Expose a log file via HTTP

LogFileExposer.java

package com.example;

import java.io.File;
import java.io.IOException;

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

import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource;
import org.springframework.http.MediaType;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.resource.ResourceHttpRequestHandler;

/**
 * Quick solution to exposes log files via HTTP.
 * Usage: localhost:8080/customLogFile?path=tomcat_access.log
 * You have to define logfile.expose.enabled for it to work
 */
@Controller
@ConditionalOnProperty(value = "logfile.expose.enabled", matchIfMissing = false)
public class LogFileExposer {

    @RequestMapping("/customLogFile")
    public void handle(@RequestParam("path") String path, HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        File file = new File("logs"); // root path
        String fileName = (new File(path)).getName();
        File fullPath = new File(file, fileName);
        Resource resource = new FileSystemResource(fullPath);
        if (!resource.exists()) {
            throw new IllegalArgumentException("Resource does not exist");
        }
        Handler handler = new Handler(resource, request.getServletContext());
        handler.handleRequest(request, response);
    }


    private static class Handler extends ResourceHttpRequestHandler {

        private final Resource resource;

        Handler(Resource resource, ServletContext servletContext) {
            this.resource = resource;
            getLocations().add(resource);
            try {
                setServletContext(servletContext);
                afterPropertiesSet();
            } catch (Exception ex) {
                throw new IllegalStateException(ex);
            }
        }

        @Override
        protected void initAllowedLocations() {
            this.getLocations().clear();
        }

        @Override
        protected Resource getResource(HttpServletRequest request) throws IOException {
            return this.resource;
        }

        @Override
        protected MediaType getMediaType(Resource resource) {
            return MediaType.TEXT_PLAIN;
        }
    }
}