第關(guān)于SpringMVC在Controller層方法的參數(shù)解析詳解實(shí)現(xiàn)和配置

按照如下方法實(shí)現(xiàn)HandlerMethodArgumentResolver，用于解析header中的client-type并轉(zhuǎn)化為ClientType。

packagemon;

importmons.lang3.StringUtils;

importorg.springframework.core.MethodParameter;

importorg.springframework.web.bind.support.WebDataBinderFactory;

importorg.springframework.web.context.request.NativeWebRequest;

importorg.springframework.web.method.support.HandlerMethodArgumentResolver;

importorg.springframework.web.method.support.ModelAndViewContainer;

publicclassCurClientTypeMethodArgumentResolverimplementsHandlerMethodArgumentResolver{

privatefinalString[]CLIENT_TYPE_HEADER_NAMES={"client-type","CLIENT-TYPE","Client-Type"};

//選擇要被注入的參數(shù)：判斷參數(shù)是否符合解析的條件

@Override

publicbooleansupportsParameter(MethodParameterparam){

returnparam.hasParameterAnnotation(ClientTypeMark.class)

ClientType.class.isAssignableFrom(param.getParameterType());

//返回值將被注入到被選中參數(shù)中

@Override

publicObjectresolveArgument(MethodParametermethodParameter,ModelAndViewContainermodelAndViewContainer,

NativeWebRequestnativeWebRequest,WebDataBinderFactorywebDataBinderFactory)throwsException{

StringclientType=null;

for(StringclientTypeHeader:CLIENT_TYPE_HEADER_NAMES){

clientType=nativeWebRequest.getHeader(clientTypeHeader);

if(StringUtils.isNotBlank(clientType)){

break;

try{

returnStringUtils.isBlank(clientType)ClientType.UNKNOWN:ClientType.valueOf(clientType.toUpperCase());

}catch(Exceptione){

returnClientType.UNKNOWN;

}

為了使得配置能夠生效，可以按照如下的方法添加解析器。

@Configuration

publicclassWebMvcConfigimplementsWebMvcConfigurer{

@Override

publicvoidaddArgumentResolvers(ListHandlerMethodArgumentResolverargumentResolvers){

//解析@CurUserId注解的參數(shù)

argumentResolvers.add(newCurClientTypeMethodArgumentResolver());

}

至此，自定義參數(shù)解析器的工作就完成了。

Spring提供解析器

當(dāng)你完成上面的自定義解析器的時候，大體就能知道Spring在Controller層的其他參數(shù)解析都是怎么實(shí)現(xiàn)的了。

如下是SpringMvc默認(rèn)的一些參數(shù)解析器。

packageorg.springframework.web.servlet.mvc.method.annotation;

publicclassRequestMappingHandlerAdapterextendsAbstractHandlerMethodAdapter

implementsBeanFactoryAware,InitializingBean{

*Returnthelistofargumentresolverstouseincludingbuilt-inresolvers

*andcustomresolversprovidedvia{@link#setCustomArgumentResolvers}.

privateListHandlerMethodArgumentResolvergetDefaultArgumentResolvers(){

ListHandlerMethodArgumentResolverresolvers=newArrayList();

//Annotation-basedargumentresolution

//解析：@RequestParam(required=false)

resolvers.add(newRequestParamMethodArgumentResolver(getBeanFactory(),false));

//解析：@RequestParamMap

resolvers.add(newRequestParamMapMethodArgumentResolver());

//解析：@PathVariable

resolvers.add(newPathVariableMethodArgumentResolver());

//解析：@PathVariableMap

resolvers.add(newPathVariableMapMethodArgumentResolver());

//解析：@MatrixVariable

resolvers.add(newMatrixVariableMethodArgumentResolver());

//解析：@MatrixVariableMap

resolvers.add(newMatrixVariableMapMethodArgumentResolver());

//解析：@ModelAttribute(required=false)

resolvers.add(newServletModelAttributeMethodProcessor(false));

//解析：@RequestBody

resolvers.add(newRequestResponseBodyMethodProcessor(getMessageConverters(),this.requestResponseBodyAdvice));

