Seal up leak when opening input stream using try-resource construct

Spring Framework's `MultipartFile.getInputStream` clearly states "The user is responsible for closing the returned stream.". This patch uses Java 7's try-with-resources construct to grab it as an `InputStream` and then use it for the copy operation.

Resolves spring-guides#43

complete/src/main/java/hello/storage/FileSystemStorageService.java

@@ -1,6 +1,7 @@
 package hello.storage;
 
 import java.io.IOException;
+import java.io.InputStream;
 import java.net.MalformedURLException;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -39,8 +40,10 @@ public void store(MultipartFile file) {
                         "Cannot store file with relative path outside current directory "
                                 + filename);
             }
-            Files.copy(file.getInputStream(), this.rootLocation.resolve(filename),
+            try (InputStream inputStream = file.getInputStream()) {
+                Files.copy(inputStream, this.rootLocation.resolve(filename),
                     StandardCopyOption.REPLACE_EXISTING);
+            }
         }
         catch (IOException e) {
             throw new StorageException("Failed to store file " + filename, e);
@@ -51,8 +54,8 @@ public void store(MultipartFile file) {
     public Stream<Path> loadAll() {
         try {
             return Files.walk(this.rootLocation, 1)
-                    .filter(path -> !path.equals(this.rootLocation))
-                    .map(path -> this.rootLocation.relativize(path));
+                .filter(path -> !path.equals(this.rootLocation))
+                .map(this.rootLocation::relativize);
         }
         catch (IOException e) {
             throw new StorageException("Failed to read stored files", e);