spring boot 2.x文件路径映射问题汇总

た入场券 2021-09-18 04:26 197阅读 0赞

当我们在运行可执行的java jar包的时候，我们肯定改变不了jar里面的内容，因此文件上传路径就成了我们必须考虑的一点问题，我们不能往直接这个jar包里面写文件，那么只能写在jar包外面，但是写到jar包外面的时候要怎么通过内置的tomcat下载文件呢？springboot给我们提供了一种方式，可以将jar包外部路径映射到jar里面。接下来我们看看如何实现。  
1、\*\*springboot2.0以前：\*\*我们通过继承WebMvcConfigurerAdapter来实现文件路径的映射。

@Configuration
    public class FileConfig extends WebMvcConfigurerAdapter { 
    
    	private String uploadPath = E://file/;
    
    	@Override
    	public void addResourceHandlers(ResourceHandlerRegistry registry) { 
    		registry.addResourceHandler("/file/**").addResourceLocations("file:" uploadPath);
    		super.addResourceHandlers(registry);
    	}
    }

2、WebMvcConfigurerAdapter的内部实现  
WebMvcConfigurerAdapter实现了WebMvcConfigurer接口的所有空方法。

@Deprecated
    public abstract class WebMvcConfigurerAdapter implements WebMvcConfigurer { 
        public WebMvcConfigurerAdapter() { }
    		
        public void configurePathMatch(PathMatchConfigurer configurer) { }
    		
        public void configureContentNegotiation(ContentNegotiationConfigurer configurer) { }
    
        public void configureAsyncSupport(AsyncSupportConfigurer configurer) { }
    
        public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) { }
    
        public void addFormatters(FormatterRegistry registry) { }
    
        public void addInterceptors(InterceptorRegistry registry) { }
    
        public void addResourceHandlers(ResourceHandlerRegistry registry) { }
    
        public void addCorsMappings(CorsRegistry registry) { }
    
        public void addViewControllers(ViewControllerRegistry registry) { }
    
        public void configureViewResolvers(ViewResolverRegistry registry) { }
    
        public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) { }
    
        public void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> returnValueHandlers) { }
    
        public void configureMessageConverters(List<HttpMessageConverter<?>> converters) { }
    
        public void extendMessageConverters(List<HttpMessageConverter<?>> converters) { }
    
        public void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) { }
    
        public void extendHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) { }
        @Nullable
        public Validator getValidator() { 
            return null;
        }
    
        @Nullable
        public MessageCodesResolver getMessageCodesResolver() { 
            return null;
        }
    }

3、WebMvcConfigurerAdapter为什么会过时？  
**这是因为由于Java的版本更新，在Java 8中，可以使用default关键词为接口添加默认的方法，Spring在升级的过程中也同步支持了Java 8中这一新特性。**  
4、新选择WebMvcConfigurer  
我们看一下它实现的接口**WebMvcConfigurer**，既然WebMvcConfigurer默认有了空实现，我们直接实现WebMvcConfigurer接口即可。

public interface WebMvcConfigurer { 
        default void configurePathMatch(PathMatchConfigurer configurer) { }
    
        default void configureContentNegotiation(ContentNegotiationConfigurer configurer) { }
    
        default void configureAsyncSupport(AsyncSupportConfigurer configurer) { }
    
        default void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) { }
    
        default void addFormatters(FormatterRegistry registry) { }
    
        default void addInterceptors(InterceptorRegistry registry) { }
    
        default void addResourceHandlers(ResourceHandlerRegistry registry) { }
    
        default void addCorsMappings(CorsRegistry registry) { }
    
        default void addViewControllers(ViewControllerRegistry registry) { }
    
        default void configureViewResolvers(ViewResolverRegistry registry) { }
    
        default void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) { }
    
        default void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> handlers) { }
    
        default void configureMessageConverters(List<HttpMessageConverter<?>> converters) { }
    
        default void extendMessageConverters(List<HttpMessageConverter<?>> converters) { }
    
        default void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) { }
    
        default void extendHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) { }
    
        @Nullable
        default Validator getValidator() { 
            return null;
        }
    
        @Nullable
        default MessageCodesResolver getMessageCodesResolver() { 
            return null;
        }
    }

5、更新后的代码如下：

@Configuration
    public class FileConfig implements WebMvcConfigurer { 
    
    	private String uploadPath = E://file/;
    
    	@Override
    	public void addResourceHandlers(ResourceHandlerRegistry registry) { 
    		registry.addResourceHandler("/file/**").addResourceLocations("file:" uploadPath);
    		super.addResourceHandlers(registry);
    	}
    }

如果各位想直接使用，且用的spring boot版本在2以上，则复制第五点到项目中就好了。最后祝广大程序猿1024快乐。多长头发，少些bug。