Spring Boot 自动引入jackson: 通过：Spring-Boot-starter-web
Jackson自动配置
这里的configurations是读取的这里：
通过反射加载JacksonAutoConfiguration:
public void configure(ObjectMapper objectMapper) {
Assert.notNull(objectMapper, "ObjectMapper must not be null");
MultiValueMap<Object, Module> modulesToRegister = new LinkedMultiValueMap<>();
if (this.findModulesViaServiceLoader) {
ObjectMapper.findModules(this.moduleClassLoader).forEach(module -> registerModule(module, modulesToRegister));
}
else if (this.findWellKnownModules) {
registerWellKnownModulesIfAvailable(modulesToRegister);
}
if (this.modules != null) {
this.modules.forEach(module -> registerModule(module, modulesToRegister));
}
if (this.moduleClasses != null) {
for (Class<? extends Module> moduleClass : this.moduleClasses) {
registerModule(BeanUtils.instantiateClass(moduleClass), modulesToRegister);
}
}
List<Module> modules = new ArrayList<>();
for (List<Module> nestedModules : modulesToRegister.values()) {
modules.addAll(nestedModules);
}
objectMapper.registerModules(modules);
if (this.dateFormat != null) {
objectMapper.setDateFormat(this.dateFormat);
}
if (this.locale != null) {
objectMapper.setLocale(this.locale);
}
if (this.timeZone != null) {
objectMapper.setTimeZone(this.timeZone);
}
if (this.annotationIntrospector != null) {
objectMapper.setAnnotationIntrospector(this.annotationIntrospector);
}
if (this.propertyNamingStrategy != null) {
objectMapper.setPropertyNamingStrategy(this.propertyNamingStrategy);
}
if (this.defaultTyping != null) {
objectMapper.setDefaultTyping(this.defaultTyping);
}
if (this.serializationInclusion != null) {
objectMapper.setSerializationInclusion(this.serializationInclusion);
}
if (this.filters != null) {
objectMapper.setFilterProvider(this.filters);
}
this.mixIns.forEach(objectMapper::addMixIn);
if (!this.serializers.isEmpty() || !this.deserializers.isEmpty()) {
SimpleModule module = new SimpleModule();
addSerializers(module);
addDeserializers(module);
objectMapper.registerModule(module);
}
this.visibilities.forEach(objectMapper::setVisibility);
customizeDefaultFeatures(objectMapper);
this.features.forEach((feature, enabled) -> configureFeature(objectMapper, feature, enabled));
if (this.handlerInstantiator != null) {
objectMapper.setHandlerInstantiator(this.handlerInstantiator);
}
else if (this.applicationContext != null) {
objectMapper.setHandlerInstantiator(
new SpringHandlerInstantiator(this.applicationContext.getAutowireCapableBeanFactory()));
}
}
上面的类中会用到一些yml中的一些配置，是在下面的代码中获取：
在WebMvcConfigurationSupport中可以看到：
public class WebMvcConfigurationSupport implements ApplicationContextAware, ServletContextAware {
private static final boolean romePresent;
private static final boolean jaxb2Present;
private static final boolean jackson2Present;
private static final boolean jackson2XmlPresent;
private static final boolean jackson2SmilePresent;
private static final boolean jackson2CborPresent;
private static final boolean gsonPresent;
private static final boolean jsonbPresent;
static {
ClassLoader classLoader = WebMvcConfigurationSupport.class.getClassLoader();
romePresent = ClassUtils.isPresent("com.rometools.rome.feed.WireFeed", classLoader);
jaxb2Present = ClassUtils.isPresent("javax.xml.bind.Binder", classLoader);
jackson2Present = ClassUtils.isPresent("com.fasterxml.jackson.databind.ObjectMapper", classLoader) &&
ClassUtils.isPresent("com.fasterxml.jackson.core.JsonGenerator", classLoader);
jackson2XmlPresent = ClassUtils.isPresent("com.fasterxml.jackson.dataformat.xml.XmlMapper", classLoader);
jackson2SmilePresent = ClassUtils.isPresent("com.fasterxml.jackson.dataformat.smile.SmileFactory", classLoader);
jackson2CborPresent = ClassUtils.isPresent("com.fasterxml.jackson.dataformat.cbor.CBORFactory", classLoader);
gsonPresent = ClassUtils.isPresent("com.google.gson.Gson", classLoader);
jsonbPresent = ClassUtils.isPresent("javax.json.bind.Jsonb", classLoader);
}
}
protected final void addDefaultHttpMessageConverters(List<HttpMessageConverter<?>> messageConverters) {
StringHttpMessageConverter stringHttpMessageConverter = new StringHttpMessageConverter();
stringHttpMessageConverter.setWriteAcceptCharset(false); // see SPR-7316
messageConverters.add(new ByteArrayHttpMessageConverter());
messageConverters.add(stringHttpMessageConverter);
messageConverters.add(new ResourceHttpMessageConverter());
messageConverters.add(new ResourceRegionHttpMessageConverter());
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 (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 (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()));
}
}
在使用Jackson进行序列化和反序列化时主要是使用MappingJackson2SmileHttpMessageConverter进行的，下一篇详细介绍一下。