Rename exception variables in empty catch blocks

The Spring codebase sometimes ignores exceptions in catch blocks on
purpose. This is often called out by an inline comment.
We should make this more obvious by renaming the exception argument in
the catch block to declare whether the exception is "ignored" or
"expected".

See gh-35047

Signed-off-by: Vincent Potucek <[email protected]>
[[email protected]: rework commit message]
Signed-off-by: Brian Clozel <[email protected]>

Author: Vincent Potucek

integration-tests/src/test/java/org/springframework/aop/framework/autoproxy/AdvisorAutoProxyCreatorIntegrationTests.java

@@ -158,8 +158,7 @@ void testRollbackRulesOnMethodPreventRollback() throws Exception {
 		try {
 			rb.echoException(new ServletException());
 		}
-		catch (ServletException ex) {
-
+		catch (ServletException ignored) {
 		}
 		assertThat(txMan.commits).as("Transaction counts match").isEqualTo(1);
 	}
@@ -272,7 +271,7 @@ public void before(Method method, Object[] args, Object target) throws Throwable
 					TransactionInterceptor.currentTransactionStatus();
 					throw new RuntimeException("Shouldn't have a transaction");
 				}
-				catch (NoTransactionException ex) {
+				catch (NoTransactionException ignored) {
 					// this is Ok
 				}
 			}

spring-aop/src/main/java/org/springframework/aop/aspectj/AspectJExpressionPointcut.java

@@ -453,9 +453,9 @@ private ShadowMatch getTargetShadowMatch(Method method, Class<?> targetClass) {
 							ClassUtils.toClassArray(ifcs), targetClass.getClassLoader());
 					targetMethod = ClassUtils.getMostSpecificMethod(targetMethod, compositeInterface);
 				}
-				catch (IllegalArgumentException ex) {
-					// Implemented interfaces probably expose conflicting method signatures...
-					// Proceed with original target method.
+				// Implemented interfaces probably expose conflicting method signatures...
+				// Proceed with original target method.
+				catch (IllegalArgumentException ignored) {
 				}
 			}
 		}
@@ -478,7 +478,7 @@ private ShadowMatch getShadowMatch(Method targetMethod, Method originalMethod) {
 					try {
 						shadowMatch = pointcutExpression.matchesMethodExecution(methodToMatch);
 					}
-					catch (ReflectionWorldException ex) {
+					catch (ReflectionWorldException ignored) {
 						// Failed to introspect target method, probably because it has been loaded
 						// in a special ClassLoader. Let's try the declaring ClassLoader instead...
 						try {
@@ -501,7 +501,7 @@ private ShadowMatch getShadowMatch(Method targetMethod, Method originalMethod) {
 						try {
 							shadowMatch = pointcutExpression.matchesMethodExecution(methodToMatch);
 						}
-						catch (ReflectionWorldException ex) {
+						catch (ReflectionWorldException ignored) {
 							// Could neither introspect the target class nor the proxy class ->
 							// let's try the original method's declaring class before we give up...
 							try {

spring-beans/src/main/java/org/springframework/beans/factory/annotation/BeanFactoryAnnotationUtils.java

@@ -208,8 +208,8 @@ public static boolean isQualifierMatch(
 					}
 				}
 			}
-			catch (NoSuchBeanDefinitionException ex) {
-				// Ignore - can't compare qualifiers for a manually registered singleton object
+			catch (NoSuchBeanDefinitionException ignored) {
+				// can't compare qualifiers for a manually registered singleton object
 			}
 		}
 		return false;

spring-context/src/main/java/org/springframework/context/support/PostProcessorRegistrationDelegate.java

@@ -523,8 +523,7 @@ private void resolveTypeStringValue(TypedStringValue typedStringValue) {
 			try {
 				typedStringValue.resolveTargetType(this.beanFactory.getBeanClassLoader());
 			}
-			catch (ClassNotFoundException ex) {
-				// ignore
+			catch (ClassNotFoundException ignored) {
 			}
 		}
 

spring-context/src/main/java/org/springframework/validation/beanvalidation/LocalValidatorFactoryBean.java

