Spring 解析器自定义

本文详细解析了Spring MVC中HandlerMethodArgumentResolver的原理、注册方式及使用场景,包括RequestParam、PathVariable等参数解析过程,以及如何自定义HandlerMethodArgumentResolver。通过实例展示了如何在Shiro框架中扩展@CurrentUser注解,实现安全上下文对象的参数注入。

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HandlerMethodArgumentResolver接口的抽象类:AbstractMessageConverterMethodArgumentResolver仅仅引入了HttpMessageConverter,即转换的工作有这些HttpMessageConverter来完成具体的转换和判断由子类来实现。 
如下:

 

public abstract class AbstractMessageConverterMethodArgumentResolver implements HandlerMethodArgumentResolver {

	protected final Log logger = LogFactory.getLog(getClass());

	protected final List<HttpMessageConverter<?>> messageConverters;

	protected final List<MediaType> allSupportedMediaTypes;
     //略
}
 AbstractMessageConverterMethodArgumentResolver 的抽象子类AbstractMessageConverterMethodProcessor仅仅是加入了对响应数据进行转换的支持。 

 

也就是AbstractMessageConverterMethodProcessor的子类不仅可以用来转换请求数据,也可以用来转换响应数据。 
AbstractMessageConverterMethodProcessor的子类HttpEntityMethodProcessor,支持请求和响应的转换,代码如下:
@Override
	public boolean supportsParameter(MethodParameter parameter) {
		return HttpEntity.class.equals(parameter.getParameterType());
	}

	@Override
	public boolean supportsReturnType(MethodParameter returnType) {
		return HttpEntity.class.isAssignableFrom(returnType.getParameterType());
	}
 AbstractMessageConverterMethodProcessor的子类RequestResponseBodyMethodProcessor:支持@RequestBody和@ResponseBody,代码如下:
@Override
	public boolean supportsParameter(MethodParameter parameter) {
               //查找参数中是否含有@RequestBody注解
		return parameter.hasParameterAnnotation(RequestBody.class);
	}

	@Override
	public boolean supportsReturnType(MethodParameter returnType) {

//查找参数中是否含有@RequestBody注解或者controller类上是否含有@RequestBody
		return ((AnnotationUtils.findAnnotation(returnType.getContainingClass(), ResponseBody.class) != null) ||
				(returnType.getMethodAnnotation(ResponseBody.class) != null));
	}
 同理RequestResponseBodyMethodProcessor也会使用相应的HttpMessageConverter来进行转换。如public Map<String,Object> testrequestBody(@RequestBody Map<String,Object> map1)则会选择MappingJackson2HttpMessageConverter或者MappingJacksonHttpMessageConverter来完成转换。
RequestParamMethodArgumentResolver支持的类型有,一种是含@RequestParam注解的参数,另一种就是简单类型,如Integer、String、Date、URI, URL,Locale等: 
public boolean supportsParameter(MethodParameter parameter) {
		Class<?> paramType = parameter.getParameterType();
		if (parameter.hasParameterAnnotation(RequestParam.class)) {
			if (Map.class.isAssignableFrom(paramType)) {
				String paramName = parameter.getParameterAnnotation(RequestParam.class).value();
				return StringUtils.hasText(paramName);
			}
			else {
				return true;
			}
		}
		else {
			if (parameter.hasParameterAnnotation(RequestPart.class)) {
				return false;
			}
			else if (MultipartFile.class.equals(paramType) || "javax.servlet.http.Part".equals(paramType.getName())) {
				return true;
			}
			else if (this.useDefaultResolution) {
				return BeanUtils.isSimpleProperty(paramType);
			}
			else {
				return false;
			}
		}
	}
 即当请求为 http://localhost:8080/test?name=abc时,处理函数若为test(String name),则对name的解析就是采用RequestParamMethodArgumentResolver来解析的。 

RequestHeaderMethodArgumentResolver:主要用来处理含有@RequestHeader注解的参数,但同时该参数又不是Map类型。如下:

