Add JSpecify nullability annotations to Spring Cloud Task

Introduce JSpecify `@NullMarked` and `@Nullable` annotations across
all modules to prevent null pointer exceptions at compile time using
ErrorProne's NullAway checker.

Changes include:

- Add `@NullMarked` to all package-info.java files to enable
  null-safety checking by default for all types in each package
- Mark nullable fields and method parameters with `@Nullable` in core
  data models (`TaskExecution`, `TaskProperties`)
- Update DAO interfaces and implementations (`TaskExecutionDao`,
  `JdbcTaskExecutionDao`, `MapTaskExecutionDao`) with proper
  nullability contracts for parameters and return types
- Add null checks using `Objects.requireNonNull` before dereferencing
  potentially nullable fields in Spring-managed beans
- Handle Spring framework patterns (`@Autowired` fields, `@Value`
  annotations, `@PostConstruct` initialization) by marking fields as
  `@Nullable` and adding runtime assertions where needed
- Update repository layer (`TaskRepository`, `SimpleTaskRepository`,
  `TaskExplorer`) with accurate null contracts
- Fix configuration classes (`DefaultTaskConfigurer`,
  `SimpleTaskAutoConfiguration`, `TaskLifecycleConfiguration`) to
  properly handle nullable dependencies
- Update batch module autoconfiguration and listener classes with
  nullability annotations
- Add nullability to stream event listeners and support classes
- Configure Maven with `.mvn/jvm.config` and `.mvn/maven.config` to
  enable ErrorProne and NullAway checking via `jspecify` profile

Author: cppwfs

.mvn/jvm.config

@@ -1 +1,11 @@
 -Xmx1024m -XX:CICompilerCount=1 -XX:TieredStopAtLevel=1 -Djava.security.egd=file:/dev/./urandom
+--add-exports jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED
+--add-exports jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED
+--add-opens jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED
+--add-opens jdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED

.mvn/maven.config

@@ -1,2 +1,3 @@
 -DaltSnapshotDeploymentRepository=repo.spring.io::default::https://repo.spring.io/libs-snapshot-local
+-Djspecify.enabled=true
 -P spring

spring-cloud-starter-single-step-batch-job/src/main/java/org/springframework/cloud/task/batch/autoconfigure/RangeConverter.java

@@ -16,6 +16,8 @@
 
 package org.springframework.cloud.task.batch.autoconfigure;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.batch.infrastructure.item.file.transform.Range;
 import org.springframework.core.convert.converter.Converter;
 
@@ -31,7 +33,7 @@
 public class RangeConverter implements Converter<String, Range> {
 
 	@Override
-	public Range convert(String source) {
+	public @Nullable Range convert(String source) {
 		if (source == null) {
 			return null;
 		}

spring-cloud-starter-single-step-batch-job/src/main/java/org/springframework/cloud/task/batch/autoconfigure/SingleStepJobAutoConfiguration.java

@@ -22,8 +22,7 @@
 import org.springframework.batch.core.job.builder.JobBuilder;
 import org.springframework.batch.core.repository.JobRepository;
 import org.springframework.batch.core.step.Step;
-import org.springframework.batch.core.step.builder.SimpleStepBuilder;
-import org.springframework.batch.core.step.builder.StepBuilder;
+import org.springframework.batch.core.step.builder.ChunkOrientedStepBuilder;
 import org.springframework.batch.infrastructure.item.ItemProcessor;
 import org.springframework.batch.infrastructure.item.ItemReader;
 import org.springframework.batch.infrastructure.item.ItemWriter;
@@ -78,16 +77,16 @@ private void validateProperties(SingleStepJobProperties properties) {
 	@ConditionalOnMissingBean
 	@ConditionalOnProperty(prefix = "spring.batch.job", name = "job-name")
 	public Job job(ItemReader<Map<String, Object>> itemReader, ItemWriter<Map<String, Object>> itemWriter) {
-
-		SimpleStepBuilder<Map<String, Object>, Map<String, Object>> stepBuilder = new StepBuilder(
-				this.properties.getStepName(), this.jobRepository)
-			.<Map<String, Object>, Map<String, Object>>chunk(this.properties.getChunkSize(), this.transactionManager)
+		Assert.state(properties.getStepName() != null, "A step name is required");
+		Assert.state(properties.getChunkSize() != null, "A chunkSize is required");
+		var chunkOrientedStepBuilder = new ChunkOrientedStepBuilder(properties.getStepName(), this.jobRepository,
+				this.properties.getChunkSize())
+			.transactionManager(this.transactionManager)
 			.reader(itemReader);
+		chunkOrientedStepBuilder.processor(this.itemProcessor);
+		Step step = chunkOrientedStepBuilder.writer(itemWriter).build();
 
