Migrate to JSpecify annotations for nullability constraints

This change also introduces NullAway to verify that all code is
correctly annotated.

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

Author: scordio

pom.xml

@@ -156,6 +156,7 @@
 		<maven-jar-plugin.version>3.4.2</maven-jar-plugin.version>
 		<spring-javaformat-maven-plugin.version>0.0.39</spring-javaformat-maven-plugin.version>
 		<error-prone.version>2.38.0</error-prone.version>
+		<nullaway.version>0.12.7</nullaway.version>
 	</properties>
 
 	<build>
@@ -226,6 +227,8 @@
 							-Xep:UnusedMethod:OFF
 							-Xep:UnusedVariable:OFF
 							-Xep:WaitNotInLoop:OFF
+							<!-- Check JSpecify annotations -->
+							-XepOpt:NullAway:OnlyNullMarked
 						</compilerArg>
 					</compilerArgs>
 					<failOnWarning>true</failOnWarning>
@@ -235,6 +238,11 @@
 							<artifactId>error_prone_core</artifactId>
 							<version>${error-prone.version}</version>
 						</path>
+						<path>
+							<groupId>com.uber.nullaway</groupId>
+							<artifactId>nullaway</artifactId>
+							<version>${nullaway.version}</version>
+						</path>
 					</annotationProcessorPaths>
 				</configuration>
 			</plugin>

spring-batch-core/src/main/java/org/springframework/batch/core/ItemProcessListener.java

@@ -15,8 +15,9 @@
  */
 package org.springframework.batch.core;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.batch.item.ItemProcessor;
-import org.springframework.lang.Nullable;
 
 /**
  * Listener interface for the processing of an item. Implementations of this interface are

spring-batch-core/src/main/java/org/springframework/batch/core/Job.java

@@ -15,8 +15,9 @@
  */
 package org.springframework.batch.core;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.batch.core.job.DefaultJobParametersValidator;
-import org.springframework.lang.Nullable;
 
 /**
  * Batch domain object representing a job. {@code Job} is an explicit abstraction

spring-batch-core/src/main/java/org/springframework/batch/core/JobExecution.java

@@ -30,7 +30,8 @@
 import java.util.concurrent.CopyOnWriteArrayList;
 
 import org.springframework.batch.item.ExecutionContext;
-import org.springframework.lang.Nullable;
+
+import org.jspecify.annotations.Nullable;
 
 /**
  * Batch domain object representing the execution of a job.

spring-batch-core/src/main/java/org/springframework/batch/core/JobParameter.java

@@ -18,9 +18,10 @@
 
 import java.io.Serializable;
 
-import org.springframework.lang.NonNull;
 import org.springframework.util.Assert;
 
+import org.jspecify.annotations.NonNull;
+
 /**
  * Domain representation of a parameter to a batch job. The identifying flag is used to
  * indicate if the parameter is to be used as part of the identification of a job

spring-batch-core/src/main/java/org/springframework/batch/core/JobParameters.java

@@ -27,9 +27,10 @@
 import java.util.List;
 import java.util.Map;
 
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
+import org.jspecify.annotations.Nullable;
+
 /**
  * Value object representing runtime parameters to a batch job. Because the parameters
  * have no individual meaning outside of the {@code JobParameters} object they are

spring-batch-core/src/main/java/org/springframework/batch/core/JobParametersBuilder.java

@@ -24,7 +24,8 @@
 import java.util.Map;
 
 import org.springframework.batch.core.repository.explore.JobExplorer;
-import org.springframework.lang.NonNull;
+
+import org.jspecify.annotations.NonNull;
 import org.springframework.util.Assert;
 
 /**

spring-batch-core/src/main/java/org/springframework/batch/core/JobParametersIncrementer.java

@@ -15,7 +15,7 @@
  */
 package org.springframework.batch.core;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Interface for obtaining the next {@link JobParameters} object in a sequence.

spring-batch-core/src/main/java/org/springframework/batch/core/JobParametersValidator.java

@@ -15,7 +15,7 @@
  */
 package org.springframework.batch.core;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Strategy interface for a {@link Job} to use in validating its parameters for an

spring-batch-core/src/main/java/org/springframework/batch/core/SpringBatchVersion.java

@@ -15,7 +15,7 @@
  */
 package org.springframework.batch.core;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Class that exposes the Spring Batch version. Fetches the "Implementation-Version"

spring-batch-core/src/main/java/org/springframework/batch/core/StepExecution.java

@@ -24,7 +24,8 @@
 import java.util.concurrent.CopyOnWriteArrayList;
 
 import org.springframework.batch.item.ExecutionContext;
-import org.springframework.lang.Nullable;
+
+import org.jspecify.annotations.Nullable;
 import org.springframework.util.Assert;
 
 /**

spring-batch-core/src/main/java/org/springframework/batch/core/StepExecutionListener.java

@@ -15,7 +15,7 @@
  */
 package org.springframework.batch.core;
 
-import org.springframework.lang.Nullable;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Listener interface for the lifecycle of a {@link Step}.

