Fix NullAway findings

Signed-off-by: Stefano Cordio <stefano.cordio@gmail.com>

Author: scordio

pom.xml

@@ -191,6 +191,7 @@
 							<!-- Check JSpecify annotations -->
 							-Xep:NullAway:ERROR
 							-XepOpt:NullAway:OnlyNullMarked
+							-XepOpt:NullAway:CustomContractAnnotations=org.springframework.lang.Contract
 						</compilerArg>
 					</compilerArgs>
 					<annotationProcessorPaths>

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/Chunk.java

@@ -16,6 +16,8 @@
 
 package org.springframework.batch.item;
 
+import org.jspecify.annotations.Nullable;
+
 import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -34,6 +36,7 @@
  * @author Dave Syer
  * @author Mahmoud Ben Hassine
  * @author Jinwoo Bae
+ * @author Stefano Cordio
  * @since 2.0
  */
 public class Chunk<W> implements Iterable<W>, Serializable {
@@ -44,7 +47,7 @@ public class Chunk<W> implements Iterable<W>, Serializable {
 
 	private final List<Exception> errors = new ArrayList<>();
 
-	private Object userData;
+	private @Nullable Object userData;
 
 	private boolean end;
 
@@ -64,8 +67,7 @@ public Chunk(List<? extends W> items) {
 		this(items, null);
 	}
 
-	public Chunk(List<? extends W> items, List<SkipWrapper<W>> skips) {
-		super();
+	public Chunk(@Nullable List<? extends W> items, @Nullable List<SkipWrapper<W>> skips) {
 		if (items != null) {
 			this.items.addAll(items);
 		}
@@ -200,7 +202,7 @@ public void clearSkips() {
 		skips.clear();
 	}
 
-	public Object getUserData() {
+	public @Nullable Object getUserData() {
 		return userData;
 	}
 
@@ -247,9 +249,9 @@ public int hashCode() {
 	 */
 	public class ChunkIterator implements Iterator<W> {
 
-		final private Iterator<W> iterator;
+		private final Iterator<W> iterator;
 
-		private W next;
+		private @Nullable W next;
 
 		public ChunkIterator(List<W> items) {
 			iterator = items.iterator();

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/ItemStreamException.java

@@ -15,12 +15,15 @@
  */
 package org.springframework.batch.item;
 
+import org.jspecify.annotations.Nullable;
+
 /**
  * Exception representing any errors encountered while processing a stream.
  *
  * @author Dave Syer
  * @author Lucas Ward
  * @author Mahmoud Ben Hassine
+ * @author Stefano Cordio
  */
 public class ItemStreamException extends RuntimeException {
 
@@ -33,11 +36,10 @@ public ItemStreamException(String message) {
 
 	/**
 	 * Constructs a new instance with a message and nested exception.
-	 * @param msg the exception message.
+	 * @param msg the exception message (can be {@code null}).
 	 * @param nested the cause of the exception.
-	 *
 	 */
-	public ItemStreamException(String msg, Throwable nested) {
+	public ItemStreamException(@Nullable String msg, Throwable nested) {
 		super(msg, nested);
 	}
 

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/ItemStreamSupport.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.batch.item;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.batch.item.util.ExecutionContextUserSupport;
 
 /**
@@ -23,6 +24,7 @@
  * @author Dave Syer
  * @author Dean de Bree
  * @author Mahmoud Ben Hassine
+ * @author Stefano Cordio
  *
  */
 public abstract class ItemStreamSupport implements ItemStream {
@@ -43,7 +45,7 @@ public void setName(String name) {
 	 * Get the name of the component
 	 * @return the name of the component
 	 */
-	public String getName() {
+	public @Nullable String getName() {
 		return executionContextUserSupport.getName();
 	}
 

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/KeyValueItemWriter.java

@@ -12,6 +12,7 @@
  */
 package org.springframework.batch.item;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.util.Assert;
@@ -22,21 +23,20 @@
  *
  * @author David Turanski
  * @author Mahmoud Ben Hassine
+ * @author Stefano Cordio
  * @since 2.2
  *
  */
 public abstract class KeyValueItemWriter<K, V> implements ItemWriter<V>, InitializingBean {
 
-	protected Converter<V, K> itemKeyMapper;
+	protected @Nullable Converter<V, K> itemKeyMapper;
 
 	protected boolean delete;
 
 	@Override
-	public void write(Chunk<? extends V> items) throws Exception {
-		if (items == null) {
-			return;
-		}
-		for (V item : items) {
+	public void write(Chunk<? extends V> chunk) throws Exception {
+		for (V item : chunk) {
+			@SuppressWarnings({ "DataFlowIssue", "NullAway" })
 			K key = itemKeyMapper.convert(item);
 			writeKeyValue(key, item);
 		}
@@ -55,7 +55,7 @@ protected void flush() throws Exception {
 	 * @param key the key
 	 * @param value the item
 	 */
-	protected abstract void writeKeyValue(K key, V value);
+	protected abstract void writeKeyValue(@Nullable K key, V value);
 
