GH-10083: Implement Nullability in XML module

Related to: #10083

* Add `@org.jspecify.annotations.NullMarked` to all the packages in the XML module
* Apply JSpecify null safety annotation improvements

Signed-off-by: Eddie Cho <[email protected]>

Author: EddieChoCho

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

@@ -1,4 +1,5 @@
 /**
  * Contains parser classes for the XML namespace support.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.xml.config;

spring-integration-xml/src/main/java/org/springframework/integration/xml/package-info.java

@@ -1,4 +1,5 @@
 /**
  * Root package of the XML Module.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.xml;

spring-integration-xml/src/main/java/org/springframework/integration/xml/result/package-info.java

@@ -3,4 +3,5 @@
  * will return {@link javax.xml.transform.Result}, possibly taking into account
  * payload instance.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.xml.result;

spring-integration-xml/src/main/java/org/springframework/integration/xml/router/XPathRouter.java

@@ -21,6 +21,7 @@
 import java.util.List;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.DOMException;
 import org.w3c.dom.Node;
 
@@ -128,7 +129,7 @@ private static class TextContentNodeMapper implements NodeMapper<Object> {
 		}
 
 		@Override
-		public Object mapNode(Node node, int nodeNum) throws DOMException {
+		public @Nullable Object mapNode(Node node, int nodeNum) throws DOMException {
 			return node.getTextContent();
 		}
 

spring-integration-xml/src/main/java/org/springframework/integration/xml/selector/XmlValidatingMessageSelector.java

@@ -20,6 +20,7 @@
 import java.io.UncheckedIOException;
 import java.util.Arrays;
 
+import org.jspecify.annotations.Nullable;
 import org.xml.sax.SAXParseException;
 
 import org.springframework.core.io.Resource;
@@ -83,7 +84,7 @@ public String getUrl() {
 	 * @param schemaType The schema type.
 	 * @throws IOException if the XmlValidatorFactory fails to create a validator
 	 */
-	public XmlValidatingMessageSelector(Resource schema, SchemaType schemaType) throws IOException {
+	public XmlValidatingMessageSelector(Resource schema, @Nullable SchemaType schemaType) throws IOException {
 		this(XmlValidatorFactory.createValidator(schema,
 				schemaType == null
 						? SchemaType.XML_SCHEMA.getUrl()
@@ -95,7 +96,7 @@ public XmlValidatingMessageSelector(XmlValidator xmlValidator) {
 		this.xmlValidator = xmlValidator;
 	}
 
-	public XmlValidatingMessageSelector(Resource schema, String schemaType) throws IOException {
+	public XmlValidatingMessageSelector(Resource schema, @Nullable String schemaType) throws IOException {
 		this(schema,
 				StringUtils.hasText(schemaType)
 						? SchemaType.valueOf(schemaType.toUpperCase().replaceFirst("-", "_"))

spring-integration-xml/src/main/java/org/springframework/integration/xml/selector/package-info.java

@@ -2,4 +2,5 @@
  * Provides XML-centric {@link org.springframework.integration.core.MessageSelector}
  * implementations.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.xml.selector;

spring-integration-xml/src/main/java/org/springframework/integration/xml/source/package-info.java

@@ -2,4 +2,5 @@
  * Provides various {@link org.springframework.integration.xml.source.SourceFactory}
  * implementations.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.xml.source;

spring-integration-xml/src/main/java/org/springframework/integration/xml/splitter/XPathMessageSplitter.java

@@ -38,6 +38,7 @@
 import javax.xml.xpath.XPathExpressionException;
 import javax.xml.xpath.XPathFactory;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Document;
 import org.w3c.dom.Node;
 import org.w3c.dom.NodeList;
@@ -82,15 +83,15 @@ public class XPathMessageSplitter extends AbstractMessageSplitter {
 
 	private final XPathExpression xpathExpression;
 
-	private javax.xml.xpath.XPathExpression jaxpExpression;
+	private javax.xml.xpath.@Nullable XPathExpression jaxpExpression;
 
 	private boolean createDocuments;
 
 	private DocumentBuilderFactory documentBuilderFactory;
 
 	private XmlPayloadConverter xmlPayloadConverter = new DefaultXmlPayloadConverter();
 
