2. 加JsonInclude注解
  3. @Data
  4. @JsonInclude(JsonInclude.Include.NON_NULL)
  5. public static class Result {
  6.     private String string1 = "hello";
  7.     private String string2;
  8. }
  9. 访问返回：
  10. {
  11.   "string1": "hello"
  12. }
  14. 方法二
  15. 注释掉Import那一行
  16. @Configuration
  17. //@Import(WebMvcAutoConfiguration.EnableWebMvcConfiguration.class)
  18. public class WebConfig implements WebMvcConfigurer, WebMvcRegistrations {
  19. }
  20.  @Data
  21. //@JsonInclude(JsonInclude.Include.NON_NULL)
  22. public static class Result {
  23.     private String string1 = "hello";
  24.     private String string2;
  25. }
  26. 访问返回：
  27. {
  28.   "string1": "hello"
  29. }

原因

  1. body是怎么返回的？

  1. public abstract class AbstractMessageConverterMethodProcessor extends AbstractMessageConverterMethodArgumentResolver
  2. 		implements HandlerMethodReturnValueHandler {
  3. 	protected <T> void writeWithMessageConverters(@Nullable T value, MethodParameter returnType,
  4. 			ServletServerHttpRequest inputMessage, ServletServerHttpResponse outputMessage)
  5. 			throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException {
  6. 	}
  7. }
  9. body是返回结果，MappingJackson2HttpMessageConverter会去转换结果，它是从this.messageConverters获取

分别看一下不去掉以及去掉 Import(WebMvcAutoConfiguration.EnableWebMvcConfiguration.class) 注解后 messageConverters 的结果

不去掉的结果

去掉的结果

可以看到，去掉之后，多了一个MappingJackson2HttpMessageConverter实例，并且这个是根据配置生成的，而且因为它的顺序在前面，所以会用这个来处理

  1. 来看一下 this.messageConverters 是怎么被赋值的

RequestResponseBodyMethodProcessor这个类是通过RequestMappingHandlerAdapter生成的

  1. public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter
  2. 		implements BeanFactoryAware, InitializingBean {
  4.     private List<HandlerMethodReturnValueHandler> getDefaultReturnValueHandlers() {
  5.         handlers.add(new RequestResponseBodyMethodProcessor(getMessageConverters(), this.contentNegotiationManager, this.requestResponseBodyAdvice)); // this
  6.         return handlers;
  7.     }
  9.     public List<HttpMessageConverter<?>> getMessageConverters() {
  10. 	return this.messageConverters; // this
  11.     }
  12. }

RequestMappingHandlerAdapter是由WebMvcConfigurationSupport生成的

  1. public class WebMvcConfigurationSupport implements ApplicationContextAware, ServletContextAware {
  2.     @Bean
  3.     public RequestMappingHandlerAdapter requestMappingHandlerAdapter(
  4. 		@Qualifier("mvcContentNegotiationManager") ContentNegotiationManager contentNegotiationManager,
  5. 		@Qualifier("mvcConversionService") FormattingConversionService conversionService,
  6. 		@Qualifier("mvcValidator") Validator validator) {
  8.     	RequestMappingHandlerAdapter adapter = createRequestMappingHandlerAdapter();
  9. 	adapter.setMessageConverters(getMessageConverters());
  10.     }
  12.     protected final List<HttpMessageConverter<?>> getMessageConverters() {
  13. 		if (this.messageConverters == null) {
  14. 			this.messageConverters = new ArrayList<>();
  15. 			configureMessageConverters(this.messageConverters);  // this
  16. 			if (this.messageConverters.isEmpty()) {
  17. 				addDefaultHttpMessageConverters(this.messageConverters); // this
  18. 			}
  19. 			extendMessageConverters(this.messageConverters);
  20. 		}
  21. 		return this.messageConverters;
  22. 	}
  24. 	protected final void addDefaultHttpMessageConverters(List<HttpMessageConverter<?>> messageConverters) {
  25. 		StringHttpMessageConverter stringHttpMessageConverter = new StringHttpMessageConverter();
  26. 		stringHttpMessageConverter.setWriteAcceptCharset(false);  // see SPR-7316
  28. 		messageConverters.add(new ByteArrayHttpMessageConverter());
  29. 		messageConverters.add(stringHttpMessageConverter);
  30. 		messageConverters.add(new ResourceHttpMessageConverter());
  31. 		messageConverters.add(new ResourceRegionHttpMessageConverter());
  33. 		if (jackson2Present) {
  34. 			Jackson2ObjectMapperBuilder builder = Jackson2ObjectMapperBuilder.json();
  35. 			if (this.applicationContext != null) {
  36. 				builder.applicationContext(this.applicationContext);
  37. 			}
  38. 			messageConverters.add(new MappingJackson2HttpMessageConverter(builder.build()));  // this
  39. 		}
  40. 		else if (gsonPresent) {
  41. 			messageConverters.add(new GsonHttpMessageConverter());
  42. 		}
  43. 		else if (jsonbPresent) {
  44. 			messageConverters.add(new JsonbHttpMessageConverter());
  45. 		}
  46. 	}
  47. }

