一個(gè)新項(xiàng)目組，為了解決Long類型轉(zhuǎn)String類型給前端，防止經(jīng)度丟失。添加了一段代碼，發(fā)現(xiàn)沒用。
我在其他項(xiàng)目上，如此，是有用的，但是放到新項(xiàng)目發(fā)現(xiàn)沒用。
其實(shí)問題還在其次，最主要的是，讓有心人，學(xué)會(huì)怎樣從源碼的角度，去分析解決問題，具體應(yīng)該怎么入手。
分析：
處理返回值是在這里
ServletInvocableHandlerMethod
public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
setResponseStatus(webRequest);
if (returnValue == null) {
if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) {
disableContentCachingIfNecessary(webRequest);
mavContainer.setRequestHandled(true);
return;
}
}
else if (StringUtils.hasText(getResponseStatusReason())) {
mavContainer.setRequestHandled(true);
return;
}
mavContainer.setRequestHandled(false);
Assert.state(this.returnValueHandlers != null, "No return value handlers");
try {
this.returnValueHandlers.handleReturnValue(
returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
}
catch (Exception ex) {
if (logger.isTraceEnabled()) {
logger.trace(formatErrorForReturnValue(returnValue), ex);
}
throw ex;
}
}
AbstractMessageConverterMethodProcessor：接著調(diào)用的是這個(gè)類的這個(gè)方法。
可以看到維護(hù)了messageConverters，轉(zhuǎn)換器就是這個(gè)，所以要看這個(gè)轉(zhuǎn)換器是怎么注入進(jìn)去的。
protected <T> void writeWithMessageConverters(@Nullable T value, MethodParameter returnType,
ServletServerHttpRequest inputMessage, ServletServerHttpResponse outputMessage)
throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException {
if (selectedMediaType != null) {
selectedMediaType = selectedMediaType.removeQualityValue();
for (HttpMessageConverter<?> converter : this.messageConverters) {
是構(gòu)造方法注入進(jìn)去的。
public AbstractMessageConverterMethodArgumentResolver(List<HttpMessageConverter<?>> converters,
@Nullable List<Object> requestResponseBodyAdvice) {
Assert.notEmpty(converters, "'messageConverters' must not be empty");
this.messageConverters = converters;
this.allSupportedMediaTypes = getAllSupportedMediaTypes(converters);
this.advice = new RequestResponseBodyAdviceChain(requestResponseBodyAdvice);
}
打斷點(diǎn)，項(xiàng)目啟動(dòng)查看調(diào)用棧，發(fā)現(xiàn)是這里注入的。
RequestMappingHandlerAdapter類。是從RequestMappingHandlerAdapter維護(hù)的messageConverts注入進(jìn)去。所以看RequestMappingHandlerAdapter類的messageConverts是怎么來的。
private List<HandlerMethodArgumentResolver> getDefaultArgumentResolvers() {
List<HandlerMethodArgumentResolver> resolvers = new ArrayList<>(30);
// Annotation-based argument resolution
resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), false));
resolvers.add(new RequestParamMapMethodArgumentResolver());
resolvers.add(new PathVariableMethodArgumentResolver());
resolvers.add(new PathVariableMapMethodArgumentResolver());
resolvers.add(new MatrixVariableMethodArgumentResolver());
resolvers.add(new MatrixVariableMapMethodArgumentResolver());
resolvers.add(new ServletModelAttributeMethodProcessor(false));
resolvers.add(new RequestResponseBodyMethodProcessor(getMessageConverters(), this.requestResponseBodyAdvice));
// 這里
resolvers.add(new RequestPartMethodArgumentResolver(getMessageConverters(), this.requestResponseBodyAdvice));
resolvers.add(new RequestHeaderMethodArgumentResolver(getBeanFactory()));
}
public List<HttpMessageConverter<?>> getMessageConverters() {
return this.messageConverters;
}
通過idea工具，查看這個(gè)變量的引用，發(fā)現(xiàn)只有兩個(gè)地方對(duì)這個(gè)變量存在set值。
一個(gè)是RequestMappingHandlerAdapter的構(gòu)造方法
public RequestMappingHandlerAdapter() {
this.messageConverters = new ArrayList<>(4);
this.messageConverters.add(new ByteArrayHttpMessageConverter());
this.messageConverters.add(new StringHttpMessageConverter());