-	private Properties outputProperties;
+	private @Nullable Properties outputProperties;
 
 	private boolean returnIterator = true;
 
@@ -292,7 +293,7 @@ private Object splitDocument(Document document) throws ParserConfigurationExcept
 	}
 
 	private Object splitNode(Node node) throws ParserConfigurationException {
-		if (this.returnIterator) {
+		if (this.returnIterator && this.jaxpExpression != null) {
 			try {
 				NodeList nodeList = (NodeList) this.jaxpExpression.evaluate(node, XPathConstants.NODESET);
 				return new NodeListIterator(nodeList);
@@ -338,7 +339,7 @@ private DocumentBuilder getNewDocumentBuilder() throws ParserConfigurationExcept
 
 	private final class NodeListIterator implements Iterator<Node> {
 
-		private final DocumentBuilder documentBuilder;
+		private final @Nullable DocumentBuilder documentBuilder;
 
 		private final NodeList nodeList;
 
@@ -360,7 +361,7 @@ public boolean hasNext() {
 		}
 
 		@Override
-		public Node next() {
+		public @Nullable Node next() {
 			if (!hasNext()) {
 				return null;
 			}

spring-integration-xml/src/main/java/org/springframework/integration/xml/splitter/package-info.java

@@ -2,4 +2,5 @@
  * Provides implementations of
  * {@link org.springframework.integration.splitter.AbstractMessageSplitter}.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.xml.splitter;

spring-integration-xml/src/main/java/org/springframework/integration/xml/transformer/AbstractXmlTransformer.java

@@ -16,6 +16,8 @@
 
 package org.springframework.integration.xml.transformer;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.integration.transformer.AbstractTransformer;
 import org.springframework.integration.xml.result.DomResultFactory;
@@ -39,9 +41,9 @@ public abstract class AbstractXmlTransformer extends AbstractTransformer {
 
 	public static final String STRING_RESULT = "StringResult";
 
-	private volatile String resultType;
+	private volatile @Nullable String resultType;
 
-	private volatile String resultFactoryName;
+	private volatile @Nullable String resultFactoryName;
 
 	private volatile ResultFactory resultFactory = new DomResultFactory();
 
@@ -58,11 +60,11 @@ public void setResultFactory(ResultFactory resultFactory) {
 		this.resultFactory = resultFactory;
 	}
 
-	public String getResultType() {
+	public @Nullable String getResultType() {
 		return this.resultType;
 	}
 
-	public String getResultFactoryName() {
+	public @Nullable String getResultFactoryName() {
 		return this.resultFactoryName;
 	}
 
@@ -85,7 +87,7 @@ protected void onInit() {
 	 * a bean definition for a {@link ResultFactory} based on either the
 	 * 'result-factory' or 'result-type' attributes.
 	 */
-	private ResultFactory configureResultFactory(String resultType, String resultFactoryName, BeanFactory beanFactory) {
+	private @Nullable ResultFactory configureResultFactory(@Nullable String resultType, @Nullable String resultFactoryName, BeanFactory beanFactory) {
 		boolean bothHaveText = StringUtils.hasText(resultFactoryName) && StringUtils.hasText(resultType);
 		ResultFactory configuredResultFactory = null;
 		Assert.state(!bothHaveText, "Only one of 'result-factory' or 'result-type' should be specified.");

spring-integration-xml/src/main/java/org/springframework/integration/xml/transformer/MarshallingTransformer.java

@@ -20,6 +20,8 @@
 
 import javax.xml.transform.Result;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessagingException;
 import org.springframework.oxm.Marshaller;
@@ -39,11 +41,11 @@ public class MarshallingTransformer extends AbstractXmlTransformer {
 
 	private final Marshaller marshaller;
 
-	private final ResultTransformer resultTransformer;
+	private final @Nullable ResultTransformer resultTransformer;
 
 	private volatile boolean extractPayload = true;
 
-	public MarshallingTransformer(Marshaller marshaller, ResultTransformer resultTransformer) {
+	public MarshallingTransformer(Marshaller marshaller, @Nullable ResultTransformer resultTransformer) {
 		Assert.notNull(marshaller, "a marshaller is required");
 		this.marshaller = marshaller;
 		this.resultTransformer = resultTransformer;

spring-integration-xml/src/main/java/org/springframework/integration/xml/transformer/ResultToStringTransformer.java

