[Issue 328] Resource not found exceptions (#329)

* Return null to indicate not found

* Add file not found exception handler

* Add external asset directory config example

* Update README.md

README.md

@@ -38,6 +38,22 @@ Here is a list of some dependencies used:
 
 The basic Spring Boot application configuration can be found at [src/main/resources/application.yml](https://github.com/vivo-community/scholars-discovery/blob/master/src/main/resources/application.yml). Here you be able to configure basic server and spring configuration as well as custom configuration for Scholars Discovery. There are several configuration POJOs to represent configurations. They can be found in [src/main/java/edu/tamu/scholars/middleware/config/model](https://github.com/vivo-community/scholars-discovery/tree/master/src/main/java/edu/tamu/scholars/middleware/config/model), and [src/main/java/edu/tamu/scholars/middleware/auth/config](https://github.com/vivo-community/scholars-discovery/tree/master/src/main/java/edu/tamu/scholars/middleware/auth/config).
 
+## Assets
+
+Assets are hosted at `/file/:id/:filename` and configured location `middleware.assets-location`.
+
+Tested options are
+
+Assets stored in src/main/resources/assets
+```
+middleware.assets-location: classpath:/assets
+```
+
+Assets stored in externally
+```
+middleware.assets-location: file:/scholars/assets
+```
+
 ### Harvesting
 
 Harvesting can be configured via ```middleware.harvesters``` and represented with [HarvesterConfig](https://github.com/vivo-community/scholars-discovery/blob/master/src/main/java/edu/tamu/scholars/middleware/config/model/HarvesterConfig.java). For each harvester, a bean will be created in which specifies the type of harvester and which document types it maps to. The reference implementation is the local triplestore harvester.
@@ -59,9 +75,7 @@ Solr is configured via ```spring.data.solr```.
 3. Start Solr
 
 ```bash
-   cd solr
-   docker build --tag=scholars/solr .
-   docker run -d -p 8983:8983 scholars/solr
+   cd solr && docker build --tag=scholars/solr . && docker run -d -p 8983:8983 scholars/solr && cd ..
 ```
 
 5. Build and Run the application

src/main/java/edu/tamu/scholars/middleware/config/WebMvcConfig.java

@@ -71,6 +71,10 @@ protected Resource getResource(String resourcePath, Resource location) throws IO
                         location = new FileUrlResource(resourcePath);
                     }
 
+                    if (!location.getFile().exists()) {
+                        location = null;
+                    }
+
                     return location;
                 }
 

src/main/java/edu/tamu/scholars/middleware/discovery/advice/DiscoveryControllerAdvice.java

@@ -1,5 +1,7 @@
 package edu.tamu.scholars.middleware.discovery.advice;
 
+import java.io.FileNotFoundException;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.http.HttpStatus;
@@ -30,4 +32,11 @@ public class DiscoveryControllerAdvice {
         return exception.getMessage();
     }
 
+    @ResponseStatus(value = HttpStatus.NOT_FOUND)
+    @ExceptionHandler(value = FileNotFoundException.class)
+    public @ResponseBody String handleFileNotFoundException(FileNotFoundException exception) {
+        logger.error(exception.getMessage(), exception);
+        return exception.getMessage();
+    }
+
 }

src/main/resources/application.yml

@@ -2,7 +2,10 @@ ui:
   url: http://localhost:4200
 
 middleware:
+  ## copy a~n to src/main/resources/assets/a~n
   assets-location: classpath:/assets
+  ## works in Windows and expected to work on Linux
+  # assets-location: file:/Users/wwelling/Development/scholars/scholars-discovery/assets
   load-defaults: true
   update-defaults: true
   allowed-origins: