关于SpringMVC在Controller层方法的参数解析详解

@Target({ElementType.PARAMETER})

@Retention(RetentionPolicy.RUNTIME)

@Documented

public @interface ClientTypeMark {

}

public enum ClientType {

    WEB,

    MOBILE,

    UNKNOWN

    ;

}

@RestController

@RequestMapping("/client")

public class ClientTypeEndpoint {



    @GetMapping("/cur")

    public ClientType getCurClientType(@ClientTypeMark ClientType clientType) {

        return clientType;

    }

}

package io.github.donespeak.springbootsamples.web.common;

import org.apache.commons.lang3.StringUtils;

import org.springframework.core.MethodParameter;

import org.springframework.web.bind.support.WebDataBinderFactory;

import org.springframework.web.context.request.NativeWebRequest;

import org.springframework.web.method.support.HandlerMethodArgumentResolver;

import org.springframework.web.method.support.ModelAndViewContainer;

public class CurClientTypeMethodArgumentResolver implements HandlerMethodArgumentResolver {

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

    // 选择要被注入的参数：判断参数是否符合解析的条件

    @Override

    public boolean supportsParameter(MethodParameter param) {

        return param.hasParameterAnnotation(ClientTypeMark.class)

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

    }

    // 返回值将被注入到被选中参数中

    @Override

    public Object resolveArgument(MethodParameter methodParameter, ModelAndViewContainer modelAndViewContainer,

            NativeWebRequest nativeWebRequest, WebDataBinderFactory webDataBinderFactory) throws Exception {

        String clientType = null;

        for (String clientTypeHeader: CLIENT_TYPE_HEADER_NAMES) {

            clientType = nativeWebRequest.getHeader(clientTypeHeader);

            if (StringUtils.isNotBlank(clientType)) {

                break;

            }

        }

        try {

            return StringUtils.isBlank(clientType) ? ClientType.UNKNOWN : ClientType.valueOf(clientType.toUpperCase());

        } catch (Exception e) {

            return ClientType.UNKNOWN;
        }
    }
}

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {

        // 解析@CurUserId注解的参数

        argumentResolvers.add(new CurClientTypeMethodArgumentResolver());

    }

}

package org.springframework.web.servlet.mvc.method.annotation;

public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter

        implements BeanFactoryAware, InitializingBean {

    ...

    /**

     * Return the list of argument resolvers to use including built-in resolvers

     * and custom resolvers provided via {@link #setCustomArgumentResolvers}.

     */

    private List<HandlerMethodArgumentResolver> getDefaultArgumentResolvers() {

        List<HandlerMethodArgumentResolver> resolvers = new ArrayList<>();

        // Annotation-based argument resolution

        // 解析：@RequestParam(required = false)

        resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), false));

        // 解析：@RequestParam Map

        resolvers.add(new RequestParamMapMethodArgumentResolver());

        // 解析：@PathVariable

        resolvers.add(new PathVariableMethodArgumentResolver());

        // 解析：@PathVariable Map

        resolvers.add(new PathVariableMapMethodArgumentResolver());

        // 解析：@MatrixVariable

        resolvers.add(new MatrixVariableMethodArgumentResolver());

        // 解析：@MatrixVariable Map

        resolvers.add(new MatrixVariableMapMethodArgumentResolver());

        // 解析：@ModelAttribute(required = false)

        resolvers.add(new ServletModelAttributeMethodProcessor(false));

        // 解析：@RequestBody

        resolvers.add(new RequestResponseBodyMethodProcessor(getMessageConverters(), this.requestResponseBodyAdvice));

        // 解析：@RequestPart

        resolvers.add(new RequestPartMethodArgumentResolver(getMessageConverters(), this.requestResponseBodyAdvice));

        // 解析：@RequestHeader

        resolvers.add(new RequestHeaderMethodArgumentResolver(getBeanFactory()));

        // 解析：@RequestHeader Map

        resolvers.add(new RequestHeaderMapMethodArgumentResolver());

        // 解析：@CookieValue

        resolvers.add(new ServletCookieValueMethodArgumentResolver(getBeanFactory()));

        // 解析：@Value

        resolvers.add(new ExpressionValueMethodArgumentResolver(getBeanFactory()));

        // 解析：@SessionAttribute

        resolvers.add(new SessionAttributeMethodArgumentResolver());

        // 解析：@RequestAttribute

        resolvers.add(new RequestAttributeMethodArgumentResolver());

        // Type-based argument resolution

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

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

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

        resolvers.add(new ServletRequestMethodArgumentResolver());

        // 解析：ServletResponse、OutputStream、Writer

        resolvers.add(new ServletResponseMethodArgumentResolver());

        // 解析：@HttpEntity、@RequestEntity

        resolvers.add(new HttpEntityMethodProcessor(getMessageConverters(), this.requestResponseBodyAdvice));

        // 解析：RedirectAttributes

        resolvers.add(new RedirectAttributesMethodArgumentResolver());

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

        resolvers.add(new ModelMethodProcessor());

        // 解析：Map, 值为ModelAndViewContainer#getModel

        resolvers.add(new MapMethodProcessor());

        // 解析：org.springframework.validation.Errors

        resolvers.add(new ErrorsMethodArgumentResolver());

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

        resolvers.add(new SessionStatusMethodArgumentResolver());

        // 解析：UriComponentsBuilder 或者 ServletUriComponentsBuilder

        resolvers.add(new UriComponentsBuilderMethodArgumentResolver());

        // Custom arguments

        if (getCustomArgumentResolvers() != null) {

            resolvers.addAll(getCustomArgumentResolvers());

        }

        // Catch-all

        // 解析：@RequestParam(required = true)

        resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), true));

        // 解析：@ModelAttribute(required = true)

        resolvers.add(new ServletModelAttributeMethodProcessor(true));

        return resolvers;
    }
    ...

}

public void doSomething(@AuthenticationPrincipal Account accout) {}

import java.util.LinkedList;

import java.util.List;

import org.springframework.beans.BeansException;

import org.springframework.beans.factory.config.BeanPostProcessor;

import org.springframework.security.web.method.annotation.AuthenticationPrincipalArgumentResolver;

import org.springframework.stereotype.Component;

import org.springframework.web.method.support.HandlerMethodArgumentResolver;

import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;

/**

 * 将 AuthenticationPrincipalArgumentResolver 移到最前面，如果不做调整，

 * 会因为ProxyingHandlerMethodArgumentResolver在AuthenticationPrincipalArgumentResolver前面，

 * 导致 @AuthenticationPrincipal Account account 无法注入

 */

public class ArgumentResolverBeanPostProcessor implements BeanPostProcessor {

    private static final String BEAN_REQUEST_MAPPING_HANDLER_ADAPTER = "requestMappingHandlerAdapter";

    @Override

    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {

        if (beanName.equals(BEAN_REQUEST_MAPPING_HANDLER_ADAPTER)) {

            RequestMappingHandlerAdapter adapter = (RequestMappingHandlerAdapter)bean;

            List<HandlerMethodArgumentResolver> argumentResolvers = adapter.getArgumentResolvers();

            LinkedList<HandlerMethodArgumentResolver> resolversAdjusted = new LinkedList<>(argumentResolvers);

            argumentResolvers.stream().forEach(r -> {

                if (AuthenticationPrincipalArgumentResolver.class.isInstance(r)) {

                    resolversAdjusted.addFirst(r);

                } else {

                    resolversAdjusted.add(r);

                }
            });
adapter.setArgumentResolvers(resolversAdjusted);

        }
        return bean;
    }

}