spring-boot配置外部静态资源的方法

import java.io.File;

import javax.servlet.Servlet;

import lombok.extern.slf4j.Slf4j;

import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
import org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration;
import org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.web.servlet.DispatcherServlet;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@Configuration
@ConditionalOnWebApplication
@ConditionalOnClass({Servlet.class, DispatcherServlet.class, WebMvcConfigurerAdapter.class})
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@Order(Ordered.HIGHEST_PRECEDENCE )
@AutoConfigureAfter(DispatcherServletAutoConfiguration.class)
@Slf4j
public class StaticResourceConfiguration extends WebMvcAutoConfiguration.WebMvcAutoConfigurationAdapter {
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        /*
        File directory = new File("");
        String path2=directory.getAbsolutePath();
        StringBuilder builder = new StringBuilder();
        builder.append("file:").append(path2).append("/m/");

        //registry.addResourceHandler("/**").addResourceLocations( builder.toString() );
        //String myExternalFilePath = "file:///C:/Temp/whatever/m/";
        log.info( builder.toString() );
        */
        
        registry.addResourceHandler("/m/**").addResourceLocations("file:m/");
        //registry.addResourceHandler("/m/**").addResourceLocations(builder.toString());

        super.addResourceHandlers(registry);
    }
}