org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor#supportsParameter
只要参数上有@RequestBody注解name就会使用RequestResponseBodyMethodProcessor来处理
public boolean supportsParameter(MethodParameter parameter) {
return parameter.hasParameterAnnotation(RequestBody.class);
}
看下具体解析过程:
org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor#resolveArgument
org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor#readWithMessageConverters
protected <T> Object readWithMessageConverters(HttpInputMessage inputMessage, MethodParameter parameter,
Type targetType) throws IOException, HttpMediaTypeNotSupportedException, HttpMessageNotReadableException {
MediaType contentType;
boolean noContentType = false;
try {
contentType = inputMessage.getHeaders().getContentType();
}
catch (InvalidMediaTypeException ex) {
throw new HttpMediaTypeNotSupportedException(ex.getMessage());
}
if (contentType == null) {
noContentType = true;
contentType = MediaType.APPLICATION_OCTET_STREAM;
}
Class<?> contextClass = parameter.getContainingClass();
Class<T> targetClass = (targetType instanceof Class ? (Class<T>) targetType : null);
if (targetClass == null) {
ResolvableType resolvableType = ResolvableType.forMethodParameter(parameter);
targetClass = (Class<T>) resolvableType.resolve();
}
HttpMethod httpMethod = (inputMessage instanceof HttpRequest ? ((HttpRequest) inputMessage).getMethod() : null);
Object body = NO_VALUE;
EmptyBodyCheckingHttpInputMessage message;
try {
message = new EmptyBodyCheckingHttpInputMessage(inputMessage);
//遍历7大对象来解析请求参数
for (HttpMessageConverter<?> converter : this.messageConverters) {
Class<HttpMessageConverter<?>> converterType = (Class<HttpMessageConverter<?>>) converter.getClass();
GenericHttpMessageConverter<?> genericConverter =
(converter instanceof GenericHttpMessageConverter ? (GenericHttpMessageConverter<?>) converter : null);
if (genericConverter != null ? genericConverter.canRead(targetType, contextClass, contentType) :
(targetClass != null && converter.canRead(targetClass, contentType))) {
if (message.hasBody()) {
HttpInputMessage msgToUse =
getAdvice().beforeBodyRead(message, parameter, targetType, converterType);
//最核心的解析部分
body = (genericConverter != null ? genericConverter.read(targetType, contextClass, msgToUse) :
((HttpMessageConverter<T>) converter).read(targetClass, msgToUse));
body = getAdvice().afterBodyRead(body, msgToUse, parameter, targetType, converterType);
}
else {
body = getAdvice().handleEmptyBody(null, message, parameter, targetType, converterType);
}
break;
}
}
}
catch (IOException ex) {
throw new HttpMessageNotReadableException("I/O error while reading input message", ex, inputMessage);
}
if (body == NO_VALUE) {
if (httpMethod == null || !SUPPORTED_METHODS.contains(httpMethod) ||
(noContentType && !message.hasBody())) {
return null;
}
throw new HttpMediaTypeNotSupportedException(contentType, this.allSupportedMediaTypes);
}
MediaType selectedContentType = contentType;
Object theBody = body;
LogFormatUtils.traceDebug(logger, traceOn -> {
String formatted = LogFormatUtils.formatValue(theBody, !traceOn);
return "Read \"" + selectedContentType + "\" to [" + formatted + "]";
});
return body;
}
此时一定要注意:一定要加上 mvc:annotation-deiven/,同时要引入jackson对应的依赖才会把MappingJackson2HttpMessageConverter这个参数解析器注入到容器,供后续遍历8大解析器来解析@RequestBody
static {
ClassLoader classLoader = AnnotationDrivenBeanDefinitionParser.class.getClassLoader();
javaxValidationPresent = ClassUtils.isPresent("javax.validation.Validator", classLoader);
romePresent = ClassUtils.isPresent("com.rometools.rome.feed.WireFeed", classLoader);
jaxb2Present = ClassUtils.isPresent("javax.xml.bind.Binder", classLoader);
//从这里可以发现一定要引入对应的包才会注入到容器中
jackson2Present = ClassUtils.isPresent("com.fasterxml.jackson.databind.ObjectMapper", classLoader) &&
ClassUtils.isPresent("com.fasterxml.jackson.core.JsonGenerator", classLoader);
}
<dependency>
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-xml</artifactId>
<version>2.11.3</version>
</dependency>
注意:RequestMappingHandlerAdapter里的afterPropertiesSet会初始化8大请求参数@ResponseBody对象
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#getDefaultArgumentResolvers
org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver#AbstractMessageConverterMethodArgumentResolver(java.util.List<org.springframework.http.converter.HttpMessageConverter<?>>, java.util.List<java.lang.Object>)
通过这行将字符串解析成对象
private Object readJavaType(JavaType javaType, HttpInputMessage inputMessage) throws IOException {
MediaType contentType = inputMessage.getHeaders().getContentType();
Charset charset = getCharset(contentType);
boolean isUnicode = ENCODINGS.containsKey(charset.name());
try {
if (inputMessage instanceof MappingJacksonInputMessage) {
Class<?> deserializationView = ((MappingJacksonInputMessage) inputMessage).getDeserializationView();
if (deserializationView != null) {
ObjectReader objectReader = this.objectMapper.readerWithView(deserializationView).forType(javaType);
if (isUnicode) {
return objectReader.readValue(inputMessage.getBody());
}
else {
Reader reader = new InputStreamReader(inputMessage.getBody(), charset);
return objectReader.readValue(reader);
}
}
}
if (isUnicode) {
return this.objectMapper.readValue(inputMessage.getBody(), javaType);
}
else {
Reader reader = new InputStreamReader(inputMessage.getBody(), charset);
return this.objectMapper.readValue(reader, javaType);
}
}