if (!shouldIgnoreXml) {
try {
this.messageConverters.add(new SourceHttpMessageConverter<>());
}
catch (Error err) {
// Ignore when no TransformerFactory implementation is available
}
}
this.messageConverters.add(new AllEncompassingFormHttpMessageConverter());
}
一個(gè)是WebMvcConfigurationSupport配置類定義的@Bean注解構(gòu)造RequestMappingHandlerAdapter 對(duì)象注入ioc容器。
于是我們知道了，原來RequestMappingHandlerAdapter 這么重要的對(duì)象是在這里通過@bean注解引入到ioc的。第一步構(gòu)建這個(gè)對(duì)象，構(gòu)建對(duì)象自然就會(huì)調(diào)用構(gòu)造方法，也就是上面提到的構(gòu)造方法里會(huì)對(duì)messageConverts進(jìn)行添加值。構(gòu)造完了之后，再調(diào)用WebMvcConfigurationSupport的getMessage方法獲取MessageConvert對(duì)象，然后添加進(jìn)去。
@Bean
public RequestMappingHandlerAdapter requestMappingHandlerAdapter(
@Qualifier("mvcContentNegotiationManager") ContentNegotiationManager contentNegotiationManager,
@Qualifier("mvcConversionService") FormattingConversionService conversionService,
@Qualifier("mvcValidator") Validator validator) {
RequestMappingHandlerAdapter adapter = createRequestMappingHandlerAdapter();
adapter.setContentNegotiationManager(contentNegotiationManager);
adapter.setMessageConverters(getMessageConverters());
adapter.setWebBindingInitializer(getConfigurableWebBindingInitializer(conversionService, validator));
adapter.setCustomArgumentResolvers(getArgumentResolvers());
adapter.setCustomReturnValueHandlers(getReturnValueHandlers());
if (jackson2Present) {
adapter.setRequestBodyAdvice(Collections.singletonList(new JsonViewRequestBodyAdvice()));
adapter.setResponseBodyAdvice(Collections.singletonList(new JsonViewResponseBodyAdvice()));
}
AsyncSupportConfigurer configurer = getAsyncSupportConfigurer();
if (configurer.getTaskExecutor() != null) {
adapter.setTaskExecutor(configurer.getTaskExecutor());
}
if (configurer.getTimeout() != null) {
adapter.setAsyncRequestTimeout(configurer.getTimeout());
}
adapter.setCallableInterceptors(configurer.getCallableInterceptors());
adapter.setDeferredResultInterceptors(configurer.getDeferredResultInterceptors());
return adapter;
}
configureMessageConverters(this.messageConverters);方法子類會(huì)維護(hù)一個(gè)WebMvcConfigurerComposite復(fù)合WebMvcConfigurer對(duì)象，然后循環(huán)調(diào)用里面的所有WebMvcConfigurer的configureMessageConverters方法，這是一種設(shè)計(jì)模式。
protected final List<HttpMessageConverter<?>> getMessageConverters() {
if (this.messageConverters == null) {
this.messageConverters = new ArrayList<>();
configureMessageConverters(this.messageConverters);
if (this.messageConverters.isEmpty()) {
addDefaultHttpMessageConverters(this.messageConverters);
}
extendMessageConverters(this.messageConverters);
}
return this.messageConverters;
}
WebMvcConfigurerComposite類。
@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
for (WebMvcConfigurer delegate : this.delegates) {
delegate.configureMessageConverters(converters);
}
}
WebMvcConfigurationSupport的addDefaultHttpMessageConverters方法會(huì)添加很多默認(rèn)的轉(zhuǎn)換器。
我這邊調(diào)試，看到，這里一共添加了8個(gè)轉(zhuǎn)換器。
protected final void addDefaultHttpMessageConverters(List<HttpMessageConverter<?>> messageConverters) {
messageConverters.add(new ByteArrayHttpMessageConverter());
messageConverters.add(new StringHttpMessageConverter());
messageConverters.add(new ResourceHttpMessageConverter());
messageConverters.add(new ResourceRegionHttpMessageConverter());
if (!shouldIgnoreXml) {
try {
messageConverters.add(new SourceHttpMessageConverter<>());
}
catch (Throwable ex) {
// Ignore when no TransformerFactory implementation is available...