-		stepBuilder.processor(this.itemProcessor);
-
-		Step step = stepBuilder.writer(itemWriter).build();
-
+		Assert.state(this.properties.getJobName() != null, "A job name is required");
 		return new JobBuilder(this.properties.getJobName(), this.jobRepository).start(step).build();
 	}
 

spring-cloud-starter-single-step-batch-job/src/main/java/org/springframework/cloud/task/batch/autoconfigure/SingleStepJobProperties.java

@@ -16,6 +16,8 @@
 
 package org.springframework.cloud.task.batch.autoconfigure;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.context.properties.ConfigurationProperties;
 
 /**
@@ -30,63 +32,63 @@ public class SingleStepJobProperties {
 	/**
 	 * Name of the step in the single step job.
 	 */
-	private String stepName;
+	private @Nullable String stepName;
 
 	/**
 	 * The number of items to process per transaction or chunk.
 	 */
-	private Integer chunkSize;
+	private @Nullable Integer chunkSize;
 
 	/**
 	 * The name of the job.
 	 */
-	private String jobName;
+	private @Nullable String jobName;
 
 	/**
 	 * Name of the step in the single step job.
 	 * @return name
 	 */
-	public String getStepName() {
+	public @Nullable String getStepName() {
 		return stepName;
 	}
 
 	/**
 	 * Set the name of the step.
 	 * @param stepName name
 	 */
-	public void setStepName(String stepName) {
+	public void setStepName(@Nullable String stepName) {
 		this.stepName = stepName;
 	}
 
 	/**
 	 * The number of items to process per transaction/chunk.
 	 * @return number of items
 	 */
-	public Integer getChunkSize() {
+	public @Nullable Integer getChunkSize() {
 		return chunkSize;
 	}
 
 	/**
 	 * Set the number of items within a transaction/chunk.
 	 * @param chunkSize number of items
 	 */
-	public void setChunkSize(Integer chunkSize) {
+	public void setChunkSize(@Nullable Integer chunkSize) {
 		this.chunkSize = chunkSize;
 	}
 
 	/**
 	 * The name of the job.
 	 * @return name
 	 */
-	public String getJobName() {
+	public @Nullable String getJobName() {
 		return jobName;
 	}
 
 	/**
 	 * Set the name of the job.
 	 * @param jobName name
 	 */
-	public void setJobName(String jobName) {
+	public void setJobName(@Nullable String jobName) {
 		this.jobName = jobName;
 	}
 

spring-cloud-starter-single-step-batch-job/src/main/java/org/springframework/cloud/task/batch/autoconfigure/flatfile/FlatFileItemReaderAutoConfiguration.java

@@ -42,6 +42,7 @@
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.cloud.task.batch.autoconfigure.RangeConverter;
 import org.springframework.context.annotation.Bean;
+import org.springframework.util.Assert;
 
