INT-4299: Add AbstractMailReceiver.autoCloseFolder

spring-integration-core/src/main/java/org/springframework/integration/endpoint/AbstractMessageSource.java

@@ -162,6 +162,9 @@ public final Message<T> receive() {
 
 	@SuppressWarnings("unchecked")
 	protected Message<T> buildMessage(Object result) {
+		if (result == null) {
+			return null;
+		}
 		Message<?> message = null;
 		Map<String, Object> headers = evaluateHeaders();
 		if (result instanceof AbstractIntegrationMessageBuilder<?>) {
@@ -181,14 +184,14 @@ else if (result instanceof Message<?>) {
 								.build();
 			}
 		}
-		else if (result != null) {
+		else {
 			message =
 					getMessageBuilderFactory()
 							.withPayload(result)
 							.copyHeaders(headers)
 							.build();
 		}
-		if (this.countsEnabled && message != null) {
+		if (this.countsEnabled) {
 			if (this.metricsCaptor != null) {
 				incrementReceiveCounter();
 			}

spring-integration-mail/src/main/java/org/springframework/integration/mail/AbstractMailReceiver.java

@@ -17,6 +17,7 @@
 package org.springframework.integration.mail;
 
 import java.io.ByteArrayOutputStream;
+import java.io.Closeable;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Date;
@@ -43,9 +44,11 @@
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.expression.Expression;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
+import org.springframework.integration.IntegrationMessageHeaderAccessor;
 import org.springframework.integration.context.IntegrationObjectSupport;
 import org.springframework.integration.expression.ExpressionUtils;
 import org.springframework.integration.mapping.HeaderMapper;
+import org.springframework.integration.support.AbstractIntegrationMessageBuilder;
 import org.springframework.messaging.MessageHeaders;
 import org.springframework.util.Assert;
 import org.springframework.util.FileCopyUtils;
@@ -103,6 +106,8 @@ public abstract class AbstractMailReceiver extends IntegrationObjectSupport impl
 
 	private boolean simpleContent;
 
+	private boolean autoCloseFolder = true;
+
 	private volatile Store store;
 
 	private volatile Folder folder;
@@ -266,6 +271,22 @@ public void setSimpleContent(boolean simpleContent) {
 		this.simpleContent = simpleContent;
 	}
 
+	/**
+	 * Configure a {@code boolean} flag to close the folder automatically after a fetch (default) or
+	 * populate an additional {@link IntegrationMessageHeaderAccessor#CLOSEABLE_RESOURCE} message header instead.
+	 * It is the downstream flow's responsibility to obtain this header and call its {@code close()} whenever
+	 * it is necessary.
+	 * <p> Keeping the folder open is useful in cases where communication with the server is needed
+	 * when parsing multipart content of the email with attachments.
+	 * <p> The {@link #setSimpleContent(boolean)} and {@link #setHeaderMapper(HeaderMapper)} options are not
+	 * affected by this flag.
+	 * @param autoCloseFolder {@code false} do not close the folder automatically after a fetch.
+	 * @since 5.2
+	 */
+	public void setAutoCloseFolder(boolean autoCloseFolder) {
+		this.autoCloseFolder = autoCloseFolder;
+	}
+
 	protected Folder getFolder() {
 		return this.folder;
 	}
@@ -357,7 +378,9 @@ public Object[] receive() throws javax.mail.MessagingException {
 				return convertMessagesIfNecessary(searchAndFilterMessages());
 			}
 			finally {
-				MailTransportUtils.closeFolder(this.folder, this.shouldDeleteMessages);
+				if (this.autoCloseFolder) {
+					closeFolder();
+				}
 			}
 		}
 		finally {
@@ -367,6 +390,16 @@ public Object[] receive() throws javax.mail.MessagingException {
 		}
 	}
 
+	private void closeFolder() {
+		this.folderReadLock.lock();
+		try {
+			MailTransportUtils.closeFolder(this.folder, this.shouldDeleteMessages);
+		}
+		finally {
+			this.folderReadLock.unlock();
+		}
+	}
+
 	private MimeMessage[] searchAndFilterMessages() throws MessagingException {
 		if (this.logger.isInfoEnabled()) {
 			this.logger.info("attempting to receive mail from folder [" + this.folder.getFullName() + "]");
@@ -395,17 +428,26 @@ private MimeMessage[] searchAndFilterMessages() throws MessagingException {
 	}
 