可以看到先调用configureMessageConverters方法，如果为空就调用addDefaultHttpMessageConverters方法添加默认的。

看一下configureMessageConverters方法

  1. class WebMvcConfigurerComposite implements WebMvcConfigurer {
  2. 	@Override
  3. 	public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
  4. 		for (WebMvcConfigurer delegate : this.delegates) {
  5. 			delegate.configureMessageConverters(converters);
  6. 		}
  7. 	}
  8. }

不去掉的结果

去掉的结果

可以看到，不去掉的话，这里只有一个我们自己定义的WebMvcConfigurer，而且是不会做任何操作的，所以就会调用addDefaultHttpMessageConverters，生成默认的。
如果去掉的话，会调用WebMvcAutoConfigurationAdapter的configureMessageConverters方法，这个方法的返回结果不会空，就不会调用addDefaultHttpMessageConverters，然后直接返回。

下面看一下这个方法。

  1. @Configuration(proxyBeanMethods = false)
  2. @ConditionalOnWebApplication(type = Type.SERVLET)
  3. @ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
  4. @ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
  5. @AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
  6. @AutoConfigureAfter({ DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,
  7. 		ValidationAutoConfiguration.class })
  8. public class WebMvcAutoConfiguration {
  9. 	@Configuration(proxyBeanMethods = false)
  10. 	@Import(EnableWebMvcConfiguration.class)
  11. 	@EnableConfigurationProperties({ WebMvcProperties.class, ResourceProperties.class })
  12. 	@Order(0)
  13. 	public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer {
  15. 		private final ObjectProvider<HttpMessageConverters> messageConvertersProvider;
  17. 		public WebMvcAutoConfigurationAdapter(ResourceProperties resourceProperties, WebMvcProperties mvcProperties,
  18. 				ListableBeanFactory beanFactory, ObjectProvider<HttpMessageConverters> messageConvertersProvider,
  19. 				ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider,
  20. 				ObjectProvider<DispatcherServletPath> dispatcherServletPath,
  21. 				ObjectProvider<ServletRegistrationBean<?>> servletRegistrations) {
  23. 			this.messageConvertersProvider = messageConvertersProvider; // this
  25. 		}
  27. 		@Override
  28. 		public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
  29. 			this.messageConvertersProvider
  30. 					.ifAvailable((customConverters) -> converters.addAll(customConverters.getConverters())); // this
  31. 		}
  32. }

