Start 6.0 version

* Upgrade to Java 17, SF-6.0, Gradle 7.2
* Upgrade to Jakarta dependencies and respective namespaces
* Fix some tests for Java 17 compatibility
* Fix wrong Javadocs
* Add some missed Javadocs
* Fix more `jakarta` namespace
* Fix WS & XML modules to use Jakarta EE
* `--add-opens` in some modules for their reflection-based tests
* Disable Kafka tests which does not work on Windows; see Apache Kafka `3.0.1`
* Upgrade to JUnit `5.8.1`
* Migrate JMS tests to Artemis
* Remove RMI module as it was deprecated before
* Fix `pr-build-workflow.yml` for Java 17
* Fix JavaDocs warnings using `Xdoclint:syntax` per module, not in the top-level `api` task
* Move docs for version `6.0`

spring-integration-file/src/test/java/org/springframework/integration/file/config/FileInboundChannelAdapterParserTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -124,16 +124,7 @@ public class FileInboundChannelAdapterParserTests {
 		Object priorityQueue = accessor.getPropertyValue("toBeReceived");
 		assertThat(priorityQueue).isInstanceOf(PriorityBlockingQueue.class);
 		Object expected = context.getBean("testComparator");
-		DirectFieldAccessor queueAccessor = new DirectFieldAccessor(priorityQueue);
-		Object innerQueue = queueAccessor.getPropertyValue("q");
-		Object actual;
-		if (innerQueue != null) {
-			actual = new DirectFieldAccessor(innerQueue).getPropertyValue("comparator");
-		}
-		else {
-			// probably running under JDK 7
-			actual = queueAccessor.getPropertyValue("comparator");
-		}
+		Object actual = ((PriorityBlockingQueue) priorityQueue).comparator();
 		assertThat(actual).as("comparator reference not set, ").isSameAs(expected);
 	}
 

spring-integration-file/src/test/java/org/springframework/integration/file/splitter/FileSplitterTests.java

@@ -32,11 +32,11 @@ import java.nio.charset.StandardCharsets;
 import java.time.Duration;
 import java.util.Date;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
-import org.mockito.Mockito;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Bean;
@@ -380,14 +380,21 @@ public class FileSplitterTests {
 		});
 		FileSplitter splitter = new FileSplitter(true, true);
 		splitter.setOutputChannel(outputChannel);
-		FileReader fileReader = Mockito.spy(new FileReader(file));
+		AtomicBoolean closeCalled = new AtomicBoolean();
+		FileReader fileReader = new FileReader(file) {
+
+			@Override public void close() throws IOException {
+				super.close();
+				closeCalled.set(true);
+			}
+		};
 		try {
 			splitter.handleMessage(new GenericMessage<>(fileReader));
 		}
 		catch (RuntimeException e) {
 			// ignore
 		}
-		Mockito.verify(fileReader).close();
+		assertThat(closeCalled.get()).isTrue();
 	}
 
 	@Configuration

spring-integration-file/src/test/java/org/springframework/integration/file/tail/FileTailingMessageProducerTests.java

@@ -18,10 +18,7 @@ package org.springframework.integration.file.tail;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.fail;
-import static org.mockito.Mockito.atLeastOnce;
 import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.spy;
-import static org.mockito.Mockito.verify;
 
 import java.io.File;
 import java.io.FileOutputStream;
@@ -30,6 +27,7 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -156,7 +154,19 @@ public class FileTailingMessageProducerTests {
 			}
 		});
 
-		File file = spy(new File(this.testDir, "foo"));
+		AtomicBoolean existsCalled = new AtomicBoolean();
+		File file = new File(this.testDir, "foo") {
+
+			@Override
+			public boolean exists() {
+				try {
+					return super.exists();
+				}
+				finally {
+					existsCalled.set(true);
+				}
+			}
+		};
 		file.delete();
 		adapter.setFile(file);
 
@@ -169,7 +179,7 @@ public class FileTailingMessageProducerTests {
 		assertThat(noFile).as("file does not exist event did not emit ").isTrue();
 		boolean noEvent = idleCountDownLatch.await(100, TimeUnit.MILLISECONDS);
 		assertThat(noEvent).as("event should not emit when no file exit").isFalse();
-		verify(file, atLeastOnce()).exists();
+		assertThat(existsCalled.get()).isTrue();
 
 		file.createNewFile();
 		boolean eventRaised = idleCountDownLatch.await(10, TimeUnit.SECONDS);