@@ -266,8 +266,8 @@ public void afterPropertiesSet() {
 				Method eclMethod = configuration.getClass().getMethod("externalClassLoader", ClassLoader.class);
 				ReflectionUtils.invokeMethod(eclMethod, configuration, this.applicationContext.getClassLoader());
 			}
-			catch (NoSuchMethodException ex) {
-				// Ignore - no Hibernate Validator 5.2+ or similar provider
+			catch (NoSuchMethodException ignored) {
+				// no Hibernate Validator 5.2+ or similar provider
 			}
 		}
 
@@ -417,8 +417,8 @@ public <T> T unwrap(@Nullable Class<T> type) {
 			try {
 				return super.unwrap(type);
 			}
-			catch (ValidationException ex) {
-				// Ignore - we'll try ValidatorFactory unwrapping next
+			catch (ValidationException ignored) {
+				// we'll try ValidatorFactory unwrapping next
 			}
 		}
 		if (this.validatorFactory != null) {

spring-context/src/test/java/org/springframework/aop/framework/AbstractAopProxyTests.java

@@ -233,8 +233,7 @@ void serializableTargetAndAdvice() throws Throwable {
 		try {
 			p2.echo(new IOException());
 		}
-		catch (IOException ex) {
-
+		catch (IOException ignored) {
 		}
 		assertThat(cta.getCalls()).isEqualTo(2);
 	}

spring-core-test/src/main/java/org/springframework/core/test/tools/CompileWithForkedClassLoaderClassLoader.java

@@ -84,8 +84,7 @@ protected Class<?> findClass(String name) throws ClassNotFoundException {
 			try (stream) {
 				return stream.readAllBytes();
 			}
-			catch (IOException ex) {
-				// ignore
+			catch (IOException ignored) {
 			}
 		}
 		return null;

spring-core/src/main/java/org/springframework/cglib/proxy/BridgeMethodResolver.java

@@ -73,7 +73,8 @@ public BridgeMethodResolver(Map declToBridge, ClassLoader classLoader) {
                 } finally {
                     is.close();
                 }
-            } catch (IOException ignored) {}
+            } catch (IOException ignored) {
+			}
         }
         return resolved;
     }

spring-core/src/main/java/org/springframework/cglib/proxy/MethodProxy.java

@@ -62,8 +62,8 @@ public static MethodProxy create(Class c1, Class c2, String desc, String name1,
 			try {
 				proxy.init();
 			}
-			catch (CodeGenerationException ex) {
-				// Ignore - to be retried when actually needed later on (possibly not at all)
+			catch (CodeGenerationException ignored) {
+				// to be retried when actually needed later on (possibly not at all)
 			}
 		}
 		// SPRING PATCH END

spring-core/src/main/java/org/springframework/core/io/support/SpringFactoriesLoader.java

@@ -438,8 +438,7 @@ private static class KotlinDelegate {
 					return constructor;
 				}
 			}
-			catch (UnsupportedOperationException ex) {
-				// ignore
+			catch (UnsupportedOperationException ignored) {
 			}
 			return null;
 		}

spring-core/src/main/java/org/springframework/util/FileCopyUtils.java

@@ -229,8 +229,7 @@ private static void close(Closeable closeable) {
 		try {
 			closeable.close();
 		}
-		catch (IOException ex) {
-			// ignore
+		catch (IOException ignored) {
 		}
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/DefaultStompSession.java

@@ -526,8 +526,7 @@ private void resetConnection() {
 			try {
 				conn.close();
 			}
-			catch (Throwable ex) {
-				// ignore
+			catch (Throwable ignored) {
 			}
 		}
 	}

spring-oxm/src/main/java/org/springframework/oxm/jaxb/Jaxb2Marshaller.java

@@ -1000,8 +1000,7 @@ private String getHost(String elementNamespace, DataHandler dataHandler) {
 				URI uri = ResourceUtils.toURI(elementNamespace);
 				return uri.getHost();
 			}
-			catch (URISyntaxException ex) {
-				// ignore
+			catch (URISyntaxException ignored) {
 			}
 			return dataHandler.getName();
 		}

spring-r2dbc/src/test/java/org/springframework/r2dbc/connection/R2dbcTransactionManagerTests.java