}
}
messageConverters.add(new AllEncompassingFormHttpMessageConverter());
if (romePresent) {
messageConverters.add(new AtomFeedHttpMessageConverter());
messageConverters.add(new RssChannelHttpMessageConverter());
}
if (!shouldIgnoreXml) {
if (jackson2XmlPresent) {
Jackson2ObjectMapperBuilder builder = Jackson2ObjectMapperBuilder.xml();
if (this.applicationContext != null) {
builder.applicationContext(this.applicationContext);
}
messageConverters.add(new MappingJackson2XmlHttpMessageConverter(builder.build()));
}
else if (jaxb2Present) {
messageConverters.add(new Jaxb2RootElementHttpMessageConverter());
}
}
if (kotlinSerializationJsonPresent) {
messageConverters.add(new KotlinSerializationJsonHttpMessageConverter());
}
if (jackson2Present) {
Jackson2ObjectMapperBuilder builder = Jackson2ObjectMapperBuilder.json();
if (this.applicationContext != null) {
builder.applicationContext(this.applicationContext);
}
messageConverters.add(new MappingJackson2HttpMessageConverter(builder.build()));
}
else if (gsonPresent) {
messageConverters.add(new GsonHttpMessageConverter());
}
else if (jsonbPresent) {
messageConverters.add(new JsonbHttpMessageConverter());
}
if (jackson2SmilePresent) {
Jackson2ObjectMapperBuilder builder = Jackson2ObjectMapperBuilder.smile();
if (this.applicationContext != null) {
builder.applicationContext(this.applicationContext);
}
messageConverters.add(new MappingJackson2SmileHttpMessageConverter(builder.build()));
}
if (jackson2CborPresent) {
Jackson2ObjectMapperBuilder builder = Jackson2ObjectMapperBuilder.cbor();
if (this.applicationContext != null) {
builder.applicationContext(this.applicationContext);
}
messageConverters.add(new MappingJackson2CborHttpMessageConverter(builder.build()));
}
}
比如添加MappingJackson2HttpMessageConverter轉(zhuǎn)換器，發(fā)現(xiàn)，builder建造者是無參構(gòu)造的，build方法也沒有傳參，所以這里是沒有提供給使用者注入?yún)?shù)的機(jī)會(huì)的。
Jackson2ObjectMapperBuilder builder = Jackson2ObjectMapperBuilder.json();
if (this.applicationContext != null) {
builder.applicationContext(this.applicationContext);
}
messageConverters.add(new MappingJackson2HttpMessageConverter(builder.build()));
getMessageConverters方法里調(diào)用這個(gè)方法，從方法名可以看出，這是擴(kuò)展messageConverters，默認(rèn)是空的方法，所以，我們可以繼承這個(gè)類，然后實(shí)現(xiàn)這個(gè)方法，達(dá)到往messageConverts注入轉(zhuǎn)換器的目的。
extendMessageConverters(this.messageConverters);
走到這里，貌似已經(jīng)分析完了，但是實(shí)際處理請(qǐng)求的時(shí)候，發(fā)現(xiàn)轉(zhuǎn)換器是10個(gè)，不是8個(gè)，那哪里還注入了轉(zhuǎn)換器呢。
HttpMessageConvertersAutoConfiguration類里會(huì)注入HttpMessageConverters對(duì)象，這里的參數(shù)converters，里面就有兩個(gè)轉(zhuǎn)換器，其中就有一個(gè)我們自定義objectMapper的轉(zhuǎn)換器。
ObjectProvider是spring新的類，用來注入的，避免不存在對(duì)象導(dǎo)致的注入空指針。
這里就有個(gè)疑問，這兩個(gè)轉(zhuǎn)換器，是哪里構(gòu)造的，并且注入到ioc容器的。
@Bean
@ConditionalOnMissingBean
public HttpMessageConverters messageConverters(ObjectProvider<HttpMessageConverter<?>> converters) {
return new HttpMessageConverters(converters.orderedStream().collect(Collectors.toList()));
}
HttpMessageConverters構(gòu)造方法，有一個(gè)參數(shù)addDefaultConverters是否添加默認(rèn)構(gòu)造器，前面分析了，默認(rèn)構(gòu)造器有8個(gè)，再加上從ioc中注入的2個(gè)，總共就是10個(gè)，對(duì)上了。
