SpringMVC源码情操陶冶-AbstractHandlerMethodMapping

承接前文SpringMVC源码情操陶冶-AbstractHandlerMapping，本文将介绍如何注册HandlerMethod对象作为handler

类结构瞧一瞧

public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMapping implements InitializingBean{}

此为抽象方法，并实现了initializingBean接口，其实主要的注册操作则是通过afterPropertiesSet()接口方法来调用的

AbstractHandlerMethodMapping#afterPropertiesSet()-初始化HandlerMethod对象

源码奉上

    @Override
    public void afterPropertiesSet() {
        initHandlerMethods();
    }

转而看initHandlerMethods()，观察是如何实现加载HandlerMethod

    
    protected void initHandlerMethods() {
        //获取springmvc上下文的所有注册的bean
        String[] beanNames = (this.detectHandlerMethodsInAncestorContexts ?
                BeanFactoryUtils.beanNamesForTypeIncludingAncestors(getApplicationContext(), Object.class) :
                getApplicationContext().getBeanNamesForType(Object.class));

        for (String beanName : beanNames) {
            if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
                Class<?> beanType = null;
                try {
                    beanType = getApplicationContext().getType(beanName);
                }
                catch (Throwable ex) {
                    // An unresolvable bean type, probably from a lazy bean - let's ignore it.
                    if (logger.isDebugEnabled()) {
                        logger.debug("Could not resolve target class for bean with name '" + beanName + "'", ex);
                    }
                }
                //isHandler()是抽象方法，主要供子类需要扫描什么类型的bean
                if (beanType != null && isHandler(beanType)) {
                    //解析其中的HandlerMethod进行注册
                    detectHandlerMethods(beanName);
                }
            }
        }
        //抽象方法，目前尚无实现
        handlerMethodsInitialized(getHandlerMethods());
    }

接下来稍微分析springmvc是如何解析bean并获取其中的HandlerMethod

AbstractHandlerMethodMapping#detectHandlerMethods()解析

源码奉上

    protected void detectHandlerMethods(final Object handler) {
        Class<?> handlerType = (handler instanceof String ?
                getApplicationContext().getType((String) handler) : handler.getClass());
        //因为有些是CGLIB代理生成的，获取真实的类
        final Class<?> userType = ClassUtils.getUserClass(handlerType);

        Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
                new MethodIntrospector.MetadataLookup<T>() {
                    @Override
                    public T inspect(Method method) {
                        try {
                            //模板方法获取handlerMethod的mapping属性
                            return getMappingForMethod(method, userType);
                        }
                        catch (Throwable ex) {
                            throw new IllegalStateException("Invalid mapping on handler class [" +
                                    userType.getName() + "]: " + method, ex);
                        }
                    }
                });

        //对查找到的HandlerMethod进行注册，保存至内部类mappingRegistry对象中
        for (Map.Entry<Method, T> entry : methods.entrySet()) {
            //作下判断，method是否从属于userType
            Method invocableMethod = AopUtils.selectInvocableMethod(entry.getKey(), userType);
            T mapping = entry.getValue();
            registerHandlerMethod(handler, invocableMethod, mapping);
        }
    }

针对唯一的实现类RequestMappingHandlerMapping，上述的mapping属性指代的是RequestMappingInfo对象，内部包含@RequestMapping注解的内部属性，比如method、params、consumes、produces、value以及对应的属性判断类

RequestMappingHandlerMapping-唯一实现类

作为HandlerMethod对象的配置者，我们主要观察其复写的几个方法

RequestMappingHandlerMapping#afterPropertiesSet()

代码奉上

    @Override
    public void afterPropertiesSet() {
        //config为RequestMappingInfo的创建对象
        this.config = new RequestMappingInfo.BuilderConfiguration();
        //设置urlPathHelper默认为UrlPathHelper.class
        this.config.setUrlPathHelper(getUrlPathHelper());
        //默认为AntPathMatcher，路径匹配校验器
        this.config.setPathMatcher(getPathMatcher());
        //是否支持后缀补充，默认为true
        this.config.setSuffixPatternMatch(this.useSuffixPatternMatch);
        //是否添加"/"后缀，默认为true
        this.config.setTrailingSlashMatch(this.useTrailingSlashMatch);
        //是否采用mediaType匹配模式，比如.json/.xml模式的匹配，默认为false      
        this.config.setRegisteredSuffixPatternMatch(this.useRegisteredSuffixPatternMatch);
        //mediaType处理类      
        this.config.setContentNegotiationManager(getContentNegotiationManager());
        //调用父类进行HandlerMethod的注册工作
        super.afterPropertiesSet();
    }

此处如何设置可通过查看博文>>>SpringMVC源码情操陶冶-AnnotationDrivenBeanDefinitionParser注解解析器

RequestMappingHandlerMapping#isHandler()-判断获取何种类型的Handler

获取@Controller/@RequestMapping注解下的handler

    @Override
    protected boolean isHandler(Class<?> beanType) {
        //优先匹配@Controller
        return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
                AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
    }

RequestMappingHandlerMapping#getMappingForMethod()-获取HandlerMethod对应的mapping属性

此处指的是RequestMappingInfo，主要包含了路径匹配策略、@RequestMapping属性匹配策略，简单源码奉上

    @Override
    protected RequestMappingInfo getMappingForMethod(Method method, Class<?> handlerType) {
        //对method以及class类都进行创建RequestMappingInfo 
        //因为@RequestMapping可以在方法上/类上应用注解
        RequestMappingInfo info = createRequestMappingInfo(method);
        if (info != null) {
            RequestMappingInfo typeInfo = createRequestMappingInfo(handlerType);
            if (typeInfo != null) {
                info = typeInfo.combine(info);
            }
        }
        return info;
    }

由代码可知，其将拼装Class上的@RequestMapping和Method上的@RequestMapping组装成RequestMappingInfo对象，其内部的属性读者有兴趣可自行去分析。

此处对createRequestMappingInfo()方法作下补充

    protected RequestMappingInfo createRequestMappingInfo(
            RequestMapping requestMapping, RequestCondition<?> customCondition) {

        return RequestMappingInfo
                .paths(resolveEmbeddedValuesInPatterns(requestMapping.path()))
                .methods(requestMapping.method())
                .params(requestMapping.params())
                .headers(requestMapping.headers())
                .consumes(requestMapping.consumes())
                .produces(requestMapping.produces())
                .mappingName(requestMapping.name())
                .customCondition(customCondition)
                .options(this.config)
                .build();
    }

小结

• 介绍AbstractHandlerMethodMapping如何创建HandlerMethod，调用者为RequestMappingHandlerMapping，其可通过mvc:annotation-driven注册，具体可查看>>>SpringMVC源码情操陶冶-AnnotationDrivenBeanDefinitionParser注解解析器

• 其中其唯一实现类RequestMappingHandlerMapping主要是获取@Controller下的@RequestMapping注解的方法将其注册为HandlerMethod对象，其余的相关信息则注册为RequestMappingInfo对象供对路径信息匹配

• 其中如何获取HandlerMethod查看前言中的链接即可

转载于:https://www.cnblogs.com/question-sky/p/7133130.html