GH-3421: Resolve throws Exception; in the API

Fixes #3421

Remove `throws Exception;` from production code to honor
the rule `Generic exceptions should never be thrown` which is enabled on SonarQube

* Rework affected usages to `try..catch` with throwing respective runtime exception
or just logging
* Some other refactoring for the affected classes

Author: artembilan

spring-integration-mail/src/main/java/org/springframework/integration/mail/transformer/AbstractMailMessageTransformer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -39,16 +39,14 @@
  * @author Gary Russell
  * @author Artem Bilan
  */
-public abstract class AbstractMailMessageTransformer<T> implements Transformer,
-		BeanFactoryAware {
+public abstract class AbstractMailMessageTransformer<T> implements Transformer, BeanFactoryAware {
 
 	private BeanFactory beanFactory;
 
 	private MessageBuilderFactory messageBuilderFactory = new DefaultMessageBuilderFactory();
 
 	private boolean messageBuilderFactorySet;
 
-
 	@Override
 	public final void setBeanFactory(BeanFactory beanFactory) {
 		this.beanFactory = beanFactory;
@@ -67,28 +65,19 @@ protected MessageBuilderFactory getMessageBuilderFactory() {
 	@Override
 	public Message<?> transform(Message<?> message) {
 		Object payload = message.getPayload();
-		if (!(payload instanceof jakarta.mail.Message)) {
+		if (!(payload instanceof jakarta.mail.Message mailMessage)) {
 			throw new MessageTransformationException(message, getClass().getSimpleName()
 					+ " requires a jakarta.mail.Message payload");
 		}
-		jakarta.mail.Message mailMessage = (jakarta.mail.Message) payload;
 		AbstractIntegrationMessageBuilder<T> builder;
-		try {
-			builder = this.doTransform(mailMessage);
-		}
-		catch (Exception e) {
-			throw new MessageTransformationException(message, "failed to transform mail message", e);
-		}
+		builder = doTransform(mailMessage);
 		if (builder == null) {
 			throw new MessageTransformationException(message, "failed to transform mail message");
 		}
-		builder.copyHeaders(extractHeaderMapFromMailMessage(mailMessage));
-		return builder.build();
+		return builder.copyHeaders(extractHeaderMapFromMailMessage(mailMessage)).build();
 	}
 
-	protected abstract AbstractIntegrationMessageBuilder<T> doTransform(jakarta.mail.Message mailMessage)
-			throws Exception; // NOSONAR
-
+	protected abstract AbstractIntegrationMessageBuilder<T> doTransform(jakarta.mail.Message mailMessage);
 
 	private static Map<String, Object> extractHeaderMapFromMailMessage(jakarta.mail.Message mailMessage) {
 		return MailUtils.extractStandardHeaders(mailMessage);

spring-integration-mail/src/main/java/org/springframework/integration/mail/transformer/MailToStringTransformer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,6 +23,7 @@
 import jakarta.mail.Part;
 
 import org.springframework.integration.support.AbstractIntegrationMessageBuilder;
+import org.springframework.integration.transformer.MessageTransformationException;
 import org.springframework.util.Assert;
 
 /**
@@ -51,27 +52,34 @@ public void setCharset(String charset) {
 	}
 
 	@Override
-	protected AbstractIntegrationMessageBuilder<String> doTransform(jakarta.mail.Message mailMessage)
-			throws Exception { // NOSONAR
+	protected AbstractIntegrationMessageBuilder<String> doTransform(jakarta.mail.Message mailMessage) {
+		try {
+			String payload;
+			Object content = mailMessage.getContent();
+			if (content instanceof String value) {
+				payload = value;
+			}
+			else if (content instanceof Multipart multipart) {
+				ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+				multipart.writeTo(outputStream);
+				payload = outputStream.toString(this.charset);
+			}
+			else if (content instanceof Part part) {
+				ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+				part.writeTo(outputStream);
+				payload = outputStream.toString(this.charset);
+			}
+			else {
+				throw new IllegalArgumentException("failed to transform contentType ["
+						+ mailMessage.getContentType() + "] to String.");
+			}
 
-		Object content = mailMessage.getContent();
-		if (content instanceof String) {
-			return this.getMessageBuilderFactory().withPayload((String) content);
+			return getMessageBuilderFactory().withPayload(payload);
 		}
-		if (content instanceof Multipart) {
-			ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
-			((Multipart) content).writeTo(outputStream);
-			return this.getMessageBuilderFactory().withPayload(
-					new String(outputStream.toByteArray(), this.charset));
+		catch (Exception ex) {
+			throw new MessageTransformationException("Cannot transform mail message", ex);
 		}
-		else if (content instanceof Part) {
-			ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
-			((Part) content).writeTo(outputStream);
-			return this.getMessageBuilderFactory().withPayload(
-					new String(outputStream.toByteArray(), this.charset));
-		}
-		throw new IllegalArgumentException("failed to transform contentType ["
-				+ mailMessage.getContentType() + "] to String.");
+
 	}
 
