Interface parameter resolution - fixed type resolution

In the actual project, we often get the following interfaces: HttpServletRequest, HttpServletResponse. We will find that we can get the object without any processing. This is the charm of fixed type parsers. In addition to the above two parameters, such as sessionstatus, servletresponse, OutputStream, writer, webrequest, multipartrequest, httpsession, prin API objects generated from cipal and InputStream can also be obtained

1, ServletRequestMethodArgumentResolver

    @Override
	public boolean supportsParameter(MethodParameter parameter) {
		Class<?> paramType = parameter.getParameterType();
		return (WebRequest.class.isAssignableFrom(paramType) ||
				ServletRequest.class.isAssignableFrom(paramType) ||
				MultipartRequest.class.isAssignableFrom(paramType) ||
				HttpSession.class.isAssignableFrom(paramType) ||
				(pushBuilder != null && pushBuilder.isAssignableFrom(paramType)) ||
				Principal.class.isAssignableFrom(paramType) ||
				InputStream.class.isAssignableFrom(paramType) ||
				Reader.class.isAssignableFrom(paramType) ||
				HttpMethod.class == paramType ||
				Locale.class == paramType ||
				TimeZone.class == paramType ||
				ZoneId.class == paramType);
	}

	@Override
	public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
			NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {

		Class<?> paramType = parameter.getParameterType();
		// WebRequest / NativeWebRequest / ServletWebRequest
		if (WebRequest.class.isAssignableFrom(paramType)) {
			if (!paramType.isInstance(webRequest)) {
				throw new IllegalStateException(
						"Current request is not of type [" + paramType.getName() + "]: " + webRequest);
			}
			return webRequest;
		}
		// ServletRequest / HttpServletRequest / MultipartRequest / MultipartHttpServletRequest
		if (ServletRequest.class.isAssignableFrom(paramType) || MultipartRequest.class.isAssignableFrom(paramType)) {
			return resolveNativeRequest(webRequest, paramType);
		}
		// HttpServletRequest required for all further argument types
		return resolveArgument(paramType, resolveNativeRequest(webRequest, HttpServletRequest.class));
	}

Processor processing description

  • If the parameter type is WebRequest, ServletRequest, MultipartRequest, HttpSession, pushBuilder,Principal,InputStream,Reader,HttpMethod,Locale,TimeZone,ZoneId
    You will use this processor. You should understand that if you need to use these parameters in the future, you can declare them directly on the method, and you don't need to get them by yourself

2, ServletResponseMethodArgumentResolver

// @since 3.1
public class ServletResponseMethodArgumentResolver implements HandlerMethodArgumentResolver {
    // It's relatively simple
    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        Class<?> paramType = parameter.getParameterType();
        return (ServletResponse.class.isAssignableFrom(paramType) || // webRequest.getNativeResponse(requiredType)
                OutputStream.class.isAssignableFrom(paramType) || //response.getOutputStream()
                Writer.class.isAssignableFrom(paramType)); //response.getWriter()
    }

    @Override
    public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
            NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
        // That's the judgment...
        if (mavContainer != null) {
            mavContainer.setRequestHandled(true);
        }
        ... 
    }
}

Processor processing description

  • If the parameter type is ServletResponse, OutputStream, the Writer will use this processor

3, SessionStatusMethodArgumentResolver

   public class SessionStatusMethodArgumentResolver implements HandlerMethodArgumentResolver {

	@Override
	public boolean supportsParameter(MethodParameter parameter) {
		return SessionStatus.class == parameter.getParameterType();
	}

	@Override
	public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
			NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {

		Assert.state(mavContainer != null, "ModelAndViewContainer is required for session status exposure");
		return mavContainer.getSessionStatus();
	}

}

Processor processing description

  • This handler is used if the parameter type is SessionStatus

4, UriComponentsBuilderMethodArgumentResolver

public class UriComponentsBuilderMethodArgumentResolver implements HandlerMethodArgumentResolver {

	@Override
	public boolean supportsParameter(MethodParameter parameter) {
		Class<?> type = parameter.getParameterType();
		return (UriComponentsBuilder.class == type || ServletUriComponentsBuilder.class == type);
	}

	@Override
	public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
			NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {

		HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
		Assert.state(request != null, "No HttpServletRequest");
		return ServletUriComponentsBuilder.fromServletMapping(request);
	}

}

Processor processing description

  • If the parameter type is UriComponentsBuilder, ServletUriComponentsBuilder will use this processor

It is very convenient to get all parts of the URL and build the URL through UriComponentsBuilder.

