拦截器配置的几种方式的实现及区别

1、@EnableWebMvc+implements WebMvcConfigurer

/**
 * WebMvcConfigurer 实现拦截器
 * @EnableWebMvc + implements WebMvcConfigurer ： 会覆盖@EnableAutoConfiguration关于WebMvcAutoConfiguration的配置
 * @author liujianxue
 * @since 2018/8/13
 */
@Configuration
@EnableWebMvc
public class WebMvcConfigurerConfig implements WebMvcConfigurer {

    @Bean
    public LoginInterceptor loginInterceptor(){
        return new LoginInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {

        registry.addInterceptor(loginInterceptor()).addPathPatterns("/tuitui/**")
                .excludePathPatterns("/swagger-ui.html","/swagger-resources/*","/v2/api-docs/*","/error");
    }

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {

        registry.addResourceHandler("/").addResourceLocations("/**");

        //swagger
        registry.addResourceHandler("swagger-ui.html")
                .addResourceLocations("classpath:/META-INF/resources/");
        registry.addResourceHandler("/webjars/**")
                .addResourceLocations("classpath:/META-INF/resources/webjars/");

    }
}

2、继承WebMvcConfigurerAdapter

/**
 * 使用WebMvcConfigurerAdapter 实现的拦截器
 * @author liujianxue
 * @since 2018/8/13
 */
@Configuration
public class WebMvcConfigurerAdapterConfig extends WebMvcConfigurerAdapter {

    @Bean
    public LoginInterceptor loginInterceptor(){
        return new LoginInterceptor();
    }

    @ConfigurationProperties(prefix = "intercept")
    public InterceptUrlConfig interceptUrlConfig(){
        return new InterceptUrlConfig();
    }


    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {

        registry.addResourceHandler("/").addResourceLocations("/**");
        super.addResourceHandlers(registry);
    }


    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        List<String> urlList = new ArrayList<>();
        /*urlList.add("/swagger-ui.html");
        urlList.add("/swagger-resources");
        urlList.add("/v2/api-docs");
        urlList.add("/configuration/ui");*/

        urlList.addAll(interceptUrlConfig().getExcluded());

        registry.addInterceptor(loginInterceptor())
                .addPathPatterns("/tuitui/**")
                .addPathPatterns("/tuitui/auth/**")
                .excludePathPatterns(urlList);
    }

    public static class InterceptUrlConfig{

        private List<String> excluded = new ArrayList<>();

        public List<String> getExcluded() {
            return excluded;
        }

        public void setExcluded(List<String> excluded) {
            this.excluded = excluded;
        }
    }

3、继承WebMvcConfigurationSupport

@Configuration
public class WebMvcConfigurationSupportConfig extends WebMvcConfigurationSupport {

    @Bean
    public LoginInterceptor loginInterceptor(){
        return new LoginInterceptor();
    }

    @Override
    protected void addInterceptors(InterceptorRegistry registry) {

        registry.addInterceptor(loginInterceptor()).addPathPatterns("/tuitui/**")
                .excludePathPatterns("/swagger-ui.html","/swagger-resources/*","/v2/api-docs/*","/error");
        super.addInterceptors(registry);
    }

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {

        registry.addResourceHandler("/").addResourceLocations("/**");

        //swagger
        registry.addResourceHandler("swagger-ui.html")
                .addResourceLocations("classpath:/META-INF/resources/");
        registry.addResourceHandler("/webjars/**")
                .addResourceLocations("classpath:/META-INF/resources/webjars/");

        super.addResourceHandlers(registry);
    }
}

4、继承DelegatingWebMvcConfiguration

/**
 * DelegatingWebMvcConfiguration 实现拦截器
 * @author liujianxue
 * @since 2018/8/13
 */
@Configuration
public class DelegatingWebMvcConfigurationConfig extends DelegatingWebMvcConfiguration {

    @Bean
    public LoginInterceptor loginInterceptor(){
        return new LoginInterceptor();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {

        registry.addInterceptor(loginInterceptor()).addPathPatterns("/tuitui/**")
                .excludePathPatterns("/swagger-ui.html","/swagger-resources/*","/v2/api-docs/*","/error");
    }

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {

        registry.addResourceHandler("/").addResourceLocations("/**");

        //swagger
        registry.addResourceHandler("swagger-ui.html")
                .addResourceLocations("classpath:/META-INF/resources/");
        registry.addResourceHandler("/webjars/**")
                .addResourceLocations("classpath:/META-INF/resources/webjars/");

    }

}

---

@EnableWebMvc是什么

直接看源码,@EnableWebMvc实际上引入一个DelegatingWebMvcConfiguration。

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Documented
@Import({DelegatingWebMvcConfiguration.class})
public @interface EnableWebMvc {
}

DelegatingWebMvcConfiguration继承了WebMvcConfigurationSupport

@Configuration
public class DelegatingWebMvcConfiguration extends WebMvcConfigurationSupport {
...

