美文网首页
springmvc 自定义RequestMappingHandl

springmvc 自定义RequestMappingHandl

作者: Shokka | 来源:发表于2019-07-09 17:15 被阅读0次

在自定义springmvc apiversion注解的过程中,由于对springmvc处理请求分发的不理解,便粗略过了一边流程(相信半个月后我就忘记了)

参考文章:

https://blog.csdn.net/roberts939299/article/details/73260485
https://www.jianshu.com/p/fd4a61c47b86

【仅供参考】 有理解错误的地方请指出

在自定义注解的过程中涉及到了RequestMappingHandlerMapping,RequestCondition两个类。衍生出了springMvc处理请求分发的主要及各类:

RequestMappingInfo:当spring启动过程中创建处理器映射对象时,会寻找所有被@Controller注解的类中被@RequestMapping注解的方法对象,然后解析方法对象的@RequestMapping注解,把解析结果封装成RequestMappingInfo对象,也就是说RequestMappingInfo对象是用来装载请求处理方法的配置信息的,每个请求处理方法对象都会对应一个RequestMappingInfo对象。

@RequestMapping注解一共有6个配置项,这6个配置项其实就是6种过滤器,限定了请求处理方法对象可处理的请求,通过这6种过滤条器把方法不能处理的请求都pass掉。

  1. PatternsRequestCondition(模式请求路径过滤器)

2. ParamsRequestCondition(请求参数过滤器)

3. HeadersRequestCondition(头字段过滤器)

4.RequestMethodsRequestCondition (请求方法过滤器)

5.ProducesRequestCondition(应答媒体类型过滤器)

6.ConsumesRequestCondition(请求媒体类型过滤器)

HandlerMapping:定义根据请求获取处理当期请求的HandlerChain的getHandler方法,其中包括实际处理逻辑的handler对象和拦截器。

AbstractHandlerMapping: 实现HandlerMapping接口的抽象类,在getHandler方法实现了拦截器的初始化和handler对象获取,其中获取handler对象的。

AbstractHandlerMethodMapping<T>: 继承AbstractHandlerMapping,定义了method handler映射关系,每一个method handler都一个唯一的T关联 。

RequestMappingInfoHandlerMapping: 继承AbstractHandlerMethodMapping<RequestMappingInfo>,定义了RequestMappingInfo与method handler的关联关系。

RequestMappingHandlerMapping继承了RequestMappingInfoHandlerMapping,处理方法的@ReqeustMapping注解,将其与method handler与@ReqeustMapping注解构建的RequestMappingInfo关联。

由于实现与继承关系都来自接口HandlerMapping(映射处理器),所以下文统称以上AbstractHandlerMapping等类为HandlerMapping。

RequestMappingInfo的初始化:

从RequestMappingInfo的介绍中得知,将访问url映射到controller方法,是由RequestMappingInfo中的信息完成的,一个controller方法对应一个RequestMappingInfo。初始化RequestMappingInfo在HandlerMapping定义并在AbstractHandlerMethodMapping中实现:

    /**
     * Scan beans in the ApplicationContext, detect and register handler methods.
     * @see #getCandidateBeanNames()
     * @see #processCandidateBean
     * @see #handlerMethodsInitialized
     */
    protected void initHandlerMethods() {
        for (String beanName : getCandidateBeanNames()) {
            if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
                processCandidateBean(beanName);
            }
        }
        handlerMethodsInitialized(getHandlerMethods());
    }
/**
     * Look for handler methods in the specified handler bean.
     * @param handler either a bean name or an actual handler instance
     * @see #getMappingForMethod
     */
    protected void detectHandlerMethods(Object handler) {
        Class<?> handlerType = (handler instanceof String ?
                obtainApplicationContext().getType((String) handler) : handler.getClass());