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/JobLocator.java

@@ -15,9 +15,10 @@
  */
 package org.springframework.batch.core.configuration;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.batch.core.Job;
 import org.springframework.batch.core.launch.NoSuchJobException;
-import org.springframework.lang.Nullable;
 
 /**
  * A runtime service locator interface for retrieving job configurations by

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/annotation/package-info.java

@@ -4,7 +4,7 @@
  * @author Michael Minella
  * @author Mahmoud Ben Hassine
  */
-@NonNullApi
+@NullMarked
 package org.springframework.batch.core.configuration.annotation;
 
-import org.springframework.lang.NonNullApi;
+import org.jspecify.annotations.NullMarked;

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/package-info.java

@@ -4,7 +4,7 @@
  * @author Michael Minella
  * @author Mahmoud Ben Hassine
  */
-@NonNullApi
+@NullMarked
 package org.springframework.batch.core.configuration;
 
-import org.springframework.lang.NonNullApi;
+import org.jspecify.annotations.NullMarked;

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/support/DefaultJobLoader.java

@@ -23,6 +23,7 @@
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.batch.core.Job;
 import org.springframework.batch.core.Step;
@@ -34,7 +35,6 @@
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ConfigurableApplicationContext;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/support/GroupAwareJob.java

@@ -15,11 +15,12 @@
  */
 package org.springframework.batch.core.configuration.support;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.batch.core.Job;
 import org.springframework.batch.core.JobExecution;
 import org.springframework.batch.core.JobParametersIncrementer;
 import org.springframework.batch.core.JobParametersValidator;
-import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 
 /**

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/support/MapJobRegistry.java

@@ -23,6 +23,8 @@
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.batch.core.Job;
 import org.springframework.batch.core.configuration.DuplicateJobException;
 import org.springframework.batch.core.configuration.JobRegistry;
@@ -31,7 +33,6 @@
 import org.springframework.beans.factory.SmartInitializingSingleton;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/support/package-info.java

@@ -4,7 +4,7 @@
  * @author Michael Minella
  * @author Mahmoud Ben Hassine
  */
-@NonNullApi
+@NullMarked
 package org.springframework.batch.core.configuration.support;
 
-import org.springframework.lang.NonNullApi;
+import org.jspecify.annotations.NullMarked;

spring-batch-core/src/main/java/org/springframework/batch/core/configuration/xml/package-info.java

@@ -4,7 +4,7 @@
  * @author Michael Minella
  * @author Mahmoud Ben Hassine
  */
-@NonNullApi
+@NullMarked
 package org.springframework.batch.core.configuration.xml;
 
-import org.springframework.lang.NonNullApi;
+import org.jspecify.annotations.NullMarked;

spring-batch-core/src/main/java/org/springframework/batch/core/converter/DefaultJobParametersConverter.java

@@ -20,12 +20,13 @@
 import java.util.Properties;
 
 import org.springframework.batch.core.JobParameter;
+
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
 import org.springframework.batch.core.JobParameters;
 import org.springframework.batch.core.JobParametersBuilder;
 import org.springframework.core.convert.support.ConfigurableConversionService;
 import org.springframework.core.convert.support.DefaultConversionService;
-import org.springframework.lang.NonNull;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 

spring-batch-core/src/main/java/org/springframework/batch/core/converter/JobParametersConverter.java

@@ -19,8 +19,9 @@
 import java.util.Properties;
 
 import org.springframework.batch.core.JobParameters;
+
+import org.jspecify.annotations.Nullable;
 import org.springframework.batch.core.JobParametersBuilder;
-import org.springframework.lang.Nullable;
 
 /**
  * A factory for {@link JobParameters} instances. A job can be executed with many possible

spring-batch-core/src/main/java/org/springframework/batch/core/converter/package-info.java

@@ -5,7 +5,7 @@
  * @author Michael Minella
  * @author Mahmoud Ben Hassine
  */
-@NonNullApi
+@NullMarked
 package org.springframework.batch.core.converter;
 