 /**
  * Autconfiguration for a {@code FlatFileItemReader}.
@@ -71,6 +72,8 @@ public FlatFileItemReader<Map<String, Object>> itemReader(@Autowired(required =
 			@Autowired(required = false) LineMapper<Map<String, Object>> lineMapper,
 			@Autowired(required = false) LineCallbackHandler skippedLinesCallback,
 			@Autowired(required = false) RecordSeparatorPolicy recordSeparatorPolicy) {
+		Assert.state(this.properties.getName() != null, "A name is required");
+		Assert.state(this.properties.getResource() != null, "A resource is required");
 		FlatFileItemReaderBuilder<Map<String, Object>> mapFlatFileItemReaderBuilder = new FlatFileItemReaderBuilder<Map<String, Object>>()
 			.name(this.properties.getName())
 			.resource(this.properties.getResource())
@@ -90,6 +93,7 @@ public FlatFileItemReader<Map<String, Object>> itemReader(@Autowired(required =
 		mapFlatFileItemReaderBuilder.skippedLinesCallback(skippedLinesCallback);
 
 		if (this.properties.isDelimited()) {
+			Assert.state(this.properties.getNames() != null, "Names are required");
 			mapFlatFileItemReaderBuilder.delimited()
 				.quoteCharacter(this.properties.getQuoteCharacter())
 				.delimiter(this.properties.getDelimiter())
@@ -99,9 +103,14 @@ public FlatFileItemReader<Map<String, Object>> itemReader(@Autowired(required =
 				.fieldSetMapper(new MapFieldSetMapper());
 		}
 		else if (this.properties.isFixedLength()) {
+			Assert.state(this.properties.getNames() != null, "Names are required");
 			RangeConverter rangeConverter = new RangeConverter();
 			List<Range> ranges = new ArrayList<>();
-			this.properties.getRanges().forEach(range -> ranges.add(rangeConverter.convert(range)));
+			this.properties.getRanges().forEach(range -> {
+				Range result = rangeConverter.convert(range);
+				Assert.state(result != null, "Range String could not converted to non-null range");
+				ranges.add(result);
+			});
 			mapFlatFileItemReaderBuilder.fixedLength()
 				.columns(ranges.toArray(new Range[0]))
 				.names(this.properties.getNames())

spring-cloud-starter-single-step-batch-job/src/main/java/org/springframework/cloud/task/batch/autoconfigure/flatfile/FlatFileItemReaderProperties.java

@@ -19,6 +19,8 @@
 import java.util.ArrayList;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.batch.infrastructure.item.file.FlatFileItemReader;
 import org.springframework.batch.infrastructure.item.file.transform.DelimitedLineTokenizer;
 import org.springframework.batch.infrastructure.item.file.transform.Range;
@@ -44,7 +46,7 @@ public class FlatFileItemReaderProperties {
 	 * {@link org.springframework.batch.infrastructure.item.ExecutionContext}. Required if
 	 * {@link #setSaveState} is set to {@code true}.
 	 */
-	private String name;
+	private @Nullable String name;
 
 	/**
 	 * Configure the maximum number of items to be read.
@@ -64,7 +66,7 @@ public class FlatFileItemReaderProperties {
 	/**
 	 * The {@link Resource} to be used as input.
 	 */
-	private Resource resource;
+	private @Nullable Resource resource;
 
 	/**
 	 * Configure whether the reader should be in strict mode (require the input
@@ -118,7 +120,7 @@ public class FlatFileItemReaderProperties {
 	/**
 	 * The names of the fields to be parsed from the file.
 	 */
-	private String[] names;
+	private String @Nullable [] names;
 
 	/**
 	 * Indicates whether the number of tokens must match the number of configured fields.
@@ -150,7 +152,7 @@ public void setSaveState(boolean saveState) {
 	 * keys.
 	 * @return the name
 	 */
-	public String getName() {
+	public @Nullable String getName() {
 		return this.name;
 	}
 
@@ -161,7 +163,7 @@ public String getName() {
 	 * @param name name of the reader instance
 	 * @see org.springframework.batch.infrastructure.item.ItemStreamSupport#setName(String)
 	 */
-	public void setName(String name) {
+	public void setName(@Nullable String name) {
 		this.name = name;
 	}
 