 	private Object[] convertMessagesIfNecessary(MimeMessage[] filteredMessages) {
-		if (this.headerMapper != null) {
+		if (this.headerMapper != null || !this.autoCloseFolder) {
 			org.springframework.messaging.Message<?>[] converted =
 					new org.springframework.messaging.Message<?>[filteredMessages.length];
 			int n = 0;
 			for (MimeMessage message : filteredMessages) {
-				Map<String, Object> headers = this.headerMapper.toHeaders(message);
-				converted[n++] =
+				Object payload = message;
+				Map<String, Object> headers = null;
+				if (this.headerMapper != null) {
+					headers = this.headerMapper.toHeaders(message);
+					payload = extractContent(message, headers);
+				}
+				AbstractIntegrationMessageBuilder<Object> messageBuilder =
 						getMessageBuilderFactory()
-								.withPayload(extractContent(message, headers))
-								.copyHeaders(headers)
-								.build();
+								.withPayload(payload)
+								.copyHeaders(headers);
+				if (!this.autoCloseFolder) {
+					messageBuilder.setHeader(IntegrationMessageHeaderAccessor.CLOSEABLE_RESOURCE,
+							(Closeable) this::closeFolder);
+				}
+				converted[n++] = messageBuilder.build();
 			}
 			return converted;
 		}
@@ -566,7 +608,7 @@ protected void setAdditionalFlags(Message message) throws MessagingException {
 	public void destroy() {
 		this.folderWriteLock.lock();
 		try {
-			MailTransportUtils.closeFolder(this.folder, this.shouldDeleteMessages);
+			closeFolder();
 			MailTransportUtils.closeService(this.store);
 			this.folder = null;
 			this.store = null;
@@ -628,11 +670,16 @@ private final class IntegrationMimeMessage extends MimeMessage {
 
 		@Override
 		public Folder getFolder() {
-			try {
-				return obtainFolderInstance();
+			if (!AbstractMailReceiver.this.autoCloseFolder) {
+				return AbstractMailReceiver.this.folder;
 			}
-			catch (MessagingException e) {
-				throw new org.springframework.messaging.MessagingException("Unable to obtain the mail folder", e);
+			else {
+				try {
+					return obtainFolderInstance();
+				}
+				catch (MessagingException e) {
+					throw new org.springframework.messaging.MessagingException("Unable to obtain the mail folder", e);
+				}
 			}
 		}
 

spring-integration-mail/src/main/java/org/springframework/integration/mail/MailReceivingMessageSource.java

@@ -21,14 +21,12 @@
 import java.util.concurrent.ConcurrentLinkedQueue;
 
 import org.springframework.integration.endpoint.AbstractMessageSource;
-import org.springframework.messaging.Message;
 import org.springframework.messaging.MessagingException;
 import org.springframework.util.Assert;
 
 /**
  * {@link org.springframework.integration.core.MessageSource} implementation that
- * delegates to a
- * {@link MailReceiver} to poll a mailbox. Each poll of the mailbox may
+ * delegates to a {@link MailReceiver} to poll a mailbox. Each poll of the mailbox may
  * return more than one message which will then be stored in a queue.
  *
  * @author Jonas Partner
@@ -69,12 +67,7 @@ protected Object doReceive() {
 				if (this.logger.isDebugEnabled()) {
 					this.logger.debug("received mail message [" + mailMessage + "]");
 				}
-				if (mailMessage instanceof Message) {
-					return getMessageBuilderFactory().fromMessage((Message<?>) mailMessage);
-				}
-				else {
-					return getMessageBuilderFactory().withPayload(mailMessage);
-				}
+				return mailMessage;
 			}
 		}
 		catch (Exception e) {

spring-integration-mail/src/main/java/org/springframework/integration/mail/config/ImapIdleChannelAdapterParser.java

@@ -23,6 +23,7 @@
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.beans.factory.xml.ParserContext;
+import org.springframework.integration.config.ExpressionFactoryBean;
 import org.springframework.integration.config.xml.AbstractChannelAdapterParser;
 import org.springframework.integration.config.xml.IntegrationNamespaceUtils;
 import org.springframework.integration.mail.ImapIdleChannelAdapter;
@@ -37,6 +38,7 @@
  * @author Mark Fisher
  * @author Oleg Zhurakousky
  * @author Gary Russell
+ * @author Artem Bilan
  */
 public class ImapIdleChannelAdapterParser extends AbstractChannelAdapterParser {
 
@@ -52,7 +54,8 @@ protected AbstractBeanDefinition doParse(Element element, ParserContext parserCo
 			IntegrationNamespaceUtils.setReferenceIfAttributeDefined(builder, txElement,
 					"synchronization-factory", "transactionSynchronizationFactory");
 		}
-		IntegrationNamespaceUtils.setReferenceIfAttributeDefined(builder, element, "task-executor", "sendingTaskExecutor");
+		IntegrationNamespaceUtils.setReferenceIfAttributeDefined(builder, element, "task-executor",
+				"sendingTaskExecutor");
 		AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();
 		IntegrationNamespaceUtils.configureAndSetAdviceChainIfPresent(null,
 				DomUtils.getChildElementByTagName(element, "transactional"), beanDefinition, parserContext);
@@ -90,15 +93,15 @@ private BeanDefinition parseImapMailReceiver(Element element, ParserContext pars
 