会注入HttpMessageConverters

  1. @Configuration
  2. @ConditionalOnClass(HttpMessageConverter.class)
  3. @AutoConfigureAfter({ GsonAutoConfiguration.class, JacksonAutoConfiguration.class,
  4. 		JsonbAutoConfiguration.class })
  5. @Import({ JacksonHttpMessageConvertersConfiguration.class,
  6. 		GsonHttpMessageConvertersConfiguration.class,
  7. 		JsonbHttpMessageConvertersConfiguration.class })
  8. public class HttpMessageConvertersAutoConfiguration {
  10. 	public HttpMessageConvertersAutoConfiguration(
  11. 			ObjectProvider<HttpMessageConverter<?>> convertersProvider) {
  12. 		this.converters = convertersProvider.orderedStream().collect(Collectors.toList());
  13. 	}
  15. 	@Bean
  16. 	@ConditionalOnMissingBean
  17. 	public HttpMessageConverters messageConverters() {
  18. 		return new HttpMessageConverters(this.converters);
  19. 	}
  21. 	public HttpMessageConverters(Collection<HttpMessageConverter<?>> additionalConverters) {
  22. 		this(true, additionalConverters);
  23. 	}
  25. 	public HttpMessageConverters(boolean addDefaultConverters,
  26. 			Collection<HttpMessageConverter<?>> converters) {
  27. 		List<HttpMessageConverter<?>> combined = getCombinedConverters(converters,
  28. 				addDefaultConverters ? getDefaultConverters() : Collections.emptyList());
  29. 		combined = postProcessConverters(combined);
  30. 		this.converters = Collections.unmodifiableList(combined);
  31. 	}
  33. 	private List<HttpMessageConverter<?>> getDefaultConverters() {
  34. 		List<HttpMessageConverter<?>> converters = new ArrayList<>();
  35. 		if (ClassUtils.isPresent("org.springframework.web.servlet.config.annotation."
  36. 				+ "WebMvcConfigurationSupport", null)) {
  37. 			converters.addAll(new WebMvcConfigurationSupport() {
  39. 				public List<HttpMessageConverter<?>> defaultMessageConverters() {
  40. 					return super.getMessageConverters(); // this
  41. 				}
  43. 			}.defaultMessageConverters());
  44. 		}
  45. 		else {
  46. 			converters.addAll(new RestTemplate().getMessageConverters());
  47. 		}
  48. 		reorderXmlConvertersToEnd(converters);
  49. 		return converters;
  50. 	}
  52. 	private List<HttpMessageConverter<?>> getCombinedConverters(
  53. 			Collection<HttpMessageConverter<?>> converters,
  54. 			List<HttpMessageConverter<?>> defaultConverters) {
  55. 		List<HttpMessageConverter<?>> combined = new ArrayList<>();
  56. 		List<HttpMessageConverter<?>> processing = new ArrayList<>(converters);
  57. 		for (HttpMessageConverter<?> defaultConverter : defaultConverters) {
  58. 			Iterator<HttpMessageConverter<?>> iterator = processing.iterator();
  59. 			while (iterator.hasNext()) {
  60. 				HttpMessageConverter<?> candidate = iterator.next();
  61. 				if (isReplacement(defaultConverter, candidate)) {
  62. 					combined.add(candidate);
  63. 					iterator.remove();
  64. 				}
  65. 			}
  66. 			combined.add(defaultConverter);
  67. 			if (defaultConverter instanceof AllEncompassingFormHttpMessageConverter) {
  68. 				configurePartConverters(
  69. 						(AllEncompassingFormHttpMessageConverter) defaultConverter,
  70. 						converters);
  71. 			}
  72. 		}
  73. 		combined.addAll(0, processing);
  74. 		return combined;
  75. 	}
  76. }

可以看到converters由两部分组成，一部分是注入的HttpMessageConverter，另一部分是WebMvcConfigurationSupport.defaultMessageConverters方法，然后进行合并，当然如果有相同的类，前面的顺序在前。

会注入MappingJackson2HttpMessageConverter

  1. @Configuration
  2. class JacksonHttpMessageConvertersConfiguration {
  3. 	@Configuration
  4. 	@ConditionalOnClass(ObjectMapper.class)
  5. 	@ConditionalOnBean(ObjectMapper.class)
  6. 	@ConditionalOnProperty(
  7. 			name = HttpMessageConvertersAutoConfiguration.PREFERRED_MAPPER_PROPERTY,
  8. 			havingValue = "jackson", matchIfMissing = true)
  9. 	protected static class MappingJackson2HttpMessageConverterConfiguration {
  11. 		@Bean
  12. 		@ConditionalOnMissingBean(value = MappingJackson2HttpMessageConverter.class,
  13. 				ignoredType = {
  14. 						"org.springframework.hateoas.mvc.TypeConstrainedMappingJackson2HttpMessageConverter",
  15. 						"org.springframework.data.rest.webmvc.alps.AlpsJsonHttpMessageConverter" })
  16. 		public MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter(
  17. 				ObjectMapper objectMapper) {
  18. 			return new MappingJackson2HttpMessageConverter(objectMapper);
  19. 		}
  21. 	}
  22. }