@Override
	public boolean supportsParameter(MethodParameter parameter) {
		return parameter.hasParameterAnnotation(RequestHeader.class)
				&& !Map.class.isAssignableFrom(parameter.getParameterType());
	}


	@Override
	protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest request) throws Exception {
		String[] headerValues = request.getHeaderValues(name);
		if (headerValues != null) {
			return (headerValues.length == 1 ? headerValues[0] : headerValues);
		}
		else {
			return null;
		}
	} 
若想获取所有的header信息:则使用另一个RequestHeaderMapMethodArgumentResolver,它则用来获取所有的header信息:
public class RequestHeaderMapMethodArgumentResolver implements HandlerMethodArgumentResolver {

//这里已经写明白了,要求参数必须含有@RequestHeader注解,并且是Map类型
	@Override
	public boolean supportsParameter(MethodParameter parameter) {
		return parameter.hasParameterAnnotation(RequestHeader.class)
				&& Map.class.isAssignableFrom(parameter.getParameterType());
	}

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

		Class<?> paramType = parameter.getParameterType();

		if (MultiValueMap.class.isAssignableFrom(paramType)) {
			MultiValueMap<String, String> result;
			if (HttpHeaders.class.isAssignableFrom(paramType)) {
				result = new HttpHeaders();
			}
			else {
				result = new LinkedMultiValueMap<String, String>();
			}
			for (Iterator<String> iterator = webRequest.getHeaderNames(); iterator.hasNext();) {
				String headerName = iterator.next();
				for (String headerValue : webRequest.getHeaderValues(headerName)) {
					result.add(headerName, headerValue);
				}
			}
			return result;
		}
		else {
			Map<String, String> result = new LinkedHashMap<String, String>();
			for (Iterator<String> iterator = webRequest.getHeaderNames(); iterator.hasNext();) {
				String headerName = iterator.next();
				String headerValue = webRequest.getHeader(headerName);
				result.put(headerName, headerValue);
			}
			return result;
		}
	}
}
  从上面的解析过程可以看出,参数类型可以是普通的Map类型,也可以是MultiValueMap或者进一步的HttpHeaders,他们与普通Map类型的区别是他们对value值后者们是以List形式存放,前者是以String形式存放。
PathVariableMethodArgumentResolver:主要针对含有@PathVariable的参数,代码如下:  
@Override
	public boolean supportsParameter(MethodParameter parameter) {
		if (!parameter.hasParameterAnnotation(PathVariable.class)) {
			return false;
		}
		if (Map.class.isAssignableFrom(parameter.getParameterType())) {
			String paramName = parameter.getParameterAnnotation(PathVariable.class).value();
			return StringUtils.hasText(paramName);
		}
		return true;
	}



@Override
	@SuppressWarnings("unchecked")
	protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest request) throws Exception {
		Map<String, String> uriTemplateVars =
			(Map<String, String>) request.getAttribute(
					HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, RequestAttributes.SCOPE_REQUEST);
		return (uriTemplateVars != null) ? uriTemplateVars.get(name) : null;
	}
  对于支持的类型也说明的很详细。首先必须含有@PathVariable注解,其次如果是Map类型,必须要指定@PathVariable的值,即这个  

ArgumentResolver只能获取一个uri变量。要想获取多个则要使用PathVariableMapMethodArgumentResolver: 

 

@Override
	public boolean supportsParameter(MethodParameter parameter) {
		PathVariable annot = parameter.getParameterAnnotation(PathVariable.class);
		return ((annot != null) && (Map.class.isAssignableFrom(parameter.getParameterType()))
				&& (!StringUtils.hasText(annot.value())));
	}