5, RedirectAttributesMethodArgumentResolver

public class RedirectAttributesMethodArgumentResolver implements HandlerMethodArgumentResolver {

	@Override
	public boolean supportsParameter(MethodParameter parameter) {
		return RedirectAttributes.class.isAssignableFrom(parameter.getParameterType());
	}

	@Override
	public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
			NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {

		Assert.state(mavContainer != null, "RedirectAttributes argument only supported on regular handler methods");

		ModelMap redirectAttributes;
		if (binderFactory != null) {
			DataBinder dataBinder = binderFactory.createBinder(webRequest, null, DataBinder.DEFAULT_OBJECT_NAME);
			redirectAttributes = new RedirectAttributesModelMap(dataBinder);
		}
		else {
			redirectAttributes  = new RedirectAttributesModelMap();
		}
		mavContainer.setRedirectModel(redirectAttributes);
		return redirectAttributes;
	}

}

Processor processing description

  • This handler is used if the parameter type is RedirectAttributes

RedirectAttributes is a function after spring MVC version 3.1. It is specially used for redirecting and jumping with parameters
If redirection is involved: multiple views can see the values passed, it is more convenient to use it.

6, ModelMethodProcessor

public class ModelMethodProcessor implements HandlerMethodArgumentResolver, HandlerMethodReturnValueHandler {

	@Override
	public boolean supportsParameter(MethodParameter parameter) {
		return Model.class.isAssignableFrom(parameter.getParameterType());
	}

	@Override
	@Nullable
	public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
			NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {

		Assert.state(mavContainer != null, "ModelAndViewContainer is required for model exposure");
		return mavContainer.getModel();
	

Processor processing description

  • This handler is used if the parameter type is Model

7, ModelAttributeMethodProcessor

public class ModelAttributeMethodProcessor implements HandlerMethodArgumentResolver, HandlerMethodReturnValueHandler {
	private final boolean annotationNotRequired;
	@Override
	public boolean supportsParameter(MethodParameter parameter) {
		return (parameter.hasParameterAnnotation(ModelAttribute.class) ||
				(this.annotationNotRequired && !BeanUtils.isSimpleProperty(parameter.getParameterType())));
	}
	@Override
	@Nullable
	public final Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
			NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {

		Assert.state(mavContainer != null, "ModelAttributeMethodProcessor requires ModelAndViewContainer");
		Assert.state(binderFactory != null, "ModelAttributeMethodProcessor requires WebDataBinderFactory");

		String name = ModelFactory.getNameForParameter(parameter);
		ModelAttribute ann = parameter.getParameterAnnotation(ModelAttribute.class);
		if (ann != null) {
			mavContainer.setBinding(name, ann.binding());
		}

		Object attribute = null;
		BindingResult bindingResult = null;

		if (mavContainer.containsAttribute(name)) {
			attribute = mavContainer.getModel().get(name);
		}
		else {
			// Create attribute instance
			try {
				attribute = createAttribute(name, parameter, binderFactory, webRequest);
			}
			catch (BindException ex) {
				if (isBindExceptionRequired(parameter)) {
					// No BindingResult parameter -> fail with BindException
					throw ex;
				}
				// Otherwise, expose null/empty value and associated BindingResult
				if (parameter.getParameterType() == Optional.class) {
					attribute = Optional.empty();
				}
				bindingResult = ex.getBindingResult();
			}
		}

		if (bindingResult == null) {
			// Bean property binding and validation;
			// skipped in case of binding failure on construction.
			WebDataBinder binder = binderFactory.createBinder(webRequest, attribute, name);
			if (binder.getTarget() != null) {
				if (!mavContainer.isBindingDisabled(name)) {
					bindRequestParameters(binder, webRequest);
				}
				validateIfApplicable(binder, parameter);
				if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {
					throw new BindException(binder.getBindingResult());
				}
			}
			// Value type adaptation, also covering java.util.Optional
			if (!parameter.getParameterType().isInstance(attribute)) {
				attribute = binder.convertIfNecessary(binder.getTarget(), parameter.getParameterType(), parameter);
			}
			bindingResult = binder.getBindingResult();
		}

		// Add resolved attribute and BindingResult at the end of the model
		Map<String, Object> bindingResultModel = bindingResult.getModel();
		mavContainer.removeAttributes(bindingResultModel);
		mavContainer.addAllAttributes(bindingResultModel);

		return attribute;
	}

Processor processing description

  • This handler is used if the parameter type uses @ ModelAttribute or is not a normal type (judged by! BeanUtils.isSimpleProperty)
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Tags: Attribute Session Spring Java

Posted on Fri, 07 Feb 2020 12:27:28 -0500 by paulieo10