springmvc收集所有controller过程-2

原创已于 2022-02-16 10:45:56 修改 · 524 阅读

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于 2022-02-16 10:45:22 首次发布

这篇博客深入解析了Spring MVC框架如何通过后置处理器查找并处理带有@Controller和@RequestMapping注解的bean。它详细介绍了AbstractHandlerMethodMapping类的角色，如何遍历bean及其方法，检查RequestMapping注解，并将URL映射注册到mappingRegistry。整个过程涉及到bean的类型检查、方法遍历以及异常处理。

//通过后置处理器来寻找所有的controller

org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping#afterPropertiesSet

org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#afterPropertiesSet

org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#initHandlerMethods

protected void initHandlerMethods() {
        for (String beanName : getCandidateBeanNames()) {
            if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
                processCandidateBean(beanName);
            }
        }
        handlerMethodsInitialized(getHandlerMethods());
    }

protected void processCandidateBean(String beanName) {
        Class<?> beanType = null;
        try {
            beanType = obtainApplicationContext().getType(beanName);
        }
        catch (Throwable ex) {
            // An unresolvable bean type, probably from a lazy bean - let's ignore it.
            if (logger.isTraceEnabled()) {
                logger.trace("Could not resolve type for bean '" + beanName + "'", ex);
            }
        }
        if (beanType != null && isHandler(beanType)) {
            detectHandlerMethods(beanName);
        }
    }

注意下面这段核心代码：org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#detectHandlerMethods

通过lambda表达式遍历所有bean中的method,然后遍历method上是否有RequestMapping注解，要注意lambda的使用方法，同时注意里面的细节：包括父类的遍历，factorybean的遍历，最后把controller上的url和method的url合并

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);
            });
        }
    }

    protected void registerHandlerMethod(Object handler, Method method, T mapping) {
        this.mappingRegistry.register(mapping, handler, method);
    }

遍历方法的过程

org.springframework.util.ReflectionUtils#doWithMethods(java.lang.Class<?>, org.springframework.util.ReflectionUtils.MethodCallback, org.springframework.util.ReflectionUtils.MethodFilter)

判断是否有@RequestMapping的过程

总结：从spring容器中获取所有bean，然后判断bean是否带有@Controller或者@RequestMapping注解，然后遍历bean中所有的方法，判断方法上是否有@RequestMapping注解，有的话则将其注入到mappingRegistry容器中

其中关系为：mapping为url；handler为bean；method为方法