又來了新的問題，HttpMessageConverters這個(gè)對(duì)象是加入了ioc容器，但是HttpservletAdapter對(duì)象的轉(zhuǎn)換器，是怎么注入進(jìn)去的呢
public HttpMessageConverters(boolean addDefaultConverters, Collection<HttpMessageConverter<?>> converters) {
List<HttpMessageConverter<?>> combined = getCombinedConverters(converters,
addDefaultConverters ? getDefaultConverters() : Collections.emptyList());
combined = postProcessConverters(combined);
this.converters = Collections.unmodifiableList(combined);
}
通過打斷點(diǎn)，給WebMvcConfigurationSupport的messageConverters變量打斷點(diǎn)，發(fā)現(xiàn)其是構(gòu)造 RequestMappingHandlerAdapter 對(duì)象的時(shí)候adapter.setMessageConverters(getMessageConverters());一下注入了10個(gè)轉(zhuǎn)換器。
所以getMessageConverters()里面應(yīng)該獲取到10個(gè)轉(zhuǎn)換器才對(duì)。通過debug運(yùn)行方法getMessageConverters()，果然返回10個(gè)轉(zhuǎn)換器。
跟進(jìn)去
protected final List<HttpMessageConverter<?>> getMessageConverters() {
if (this.messageConverters == null) {
this.messageConverters = new ArrayList<>();
configureMessageConverters(this.messageConverters);
if (this.messageConverters.isEmpty()) {
addDefaultHttpMessageConverters(this.messageConverters);
}
extendMessageConverters(this.messageConverters);
}
return this.messageConverters;
}
@Bean
public RequestMappingHandlerAdapter requestMappingHandlerAdapter(
@Qualifier("mvcContentNegotiationManager") ContentNegotiationManager contentNegotiationManager,
@Qualifier("mvcConversionService") FormattingConversionService conversionService,
@Qualifier("mvcValidator") Validator validator) {
RequestMappingHandlerAdapter adapter = createRequestMappingHandlerAdapter();
adapter.setContentNegotiationManager(contentNegotiationManager);
adapter.setMessageConverters(getMessageConverters());
跟進(jìn)去來到這里，WebMvcConfigurerComposite復(fù)合WebMvcConfigurer里面維護(hù)很多個(gè)WebMvcConfigurer，依次調(diào)用configureMessageConverters方法。
@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
for (WebMvcConfigurer delegate : this.delegates) {
delegate.configureMessageConverters(converters);
}
}
其中一個(gè)WebMvcAutoConfigurationAdapter，調(diào)用其configureMessageConverters方法，發(fā)現(xiàn)了messageConvertersProvider變量，這個(gè)變量是ObjectProvider類，這個(gè)類就是spring用來依賴注入的，看構(gòu)造方法，所以，這里spring會(huì)自動(dòng)把HttpMessageConverters注入進(jìn)來，前面說了HttpMessageConverters類有包含我們定義好的ObjectMapper的轉(zhuǎn)換器。
不過這個(gè)類是延遲加載的，沒有調(diào)用其獲取對(duì)象方法的時(shí)候，是不會(huì)構(gòu)造注入的
private final ObjectProvider<HttpMessageConverters> messageConvertersProvider;
@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
this.messageConvertersProvider
.ifAvailable((customConverters) -> converters.addAll(customConverters.getConverters()));
}
public WebMvcAutoConfigurationAdapter(
org.springframework.boot.autoconfigure.web.ResourceProperties resourceProperties,
WebProperties webProperties, WebMvcProperties mvcProperties, ListableBeanFactory beanFactory,
ObjectProvider<HttpMessageConverters> messageConvertersProvider,
ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider,
ObjectProvider<DispatcherServletPath> dispatcherServletPath,