@@ -219,7 +221,7 @@ public void setComments(List<String> comments) {
 	 * The input file for the {@code FlatFileItemReader}.
 	 * @return a Resource
 	 */
-	public Resource getResource() {
+	public @Nullable Resource getResource() {
 		return this.resource;
 	}
 
@@ -228,7 +230,7 @@ public Resource getResource() {
 	 * @param resource the input to the reader.
 	 * @see FlatFileItemReader#setResource(Resource)
 	 */
-	public void setResource(Resource resource) {
+	public void setResource(@Nullable Resource resource) {
 		this.resource = resource;
 	}
 
@@ -391,15 +393,15 @@ public void setRanges(List<String> ranges) {
 	 * Names of each column.
 	 * @return names
 	 */
-	public String[] getNames() {
+	public String @Nullable [] getNames() {
 		return this.names;
 	}
 
 	/**
 	 * The names of the fields to be parsed from the file.
 	 * @param names names of fields
 	 */
-	public void setNames(String[] names) {
+	public void setNames(String @Nullable [] names) {
 		this.names = names;
 	}
 

spring-cloud-starter-single-step-batch-job/src/main/java/org/springframework/cloud/task/batch/autoconfigure/flatfile/FlatFileItemWriterAutoConfiguration.java

@@ -35,6 +35,7 @@
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
 import org.springframework.core.io.WritableResource;
+import org.springframework.util.Assert;
 
 /**
  * Autoconfiguration for a {@code FlatFileItemWriter}.
@@ -47,7 +48,7 @@
 @AutoConfigureAfter(BatchAutoConfiguration.class)
 public class FlatFileItemWriterAutoConfiguration {
 
-	private FlatFileItemWriterProperties properties;
+	private final FlatFileItemWriterProperties properties;
 
 	@Autowired(required = false)
 	private LineAggregator<Map<String, Object>> lineAggregator;
@@ -78,7 +79,8 @@ else if ((this.properties.isFormatted() || this.properties.isDelimited()) && thi
 			throw new IllegalStateException(
 					"A LineAggregator must be configured if the " + "output is not formatted or delimited");
 		}
-
+		Assert.state(this.properties.getName() != null, "name must not be null");
+		Assert.state(this.properties.getResource() != null, "resource must not be null");
 		FlatFileItemWriterBuilder<Map<String, Object>> builder = new FlatFileItemWriterBuilder<Map<String, Object>>()
 			.name(this.properties.getName())
 			.resource((WritableResource) this.properties.getResource())
@@ -101,10 +103,13 @@ else if ((this.properties.isFormatted() || this.properties.isDelimited()) && thi
 				delimitedBuilder.fieldExtractor(this.fieldExtractor);
 			}
 			else {
+				Assert.state(this.properties.getNames() != null, "names must not be null");
 				delimitedBuilder.fieldExtractor(new MapFieldExtractor(this.properties.getNames()));
 			}
 		}
 		else if (this.properties.isFormatted()) {
+			Assert.state(this.properties.getFormat() != null, "format must not be null");
+
 			FlatFileItemWriterBuilder.FormattedBuilder<Map<String, Object>> formattedBuilder = builder.formatted()
 				.format(this.properties.getFormat())
 				.locale(this.properties.getLocale())
@@ -115,6 +120,7 @@ else if (this.properties.isFormatted()) {
 				formattedBuilder.fieldExtractor(this.fieldExtractor);
 			}
 			else {
+				Assert.state(this.properties.getNames() != null, "names must not be null");
 				formattedBuilder.fieldExtractor(new MapFieldExtractor(this.properties.getNames()));
 			}
 		}
@@ -131,7 +137,7 @@ else if (this.lineAggregator != null) {
 	 */
 	public static class MapFieldExtractor implements FieldExtractor<Map<String, Object>> {
 
-		private String[] names;
+		private final String[] names;
 
 		public MapFieldExtractor(String[] names) {
 			this.names = names;