会注入ObjectMapper相关的实例

  1. @Configuration
  2. @ConditionalOnClass(ObjectMapper.class)
  3. public class JacksonAutoConfiguration {
  5.         // 注入jacksonObjectMapper
  6. 	@Configuration
  7. 	@ConditionalOnClass(Jackson2ObjectMapperBuilder.class)
  8. 	static class JacksonObjectMapperConfiguration {
  9. 		@Bean
  10. 		@Primary
  11. 		@ConditionalOnMissingBean
  12. 		public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) {
  13. 			return builder.createXmlMapper(false).build();
  14. 		}
  15. 	}
  16.         
  17.         // 注入jacksonObjectMapperBuilder
  18. 	@Configuration
  19. 	@ConditionalOnClass(Jackson2ObjectMapperBuilder.class)
  20. 	static class JacksonObjectMapperBuilderConfiguration {
  21. 		private final ApplicationContext applicationContext;
  23. 		JacksonObjectMapperBuilderConfiguration(ApplicationContext applicationContext) {
  24. 			this.applicationContext = applicationContext;
  25. 		}
  27. 		@Bean
  28. 		@ConditionalOnMissingBean
  29. 		public Jackson2ObjectMapperBuilder jacksonObjectMapperBuilder(
  30. 				List<Jackson2ObjectMapperBuilderCustomizer> customizers) {
  31. 			Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
  32. 			builder.applicationContext(this.applicationContext);
  33. 			customize(builder, customizers);
  34. 			return builder;
  35. 		}
  37. 		private void customize(Jackson2ObjectMapperBuilder builder,
  38. 				List<Jackson2ObjectMapperBuilderCustomizer> customizers) {
  39. 			for (Jackson2ObjectMapperBuilderCustomizer customizer : customizers) {
  40. 				customizer.customize(builder);
  41. 			}
  42. 		}
  44. 	}
  46.         // 注入standardJacksonObjectMapperBuilderCustomizer
  47. 	@Configuration
  48. 	@ConditionalOnClass(Jackson2ObjectMapperBuilder.class)
  49. 	@EnableConfigurationProperties(JacksonProperties.class)
  50. 	static class Jackson2ObjectMapperBuilderCustomizerConfiguration {
  52. 		@Bean
  53. 		StandardJackson2ObjectMapperBuilderCustomizer standardJacksonObjectMapperBuilderCustomizer(
  54. 				ApplicationContext applicationContext, JacksonProperties jacksonProperties) {
  55. 			return new StandardJackson2ObjectMapperBuilderCustomizer(applicationContext, jacksonProperties);
  56. 		}
  58. 		static final class StandardJackson2ObjectMapperBuilderCustomizer
  59. 				implements Jackson2ObjectMapperBuilderCustomizer, Ordered {
  60. 			private final JacksonProperties jacksonProperties;
  62. 			@Override
  63. 			public void customize(Jackson2ObjectMapperBuilder builder) {
  64. 				if (this.jacksonProperties.getDefaultPropertyInclusion() != null) {
  65. 					builder.serializationInclusion(this.jacksonProperties.getDefaultPropertyInclusion());
  66. 				}
  67. 			}
  68. 		}
  70.         }
  71. }
  73. // 会注入JacksonProperties
  74. @ConfigurationProperties(prefix = "spring.jackson")
  75. public class JacksonProperties {
  76. 	private JsonInclude.Include defaultPropertyInclusion;
  77. }

这个过程就生成了一个新的根据配置文件配置的MappingJackson2HttpMessageConverter，并把它添加到messageConverters中

总结

最后还有一种不去掉import注解就可以解决的方法，就是采用和WebMvcAutoConfigurationAdapter一样的方法，如下：

  1. @Configuration
  2. @Import(WebMvcAutoConfiguration.EnableWebMvcConfiguration.class)
  3. public class WebConfig implements WebMvcConfigurer, WebMvcRegistrations {
  5.     private final ObjectProvider<HttpMessageConverters> messageConvertersProvider;
  7.     public WebConfig(ObjectProvider<HttpMessageConverters> messageConvertersProvider) {
  8.         this.messageConvertersProvider = messageConvertersProvider;
  9.     }
  11.     @Override
  12.     public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
  13.         this.messageConvertersProvider.ifAvailable((customConverters) -> converters
  14.                 .addAll(customConverters.getConverters()));
  15.     }
  16. }

参考

Spring Boot 中自定义 SpringMVC 配置，到底继承谁？
自定义SpringBoot默认MVC配置？好几个坑，这篇文章必须珍藏

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原文链接 : https://www.cnblogs.com/eaglelihh/p/17093029.html

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