ObjectProvider<ServletRegistrationBean<?>> servletRegistrations) {
this.resourceProperties = resourceProperties.hasBeenCustomized() ? resourceProperties
: webProperties.getResources();
this.mvcProperties = mvcProperties;
this.beanFactory = beanFactory;
this.messageConvertersProvider = messageConvertersProvider;
this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizerProvider.getIfAvailable();
this.dispatcherServletPath = dispatcherServletPath;
this.servletRegistrations = servletRegistrations;
this.mvcProperties.checkConfiguration();
}
本來分析到這里就結(jié)束了，但是，問題來了
之前為什么會(huì)分析這個(gè)代碼呢，因?yàn)槲覟榱私鉀QLong類型轉(zhuǎn)String類型給前端，防止經(jīng)度丟失。添加了一段代碼，發(fā)現(xiàn)沒用。
我在其他項(xiàng)目上，如此，是有用的，但是放到新項(xiàng)目發(fā)現(xiàn)沒用。
代碼如下：
@Configuration
public class JacksonConfig {
/***
* 控制層返回json時(shí)處理LocalDateTime
*
* @Title: getObjectMapper
* @return
*/
@Bean(name = "mapperObject")
public ObjectMapper getObjectMapper() {
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
JavaTimeModule javaTimeModule = new JavaTimeModule();
// 處理json返回?cái)?shù)據(jù)時(shí)將LocalDateTime LocalDate LocalTime轉(zhuǎn)換成字符串
javaTimeModule.addSerializer(LocalDateTime.class,
new LocalDateTimeSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
javaTimeModule.addSerializer(LocalDate.class,
new LocalDateSerializer(DateTimeFormatter.ofPattern("yyyy-MM-dd")));
javaTimeModule.addSerializer(LocalTime.class, new LocalTimeSerializer(DateTimeFormatter.ofPattern("HH:mm:ss")));
// 將long類型轉(zhuǎn)成String,js針對(duì)long類型的精度小于java
javaTimeModule.addSerializer(Long.class, ToStringSerializer.instance);
// @RequestBody 接受的字符串自動(dòng)轉(zhuǎn)成LocalDateTime LocalDate LocalTime
javaTimeModule.addDeserializer(LocalDateTime.class,
new LocalDateTimeDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")));
javaTimeModule.addDeserializer(LocalDate.class,
new LocalDateDeserializer(DateTimeFormatter.ofPattern("yyyy-MM-dd")));
javaTimeModule.addDeserializer(LocalTime.class,
new LocalTimeDeserializer(DateTimeFormatter.ofPattern("HH:mm:ss")));
// SimpleModule xssModule = new SimpleModule("HTML XSS");
//xssModule.addSerializer(new XssJsonSerializer(String.class));
// xssModule.addDeserializer(String.class, new XssJsonDeserializer(String.class));
// objectMapper.registerModule(xssModule);
objectMapper.registerModules(javaTimeModule);
return objectMapper;
}
}
問題分析：前面說了，WebMvcAutoConfiguration會(huì)通過ObjectProvider延遲注入HttpMessageConverters對(duì)象。然后通過configureMessageConverters方法注入進(jìn)去的，但是通過debug發(fā)現(xiàn)，代碼根本不會(huì)進(jìn)入這里。
public WebMvcAutoConfigurationAdapter(
org.springframework.boot.autoconfigure.web.ResourceProperties resourceProperties,
WebProperties webProperties, WebMvcProperties mvcProperties, ListableBeanFactory beanFactory,
ObjectProvider<HttpMessageConverters> messageConvertersProvider,
ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider,
ObjectProvider<DispatcherServletPath> dispatcherServletPath,
ObjectProvider<ServletRegistrationBean<?>> servletRegistrations) {
this.resourceProperties = resourceProperties.hasBeenCustomized() ? resourceProperties
: webProperties.getResources();