@@ -28,6 +28,8 @@
 import javax.xml.transform.dom.DOMResult;
 import javax.xml.transform.dom.DOMSource;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.MessagingException;
 import org.springframework.util.Assert;
 import org.springframework.xml.transform.StringResult;
@@ -48,7 +50,7 @@ public class ResultToStringTransformer implements ResultTransformer {
 
 	private final TransformerFactory transformerFactory;
 
-	private Properties outputProperties;
+	private @Nullable Properties outputProperties;
 
 	public ResultToStringTransformer() {
 		this.transformerFactory = TransformerFactoryUtils.newInstance();

spring-integration-xml/src/main/java/org/springframework/integration/xml/transformer/UnmarshallingTransformer.java

@@ -27,6 +27,7 @@
 import javax.xml.transform.dom.DOMSource;
 import javax.xml.transform.stream.StreamSource;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Document;
 
 import org.springframework.integration.transformer.AbstractPayloadTransformer;
@@ -68,7 +69,7 @@ public class UnmarshallingTransformer extends AbstractPayloadTransformer<Object,
 
 	private boolean alwaysUseSourceFactory = false;
 
-	private MimeMessageUnmarshallerHelper mimeMessageUnmarshallerHelper;
+	private @Nullable MimeMessageUnmarshallerHelper mimeMessageUnmarshallerHelper;
 
 	public UnmarshallingTransformer(Unmarshaller unmarshaller) {
 		this.unmarshaller = unmarshaller;
@@ -162,7 +163,7 @@ private static class MimeMessageUnmarshallerHelper {
 			this.delegate = unmarshaller;
 		}
 
-		Object maybeUnmarshalMimeMessage(Object payload) throws IOException {
+		@Nullable Object maybeUnmarshalMimeMessage(Object payload) throws IOException {
 			if (payload instanceof org.springframework.ws.mime.MimeMessage mimeMessage) {
 				return org.springframework.ws.support.MarshallingUtils.unmarshal(this.delegate,
 					mimeMessage);

spring-integration-xml/src/main/java/org/springframework/integration/xml/transformer/XPathTransformer.java

@@ -16,6 +16,7 @@
 
 package org.springframework.integration.xml.transformer;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Node;
 
 import org.springframework.integration.transformer.AbstractTransformer;
@@ -50,7 +51,7 @@ public class XPathTransformer extends AbstractTransformer {
 
 	private volatile XPathEvaluationType evaluationType = XPathEvaluationType.STRING_RESULT;
 
-	private volatile NodeMapper<?> nodeMapper;
+	private volatile @Nullable NodeMapper<?> nodeMapper;
 
 	/**
 	 * Create an {@link XPathTransformer} that will create an XPath expression from the given String
@@ -110,7 +111,7 @@ public String getComponentType() {
 	}
 
 	@Override
-	protected Object doTransform(Message<?> message) {
+	protected @Nullable Object doTransform(Message<?> message) {
 		Node node = this.converter.convertToNode(message.getPayload());
 		Object result = null;
 		if (this.nodeMapper != null) {

spring-integration-xml/src/main/java/org/springframework/integration/xml/transformer/XsltPayloadTransformer.java

@@ -33,6 +33,7 @@
 import javax.xml.transform.dom.DOMSource;
 import javax.xml.transform.stream.StreamSource;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Document;
 
 import org.springframework.beans.factory.BeanClassLoaderAware;
@@ -89,17 +90,19 @@
  */
 public class XsltPayloadTransformer extends AbstractXmlTransformer implements BeanClassLoaderAware {
 
-	private final ResultTransformer resultTransformer;
+	private final @Nullable ResultTransformer resultTransformer;
 
-	private final Resource xslResource;
+	private final @Nullable Resource xslResource;
 
+	@SuppressWarnings("NullAway.Init")
 	private Templates templates;
 
-	private String transformerFactoryClassName;
+	private @Nullable String transformerFactoryClassName;
 
+	@SuppressWarnings("NullAway.Init")
 	private volatile StandardEvaluationContext evaluationContext;
 
