Spring跨域处理多种方式(<mvc:cors>,@CrossOrigin)

  简单来说, 会根据请求头的Origin,判断是否为跨域请求. 通过设置responseHeaders(Access-Control-Allow-Origin等), 来允许跨域请求.(注意OPTIONS请求才会设置其他Access-Control-Allow-*头)   总的来说, 可以在Filter(CorsFilter) 或 Interceptor(CorsInterceptor)中判断并设置处理headers.(当然Spring提供的类, 最后的都复用同一个类DefaultCorsProcessor).   可以基于xml或纯java配置, 源码分析基于Spring 5.2.5, 为了简洁会省去部分源码.

方式一: @CrossOrigin

可以在类或方法上添加, 最终会保存到Map<HandlerMethod,CorsConfiguration>(参考源码:AbstractHandlerMethodMapping,MappingRegistry)

该方式是基于Interceptor,参考源码:

// 基于RequestMappingHandlerMapping分析
public abstract class AbstractHandlerMapping {
          
   
    @Override
	public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
          
   
		// ...
		if (hasCorsConfigurationSource(handler) || CorsUtils.isPreFlightRequest(request)) {
          
   
			CorsConfiguration config = (this.corsConfigurationSource != null this.corsConfigurationSource.getCorsConfiguration(request) : null);
            // 找到cors配置
			CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
			config = (config != null ? config.combine(handlerConfig) : handlerConfig);
			executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
		}

		return executionChain;
	}
    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 {
          
   
            // 创建拦截器
			chain.addInterceptor(0, new CorsInterceptor(config));
		}
		return chain;
	}
}

从第8行和第25行得出, 找到cors配置并创建CorsInterceptor拦截器, 拦截器最终会调用DefaultCorsProcessor

public class DefaultCorsProcessor implements CorsProcessor {
          
   
    protected boolean handleInternal(ServerHttpRequest request, ServerHttpResponse response,
			CorsConfiguration config, boolean preFlightRequest) throws IOException {
          
   
        // ...
        responseHeaders.setAccessControlAllowOrigin(allowOrigin);
        if (preFlightRequest) {
          
   
            responseHeaders.setAccessControlAllowMethods(allowMethods);
        }
        // ...        
    }
}

@CrossOrigin 缺省存在默认值, 具体看注解和CorsConfiguration#applyPermitDefaultValues

方式二: <mvc:cors>

在xml中配置, 与@CrossOrigin不同的是, 可以可以自定mapping, 从而配置整个项目, 其他是类似的也是基于Interceptor

<mvc:cors>
    <mvc:mapping path="/**" />
</mvc:cors>

mapping上还有其他自定义选项

方式三: CorsFilter

该方式类似于方式二, 不过是基于Filter, 当然背后走的是同一套逻辑.

@Configuration
public class MyConfiguration {
          
   

    @Bean
    public FilterRegistrationBean corsFilter() {
          
   
        CorsConfiguration config = new CorsConfiguration();
        config.setAllowCredentials(true);
        config.addAllowedOrigin("*");
        config.addAllowedHeader("*");
        config.addAllowedMethod("*");
        UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
        source.registerCorsConfiguration("/**", config); // 类似方式二
        FilterRegistrationBean bean = new FilterRegistrationBean(new CorsFilter(source));
        bean.setOrder(0);
        return bean;
    }
}