this.mvcProperties = mvcProperties;
this.beanFactory = beanFactory;
this.messageConvertersProvider = messageConvertersProvider;
this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizerProvider.getIfAvailable();
this.dispatcherServletPath = dispatcherServletPath;
this.servletRegistrations = servletRegistrations;
this.mvcProperties.checkConfiguration();
}
@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
this.messageConvertersProvider
.ifAvailable((customConverters) -> converters.addAll(customConverters.getConverters()));
}
HttpMessageConvertersAutoConfiguration配置類里會(huì)裝載HttpMessageConverters ，通過debug，發(fā)現(xiàn)，這里裝載的轉(zhuǎn)換器，是有我們自己定義ObjectMapper的轉(zhuǎn)換器的。所以到這里是沒問題的。
@Bean
@ConditionalOnMissingBean
public HttpMessageConverters messageConverters(ObjectProvider<HttpMessageConverter<?>> converters) {
return new HttpMessageConverters(converters.orderedStream().collect(Collectors.toList()));
}
所以有理由懷疑，之前的循環(huán)依次調(diào)用WebMvcConfigurer里沒有我們的WebMvcAutoConfiguration。
@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
for (WebMvcConfigurer delegate : this.delegates) {
delegate.configureMessageConverters(converters);
}
}
發(fā)現(xiàn)果然沒有WebMvcAutoConfiguration，下面是兩個(gè)不同項(xiàng)目的對(duì)比，同時(shí)通過打斷點(diǎn)，查看this對(duì)象，發(fā)現(xiàn)一個(gè)項(xiàng)目的this是WebMvcAutoConfiguration$EnableWebMvcConfiguration
一個(gè)是DelegatingWebMvcConfiguration。
然后我們來看為什么沒有WebMvcAutoConfiguration
看注解當(dāng)沒有WebMvcConfigurationSupport類的時(shí)候，才會(huì)構(gòu)建這個(gè)WebMvcAutoConfiguration。那就打斷點(diǎn)在WebMvcConfigurationSupport方法里。
發(fā)現(xiàn)會(huì)構(gòu)建，并且this對(duì)象是DelegatingWebMvcConfiguration
@Configuration(proxyBeanMethods = false)
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,
ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {
然后看DelegatingWebMvcConfiguration的子類，看注解說這個(gè)配置類等價(jià)于@EnableWebMvc注解，
/**
* Configuration equivalent to {@code @EnableWebMvc}.
*/
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(WebProperties.class)
public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration implements ResourceLoaderAware {
private final Resources resourceProperties;
然后我們的項(xiàng)目啟動(dòng)類上加了EnableWebMvc注解，其會(huì)通過import注解注入DelegatingWebMvcConfiguration類。
至此，謎底解開。
@EnableAsync(proxyTargetClass = true)
@EnableWebMvc
@SpringBootApplication(exclude = { DataSourceAutoConfiguration.class, SecurityAutoConfiguration.class })
@MapperScan({"com.bigfire.business.mapper",
"com.bigfire.system.mapper",
"com.bigfire.**.mapper", "com.bigfire.**.mapperextend"})
public class BigSkyP01ZaihaiApplication
}
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Import(DelegatingWebMvcConfiguration.class)
public @interface EnableWebMvc {
}
結(jié)論：一個(gè)項(xiàng)目啟動(dòng)類使用了EnableWebMvc注解，導(dǎo)致注入了DelegatingWebMvcConfiguration類，之后就不會(huì)注入WebMvcAutoConfiguration類，之后就不會(huì)通過ObjectProvider延遲注入HttpMessageConverters，而我們自己定義的ObjectMapper是在HttpMessageConverters里，在WebMvcConfigurerComposite循環(huán)配置HttpMessageConverter的時(shí)候就不會(huì)調(diào)用WebMvcAutoConfiguration的配置方法：configureContentNegotiation，就不會(huì)注入自定義的ObjectMapper。
