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Spring-MVC 跨域

CrossOrigin 注解

通过注解设置跨域 demo 如下

package com.huifer.source.controller;

import org.springframework.web.bind.annotation.*;

import java.util.HashMap;

@CrossOrigin(maxAge = 3600)
@RequestMapping("/")
@RestController
public class JSONController {
    @ResponseBody
    @GetMapping(value = "/json")
    public Object ob() {
        HashMap<String, String> hashMap = new HashMap<>();
        hashMap.put("1", "a");
        return hashMap;
    }
}

切入点:

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

org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.MappingRegistry#register方法

        /**
         * 注册方法 将controller 相关信息存储
         *
         * @param mapping 请求地址
         * @param handler 处理类
         * @param method  函数
         */
        public void register(T mapping, Object handler, Method method) {
            // 上锁
            this.readWriteLock.writeLock().lock();
            try {
                // 创建 HandlerMethod , 通过 handler 创建处理的对象(controller)
                HandlerMethod handlerMethod = createHandlerMethod(handler, method);
                assertUniqueMethodMapping(handlerMethod, mapping);
                // 设置值
                this.mappingLookup.put(mapping, handlerMethod);

                // 获取url
                List<String> directUrls = getDirectUrls(mapping);
                for (String url : directUrls) {
                    // 设置
                    this.urlLookup.add(url, mapping);
                }

                String name = null;
                if (getNamingStrategy() != null) {
                    name = getNamingStrategy().getName(handlerMethod, mapping);
                    addMappingName(name, handlerMethod);
                }

                /**
                 * 跨域设置
                 * {@link org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping#initCorsConfiguration(Object, Method, RequestMappingInfo)}
                 **/
                CorsConfiguration corsConfig = initCorsConfiguration(handler, method, mapping);
                if (corsConfig != null) {
                    this.corsLookup.put(handlerMethod, corsConfig);
                }

                this.registry.put(mapping, new MappingRegistration<>(mapping, handlerMethod, directUrls, name));
            }
            finally {
                // 开锁
                this.readWriteLock.writeLock().unlock();
            }
        }

着重查看**CorsConfiguration**初始化方法
- org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping#initCorsConfiguration

@Override
    protected CorsConfiguration initCorsConfiguration(Object handler, Method method, RequestMappingInfo mappingInfo) {
        // 重新创建,为什么不作为参数传递: 还有别的实现方法
        HandlerMethod handlerMethod = createHandlerMethod(handler, method);
        // 获取bean
        Class<?> beanType = handlerMethod.getBeanType();

        // 获取注解信息
        CrossOrigin typeAnnotation = AnnotatedElementUtils.findMergedAnnotation(beanType, CrossOrigin.class);
        CrossOrigin methodAnnotation = AnnotatedElementUtils.findMergedAnnotation(method, CrossOrigin.class);

        if (typeAnnotation == null && methodAnnotation == null) {
            return null;
        }

        CorsConfiguration config = new CorsConfiguration();
        // 更新跨域信息
        updateCorsConfig(config, typeAnnotation);
        updateCorsConfig(config, methodAnnotation);

        if (CollectionUtils.isEmpty(config.getAllowedMethods())) {
            for (RequestMethod allowedMethod : mappingInfo.getMethodsCondition().getMethods()) {
                config.addAllowedMethod(allowedMethod.name());
            }
        }
        // 返回跨域配置默认值
        return config.applyPermitDefaultValues();
    }

信息截图:

updateCorsConfig

该方法对原有的配置信息做补充

    private void updateCorsConfig(CorsConfiguration config, @Nullable CrossOrigin annotation) {
        if (annotation == null) {
            return;
        }
        for (String origin : annotation.origins()) {
            config.addAllowedOrigin(resolveCorsAnnotationValue(origin));
        }
        for (RequestMethod method : annotation.methods()) {
            config.addAllowedMethod(method.name());
        }
        for (String header : annotation.allowedHeaders()) {
            config.addAllowedHeader(resolveCorsAnnotationValue(header));
        }
        for (String header : annotation.exposedHeaders()) {
            config.addExposedHeader(resolveCorsAnnotationValue(header));
        }

