Add JSpecify Nullability to the xml parsers package

* Tests were updated
* Test XML files updated to handle non nullable attributes and parameters
* In some cases I reformatted the whole xml file vs the changed section.   If this is a problem I'll undo.
* In many circumstances the chances of having null, should not happen, so `Objects.requireNonNull` was used.  But wonder if we should use Assert.state and have a message.   Thoughts?
* Removed @nullable from requested locations
* Added requested `@SuppressWarning("NullAway")` to specified locations
* Removed format changes from XML file that was mistakingly pushed.
* Resolved Nullability compile time errors from where the @nullable was removed
* PointToPointChannelParser requires a null check on line 82 because builder because it may not have been set.   With this assert we can throw away the previous bogus exception

* Remove correlation and release strategy entries from  context-xml files
Remove CassandraParserUtilsTests.   Other tests provide the coverage required.
Readd method variable for readability

* Remove @nullable from buildBeanDefinition in both AbstractChannelParser andk KafkaChannelParser

Add dummy exceptions to be applied below calls to .error so that NullAway knows that it will not return null
Make sure dummy exceptions have a consistent message describing why they are there

* Add blank line to improve readability in `AbstractPollingInboundChannelAdapterParser` class.

Replace stock exception for NullAway to signal that `error` will throw an exception with the message passed to the `error` method.

Author: cppwfs

spring-integration-cassandra/src/main/java/org/springframework/integration/cassandra/config/xml/CassandraParserUtils.java

@@ -18,6 +18,7 @@
 
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Element;
 
 import org.springframework.beans.factory.config.BeanDefinition;
@@ -91,7 +92,7 @@ public static void processOutboundTypeAttributes(Element element, ParserContext
 
 	}
 
-	public static boolean areMutuallyExclusive(String query, BeanDefinition statementExpressionDef,
+	private static boolean areMutuallyExclusive(String query, @Nullable BeanDefinition statementExpressionDef,
 			String ingestQuery) {
 
 		return !StringUtils.hasText(query) && statementExpressionDef == null && !StringUtils.hasText(ingestQuery)

spring-integration-cassandra/src/test/java/org/springframework/integration/cassandra/config/CassandraParserUtilsTests.java

@@ -1,4 +1,5 @@
 /**
  * Provides classes supporting annotation-based configuration.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.config.annotation;

spring-integration-core/src/main/java/org/springframework/integration/config/annotation/package-info.java

@@ -16,6 +16,7 @@
 
 package org.springframework.integration.config.xml;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Element;
 
 import org.springframework.beans.MutablePropertyValues;
@@ -61,6 +62,7 @@ else if (!StringUtils.hasText(id)) {
 		return id;
 	}
 
+	@SuppressWarnings("NullAway")
 	@Override
 	protected final AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) {
 		String channelName = element.getAttribute("channel");
@@ -88,7 +90,7 @@ protected final AbstractBeanDefinition parseInternal(Element element, ParserCont
 		return beanDefinition;
 	}
 
-	private String createDirectChannel(Element element, ParserContext parserContext) {
+	private @Nullable String createDirectChannel(Element element, ParserContext parserContext) {
 		if (parserContext.isNested()) {
 			return null;
 		}

spring-integration-core/src/main/java/org/springframework/integration/config/xml/AbstractChannelAdapterParser.java

@@ -19,6 +19,7 @@
 import java.util.Collection;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Element;
 
 import org.springframework.beans.factory.BeanDefinitionStoreException;
@@ -85,7 +86,7 @@ protected String getInputChannelAttributeName() {
 	}
 
 	@Override
-	protected final AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) {
+	protected final @Nullable AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) {
 		BeanDefinitionBuilder handlerBuilder = parseHandler(element, parserContext);
 		IntegrationNamespaceUtils.setValueIfAttributeDefined(handlerBuilder, element, "output-channel",
 				"outputChannelName");
@@ -178,6 +179,7 @@ private void poller(Element element, ParserContext parserContext, BeanDefinition
 		}
 	}
 
+	@SuppressWarnings("NullAway") // Dataflow analysis limitation
 	private void registerChannelForCreation(ParserContext parserContext, String inputChannelName,
 			BeanDefinitionBuilder consumerEndpointBuilder) {
 