-	private Map<String, Expression> xslParameterMappings;
+	private @Nullable Map<String, Expression> xslParameterMappings;
 
 	private SourceFactory sourceFactory = new DomSourceFactory();
 
@@ -109,15 +112,15 @@ public class XsltPayloadTransformer extends AbstractXmlTransformer implements Be
 
 	private boolean alwaysUseResultFactory = false;
 
-	private String[] xsltParamHeaders;
+	private String @Nullable [] xsltParamHeaders;
 
 	public XsltPayloadTransformer(Templates templates) {
 		this(templates, null);
 	}
 
-	private ClassLoader classLoader;
+	private @Nullable ClassLoader classLoader;
 
-	public XsltPayloadTransformer(Templates templates, ResultTransformer resultTransformer) {
+	public XsltPayloadTransformer(Templates templates, @Nullable ResultTransformer resultTransformer) {
 		Assert.notNull(templates, "'templates' must not be null.");
 		this.templates = templates;
 		this.resultTransformer = resultTransformer;
@@ -136,8 +139,8 @@ public XsltPayloadTransformer(Resource xslResource, String transformerFactoryCla
 		this(xslResource, null, transformerFactoryClassName);
 	}
 
-	public XsltPayloadTransformer(Resource xslResource, ResultTransformer resultTransformer,
-			String transformerFactoryClassName) {
+	public XsltPayloadTransformer(Resource xslResource, @Nullable ResultTransformer resultTransformer,
+			@Nullable String transformerFactoryClassName) {
 
 		Assert.notNull(xslResource, "'xslResource' must not be null.");
 		Assert.isTrue(xslResource instanceof ClassPathResource ||
@@ -230,6 +233,7 @@ protected void onInit() {
 		this.evaluationContext = ExpressionUtils.createStandardEvaluationContext(getBeanFactory());
 		if (this.templates == null) {
 			try {
+				Assert.notNull(this.xslResource, "'xslResource' must not be null.");
 				TransformerFactory transformerFactory = createTransformerFactory();
 				this.templates = transformerFactory.newTemplates(createStreamSourceOnResource(this.xslResource));
 			}

spring-integration-xml/src/main/java/org/springframework/integration/xml/transformer/package-info.java

@@ -1,4 +1,5 @@
 /**
  * Provides Transformer and Enricher implementations.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.xml.transformer;

spring-integration-xml/src/main/java/org/springframework/integration/xml/transformer/support/XPathExpressionEvaluatingHeaderValueMessageProcessor.java

@@ -16,6 +16,7 @@
 
 package org.springframework.integration.xml.transformer.support;
 
+import org.jspecify.annotations.Nullable;
 import org.w3c.dom.Node;
 
 import org.springframework.beans.BeansException;
@@ -55,9 +56,9 @@ public class XPathExpressionEvaluatingHeaderValueMessageProcessor implements Hea
 
 	private XPathEvaluationType evaluationType = XPathEvaluationType.STRING_RESULT;
 
-	private TypeDescriptor headerTypeDescriptor;
+	private @Nullable TypeDescriptor headerTypeDescriptor;
 
-	private Boolean overwrite;
+	private @Nullable Boolean overwrite;
 
 	public XPathExpressionEvaluatingHeaderValueMessageProcessor(String expression) {
 		this(expression, new DefaultXmlPayloadConverter());
@@ -107,7 +108,7 @@ public void setOverwrite(Boolean overwrite) {
 	}
 
 	@Override
-	public Boolean isOverwrite() {
+	public @Nullable Boolean isOverwrite() {
 		return this.overwrite;
 	}
 
@@ -120,7 +121,7 @@ public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
 	}
 
 	@Override
-	public Object processMessage(Message<?> message) {
+	public @Nullable Object processMessage(Message<?> message) {
 		Node node = this.converter.convertToNode(message.getPayload());
 		Object result = this.evaluationType.evaluateXPath(this.expression, node);
 		if (result instanceof String string && string.isEmpty()) {

spring-integration-xml/src/main/java/org/springframework/integration/xml/transformer/support/package-info.java

@@ -4,4 +4,5 @@
  * @since 3.0
  *
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.xml.transformer.support;