@@ -710,8 +710,7 @@ public Mono<Void> afterCompletion(int status) {
 			try {
 				return Mono.fromRunnable(() -> doAfterCompletion(status));
 			}
-			catch (Throwable ex) {
-				// ignore
+			catch (Throwable ignored) {
 			}
 
 			return Mono.empty();

spring-test/src/main/java/org/springframework/mock/http/client/MockClientHttpResponse.java

@@ -100,8 +100,7 @@ public void close() {
 		try {
 			getBody().close();
 		}
-		catch (IOException ex) {
-			// ignore
+		catch (IOException ignored) {
 		}
 	}
 

spring-test/src/main/java/org/springframework/mock/web/MockHttpServletRequest.java

@@ -1129,8 +1129,7 @@ private long parseDateHeader(String name, String value) {
 			try {
 				return simpleDateFormat.parse(value).getTime();
 			}
-			catch (ParseException ex) {
-				// ignore
+			catch (ParseException ignored) {
 			}
 		}
 		throw new IllegalArgumentException("Cannot parse date value '" + value + "' for '" + name + "' header");

spring-web/src/main/java/org/springframework/http/HttpHeaders.java

@@ -1223,8 +1223,7 @@ public void setHost(@Nullable InetSocketAddress host) {
 			try {
 				port = Integer.parseInt(portString);
 			}
-			catch (NumberFormatException ex) {
-				// ignore
+			catch (NumberFormatException ignored) {
 			}
 		}
 

spring-web/src/main/java/org/springframework/http/client/HttpComponentsClientHttpResponse.java

@@ -89,8 +89,7 @@ public void close() {
 				this.httpResponse.close();
 			}
 		}
-		catch (IOException ex) {
-			// Ignore exception on close...
+		catch (IOException ignored) {
 		}
 	}
 

spring-web/src/main/java/org/springframework/http/client/ReactorClientHttpResponse.java

@@ -108,8 +108,7 @@ public void close() {
 			StreamUtils.drain(body);
 			body.close();
 		}
-		catch (IOException ex) {
-			// ignore
+		catch (IOException ignored) {
 		}
 	}
 

spring-web/src/main/java/org/springframework/http/client/reactive/HttpComponentsClientHttpResponse.java

@@ -119,8 +119,7 @@ else if (expiresAttribute != null) {
 				ZonedDateTime expiresDate = ZonedDateTime.parse(expiresAttribute, DateTimeFormatter.RFC_1123_DATE_TIME);
 				return Duration.between(ZonedDateTime.now(expiresDate.getZone()), expiresDate).toSeconds();
 			}
-			catch (DateTimeParseException ex) {
-				// ignore
+			catch (DateTimeParseException ignored) {
 			}
 		}
 		return -1;

spring-web/src/main/java/org/springframework/http/converter/ResourceHttpMessageConverter.java

@@ -158,20 +158,20 @@ protected void writeContent(Resource resource, HttpOutputMessage outputMessage)
 				in.transferTo(out);
 				out.flush();
 			}
-			catch (NullPointerException ex) {
-				// ignore, see SPR-13620
+			catch (NullPointerException ignored) {
+				// see SPR-13620
 			}
 			finally {
 				try {
 					in.close();
 				}
-				catch (Throwable ex) {
-					// ignore, see SPR-12999
+				catch (Throwable ignored) {
+					// see SPR-12999
 				}
 			}
 		}
-		catch (FileNotFoundException ex) {
-			// ignore, see SPR-12999
+		catch (FileNotFoundException ignored) {
+			// see SPR-12999
 		}
 	}
 

spring-web/src/main/java/org/springframework/http/converter/ResourceRegionHttpMessageConverter.java

@@ -183,8 +183,7 @@ protected void writeResourceRegion(ResourceRegion region, HttpOutputMessage outp
 			try {
 				in.close();
 			}
-			catch (IOException ex) {
-				// ignore
+			catch (IOException ignored) {
 			}
 		}
 	}
@@ -244,8 +243,7 @@ private void writeResourceRegionCollection(Collection<ResourceRegion> resourceRe
 					in.close();
 				}
 			}
-			catch (IOException ex) {
-				// ignore
+			catch (IOException ignored) {
 			}
 		}
 

spring-web/src/main/java/org/springframework/http/converter/xml/SourceHttpMessageConverter.java