@@ -194,13 +196,11 @@ private void registerChannelForCreation(ParserContext parserContext, String inpu
 			if (vh == null) { //although it should never happen if it does we can fix it
 				caValues.addIndexedArgumentValue(0, new ManagedSet<String>());
 			}
-
 			@SuppressWarnings("unchecked")
 			Collection<String> channelCandidateNames =
 					(Collection<String>) caValues.getArgumentValue(0, Collection.class)
-							.getValue(); // NOSONAR see comment above
-			channelCandidateNames.add(inputChannelName); // NOSONAR
-
+							.getValue();
+			channelCandidateNames.add(inputChannelName);
 			consumerEndpointBuilder.addDependsOn(IntegrationContextUtils.AUTO_CREATE_CHANNEL_CANDIDATES_BEAN_NAME);
 		}
 		else {

spring-integration-core/src/main/java/org/springframework/integration/config/xml/AbstractConsumerEndpointParser.java

@@ -16,6 +16,7 @@
 
 package org.springframework.integration.config.xml;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Element;
 
 import org.springframework.beans.BeanMetadataElement;
@@ -65,7 +66,7 @@ public abstract class AbstractCorrelatingMessageHandlerParser extends AbstractCo
 
 	private static final String RELEASE_LOCK = "release-lock-before-send";
 
-	protected void doParse(BeanDefinitionBuilder builder, Element element, BeanMetadataElement processor,
+	protected void doParse(BeanDefinitionBuilder builder, Element element, @Nullable BeanMetadataElement processor,
 			ParserContext parserContext) {
 		IntegrationNamespaceUtils.injectPropertyWithAdapter(CORRELATION_STRATEGY_REF_ATTRIBUTE,
 				CORRELATION_STRATEGY_METHOD_ATTRIBUTE,

spring-integration-core/src/main/java/org/springframework/integration/config/xml/AbstractCorrelatingMessageHandlerParser.java

@@ -16,6 +16,7 @@
 
 package org.springframework.integration.config.xml;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Element;
 
 import org.springframework.beans.factory.config.BeanDefinition;
@@ -65,7 +66,6 @@ else if (hasRef && hasExpression) {
 			parserContext.getReaderContext().error(
 					"Only one of 'ref' or 'expression' is permitted, not both, on element " +
 							IntegrationNamespaceUtils.createElementDescription(element) + ".", source);
-			return null;
 		}
 		else if (hasRef) {
 			builder.addPropertyReference("targetObject", ref);
@@ -77,7 +77,6 @@ else if (!this.hasDefaultOption()) {
 			parserContext.getReaderContext().error("Exactly one of the 'ref' attribute, 'expression' attribute, " +
 					"or inner bean (<bean/>) definition is required for element " +
 					IntegrationNamespaceUtils.createElementDescription(element) + ".", source);
-			return null;
 		}
 		methodAttribute(element, parserContext, source, builder, innerDefinition, hasRef, hasExpression,
 				expressionElement);
@@ -87,9 +86,9 @@ else if (!this.hasDefaultOption()) {
 		return builder;
 	}
 
-	private void innerDefinition(Element element, ParserContext parserContext, Object source,
+	private void innerDefinition(Element element, ParserContext parserContext, @Nullable Object source,
 			BeanDefinitionBuilder builder, BeanComponentDefinition innerDefinition, boolean hasRef,
-			boolean hasExpression, Element expressionElement) {
+			boolean hasExpression, @Nullable Element expressionElement) {
 		if (hasRef || hasExpression || expressionElement != null) {
 			parserContext.getReaderContext().error(
 					"Neither 'ref' nor 'expression' are permitted when an inner bean (<bean/>) is configured on element " +
@@ -98,9 +97,9 @@ private void innerDefinition(Element element, ParserContext parserContext, Objec
 		builder.addPropertyValue("targetObject", innerDefinition);
 	}
 
