Add nullability annotations to core/spring-boot

See gh-46587

Author: mhalbritter

config/checkstyle/checkstyle-suppressions.xml

@@ -86,4 +86,8 @@
 	<suppress files="ConfigurationPropertyCaching\.java" checks="SpringJavadoc" message="\@since"/>
 	<suppress files="StructuredLoggingJsonMembersCustomizer\.java" checks="SpringJavadoc" message="\@since"/>
 	<suppress files="FieldValues\.java" checks="SimplifyBooleanExpression" />
+	<!-- jspecify: https://github.com/spring-io/spring-javaformat/issues/454 -->
+	<suppress files="PemPrivateKeyParser\.java" checks="NoWhitespaceBefore" message="'...' is preceded with whitespace"/>
+	<suppress files="Bindable\.java" checks="NoWhitespaceBefore" message="'...' is preceded with whitespace"/>
+	<suppress files="LambdaSafe\.java" checks="NoWhitespaceBefore" message="'...' is preceded with whitespace"/>
 </suppressions>

core/spring-boot/src/main/java/org/springframework/boot/ApplicationArguments.java

@@ -19,6 +19,8 @@
 import java.util.List;
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
+
 /**
  * Provides access to the arguments that were used to run a {@link SpringApplication}.
  *
@@ -63,7 +65,7 @@ public interface ApplicationArguments {
 	 * @param name the name of the option
 	 * @return a list of option values for the given name
 	 */
-	List<String> getOptionValues(String name);
+	@Nullable List<String> getOptionValues(String name);
 
 	/**
 	 * Return the collection of non-option arguments parsed.

core/spring-boot/src/main/java/org/springframework/boot/ApplicationContextFactory.java

@@ -18,6 +18,8 @@
 
 import java.util.function.Supplier;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.BeanUtils;
 import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.core.env.ConfigurableEnvironment;
@@ -46,11 +48,12 @@ public interface ApplicationContextFactory {
 	 * Return the {@link Environment} type expected to be set on the
 	 * {@link #create(WebApplicationType) created} application context. The result of this
 	 * method can be used to convert an existing environment instance to the correct type.
-	 * @param webApplicationType the web application type
+	 * @param webApplicationType the web application type or {@code null}
 	 * @return the expected application context type or {@code null} to use the default
 	 * @since 2.6.14
 	 */
-	default Class<? extends ConfigurableEnvironment> getEnvironmentType(WebApplicationType webApplicationType) {
+	default @Nullable Class<? extends ConfigurableEnvironment> getEnvironmentType(
+			@Nullable WebApplicationType webApplicationType) {
 		return null;
 	}
 
@@ -59,11 +62,11 @@ default Class<? extends ConfigurableEnvironment> getEnvironmentType(WebApplicati
 	 * {@link #create(WebApplicationType) created} application context. The result of this
 	 * method must match the type returned by
 	 * {@link #getEnvironmentType(WebApplicationType)}.
-	 * @param webApplicationType the web application type
+	 * @param webApplicationType the web application type or {@code null}
 	 * @return an environment instance or {@code null} to use the default
 	 * @since 2.6.14
 	 */
-	default ConfigurableEnvironment createEnvironment(WebApplicationType webApplicationType) {
+	default @Nullable ConfigurableEnvironment createEnvironment(@Nullable WebApplicationType webApplicationType) {
 		return null;
 	}
 
@@ -73,7 +76,7 @@ default ConfigurableEnvironment createEnvironment(WebApplicationType webApplicat
 	 * @param webApplicationType the web application type
 	 * @return the newly created application context
 	 */
-	ConfigurableApplicationContext create(WebApplicationType webApplicationType);
+	ConfigurableApplicationContext create(@Nullable WebApplicationType webApplicationType);
 
 	/**
 	 * Creates an {@code ApplicationContextFactory} that will create contexts by

core/spring-boot/src/main/java/org/springframework/boot/ApplicationEnvironment.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.context.properties.source.ConfigurationPropertySources;
 import org.springframework.core.env.ConfigurablePropertyResolver;
 import org.springframework.core.env.MutablePropertySources;
@@ -29,12 +31,12 @@
 class ApplicationEnvironment extends StandardEnvironment {
 
 	@Override
-	protected String doGetActiveProfilesProperty() {
+	protected @Nullable String doGetActiveProfilesProperty() {
 		return null;
 	}
 
 	@Override
-	protected String doGetDefaultProfilesProperty() {
+	protected @Nullable String doGetDefaultProfilesProperty() {
 		return null;
 	}
 

core/spring-boot/src/main/java/org/springframework/boot/ApplicationInfoPropertySource.java

@@ -19,6 +19,8 @@
 import java.util.HashMap;
 import java.util.Map;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.boot.origin.Origin;
 import org.springframework.boot.origin.OriginLookup;
 import org.springframework.boot.system.ApplicationPid;
@@ -38,7 +40,7 @@ class ApplicationInfoPropertySource extends MapPropertySource implements OriginL
 
 	static final String NAME = "applicationInfo";
 
-	ApplicationInfoPropertySource(Class<?> mainClass) {
+	ApplicationInfoPropertySource(@Nullable Class<?> mainClass) {
 		super(NAME, getProperties(readVersion(mainClass)));
 	}
 
@@ -47,7 +49,7 @@ class ApplicationInfoPropertySource extends MapPropertySource implements OriginL
 	}
 
 	@Override
-	public Origin getOrigin(String key) {
+	public @Nullable Origin getOrigin(String key) {
 		return null;
 	}
 
