INT-1801 fixed the NPE during shutdown of Mail receiver, fixed the dead code in ImapIdleChannelAdapter, polished IdleTask (it now throws IllegalStateException which means resubmit after delay or SI MessagingException if resubmit flag is set to 'false')

spring-integration-mail/src/test/java/org/springframework/integration/mail/ImapMailReceiverTests.java

@@ -25,20 +25,26 @@ import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 import java.util.Properties;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import javax.mail.Flags;
 import javax.mail.Flags.Flag;
 import javax.mail.Folder;
 import javax.mail.Message;
+import javax.mail.Store;
+import javax.mail.URLName;
 import javax.mail.internet.MimeMessage;
+import javax.mail.search.SearchTerm;
 
 import org.junit.Test;
 import org.mockito.Mockito;
 import org.mockito.invocation.InvocationOnMock;
 import org.mockito.stubbing.Answer;
+
 import org.springframework.beans.DirectFieldAccessor;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
+import org.springframework.integration.MessagingException;
 import org.springframework.integration.channel.DirectChannel;
 import org.springframework.integration.channel.QueueChannel;
 import org.springframework.integration.core.PollableChannel;
@@ -56,6 +62,8 @@ import com.sun.mail.imap.IMAPFolder;
  */
 public class ImapMailReceiverTests {
 	
+	private AtomicInteger failed = new AtomicInteger(0);
+	
 	@Test
 	public void receiveAndMarkAsReadDontDelete() throws Exception{
 		AbstractMailReceiver receiver = new ImapMailReceiver();
@@ -344,4 +352,46 @@ public class ImapMailReceiverTests {
 		assertNotNull(replMessage);
 		assertEquals("Failed", ((Exception) replMessage.getPayload()).getCause().getMessage());
 	}
+	
+	@Test // see INT-1801
+	public void testImapLifecycleForRaceCondition() throws Exception{
+	
+		for (int i = 0; i < 1000; i++) {
+			final ImapMailReceiver receiver = new ImapMailReceiver("imap://foo");
+			Store store = mock(Store.class);
+			Folder folder = mock(Folder.class);
+			when(folder.exists()).thenReturn(true);
+			when(folder.isOpen()).thenReturn(true);
+			when(folder.search((SearchTerm) Mockito.any())).thenReturn(new Message[]{});
+			when(store.getFolder(Mockito.any(URLName.class))).thenReturn(folder);
+			DirectFieldAccessor df = new DirectFieldAccessor(receiver);
+			df.setPropertyValue("store", store);
+			
+			new Thread(new Runnable() {
+				public void run(){
+					try {
+						receiver.receive();
+					} catch (MessagingException e) {
+						if (e.getCause() instanceof NullPointerException){
+							e.printStackTrace();
+							failed.getAndIncrement();
+						}
+					}
+					
+				}
+			}).start();
+			
+			new Thread(new Runnable() {
+				public void run(){
+					try {
+						receiver.destroy();
+					} catch (Exception ignore) {
+						// ignore
+						ignore.printStackTrace();
+					}
+				}
+			}).start();
+		}
+		assertEquals(0, failed.get());
+	}
 }