-	private void scriptElement(Element element, ParserContext parserContext, Object source,
+	private void scriptElement(Element element, ParserContext parserContext, @Nullable Object source,
 			BeanDefinitionBuilder builder, boolean hasRef, boolean hasExpression, Element scriptElement,
-			Element expressionElement) {
+			@Nullable Element expressionElement) {
 		if (hasRef || hasExpression || expressionElement != null) {
 			parserContext.getReaderContext().error(
 					"Neither 'ref' nor 'expression' are permitted when an inner script element is configured on element " +
@@ -110,7 +109,7 @@ private void scriptElement(Element element, ParserContext parserContext, Object
 		builder.addPropertyValue("targetObject", scriptBeanDefinition);
 	}
 
-	private void expressionElement(Element element, ParserContext parserContext, Object source,
+	private void expressionElement(Element element, ParserContext parserContext, @Nullable Object source,
 			BeanDefinitionBuilder builder, boolean hasRef, boolean hasExpression, Element expressionElement) {
 		if (hasRef || hasExpression) {
 			parserContext.getReaderContext().error(
@@ -126,9 +125,9 @@ private void expressionElement(Element element, ParserContext parserContext, Obj
 		builder.addPropertyValue("expression", dynamicExpressionBuilder.getBeanDefinition());
 	}
 
-	private void methodAttribute(Element element, ParserContext parserContext, Object source,
-			BeanDefinitionBuilder builder, BeanComponentDefinition innerDefinition, boolean hasRef,
-			boolean hasExpression, Element expressionElement) {
+	private void methodAttribute(Element element, ParserContext parserContext, @Nullable Object source,
+			BeanDefinitionBuilder builder, @Nullable BeanComponentDefinition innerDefinition, boolean hasRef,
+			boolean hasExpression, @Nullable Element expressionElement) {
 		String method = element.getAttribute(METHOD_ATTRIBUTE);
 		if (StringUtils.hasText(method)) {
 			if (hasExpression || expressionElement != null) {

spring-integration-core/src/main/java/org/springframework/integration/config/xml/AbstractDelegatingConsumerEndpointParser.java

@@ -18,6 +18,7 @@
 
 import java.util.concurrent.atomic.AtomicBoolean;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Element;
 
 import org.springframework.beans.factory.config.BeanDefinition;
@@ -47,7 +48,7 @@ public abstract class AbstractIntegrationNamespaceHandler extends NamespaceHandl
 	private final AtomicBoolean initialized = new AtomicBoolean();
 
 	@Override
-	public final BeanDefinition parse(Element element, ParserContext parserContext) {
+	public final @Nullable BeanDefinition parse(Element element, ParserContext parserContext) {
 		if (!this.initialized.getAndSet(true)) {
 			BeanDefinitionRegistry registry = parserContext.getRegistry();
 			new IntegrationRegistrar().registerBeanDefinitions(null, registry);

spring-integration-core/src/main/java/org/springframework/integration/config/xml/AbstractIntegrationNamespaceHandler.java

@@ -16,6 +16,7 @@
 
 package org.springframework.integration.config.xml;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Element;
 
 import org.springframework.beans.factory.config.BeanDefinition;
@@ -82,7 +83,7 @@ protected AbstractBeanDefinition doParse(Element element, ParserContext parserCo
 	}
 
 	private void configureRequestHandlerAdviceChain(Element element, ParserContext parserContext,
-			BeanDefinition handlerBeanDefinition, BeanDefinitionBuilder consumerBuilder) {
+			BeanDefinition handlerBeanDefinition, @Nullable BeanDefinitionBuilder consumerBuilder) {
 		Element txElement = DomUtils.getChildElementByTagName(element, "transactional");
 		Element adviceChainElement = DomUtils.getChildElementByTagName(element,
 				IntegrationNamespaceUtils.REQUEST_HANDLER_ADVICE_CHAIN);

spring-integration-core/src/main/java/org/springframework/integration/config/xml/AbstractOutboundChannelAdapterParser.java

@@ -59,6 +59,8 @@ else if (source instanceof RuntimeBeanReference runtimeBeanReference) {
 		}
 		else {
 			parserContext.getReaderContext().error("Wrong 'source' type: must be 'BeanDefinition' or 'RuntimeBeanReference'", source);
+			// This exception is meant to signal to NullAway that the error method throws an exception
+			throw new IllegalStateException("Wrong 'source' type: must be 'BeanDefinition' or 'RuntimeBeanReference'");
 		}
 
 		adapterBuilder.addPropertyReference("source", sourceBeanName);