spring boot 2.x静态资源会被HandlerInterceptor拦截的原因和解决方法

在spring boot 1.5.x中，resources/static目录下的静态资源可以直接访问，并且访问路径上不用带static，比如静态资源放置位置如下图所示：

那么访问静态资源的路径可以是：

• http://localhost:8080/views/demoindex.html

• http://localhost:8080/res/js/jquery.min.js

当有配置自定义HandlerInterceptor拦截器时，请求以上静态资源路径不会被拦截。自定义HandlerInterceptor拦截器源码如下：

package com.itopener.demo.config;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

public class LoginRequiredInterceptor extends HandlerInterceptorAdapter {

    private final Logger logger = LoggerFactory.getLogger(LoginRequiredInterceptor.class);

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        logger.info(request.getRequestURI());
        return super.preHandle(request, response, handler);
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        logger.info(request.getRequestURI());
        super.afterCompletion(request, response, handler, ex);
    }
}

配置如下：

package com.itopener.demo.config;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@Configuration
public class WebMvcConfiguration extends WebMvcConfigurerAdapter {

    private final Logger logger = LoggerFactory.getLogger(WebMvcConfiguration.class);

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        logger.info("add interceptors");
        registry.addInterceptor(new LoginRequiredInterceptor());
    }

}

访问静态资源时路径上不用加static目录：

当spring boot版本升级为2.x时，访问静态资源就会被HandlerInterceptor拦截

这样对于利用HandlerInterceptor来处理访问权限或其他相关的功能就会受影响，跟踪源码查看原因，是因为spring boot 2.x依赖的spring 5.x版本，相对于spring boot 1.5.x依赖的spring 4.3.x版本而言，针对资源的拦截器初始化时有区别，具体源码在WebMvcConfigurationSupport中，spring 4.3.x源码如下：

/**
 * Return a handler mapping ordered at Integer.MAX_VALUE-1 with mapped
 * resource handlers. To configure resource handling, override
 * {@link #addResourceHandlers}.
 */
@Bean
public HandlerMapping resourceHandlerMapping() {
    ResourceHandlerRegistry registry = new ResourceHandlerRegistry(this.applicationContext,
                this.servletContext, mvcContentNegotiationManager());
    addResourceHandlers(registry);

    AbstractHandlerMapping handlerMapping = registry.getHandlerMapping();
    if (handlerMapping != null) {
        handlerMapping.setPathMatcher(mvcPathMatcher());
        handlerMapping.setUrlPathHelper(mvcUrlPathHelper());
        // 此处固定添加了一个Interceptor
        handlerMapping.setInterceptors(new ResourceUrlProviderExposingInterceptor(mvcResourceUrlProvider()));
        handlerMapping.setCorsConfigurations(getCorsConfigurations());
        }
    else {
        handlerMapping = new EmptyHandlerMapping();
    }
    return handlerMapping;
}

而spring 5.x的源码如下：

/**
 * Return a handler mapping ordered at Integer.MAX_VALUE-1 with mapped
 * resource handlers. To configure resource handling, override
 * {@link #addResourceHandlers}.
 */
@Bean
public HandlerMapping resourceHandlerMapping() {
    Assert.state(this.applicationContext != null, "No ApplicationContext set");
    Assert.state(this.servletContext != null, "No ServletContext set");

    ResourceHandlerRegistry registry = new ResourceHandlerRegistry(this.applicationContext,
                this.servletContext, mvcContentNegotiationManager(), mvcUrlPathHelper());
    addResourceHandlers(registry);

    AbstractHandlerMapping handlerMapping = registry.getHandlerMapping();
    if (handlerMapping != null) {
        handlerMapping.setPathMatcher(mvcPathMatcher());
        handlerMapping.setUrlPathHelper(mvcUrlPathHelper());
        // 此处是将所有的HandlerInterceptor都添加了（包含自定义的HandlerInterceptor）
        handlerMapping.setInterceptors(getInterceptors());
        handlerMapping.setCorsConfigurations(getCorsConfigurations());
    }
    else {
        handlerMapping = new EmptyHandlerMapping();
    }
    return handlerMapping;
}

/**
 * Provide access to the shared handler interceptors used to configure
 * {@link HandlerMapping} instances with. This method cannot be overridden,
 * use {@link #addInterceptors(InterceptorRegistry)} instead.
 */
protected final Object[] getInterceptors() {
    if (this.interceptors == null) {
        InterceptorRegistry registry = new InterceptorRegistry();
        // 此处传入新new的registry对象，在配置类当中设置自定义的HandlerInterceptor后即可获取到
        addInterceptors(registry);
        registry.addInterceptor(new ConversionServiceExposingInterceptor(mvcConversionService()));
        registry.addInterceptor(new ResourceUrlProviderExposingInterceptor(mvcResourceUrlProvider()));
        this.interceptors = registry.getInterceptors();
    }
    return this.interceptors.toArray();
}

从源码当中可以看出，使用spring 5.x时，静态资源也会执行自定义的拦截器，因此在配置拦截器的时候需要指定排除静态资源的访问路径，即配置改为如下即可：

package com.itopener.demo.config;

import java.util.Arrays;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

/**
 * @author fuwei.deng
 * @date 2018年4月13日 下午3:32:54
 * @version 1.0.0
 */
@Configuration
public class WebMvcConfiguration implements WebMvcConfigurer {

    private final Logger logger = LoggerFactory.getLogger(WebMvcConfiguration.class);

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        logger.info("add interceptors");
        registry.addInterceptor(new LoginRequiredInterceptor()).excludePathPatterns(Arrays.asList("/views/**", "/res/**"));
    }
}

这样就可以和spring boot 1.5.x一样的方式使用了。不过从源码当中可以看出，每个静态资源的请求都会被自定义Interceptor拦截，只是通过访问路径判断后不会执行拦截器的内容，所以spring 5.x相对于spring 4.3.x而言，这部分处理的性能会更低一些

说明：

• 本文中测试使用的具体版本：

  • spring-boot-1.5.3.RELEASE（相对应的spring版本是spring-webmvc-4.3.8.RELEASE）

  • spring-boot-2.0.1.RELEASE（相对应的spring版本是spring-webmvc-5.0.5.RELEASE）

• 关于配置类，在spring boot 2.x已经改为最低支持jdk8版本，而jdk8中的接口允许有默认实现，所以已经废弃掉WebMvcConfigurerAdapter适配类，而改为直接实现WebMvcConfigurer接口