1,
public interface HandlerMethodReturnValueHandler {
/**
* Whether the given {@linkplain MethodParameter method return type} is
* supported by this handler.
*
* @param returnType the method return type to check
* @return {@code true} if this handler supports the supplied return type;
* {@code false} otherwise
*/
boolean supportsReturnType(MethodParameter returnType);
/**
* Handle the given return value by adding attributes to the model and
* setting a view or setting the
* {@link ModelAndViewContainer#setRequestHandled} flag to {@code true}
* to indicate the response has been handled directly.
*
* @param returnValue the value returned from the handler method
* @param returnType the type of the return value. This type must have
* previously been passed to
* {@link #supportsReturnType(org.springframework.core.MethodParameter)}
* and it must have returned {@code true}
* @param mavContainer the ModelAndViewContainer for the current request
* @param webRequest the current request
* @throws Exception if the return value handling results in an error
*/
void handleReturnValue(Object returnValue,
MethodParameter returnType,
ModelAndViewContainer mavContainer,
NativeWebRequest webRequest) throws Exception;
}
2,
public class RequestResponseBodyMethodProcessor extends AbstractMessageConverterMethodProcessor {
public RequestResponseBodyMethodProcessor(List<HttpMessageConverter<?>> messageConverters) {
super(messageConverters);
}
public boolean supportsParameter(MethodParameter parameter) {
return parameter.hasParameterAnnotation(RequestBody.class);
}
public boolean supportsReturnType(MethodParameter returnType) {
return returnType.getMethodAnnotation(ResponseBody.class) != null;
}
public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
Object arg = readWithMessageConverters(webRequest, parameter, parameter.getParameterType());
Annotation[] annotations = parameter.getParameterAnnotations();
for (Annotation annot : annotations) {
if (annot.annotationType().getSimpleName().startsWith("Valid")) {
String name = Conventions.getVariableNameForParameter(parameter);
WebDataBinder binder = binderFactory.createBinder(webRequest, arg, name);
Object hints = AnnotationUtils.getValue(annot);
binder.validate(hints instanceof Object[] ? (Object[]) hints : new Object[] {hints});
BindingResult bindingResult = binder.getBindingResult();
if (bindingResult.hasErrors()) {
throw new MethodArgumentNotValidException(parameter, bindingResult);
}
}
}
return arg;
}
public void handleReturnValue(Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest)
throws IOException, HttpMediaTypeNotAcceptableException {
mavContainer.setRequestHandled(true);
if (returnValue != null) {
writeWithMessageConverters(returnValue, returnType, webRequest);
}
}
}
3,AbstractMessageConverterMethodProcessor
protected <T> void writeWithMessageConverters(T returnValue,
MethodParameter returnType,
NativeWebRequest webRequest)
throws IOException, HttpMediaTypeNotAcceptableException {
ServletServerHttpRequest inputMessage = createInputMessage(webRequest);
ServletServerHttpResponse outputMessage = createOutputMessage(webRequest);
writeWithMessageConverters(returnValue, returnType, inputMessage, outputMessage);
}
4,AbstractMessageConverterMethodProcessor
public final void write(T t, MediaType contentType, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException {
HttpHeaders headers = outputMessage.getHeaders();
if (headers.getContentType() == null) {
if (contentType == null || contentType.isWildcardType() || contentType.isWildcardSubtype()) {
contentType = getDefaultContentType(t);
}
if (contentType != null) {
headers.setContentType(contentType);
}
}
if (headers.getContentLength() == -1) {
Long contentLength = getContentLength(t, headers.getContentType());
if (contentLength != null) {
headers.setContentLength(contentLength);
}
}
writeInternal(t, outputMessage);
outputMessage.getBody().flush();
}
5,MappingJacksonHttpMessageConverter
protected void writeInternal(Object object, HttpOutputMessage outputMessage)
throws IOException, HttpMessageNotWritableException {
JsonEncoding encoding = getJsonEncoding(outputMessage.getHeaders().getContentType());
JsonGenerator jsonGenerator =
this.objectMapper.getJsonFactory().createJsonGenerator(outputMessage.getBody(), encoding);
// A workaround for JsonGenerators not applying serialization features
// https://github.com/FasterXML/jackson-databind/issues/12
if (this.objectMapper.getSerializationConfig().isEnabled(SerializationConfig.Feature.INDENT_OUTPUT)) {
jsonGenerator.useDefaultPrettyPrinter();
}
try {
if (this.prefixJson) {
jsonGenerator.writeRaw("{} && ");
}
this.objectMapper.writeValue(jsonGenerator, object);
}
catch (JsonProcessingException ex) {
throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex);
}
}