@@ -270,8 +270,7 @@ private StreamSource readStreamSource(InputStream body) throws IOException {
 				transform(t, new StreamResult(os));
 				return os.count;
 			}
-			catch (TransformerException ex) {
-				// ignore
+			catch (TransformerException ignored) {
 			}
 		}
 		return null;

spring-web/src/main/java/org/springframework/http/server/reactive/AbstractListenerWriteProcessor.java

@@ -439,8 +439,7 @@ public <T> void onNext(AbstractListenerWriteProcessor<T> processor, T data) {
 				// ignore
 			}
 			@Override
-			public <T> void onError(AbstractListenerWriteProcessor<T> processor, Throwable ex) {
-				// ignore
+			public <T> void onError(AbstractListenerWriteProcessor<T> processor, Throwable ignored) {
 			}
 			@Override
 			public <T> void onComplete(AbstractListenerWriteProcessor<T> processor) {

spring-web/src/main/java/org/springframework/http/server/reactive/ServletHttpHandlerAdapter.java

@@ -309,26 +309,23 @@ private static void delegateTimeout(AsyncListener listener, AsyncEvent event) {
 			try {
 				listener.onTimeout(event);
 			}
-			catch (Exception ex) {
-				// Ignore
+			catch (Exception ignored) {
 			}
 		}
 
 		private static void delegateError(AsyncListener listener, AsyncEvent event) {
 			try {
 				listener.onError(event);
 			}
-			catch (Exception ex) {
-				// Ignore
+			catch (Exception ignored) {
 			}
 		}
 
 		private static void delegateComplete(AsyncListener listener, AsyncEvent event) {
 			try {
 				listener.onComplete(event);
 			}
-			catch (Exception ex) {
-				// Ignore
+			catch (Exception ignored) {
 			}
 		}
 

spring-web/src/main/java/org/springframework/web/client/HttpMessageConverterExtractor.java

@@ -152,8 +152,7 @@ private static byte[] getResponseBody(ClientHttpResponse response) {
 		try {
 			return FileCopyUtils.copyToByteArray(response.getBody());
 		}
-		catch (IOException ex) {
-			// ignore
+		catch (IOException ignored) {
 		}
 		return new byte[0];
 	}

spring-web/src/main/java/org/springframework/web/context/request/async/CallableInterceptorChain.java

@@ -113,8 +113,7 @@ private void cancelTask() {
 			try {
 				future.cancel(true);
 			}
-			catch (Throwable ex) {
-				// Ignore
+			catch (Throwable ignored) {
 			}
 		}
 	}

spring-web/src/main/java/org/springframework/web/context/request/async/StandardServletAsyncWebRequest.java

@@ -235,8 +235,7 @@ private int tryObtainLock() {
 					break;
 				}
 			}
-			catch (InterruptedException ex) {
-				// ignore
+			catch (InterruptedException ignored) {
 			}
 		}
 

spring-web/src/main/java/org/springframework/web/context/support/ServletContextResource.java

@@ -122,8 +122,7 @@ public boolean isReadable() {
 			try {
 				is.close();
 			}
-			catch (IOException ex) {
-				// ignore
+			catch (IOException ignored) {
 			}
 			return true;
 		}

spring-web/src/main/java/org/springframework/web/service/registry/HttpServiceProxyRegistryFactoryBean.java

@@ -151,8 +151,7 @@ private static void addGroupAdapter(
 				Class<?> clazz = ClassUtils.forName(className, HttpServiceGroupAdapter.class.getClassLoader());
 				groupAdapters.put(clientType, (HttpServiceGroupAdapter<?>) BeanUtils.instantiateClass(clazz));
 			}
-			catch (ClassNotFoundException ex) {
-				// ignore
+			catch (ClassNotFoundException ignored) {
 			}
 		}
 	}

spring-web/src/test/java/org/springframework/web/context/request/RequestContextListenerTests.java

@@ -93,7 +93,7 @@ void requestContextListenerWithDifferentThread() {
 		try {
 			thread.join();
 		}
-		catch (InterruptedException ex) {
+		catch (InterruptedException ignored) {
 		}
 		// Still bound to original thread, but at least completed.
 		assertThat(RequestContextHolder.getRequestAttributes()).isNotNull();