 		String selectorExpression = element.getAttribute("mail-filter-expression");
 
-		RootBeanDefinition expressionDef = null;
 		if (StringUtils.hasText(selectorExpression)) {
-			expressionDef = new RootBeanDefinition("org.springframework.integration.config.ExpressionFactoryBean");
+			RootBeanDefinition expressionDef = new RootBeanDefinition(ExpressionFactoryBean.class);
 			expressionDef.getConstructorArgumentValues().addGenericArgumentValue(selectorExpression);
 			receiverBuilder.addPropertyValue("selectorExpression", expressionDef);
 		}
 		IntegrationNamespaceUtils.setReferenceIfAttributeDefined(receiverBuilder, element, "header-mapper");
 		IntegrationNamespaceUtils.setValueIfAttributeDefined(receiverBuilder, element, "embedded-parts-as-bytes");
 		IntegrationNamespaceUtils.setValueIfAttributeDefined(receiverBuilder, element, "simple-content");
+		IntegrationNamespaceUtils.setValueIfAttributeDefined(receiverBuilder, element, "auto-close-folder");
 
 		return receiverBuilder.getBeanDefinition();
 	}

spring-integration-mail/src/main/java/org/springframework/integration/mail/config/MailInboundChannelAdapterParser.java

@@ -23,6 +23,7 @@
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.beans.factory.xml.ParserContext;
+import org.springframework.integration.config.ExpressionFactoryBean;
 import org.springframework.integration.config.xml.AbstractPollingInboundChannelAdapterParser;
 import org.springframework.integration.config.xml.IntegrationNamespaceUtils;
 import org.springframework.integration.mail.MailReceivingMessageSource;
@@ -36,6 +37,7 @@
  * @author Mark Fisher
  * @author Oleg Zhurakousky
  * @author Gary Russell
+ * @author Artem Bilan
  */
 public class MailInboundChannelAdapterParser extends AbstractPollingInboundChannelAdapterParser {
 
@@ -87,15 +89,15 @@ private BeanDefinition parseMailReceiver(Element element, ParserContext parserCo
 
 		String selectorExpression = element.getAttribute("mail-filter-expression");
 
-		RootBeanDefinition expressionDef = null;
 		if (StringUtils.hasText(selectorExpression)) {
-			expressionDef = new RootBeanDefinition("org.springframework.integration.config.ExpressionFactoryBean");
+			RootBeanDefinition expressionDef = new RootBeanDefinition(ExpressionFactoryBean.class);
 			expressionDef.getConstructorArgumentValues().addGenericArgumentValue(selectorExpression);
 			receiverBuilder.addPropertyValue("selectorExpression", expressionDef);
 		}
 		IntegrationNamespaceUtils.setReferenceIfAttributeDefined(receiverBuilder, element, "header-mapper");
 		IntegrationNamespaceUtils.setValueIfAttributeDefined(receiverBuilder, element, "embedded-parts-as-bytes");
 		IntegrationNamespaceUtils.setValueIfAttributeDefined(receiverBuilder, element, "simple-content");
+		IntegrationNamespaceUtils.setValueIfAttributeDefined(receiverBuilder, element, "auto-close-folder");
 
 		return receiverBuilder.getBeanDefinition();
 	}

spring-integration-mail/src/main/java/org/springframework/integration/mail/config/MailReceiverFactoryBean.java

@@ -81,6 +81,8 @@ public class MailReceiverFactoryBean extends AbstractFactoryBean<MailReceiver> {
 
 	private Boolean simpleContent;
 
+	private Boolean autoCloseFolder;
+
 	public void setStoreUri(@Nullable String storeUri) {
 		this.storeUri = storeUri;
 	}
@@ -141,6 +143,10 @@ public void setSimpleContent(@Nullable Boolean simpleContent) {
 		this.simpleContent = simpleContent;
 	}
 
+	public void setAutoCloseFolder(@Nullable Boolean autoCloseFolder) {
+		this.autoCloseFolder = autoCloseFolder;
+	}
+
 	@Override
 	protected MailReceiver createInstance() {
 		if (this.receiver == null) {
@@ -211,6 +217,9 @@ private MailReceiver createReceiver() { // NOSONAR
 		if (this.simpleContent != null) {
 			mailReceiver.setSimpleContent(this.simpleContent);
 		}
+		if (this.autoCloseFolder != null) {
+			mailReceiver.setAutoCloseFolder(this.autoCloseFolder);
+		}
 		mailReceiver.afterPropertiesSet();
 		return mailReceiver;
 	}

spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/ImapIdleChannelAdapterSpec.java