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

		@SuppressWarnings("unchecked")
		Map<String, String> uriTemplateVars =
				(Map<String, String>) webRequest.getAttribute(
						HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, RequestAttributes.SCOPE_REQUEST);

		if (!CollectionUtils.isEmpty(uriTemplateVars)) {
			return new LinkedHashMap<String, String>(uriTemplateVars);
		}
		else {
			return Collections.emptyMap();
		}
	}

 它要求必须含有@PathVariable注解,并且必须是Map类型,并且@PathVariable注解的value没有值。同时我们可以从PathVariableMapMethodArgumentResolver和PathVariableMethodArgumentResolver上面看出,他们的取值都是从request的属性上进行获取的webRequest.getAttribute( 

 

HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, RequestAttributes.SCOPE_REQUEST);也就是说,在解析完@RequestMapping匹配工作后,便将这些参数设置进request的属性上,属性名为HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE。其他的HandlerMethodArgumentResolver可以自行研究,这里不再说明。 

 

至此,我们就要说明下HandlerMethodArgumentResolver的注册来源: 
它的来源分为两部分,一部分spring默认的HandlerMethodArgumentResolver,另一部分就是我们自定义的HandlerMethodArgumentResolver。 
还是先看mvc:annotation-driven中配置自定义的HandlerMethodArgumentResolver:
 

 

<mvc:annotation-driven >
		<mvc:argument-resolvers>
			<bean class="xxx"></bean>
		</mvc:argument-resolvers>
	</mvc:annotation-driven>  

 

 

在mvc:argument-resolvers标签下配置相应的自定义的HandlerMethodArgumentResolver。 
然后在mvc:annotation-driven的注解驱动类AnnotationDrivenBeanDefinitionParser中会有这样的代码:
 

 

ManagedList<?> argumentResolvers = getArgumentResolvers(element, parserContext);

//略
if (argumentResolvers != null) {
			handlerAdapterDef.getPropertyValues().add("customArgumentResolvers", argumentResolvers);
		}

 其中getArgumentResolvers就是获取我们自定义的HandlerMethodArgumentResolver 

 

 

private ManagedList<?> getArgumentResolvers(Element element, ParserContext parserContext) {
		Element resolversElement = DomUtils.getChildElementByTagName(element, "argument-resolvers");
		if (resolversElement != null) {
			ManagedList<BeanDefinitionHolder> argumentResolvers = extractBeanSubElements(resolversElement, parserContext);
			return wrapWebArgumentResolverBeanDefs(argumentResolvers, parserContext);
		}
		return null;
	}

 从上面的代码可以看出,获取我们自定义的HandlerMethodArgumentResolver然后把它设置进RequestMappingHandlerAdapter的customArgumentResolvers参数中,RequestMappingHandlerAdapter有两个与HandlerMethodArgumentResolver有关的参数:

 

 

private List<HandlerMethodArgumentResolver> customArgumentResolvers;
private HandlerMethodArgumentResolverComposite argumentResolvers;

 HandlerMethodArgumentResolverComposite 也仅仅是内部存放一个List<HandlerMethodArgumentResolver>集合,同时本身又继承HandlerMethodArgumentResolver,所以它的实现都是靠内部的List<HandlerMethodArgumentResolver>集合来实现的。 

 

 

private final List<HandlerMethodArgumentResolver> argumentResolvers =
			new LinkedList<HandlerMethodArgumentResolver>();

//使用了适合高并发的ConcurrentHashMap来进行缓存
	private final Map<MethodParameter, HandlerMethodArgumentResolver> argumentResolverCache =
			new ConcurrentHashMap<MethodParameter, HandlerMethodArgumentResolver>(256);


	/**
	 * Return a read-only list with the contained resolvers, or an empty list.
	 */
	public List<HandlerMethodArgumentResolver> getResolvers() {
		return Collections.unmodifiableList(this.argumentResolvers);
	}

	/**
	 * Whether the given {@linkplain MethodParameter method parameter} is supported by any registered
	 * {@link HandlerMethodArgumentResolver}.
	 */
	@Override
	public boolean supportsParameter(MethodParameter parameter) {
		return getArgumentResolver(parameter) != null;
	}