//解析：@RequestPart

resolvers.add(newRequestPartMethodArgumentResolver(getMessageConverters(),this.requestResponseBodyAdvice));

//解析：@RequestHeader

resolvers.add(newRequestHeaderMethodArgumentResolver(getBeanFactory()));

//解析：@RequestHeaderMap

resolvers.add(newRequestHeaderMapMethodArgumentResolver());

//解析：@CookieValue

resolvers.add(newServletCookieValueMethodArgumentResolver(getBeanFactory()));

//解析：@Value

resolvers.add(newExpressionValueMethodArgumentResolver(getBeanFactory()));

//解析：@SessionAttribute

resolvers.add(newSessionAttributeMethodArgumentResolver());

//解析：@RequestAttribute

resolvers.add(newRequestAttributeMethodArgumentResolver());

//Type-basedargumentresolution

//解析：WebRequest、ServletRequest、MultipartRequest、HttpSession、

//Principal、Locale、TimeZone、java.time.ZoneId、InputStream

//java.io.Reader、org.springframework.http.HttpMethod

resolvers.add(newServletRequestMethodArgumentResolver());

//解析：ServletResponse、OutputStream、Writer

resolvers.add(newServletResponseMethodArgumentResolver());

//解析：@HttpEntity、@RequestEntity

resolvers.add(newHttpEntityMethodProcessor(getMessageConverters(),this.requestResponseBodyAdvice));

//解析：RedirectAttributes

resolvers.add(newRedirectAttributesMethodArgumentResolver());

//解析：org.springframework.ui.Model,值為ModelAndViewContainer#getModel

resolvers.add(newModelMethodProcessor());

//解析：Map,值為ModelAndViewContainer#getModel

resolvers.add(newMapMethodProcessor());

//解析：org.springframework.validation.Errors

resolvers.add(newErrorsMethodArgumentResolver());

//解析：org.springframework.web.bind.support.SessionStatus

resolvers.add(newSessionStatusMethodArgumentResolver());

//解析：UriComponentsBuilder或者ServletUriComponentsBuilder

resolvers.add(newUriComponentsBuilderMethodArgumentResolver());

//Customarguments

if(getCustomArgumentResolvers()!=null){

resolvers.addAll(getCustomArgumentResolvers());

//Catch-all

//解析：@RequestParam(required=true)

resolvers.add(newRequestParamMethodArgumentResolver(getBeanFactory(),true));

//解析：@ModelAttribute(required=true)

resolvers.add(newServletModelAttributeMethodProcessor(true));

returnresolvers;

一些使用Tricky

調(diào)整解析器的順序

在一次使用springsecurity的開發(fā)中，定義的UserDetials實(shí)現(xiàn)類在實(shí)現(xiàn)UserDetails的同時還是實(shí)現(xiàn)了一個Account接口，在使用時，希望實(shí)現(xiàn)如下的效果。

publicvoiddoSomething(@AuthenticationPrincipalAccountaccout){}

但因?yàn)橥瑫r使用了，spring-data，spring-data提供的ProxyingHandlerMethodArgumentResolver會在AuthenticationPrincipalArgumentResolver前面對Account進(jìn)行注入處理。ProxyingHandlerMethodArgumentResolver會攔截掉所有非org.springframework中定義的接口，并嘗試賦值。為了能夠正常賦值給Account，需要調(diào)整兩者的位置。實(shí)現(xiàn)如下：

importjava.util.LinkedList;

importjava.util.List;

importorg.springframework.beans.BeansException;

importorg.springframework.beans.factory.config.BeanPostProcessor;

importorg.springframework.security.web.method.annotation.AuthenticationPrincipalArgumentResolver;

importorg.springframework.stereotype.Component;

importorg.springframework.web.method.support.HandlerMethodArgumentResolver;

importorg.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;

*將AuthenticationPrincipalArgumentResolver移到最前面，如果不做調(diào)整，

*會因?yàn)镻roxyingHandlerMethodArgumentResolver在AuthenticationPrincipalArgumentResolver前面，

*導(dǎo)致@AuthenticationPrincipalAccountaccount無法注入

publicclassArgumentResolverBeanPostProcessorimplementsBeanPostProcessor{

privatestaticfinalStringBEAN_REQUEST_MAPP