-import org.springframework.lang.NonNullApi;
+import org.jspecify.annotations.NullMarked;

spring-batch-core/src/main/java/org/springframework/batch/core/job/AbstractJob.java

@@ -29,6 +29,7 @@
 import io.micrometer.observation.ObservationRegistry;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.batch.core.BatchStatus;
 import org.springframework.batch.core.ExitStatus;
@@ -58,7 +59,6 @@
 import org.springframework.batch.repeat.RepeatException;
 import org.springframework.beans.factory.BeanNameAware;
 import org.springframework.beans.factory.InitializingBean;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 

spring-batch-core/src/main/java/org/springframework/batch/core/job/CompositeJobParametersValidator.java

@@ -18,10 +18,11 @@
 import java.util.List;
 
 import org.springframework.batch.core.JobParameters;
+
+import org.jspecify.annotations.Nullable;
 import org.springframework.batch.core.JobParametersInvalidException;
 import org.springframework.batch.core.JobParametersValidator;
 import org.springframework.beans.factory.InitializingBean;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

spring-batch-core/src/main/java/org/springframework/batch/core/job/DefaultJobParametersValidator.java

@@ -22,12 +22,12 @@
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.batch.core.JobParameters;
 import org.springframework.batch.core.JobParametersInvalidException;
 import org.springframework.batch.core.JobParametersValidator;
 import org.springframework.beans.factory.InitializingBean;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**

spring-batch-core/src/main/java/org/springframework/batch/core/job/builder/package-info.java

@@ -4,7 +4,7 @@
  * @author Michael Minella
  * @author Mahmoud Ben Hassine
  */
-@NonNullApi
+@NullMarked
 package org.springframework.batch.core.job.builder;
 
-import org.springframework.lang.NonNullApi;
+import org.jspecify.annotations.NullMarked;

spring-batch-core/src/main/java/org/springframework/batch/core/job/flow/FlowExecutor.java

@@ -15,13 +15,14 @@
  */
 package org.springframework.batch.core.job.flow;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.batch.core.JobExecution;
 import org.springframework.batch.core.JobInterruptedException;
 import org.springframework.batch.core.StartLimitExceededException;
 import org.springframework.batch.core.Step;
 import org.springframework.batch.core.StepExecution;
 import org.springframework.batch.core.repository.JobRestartException;
-import org.springframework.lang.Nullable;
 
 /**
  * Context and execution strategy for {@link FlowJob} to allow it to delegate its

spring-batch-core/src/main/java/org/springframework/batch/core/job/flow/JobExecutionDecider.java

@@ -15,9 +15,10 @@
  */
 package org.springframework.batch.core.job.flow;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.batch.core.JobExecution;
 import org.springframework.batch.core.StepExecution;
-import org.springframework.lang.Nullable;
 
 /**
  * Interface allowing for programmatic access to the decision on what the status of a flow

spring-batch-core/src/main/java/org/springframework/batch/core/job/flow/JobFlowExecutor.java

@@ -16,6 +16,8 @@
 
 package org.springframework.batch.core.job.flow;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.batch.core.BatchStatus;
 import org.springframework.batch.core.ExitStatus;
 import org.springframework.batch.core.JobExecution;
@@ -26,7 +28,6 @@
 import org.springframework.batch.core.job.StepHandler;
 import org.springframework.batch.core.repository.JobRepository;
 import org.springframework.batch.core.repository.JobRestartException;
-import org.springframework.lang.Nullable;
 
 /**
  * Implementation of {@link FlowExecutor} for use in components that need to execute a

spring-batch-core/src/main/java/org/springframework/batch/core/job/flow/package-info.java

@@ -4,7 +4,7 @@
  * @author Michael Minella
  * @author Mahmoud Ben Hassine
  */
-@NonNullApi
+@NullMarked
 package org.springframework.batch.core.job.flow;
 
-import org.springframework.lang.NonNullApi;
+import org.jspecify.annotations.NullMarked;

spring-batch-core/src/main/java/org/springframework/batch/core/job/flow/support/StateTransition.java

@@ -18,12 +18,13 @@
 import org.springframework.batch.core.ExitStatus;
 import org.springframework.batch.core.job.flow.State;
 import org.springframework.batch.support.PatternMatcher;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
 import java.util.Objects;
 
+import org.jspecify.annotations.Nullable;
+
 /**
  * Value object representing a potential transition from one {@link State} to another. The
  * originating State name and the next {@link State} to execute are linked by a pattern