 	/**
 	 * afterPropertiesSet() hook

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/SkipWrapper.java

@@ -23,13 +23,14 @@
  *
  * @author Dave Syer
  * @author Mahmoud Ben Hassine
+ * @author Stefano Cordio
  *
  */
 public class SkipWrapper<T> {
 
-	final private Throwable exception;
+	private final @Nullable Throwable exception;
 
-	final private T item;
+	private final @Nullable T item;
 
 	/**
 	 * @param item the item being wrapped.
@@ -38,7 +39,7 @@ public SkipWrapper(T item) {
 		this(item, null);
 	}
 
-	public SkipWrapper(T item, @Nullable Throwable e) {
+	public SkipWrapper(@Nullable T item, @Nullable Throwable e) {
 		this.item = item;
 		this.exception = e;
 	}
@@ -55,7 +56,7 @@ public SkipWrapper(T item, @Nullable Throwable e) {
 	 * Public getter for the item.
 	 * @return the item
 	 */
-	public T getItem() {
+	public @Nullable T getItem() {
 		return item;
 	}
 

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/SpELItemKeyMapper.java

@@ -12,30 +12,29 @@
  */
 package org.springframework.batch.item;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.expression.Expression;
-import org.springframework.expression.ExpressionParser;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
 
 /**
  * An implementation of {@link Converter} that uses SpEL to map a Value to a key
  *
  * @author David Turanski
+ * @author Stefano Cordio
  * @since 2.2
  */
 public class SpELItemKeyMapper<K, V> implements Converter<V, K> {
 
-	private final ExpressionParser parser = new SpelExpressionParser();
-
 	private final Expression parsedExpression;
 
 	public SpELItemKeyMapper(String keyExpression) {
-		parsedExpression = parser.parseExpression(keyExpression);
+		parsedExpression = new SpelExpressionParser().parseExpression(keyExpression);
 	}
 
 	@SuppressWarnings("unchecked")
 	@Override
-	public K convert(V item) {
+	public @Nullable K convert(V item) {
 		return (K) parsedExpression.getValue(item);
 	}
 

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/adapter/AbstractMethodInvokingDelegator.java

@@ -22,6 +22,7 @@
 import java.util.Arrays;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
@@ -41,12 +42,13 @@
  * @author Robert Kasanicky
  * @author Mahmoud Ben Hassine
  * @author Glenn Renfro
+ * @author Stefano Cordio
  */
 public abstract class AbstractMethodInvokingDelegator<T> implements InitializingBean {
 
-	private Object targetObject;
+	private @Nullable Object targetObject;
 
-	private String targetMethod;
+	private @Nullable String targetMethod;
 
 	private Object[] arguments;
 
@@ -88,7 +90,7 @@ protected T invokeDelegateMethodWithArguments(Object[] args) throws Exception {
 	/**
 	 * Create a new configured instance of {@link MethodInvoker}.
 	 */
-	private MethodInvoker createMethodInvoker(Object targetObject, String targetMethod) {
+	private MethodInvoker createMethodInvoker(@Nullable Object targetObject, @Nullable String targetMethod) {
 		HippyMethodInvoker invoker = new HippyMethodInvoker();
 		invoker.setTargetObject(targetObject);
 		invoker.setTargetMethod(targetMethod);
@@ -220,15 +222,15 @@ protected Object[] getArguments() {
 	 * @return the object on which the method will be invoked.
 	 * @since 5.1
 	 */
-	protected Object getTargetObject() {
+	protected @Nullable Object getTargetObject() {
 		return targetObject;
 	}
 
 	/**
 	 * @return the name of the method to be invoked.
 	 * @since 5.1
 	 */
-	protected String getTargetMethod() {
+	protected @Nullable String getTargetMethod() {
 		return targetMethod;
 	}
 

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/adapter/HippyMethodInvoker.java

@@ -23,8 +23,8 @@
 
 /**
  * A {@link MethodInvoker} that is a bit relaxed about its arguments. You can give it
- * arguments in the wrong order or you can give it too many arguments and it will try and
- * find a method that matches a subset.
+ * arguments in the wrong order, or you can give it too many arguments, and it will try
+ * and find a method that matches a subset.
  *
  * @author Dave Syer
  * @since 2.1

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/adapter/PropertyExtractingDelegatingItemWriter.java

@@ -16,8 +16,7 @@
 
 package org.springframework.batch.item.adapter;
 
-import java.util.Arrays;
-
+import org.jspecify.annotations.Nullable;
 import org.springframework.batch.item.Chunk;
 import org.springframework.batch.item.ItemWriter;
 import org.springframework.beans.BeanWrapper;
@@ -41,7 +40,7 @@
 public class PropertyExtractingDelegatingItemWriter<T> extends AbstractMethodInvokingDelegator<T>
 		implements ItemWriter<T> {
 
-	private String[] fieldsUsedAsTargetMethodArguments;
+	private @Nullable String[] fieldsUsedAsTargetMethodArguments;
 
 	/**
 	 * Extracts values from item's fields named in fieldsUsedAsTargetMethodArguments and