ClassPathResource.isReadable() returns false for content length 0

Issue: SPR-16832

Author: jhoeller

spring-core/src/main/java/org/springframework/core/io/AbstractFileResolvingResource.java

@@ -80,7 +80,7 @@ else if (code == HttpURLConnection.HTTP_NOT_FOUND) {
 				}
 			}
 		}
-		catch (Exception ex) {
+		catch (IOException ex) {
 			return false;
 		}
 	}
@@ -110,18 +110,18 @@ public boolean isReadable() {
 				if (contentLength > 0) {
 					return true;
 				}
-				else if (contentLength < 0) {
+				else if (contentLength == 0) {
+					// Empty file or directory -> not considered readable...
 					return false;
 				}
-				// 0 length: either an empty file or a directory...
-				// On current JDKs, this will trigger an NPE from within the close() call
-				// for directories, only returning true for actual files with 0 length.
-				getInputStream().close();
-				return true;
+				else {
+					// Fall back to stream existence: can we open the stream?
+					getInputStream().close();
+					return true;
+				}
 			}
 		}
-		catch (Exception ex) {
-			// Usually an IOException but potentially a NullPointerException (see above)
+		catch (IOException ex) {
 			return false;
 		}
 	}
@@ -135,7 +135,7 @@ public boolean isFile() {
 			}
 			return ResourceUtils.URL_PROTOCOL_FILE.equals(url.getProtocol());
 		}
-		catch (Exception ex) {
+		catch (IOException ex) {
 			return false;
 		}
 	}
@@ -186,7 +186,7 @@ protected boolean isFile(URI uri) {
 			}
 			return ResourceUtils.URL_PROTOCOL_FILE.equals(uri.getScheme());
 		}
-		catch (Exception ex) {
+		catch (IOException ex) {
 			return false;
 		}
 	}

spring-core/src/main/java/org/springframework/core/io/Resource.java

@@ -60,7 +60,7 @@ public interface Resource extends InputStreamSource {
 	boolean exists();
 
 	/**
-	 * Indicate whether the contents of this resource can be read via
+	 * Indicate whether non-empty contents of this resource can be read via
 	 * {@link #getInputStream()}.
 	 * <p>Will be {@code true} for typical resource descriptors that exist
 	 * since it strictly implies {@link #exists()} semantics as of 5.1.