所以@EnableWebMvc=继承DelegatingWebMvcConfiguration=继承WebMvcConfigurationSupport

@EnableWebMvc和@EnableAutoConfiguration的关系

@EnableAutoConfiguration是springboot项目的启动类注解@SpringBootApplication的子元素，主要功能为自动配置。

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(
    excludeFilters = {@Filter(
    type = FilterType.CUSTOM,
    classes = {TypeExcludeFilter.class}
), @Filter(
    type = FilterType.CUSTOM,
    classes = {AutoConfigurationExcludeFilter.class}
)}
)
public @interface SpringBootApplication {
...
}

@EnableAutoConfiguration实际是导入了EnableAutoConfigurationImportSelector和Registrar两个类

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import({AutoConfigurationImportSelector.class})
public @interface EnableAutoConfiguration {
...
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import({Registrar.class})
public @interface AutoConfigurationPackage {
}
这两个类的具体原理有些复杂，不太清除，主要内容是通过SpringFactoriesLoader.loadFactoryNames()导入jar下面的配置文件META-INF/spring.factories

 protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
        List<String> configurations = SpringFactoriesLoader.loadFactoryNames(this.getSpringFactoriesLoaderFactoryClass(), this.getBeanClassLoader());
        Assert.notEmpty(configurations, "No auto configuration classes found in META-INF/spring.factories. If you are using a custom packaging, make sure that file is correct.");
        return configurations;
    }

配置文件中的内容如下

# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration,\
...
org.springframework.boot.autoconfigure.web.servlet.HttpEncodingAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.MultipartAutoConfiguration,\
org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration,\
...

其中有WebMvcAutoConfiguration,WebMvcAutoConfiguration源码如下

@Configuration
@ConditionalOnWebApplication(
    type = Type.SERVLET
)
@ConditionalOnClass({Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class})
@ConditionalOnMissingBean({WebMvcConfigurationSupport.class})
@AutoConfigureOrder(-2147483638)
@AutoConfigureAfter({DispatcherServletAutoConfiguration.class, ValidationAutoConfiguration.class})
public class WebMvcAutoConfiguration {
...
}

@ConditionalOnMissingBean({WebMvcConfigurationSupport.class})意思是如果存在它修饰的类的bean

,则不需要再创建这个bean。

由此可得出结论：

如果有配置文件继承了DelegatingWebMvcConfiguration，

或者WebMvcConfigurationSupport，或者配置文件有@EnableWebMvc，那么 @EnableAutoConfiguration 中的

WebMvcAutoConfiguration 将不会被自动配置，而是使用WebMvcConfigurationSupport的配置。

@EnableWebMvc,WebMvcConfigurationSupport,WebMvcConfigurer和WebMvcConfigurationAdapter使用

WebMvcConfigurationAdapter已经废弃，最好用implements WebMvcConfigurer代替

@Configuration
public class MyConfig implements WebMvcConfigurer {
    
}

如果使用继承,WebMvcConfigurationSupport，DelegatingWebMvcConfiguration，或者使用@EnableWebMvc，

需要注意会覆盖application.properties中关于WebMvcAutoConfiguration的设置，需要在自定义配置中实现，如

拦截器配置WebMvcConfigurerAdapter过时使用WebMvcConfigurationSupport来代替 新坑

示例如下

Configuration
@EnableWebMvc
public class MyConfig implements WebMvcConfigurer {

}
@Configuration
public class MyConfig extends WebMvcConfigurationSupport {

}
@Configuration
public class MyConfig extends DelegatingWebMvcConfiguration {

}
上面代码中需要在类中实现关于WebMvcAutoConfiguration的配置，而不是在application.properties中。

总结

implements WebMvcConfigurer ： 不会覆盖@EnableAutoConfiguration关于WebMvcAutoConfiguration的配置

@EnableWebMvc + implements WebMvcConfigurer ： 会覆盖@EnableAutoConfiguration关于WebMvcAutoConfiguration的配置

extends WebMvcConfigurationSupport ：会覆盖@EnableAutoConfiguration关于WebMvcAutoConfiguration的配置

extends DelegatingWebMvcConfiguration ：会覆盖@EnableAutoConfiguration关于WebMvcAutoConfiguration的配置