	/**
	 * Iterate over registered {@link HandlerMethodArgumentResolver}s and invoke the one that supports it.
	 * @exception IllegalStateException if no suitable {@link HandlerMethodArgumentResolver} is found.
	 */
	@Override
	public Object resolveArgument(
			MethodParameter parameter, ModelAndViewContainer mavContainer,
			NativeWebRequest webRequest, WebDataBinderFactory binderFactory)
			throws Exception {

		HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter);
		Assert.notNull(resolver, "Unknown parameter type [" + parameter.getParameterType().getName() + "]");
		return resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory);
	}

	/**
	 * Find a registered {@link HandlerMethodArgumentResolver} that supports the given method parameter.
	 */
	private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {
		HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);
		if (result == null) {
			for (HandlerMethodArgumentResolver methodArgumentResolver : this.argumentResolvers) {
				if (logger.isTraceEnabled()) {
					logger.trace("Testing if argument resolver [" + methodArgumentResolver + "] supports [" +
							parameter.getGenericParameterType() + "]");
				}
				if (methodArgumentResolver.supportsParameter(parameter)) {
					result = methodArgumentResolver;
					this.argumentResolverCache.put(parameter, result);
					break;
				}
			}
		}
		return result;
	}

 在RequestMappingHandlerAdapter完成参数设置后,会调用afterPropertiesSet方法 

 

@Override
	public void afterPropertiesSet() {
		if (this.argumentResolvers == null) {
			List<HandlerMethodArgumentResolver> resolvers = getDefaultArgumentResolvers();
			this.argumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers);
		}
		if (this.initBinderArgumentResolvers == null) {
			List<HandlerMethodArgumentResolver> resolvers = getDefaultInitBinderArgumentResolvers();
			this.initBinderArgumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers);
		}
		if (this.returnValueHandlers == null) {
			List<HandlerMethodReturnValueHandler> handlers = getDefaultReturnValueHandlers();
			this.returnValueHandlers = new HandlerMethodReturnValueHandlerComposite().addHandlers(handlers);
		}
		initControllerAdviceCache();
	}

 getDefaultArgumentResolvers方法完成了所有的HandlerMethodArgumentResolver的汇总,如下: 

private List<HandlerMethodArgumentResolver> getDefaultArgumentResolvers() {
		List<HandlerMethodArgumentResolver> resolvers = new ArrayList<HandlerMethodArgumentResolver>();

		// 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()));
		resolvers.add(new RequestPartMethodArgumentResolver(getMessageConverters()));
		resolvers.add(new RequestHeaderMethodArgumentResolver(getBeanFactory()));
		resolvers.add(new RequestHeaderMapMethodArgumentResolver());
		resolvers.add(new ServletCookieValueMethodArgumentResolver(getBeanFactory()));
		resolvers.add(new ValueMethodArgumentResolver(getBeanFactory()));

		// Type-based argument resolution
		resolvers.add(new ServletRequestMethodArgumentResolver());
		resolvers.add(new ServletResponseMethodArgumentResolver());
		resolvers.add(new HttpEntityMethodProcessor(getMessageConverters()));
		resolvers.add(new RedirectAttributesMethodArgumentResolver());
		resolvers.add(new ModelMethodProcessor());
		resolvers.add(new MapMethodProcessor());
		resolvers.add(new ErrorsMethodArgumentResolver());
		resolvers.add(new SessionStatusMethodArgumentResolver());
		resolvers.add(new UriComponentsBuilderMethodArgumentResolver());

		// Custom arguments
//获取我们自定义的HandlerMethodArgumentResolver
		if (getCustomArgumentResolvers() != null) {
			resolvers.addAll(getCustomArgumentResolvers());
		}

		// Catch-all
		resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), true));
		resolvers.add(new ServletModelAttributeMethodProcessor(true));

		return resolvers;
	}

 不仅汇总了spring默认的,同时加进来我们自定义的HandlerMethodArgumentResolver。

 