        if (handlerType != null) {
            Class<?> userType = ClassUtils.getUserClass(handlerType);
            Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
                    (MethodIntrospector.MetadataLookup<T>) method -> {
                        try {
                            return getMappingForMethod(method, userType);
                        }
                        catch (Throwable ex) {
                            throw new IllegalStateException("Invalid mapping on handler class [" +
                                    userType.getName() + "]: " + method, ex);
                        }
                    });
            if (logger.isTraceEnabled()) {
                logger.trace(formatMappings(userType, methods));
            }
            methods.forEach((method, mapping) -> {
                Method invocableMethod = AopUtils.selectInvocableMethod(method, userType);
                registerHandlerMethod(handler, invocableMethod, mapping);
            });
        }
    }
@Nullable
    private RequestMappingInfo createRequestMappingInfo(AnnotatedElement element) {
        RequestMapping requestMapping = AnnotatedElementUtils.findMergedAnnotation(element, RequestMapping.class);
        RequestCondition<?> condition = (element instanceof Class ?
                getCustomTypeCondition((Class<?>) element) : getCustomMethodCondition((Method) element));
        return (requestMapping != null ? createRequestMappingInfo(requestMapping, condition) : null);
    }

detectHandlerMethods跟踪到最后,在RequestMappingHandlerMapping中有createRequestMappingInfo方法,用于通过@RequestMapping注解生成RequestMappingInfo

@Nullable

 private RequestMappingInfo createRequestMappingInfo(AnnotatedElement element) {

 RequestMapping requestMapping = AnnotatedElementUtils.findMergedAnnotation(element, RequestMapping.class);

 RequestCondition<?> condition = (element instanceof Class ?

 getCustomTypeCondition((Class<?>) element) : getCustomMethodCondition((Method) element));

 return (requestMapping != null ? createRequestMappingInfo(requestMapping, condition) : null);

 }

protected RequestMappingInfo createRequestMappingInfo(

 RequestMapping requestMapping, @Nullable RequestCondition<?> customCondition) {

 RequestMappingInfo.Builder builder = RequestMappingInfo

 .paths(resolveEmbeddedValuesInPatterns(requestMapping.path()))

 .methods(requestMapping.method())

 .params(requestMapping.params())

 .headers(requestMapping.headers())

 .consumes(requestMapping.consumes())

 .produces(requestMapping.produces())

 .mappingName(requestMapping.name());

 if (customCondition != null) {

 builder.customCondition(customCondition);

 }

 return builder.options(this.config).build();

 }

这里注意getCustomMethodCondition方法,在自定义handlerMapping会使用到。

处理请求分发的流程:

https://www.jianshu.com/p/6f841d81ed72

详情看转载文章,这里提取一些文章没讲到的点:

  1. 一个DispatcherServlet拥有多个handlerMapping等
 /** List of HandlerMappings used by this servlet. */

 @Nullable

 private List<HandlerMapping> handlerMappings;

 /** List of HandlerAdapters used by this servlet. */

 @Nullable

 private List<HandlerAdapter> handlerAdapters;

 /** List of HandlerExceptionResolvers used by this servlet. */

 @Nullable

 private List<HandlerExceptionResolver> handlerExceptionResolvers;

  1. RequestMappingInfo类中封装了过滤器Condition,用于筛选出合适的RequestMappingInfo。
public final class RequestMappingInfo implements RequestCondition<RequestMappingInfo> {

 @Nullable

 private final String name;

 private final PatternsRequestCondition patternsCondition;

 private final RequestMethodsRequestCondition methodsCondition;

 private final ParamsRequestCondition paramsCondition;

 private final HeadersRequestCondition headersCondition;

 private final ConsumesRequestCondition consumesCondition;

 private final ProducesRequestCondition producesCondition;

 private final RequestConditionHolder customConditionHolder;

}

  1. 有些看文章思路不清晰的地方,跟进去源码看会好懂很多,这篇文章让我受益匪浅,半个月后我再来看一遍哈哈哈哈。

相关文章

网友评论

      本文标题:springmvc 自定义RequestMappingHandl

      本文链接:https://www.haomeiwen.com/subject/fkaxkctx.html