        String allowCredentials = resolveCorsAnnotationValue(annotation.allowCredentials());
        if ("true".equalsIgnoreCase(allowCredentials)) {
            config.setAllowCredentials(true);
        }
        else if ("false".equalsIgnoreCase(allowCredentials)) {
            config.setAllowCredentials(false);
        }
        else if (!allowCredentials.isEmpty()) {
            throw new IllegalStateException("@CrossOrigin's allowCredentials value must be \"true\", \"false\", " +
                    "or an empty string (\"\"): current value is [" + allowCredentials + "]");
        }

        if (annotation.maxAge() >= 0 && config.getMaxAge() == null) {
            config.setMaxAge(annotation.maxAge());
        }
    }

最终解析结果

解析完成后放入 corsLookup对象中类:org.springframework.web.servlet.handler.AbstractHandlerMethodMapping

                if (corsConfig != null) {
                    this.corsLookup.put(handlerMethod, corsConfig);
                }

xml 配置方式

    <mvc:cors>
        <mvc:mapping path="/**"
                     allowed-origins="http://domain1.com, http://domain2.com"
                     allowed-methods="GET, PUT"
                     allowed-headers="header1, header2, header3"
                     exposed-headers="header1, header2" allow-credentials="false"
                     max-age="3600" />

        <mvc:mapping path="/**"
                     allowed-origins="http://domain1.com" />
    </mvc:cors>

mvc标签解析类: org.springframework.web.servlet.config.MvcNamespaceHandler，这个类对 Spring 配置文件中的<mvc:xxx>标签做了解析设定，如这次我们的关注点**CORS**

public class MvcNamespaceHandler extends NamespaceHandlerSupport {

    /**
     * 初始化一些SpringMvc 的解析类
     */
    @Override
    public void init() {
        // 注解驱动
        registerBeanDefinitionParser("annotation-driven", new AnnotationDrivenBeanDefinitionParser());
        // 默认的 servlet 处理器
        registerBeanDefinitionParser("default-servlet-handler", new DefaultServletHandlerBeanDefinitionParser());
        // 拦截器
        registerBeanDefinitionParser("interceptors", new InterceptorsBeanDefinitionParser());
        // 资源
        registerBeanDefinitionParser("resources", new ResourcesBeanDefinitionParser());
        // 视图控制器
        registerBeanDefinitionParser("view-controller", new ViewControllerBeanDefinitionParser());
        // 重定向视图控制器
        registerBeanDefinitionParser("redirect-view-controller", new ViewControllerBeanDefinitionParser());
        registerBeanDefinitionParser("status-controller", new ViewControllerBeanDefinitionParser());
        // 视图解析器
        registerBeanDefinitionParser("view-resolvers", new ViewResolversBeanDefinitionParser());
        // tiles 处理器
        registerBeanDefinitionParser("tiles-configurer", new TilesConfigurerBeanDefinitionParser());

        registerBeanDefinitionParser("freemarker-configurer", new FreeMarkerConfigurerBeanDefinitionParser());
        registerBeanDefinitionParser("groovy-configurer", new GroovyMarkupConfigurerBeanDefinitionParser());

        registerBeanDefinitionParser("script-template-configurer", new ScriptTemplateConfigurerBeanDefinitionParser());
        // 跨域处理
        registerBeanDefinitionParser("cors", new CorsBeanDefinitionParser());
    }

}

CorsBeanDefinitionParser

类图

解析

实现BeanDefinitionParser 接口的都有一个parse方法直接看方法.
- 通过查看我们可以知道最终目的获取 xml 标签中的属性,对 CorsConfiguration进行初始化，最后 Spring 中注册

public class CorsBeanDefinitionParser implements BeanDefinitionParser {

    @Override
    @Nullable
    public BeanDefinition parse(Element element, ParserContext parserContext) {