@@ -269,6 +269,21 @@ public ImapIdleChannelAdapterSpec embeddedPartsAsBytes(boolean embeddedPartsAsBy
 		return _this();
 	}
 
+	/**
+	 * When configured to {@code false}, the folder is not closed automatically after a fetch.
+	 * It is the target application's responsibility to close it using the
+	 * {@link org.springframework.integration.IntegrationMessageHeaderAccessor#CLOSEABLE_RESOURCE} header
+	 * from the message produced by this channel adapter.
+	 * @param autoCloseFolder set to {@code false} to keep folder opened.
+	 * @return the spec.
+	 * @since 5.2
+	 * @see ImapMailReceiver#setAutoCloseFolder(boolean)
+	 */
+	public ImapIdleChannelAdapterSpec autoCloseFolder(boolean autoCloseFolder) {
+		assertReceiver();
+		this.receiver.setAutoCloseFolder(autoCloseFolder);
+		return _this();
+	}
 
 	/**
 	 * Configure a {@link TransactionSynchronizationFactory}. Usually used to synchronize

spring-integration-mail/src/main/java/org/springframework/integration/mail/dsl/MailInboundChannelAdapterSpec.java

@@ -253,6 +253,22 @@ public S simpleContent(boolean simpleContent) {
 		return _this();
 	}
 
+	/**
+	 * When configured to {@code false}, the folder is not closed automatically after a fetch.
+	 * It is the target application's responsibility to close it using the
+	 * {@link org.springframework.integration.IntegrationMessageHeaderAccessor#CLOSEABLE_RESOURCE} header
+	 * from the message produced by this channel adapter.
+	 * @param autoCloseFolder set to {@code false} to keep folder opened.
+	 * @return the spec.
+	 * @since 5.2
+	 * @see AbstractMailReceiver#setAutoCloseFolder(boolean)
+	 */
+	public S autoCloseFolder(boolean autoCloseFolder) {
+		assertReceiver();
+		this.receiver.setAutoCloseFolder(autoCloseFolder);
+		return _this();
+	}
+
 	@Override
 	public Map<Object, String> getComponentsToRegister() {
 		return Collections.singletonMap(this.receiver, this.receiver.getComponentName());

spring-integration-mail/src/main/resources/org/springframework/integration/mail/config/spring-integration-mail-5.2.xsd

@@ -416,6 +416,16 @@
 				<xsd:union memberTypes="xsd:boolean xsd:string"/>
 			</xsd:simpleType>
 		</xsd:attribute>
+		<xsd:attribute name="auto-close-folder" default="true">
+			<xsd:annotation>
+				<xsd:documentation>
+					Default 'true' - close folder automatically after fetch, before producing messages.
+				</xsd:documentation>
+			</xsd:annotation>
+			<xsd:simpleType>
+				<xsd:union memberTypes="xsd:boolean xsd:string"/>
+			</xsd:simpleType>
+		</xsd:attribute>
 	</xsd:attributeGroup>
 
 </xsd:schema>

spring-integration-mail/src/test/java/org/springframework/integration/mail/config/ImapIdleChannelAdapterParserTests-context.xml

@@ -38,6 +38,7 @@
 			header-mapper="mapper"
 			simple-content="true"
 			embedded-parts-as-bytes="false"
+			auto-close-folder="false"
 			should-delete-messages="true"/>
 
 	<bean id="mapper" class="org.springframework.integration.mail.support.DefaultMailHeaderMapper" />

spring-integration-mail/src/test/java/org/springframework/integration/mail/config/ImapIdleChannelAdapterParserTests.java

@@ -84,6 +84,7 @@ public void simpleAdapter() {
 		assertThat(receiverAccessor.getPropertyValue("embeddedPartsAsBytes")).isEqualTo(Boolean.FALSE);
 		assertThat(receiverAccessor.getPropertyValue("headerMapper")).isNotNull();
 		assertThat(receiverAccessor.getPropertyValue("simpleContent")).isEqualTo(Boolean.TRUE);
+		assertThat(receiverAccessor.getPropertyValue("autoCloseFolder")).isEqualTo(false);
 	}
 
 	@Test

spring-integration-mail/src/test/java/org/springframework/integration/mail/config/InboundChannelAdapterParserTests-context.xml

@@ -16,6 +16,7 @@
 	<mail:inbound-channel-adapter id="pop3ShouldDeleteTrue"
 		store-uri="pop3:test" channel="testChannel" should-delete-messages="true"
 		header-mapper="mapper" embedded-parts-as-bytes="false"
+		auto-close-folder="false"
 		auto-startup="false" />
 
 	<mail:inbound-channel-adapter id="pop3ShouldDeleteFalse"