 

 

 

 

自从spring3.1 开始就有了这个接口,可以为@RequestMapping标注的方法扩展传入的参数。 
以shiro为例,扩展一个标注,@CurrentUser,只要有这个标注,就可以在shiro的安全上下文中取出适当的对象直接从参数传入,request响应函数。 

Java代码   收藏代码
  1. import java.lang.annotation.Documented;  
  2. import java.lang.annotation.ElementType;  
  3. import java.lang.annotation.Retention;  
  4. import java.lang.annotation.RetentionPolicy;  
  5. import java.lang.annotation.Target;  
  6.   
  7. @Documented  
  8. @Target({ElementType.PARAMETER})  
  9. @Retention(RetentionPolicy.RUNTIME)  
  10. public @interface CurrentUser {  
  11. }  

 

Java代码   收藏代码
  1. @RequestMapping(value = "/test1")  
  2. public @ResponseBody String test1(@CurrentUser Long userId) {  
  3.     return userId.toString();  
  4. }  
  5.   
  6. @RequestMapping(value = "/test2")  
  7. public @ResponseBody String test2(@CurrentUser UserDetails userDetails) {  
  8.     return userDetails.toString();  
  9. }  

 

Java代码   收藏代码
  1. import java.lang.annotation.Annotation;  
  2.   
  3. import org.springframework.core.MethodParameter;  
  4. import org.springframework.web.bind.support.WebDataBinderFactory;  
  5. import org.springframework.web.context.request.NativeWebRequest;  
  6. import org.springframework.web.method.support.HandlerMethodArgumentResolver;  
  7. import org.springframework.web.method.support.ModelAndViewContainer;  
  8.   
  9. import com.github.yingzhuo.mycar2.annotation.CurrentUser;  
  10. import com.github.yingzhuo.mycar2.security.SecurityUtils;  
  11. import com.github.yingzhuo.mycar2.security.UserDetails;  
  12.   
  13. public class CurrentUserHandlerMethodArgumentResolver implements HandlerMethodArgumentResolver {  
  14.   
  15.     @Override  
  16.     public boolean supportsParameter(MethodParameter parameter) {  
  17.         Class<?> klass = parameter.getParameterType();  
  18.         if (klass.isAssignableFrom(UserDetails.class) || klass.isAssignableFrom(Long.class)) {  
  19.             Annotation[] as = parameter.getParameterAnnotations();  
  20.             for (Annotation a : as) {  
  21.                 if (a.annotationType() == CurrentUser.class) {  
  22.                     return true;  
  23.                 }  
  24.             }  
  25.         }  
  26.         return false;  
  27.     }  
  28.   
  29.     @Override  
  30.     public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest,  
  31.             WebDataBinderFactory binderFactory) throws Exception {  
  32.           
  33.         if ((SecurityUtils.isAuthenticated() || SecurityUtils.isRemembered()) == false) {  
  34.             return null;  
  35.         }  
  36.           
  37.         Class<?> klass = parameter.getParameterType();  
  38.           
  39.         UserDetails userDetails = SecurityUtils.getUserDetails();  
  40.           
  41.         if (klass.isAssignableFrom(UserDetails.class)) {  
  42.             return SecurityUtils.getUserDetails();  
  43.         }  
  44.           
  45.         if (klass.isAssignableFrom(Long.class)) {  
  46.             return userDetails != null ? userDetails.getId() : null;  
  47.         }  
  48.           
  49.         return null;  
  50.     }  
  51. }  


最后,需要配置一下 

Xml代码   收藏代码
  1. <mvc:annotation-driven>  
  2.     <mvc:argument-resolvers>  
  3.         <bean class="xxx.yyy.CurrentUserHandlerMethodArgumentResolver" />  
  4.     </mvc:argument-resolvers>  
  5. </mvc:annotation-driven>  
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