        Map<String, CorsConfiguration> corsConfigurations = new LinkedHashMap<>();
        List<Element> mappings = DomUtils.getChildElementsByTagName(element, "mapping");

        if (mappings.isEmpty()) {
            // 最简配置
            CorsConfiguration config = new CorsConfiguration().applyPermitDefaultValues();
            corsConfigurations.put("/**", config);
        }
        else {
            // 单个 mapping 处理
            // mvc:mapping 标签
            for (Element mapping : mappings) {
                // 跨域配置
                CorsConfiguration config = new CorsConfiguration();
                // 处理每个属性值,并且赋值
                if (mapping.hasAttribute("allowed-origins")) {
                    String[] allowedOrigins = StringUtils.tokenizeToStringArray(mapping.getAttribute("allowed-origins"), ",");
                    config.setAllowedOrigins(Arrays.asList(allowedOrigins));
                }
                if (mapping.hasAttribute("allowed-methods")) {
                    String[] allowedMethods = StringUtils.tokenizeToStringArray(mapping.getAttribute("allowed-methods"), ",");
                    config.setAllowedMethods(Arrays.asList(allowedMethods));
                }
                if (mapping.hasAttribute("allowed-headers")) {
                    String[] allowedHeaders = StringUtils.tokenizeToStringArray(mapping.getAttribute("allowed-headers"), ",");
                    config.setAllowedHeaders(Arrays.asList(allowedHeaders));
                }
                if (mapping.hasAttribute("exposed-headers")) {
                    String[] exposedHeaders = StringUtils.tokenizeToStringArray(mapping.getAttribute("exposed-headers"), ",");
                    config.setExposedHeaders(Arrays.asList(exposedHeaders));
                }
                if (mapping.hasAttribute("allow-credentials")) {
                    config.setAllowCredentials(Boolean.parseBoolean(mapping.getAttribute("allow-credentials")));
                }
                if (mapping.hasAttribute("max-age")) {
                    config.setMaxAge(Long.parseLong(mapping.getAttribute("max-age")));
                }
                corsConfigurations.put(mapping.getAttribute("path"), config.applyPermitDefaultValues());
            }
        }

        // 注册到 Spring
        MvcNamespaceUtils.registerCorsConfigurations(
                corsConfigurations, parserContext, parserContext.extractSource(element));
        return null;
    }

}

属性截图
- 可以看出这个是我们的第一个跨域配置的信息

注册方法

    public static RuntimeBeanReference registerCorsConfigurations(
            @Nullable Map<String, CorsConfiguration> corsConfigurations,
            ParserContext context, @Nullable Object source) {
        // 判断是否包含跨域bean(beanName:mvcCorsConfigurations)
        if (!context.getRegistry().containsBeanDefinition(CORS_CONFIGURATION_BEAN_NAME)) {
            RootBeanDefinition corsDef = new RootBeanDefinition(LinkedHashMap.class);
            corsDef.setSource(source);
            corsDef.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
            if (corsConfigurations != null) {
                corsDef.getConstructorArgumentValues().addIndexedArgumentValue(0, corsConfigurations);
            }
            context.getReaderContext().getRegistry().registerBeanDefinition(CORS_CONFIGURATION_BEAN_NAME, corsDef);
            // 注册组件,并且通知监听器
            context.registerComponent(new BeanComponentDefinition(corsDef, CORS_CONFIGURATION_BEAN_NAME));
        }
        else if (corsConfigurations != null) {
            // 注册bean
            BeanDefinition corsDef = context.getRegistry().getBeanDefinition(CORS_CONFIGURATION_BEAN_NAME);
            corsDef.getConstructorArgumentValues().addIndexedArgumentValue(0, corsConfigurations);
        }
        return new RuntimeBeanReference(CORS_CONFIGURATION_BEAN_NAME);
    }

CorsConfiguration

跨域信息

  /**
     * 允许请求源
     */
    @Nullable
    private List<String> allowedOrigins;

    /**
     * 允许的http方法
     */
    @Nullable
    private List<String> allowedMethods;

    /**
     *
     */
    @Nullable
    private List<HttpMethod> resolvedMethods = DEFAULT_METHODS;

    /**
     * 允许的请求头
     */
    @Nullable
    private List<String> allowedHeaders;

    /**
     * 返回的响应头
     */
    @Nullable
    private List<String> exposedHeaders;

    /**
     * 是否允许携带 cookies
     */
    @Nullable
    private Boolean allowCredentials;