 }

spring-integration-websocket/src/main/java/org/springframework/integration/websocket/WebSocketListener.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -42,25 +42,20 @@ public interface WebSocketListener extends SubProtocolCapable {
 	 * Handle the received {@link WebSocketMessage}.
 	 * @param session the WebSocket session
 	 * @param message the WebSocket message
-	 * @throws Exception the 'onMessage' Exception
 	 */
-	void onMessage(WebSocketSession session, WebSocketMessage<?> message)
-			throws Exception; // NOSONAR Remove in 5.2
+	void onMessage(WebSocketSession session, WebSocketMessage<?> message);
 
 	/**
 	 * Invoked after a {@link WebSocketSession} has started.
 	 * @param session the WebSocket session
-	 * @throws Exception the 'afterSessionStarted' Exception
 	 */
-	void afterSessionStarted(WebSocketSession session) throws Exception; // NOSONAR Remove in 5.2
+	void afterSessionStarted(WebSocketSession session);
 
 	/**
 	 * Invoked after a {@link WebSocketSession} has ended.
 	 * @param session the WebSocket session
 	 * @param closeStatus the reason why the session was closed
-	 * @throws Exception the 'afterSessionEnded' Exception
 	 */
-	void afterSessionEnded(WebSocketSession session, CloseStatus closeStatus)
-			throws Exception; // NOSONAR Remove in 5.2
+	void afterSessionEnded(WebSocketSession session, CloseStatus closeStatus);
 
 }

spring-integration-websocket/src/main/java/org/springframework/integration/websocket/inbound/WebSocketInboundChannelAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2021 the original author or authors.
+ * Copyright 2014-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -224,39 +224,54 @@ public List<String> getSubProtocols() {
 	}
 
 	@Override
-	public void afterSessionStarted(WebSocketSession session) throws Exception { // NOSONAR Thrown from the delegate
+	public void afterSessionStarted(WebSocketSession session) {
 		if (isActive()) {
-			SubProtocolHandler protocolHandler = this.subProtocolHandlerRegistry.findProtocolHandler(session);
-			protocolHandler.afterSessionStarted(session, this.subProtocolHandlerChannel);
-			if (!this.server && protocolHandler instanceof StompSubProtocolHandler) {
-				StompHeaderAccessor accessor = StompHeaderAccessor.create(StompCommand.CONNECT);
-				accessor.setSessionId(session.getId());
-				accessor.setLeaveMutable(true);
-				accessor.setAcceptVersion("1.1,1.2");
-
-				Message<?> connectMessage = MessageBuilder.createMessage(EMPTY_PAYLOAD, accessor.getMessageHeaders());
-				protocolHandler.handleMessageToClient(session, connectMessage);
+			try {
+				SubProtocolHandler protocolHandler = this.subProtocolHandlerRegistry.findProtocolHandler(session);
+				protocolHandler.afterSessionStarted(session, this.subProtocolHandlerChannel);
+				if (!this.server && protocolHandler instanceof StompSubProtocolHandler) {
+					StompHeaderAccessor accessor = StompHeaderAccessor.create(StompCommand.CONNECT);
+					accessor.setSessionId(session.getId());
+					accessor.setLeaveMutable(true);
+					accessor.setAcceptVersion("1.1,1.2");
+
+					Message<?> connectMessage =
+							MessageBuilder.createMessage(EMPTY_PAYLOAD, accessor.getMessageHeaders());
+					protocolHandler.handleMessageToClient(session, connectMessage);
+				}
+			}
+			catch (Exception ex) {
+				logger.error(ex, () -> "WebSocketHandler.afterConnectionEstablished threw exception in " + this);
 			}
 		}
 	}
 
 	@Override
-	public void afterSessionEnded(WebSocketSession session, CloseStatus closeStatus)
-			throws Exception { // NOSONAR Thrown from the delegate
+	public void afterSessionEnded(WebSocketSession session, CloseStatus closeStatus) {
 
 		if (isActive()) {
-			this.subProtocolHandlerRegistry.findProtocolHandler(session)
-					.afterSessionEnded(session, closeStatus, this.subProtocolHandlerChannel);
+			try {
+				this.subProtocolHandlerRegistry.findProtocolHandler(session)
+						.afterSessionEnded(session, closeStatus, this.subProtocolHandlerChannel);
+			}
+			catch (Exception ex) {
+				logger.warn(ex, () -> "Unhandled exception after connection closed for " + this);
+			}
 		}
 	}
 
 	@Override
-	public void onMessage(WebSocketSession session, WebSocketMessage<?> webSocketMessage)
-			throws Exception { // NOSONAR Thrown from the delegate
-
+	public void onMessage(WebSocketSession session, WebSocketMessage<?> webSocketMessage) {
 		if (isActive()) {
-			this.subProtocolHandlerRegistry.findProtocolHandler(session)
-					.handleMessageFromClient(session, webSocketMessage, this.subProtocolHandlerChannel);
+			try {
+				this.subProtocolHandlerRegistry.findProtocolHandler(session)
+						.handleMessageFromClient(session, webSocketMessage, this.subProtocolHandlerChannel);
+			}
+			catch (Exception ex) {
+				logger.error(ex,
+						() -> "SubProtocolHandler.handleMessageFromClient threw an exception on message: " +
+								webSocketMessage + " in " + this);
+			}
 		}
 	}