    /**
     * 存货有效期
     */
    @Nullable
    private Long maxAge;

处理请求

请求处理的一部分，前置后置都还有其他处理，这里只对跨域请求进行说明

    @Override
    @Nullable
    public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
        Object handler = getHandlerInternal(request);
        if (handler == null) {
            handler = getDefaultHandler();
        }
        if (handler == null) {
            return null;
        }
        // Bean name or resolved handler?
        if (handler instanceof String) {
            String handlerName = (String) handler;
            handler = obtainApplicationContext().getBean(handlerName);
        }

        HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);

        if (logger.isTraceEnabled()) {
            logger.trace("Mapped to " + handler);
        }
        else if (logger.isDebugEnabled() && !request.getDispatcherType().equals(DispatcherType.ASYNC)) {
            logger.debug("Mapped to " + executionChain.getHandler());
        }

        // 判断是否为跨域请求
        if (CorsUtils.isCorsRequest(request)) {
            CorsConfiguration globalConfig = this.corsConfigurationSource.getCorsConfiguration(request);
            // 当前请求的跨域配置
            CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
            CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
            executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
        }

        return executionChain;
    }

判断是否跨域

org.springframework.web.cors.CorsUtils#isCorsRequest

    public static boolean isCorsRequest(HttpServletRequest request) {
        // 是否携带 请求头:Origin
        return (request.getHeader(HttpHeaders.ORIGIN) != null);
    }

获取跨域信息

        // 判断是否为跨域请求
        if (CorsUtils.isCorsRequest(request)) {
            CorsConfiguration globalConfig = this.corsConfigurationSource.getCorsConfiguration(request);
            // 当前请求的跨域配置
            CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
            CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
            executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
        }

跨域拦截器创建

    protected HandlerExecutionChain getCorsHandlerExecutionChain(HttpServletRequest request,
                                                                 HandlerExecutionChain chain, @Nullable CorsConfiguration config) {

        if (CorsUtils.isPreFlightRequest(request)) {
            HandlerInterceptor[] interceptors = chain.getInterceptors();
            chain = new HandlerExecutionChain(new PreFlightHandler(config), interceptors);
        }
        else {
            // 创建跨域拦截器
            chain.addInterceptor(new CorsInterceptor(config));
        }
        return chain;
    }

跨域拦截器

    /**
     * 跨域拦截器
     */
    private class CorsInterceptor extends HandlerInterceptorAdapter implements CorsConfigurationSource {

        @Nullable
        private final CorsConfiguration config;

        public CorsInterceptor(@Nullable CorsConfiguration config) {
            this.config = config;
        }

        @Override
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
                throws Exception {

            return corsProcessor.processRequest(this.config, request, response);
        }

        @Override
        @Nullable
        public CorsConfiguration getCorsConfiguration(HttpServletRequest request) {
            return this.config;
        }
    }

DefaultCorsProcessor

经过跨域拦截器 **CorsInterceptor**之后会调用

    @Override
    @SuppressWarnings("resource")
    public boolean processRequest(@Nullable CorsConfiguration config, HttpServletRequest request,
                                  HttpServletResponse response) throws IOException {

        // 判断是否跨域请求
        if (!CorsUtils.isCorsRequest(request)) {
            return true;
        }

        ServletServerHttpResponse serverResponse = new ServletServerHttpResponse(response);
        // 判断是否有 Access-Control-Allow-Origin
        if (responseHasCors(serverResponse)) {
            logger.trace("Skip: response already contains \"Access-Control-Allow-Origin\"");
            return true;
        }

        ServletServerHttpRequest serverRequest = new ServletServerHttpRequest(request);
        if (WebUtils.isSameOrigin(serverRequest)) {
            logger.trace("Skip: request is from same origin");
            return true;
        }

        boolean preFlightRequest = CorsUtils.isPreFlightRequest(request);
        if (config == null) {
            if (preFlightRequest) {
                rejectRequest(serverResponse);
                return false;
            }
            else {
                return true;
            }
        }

        return handleInternal(serverRequest, serverResponse, config, preFlightRequest);
    }

模拟请求

GET http://localhost:9999/json
Origin: localhost

变量截图

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