@@ -56,7 +58,7 @@ public boolean isImmutable() {
 		return true;
 	}
 
-	private static Map<String, Object> getProperties(String applicationVersion) {
+	private static Map<String, Object> getProperties(@Nullable String applicationVersion) {
 		Map<String, Object> result = new HashMap<>();
 		if (StringUtils.hasText(applicationVersion)) {
 			result.put("spring.application.version", applicationVersion);
@@ -68,7 +70,7 @@ private static Map<String, Object> getProperties(String applicationVersion) {
 		return result;
 	}
 
-	private static String readVersion(Class<?> applicationClass) {
+	private static @Nullable String readVersion(@Nullable Class<?> applicationClass) {
 		Package sourcePackage = (applicationClass != null) ? applicationClass.getPackage() : null;
 		return (sourcePackage != null) ? sourcePackage.getImplementationVersion() : null;
 	}

core/spring-boot/src/main/java/org/springframework/boot/ApplicationProperties.java

@@ -19,12 +19,15 @@
 import java.util.LinkedHashSet;
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.aot.hint.RuntimeHints;
 import org.springframework.aot.hint.RuntimeHintsRegistrar;
 import org.springframework.boot.Banner.Mode;
 import org.springframework.boot.context.properties.bind.BindableRuntimeHintsRegistrar;
 import org.springframework.boot.logging.LoggingSystemProperty;
 import org.springframework.core.env.Environment;
+import org.springframework.util.Assert;
 
 /**
  * Spring application properties.
@@ -48,7 +51,7 @@ class ApplicationProperties {
 	/**
 	 * Mode used to display the banner when the application runs.
 	 */
-	private Banner.Mode bannerMode;
+	private Banner.@Nullable Mode bannerMode;
 
 	/**
 	 * Whether to keep the application alive even if there are no more non-daemon threads.
@@ -80,7 +83,7 @@ class ApplicationProperties {
 	 * Flag to explicitly request a specific type of web application. If not set,
 	 * auto-detected based on the classpath.
 	 */
-	private WebApplicationType webApplicationType;
+	private @Nullable WebApplicationType webApplicationType;
 
 	boolean isAllowBeanDefinitionOverriding() {
 		return this.allowBeanDefinitionOverriding;
@@ -102,12 +105,13 @@ Mode getBannerMode(Environment environment) {
 		if (this.bannerMode != null) {
 			return this.bannerMode;
 		}
-		boolean structuredLoggingEnabled = environment
-			.containsProperty(LoggingSystemProperty.CONSOLE_STRUCTURED_FORMAT.getApplicationPropertyName());
+		String applicationPropertyName = LoggingSystemProperty.CONSOLE_STRUCTURED_FORMAT.getApplicationPropertyName();
+		Assert.state(applicationPropertyName != null, "applicationPropertyName must not be null");
+		boolean structuredLoggingEnabled = environment.containsProperty(applicationPropertyName);
 		return (structuredLoggingEnabled) ? Mode.OFF : Banner.Mode.CONSOLE;
 	}
 
-	void setBannerMode(Mode bannerMode) {
+	void setBannerMode(@Nullable Mode bannerMode) {
 		this.bannerMode = bannerMode;
 	}
 
@@ -151,18 +155,18 @@ void setSources(Set<String> sources) {
 		this.sources = new LinkedHashSet<>(sources);
 	}
 
-	WebApplicationType getWebApplicationType() {
+	@Nullable WebApplicationType getWebApplicationType() {
 		return this.webApplicationType;
 	}
 
-	void setWebApplicationType(WebApplicationType webApplicationType) {
+	void setWebApplicationType(@Nullable WebApplicationType webApplicationType) {
 		this.webApplicationType = webApplicationType;
 	}
 
 	static class ApplicationPropertiesRuntimeHints implements RuntimeHintsRegistrar {
 
 		@Override
-		public void registerHints(RuntimeHints hints, ClassLoader classLoader) {
+		public void registerHints(RuntimeHints hints, @Nullable ClassLoader classLoader) {
 			BindableRuntimeHintsRegistrar.forTypes(ApplicationProperties.class).registerHints(hints, classLoader);
 		}
 

core/spring-boot/src/main/java/org/springframework/boot/Banner.java

@@ -18,6 +18,8 @@
 
 import java.io.PrintStream;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.core.env.Environment;
 
 /**
@@ -34,10 +36,10 @@ public interface Banner {
 	/**
 	 * Print the banner to the specified print stream.
 	 * @param environment the spring environment
-	 * @param sourceClass the source class for the application
+	 * @param sourceClass the source class for the application or {@code null}
 	 * @param out the output print stream
 	 */
-	void printBanner(Environment environment, Class<?> sourceClass, PrintStream out);
+	void printBanner(Environment environment, @Nullable Class<?> sourceClass, PrintStream out);
 
 	/**
 	 * An enumeration of possible values for configuring the Banner.

core/spring-boot/src/main/java/org/springframework/boot/BeanDefinitionLoader.java

@@ -23,6 +23,7 @@
 import java.util.regex.Pattern;
 
 import groovy.lang.Closure;
+import org.jspecify.annotations.Nullable;
 
 import org.springframework.beans.BeanUtils;
 import org.springframework.beans.factory.BeanDefinitionStoreException;
@@ -68,11 +69,11 @@ class BeanDefinitionLoader {
 
 	private final AbstractBeanDefinitionReader xmlReader;
 
-	private final BeanDefinitionReader groovyReader;
+	private final @Nullable BeanDefinitionReader groovyReader;
 
 	private final ClassPathBeanDefinitionScanner scanner;
 
-	private ResourceLoader resourceLoader;
+	private @Nullable ResourceLoader resourceLoader;
 
 	/**
 	 * Create a new {@link BeanDefinitionLoader} that will load beans into the specified
@@ -86,7 +87,7 @@ class BeanDefinitionLoader {
 		this.sources = sources;
 		this.annotatedReader = new AnnotatedBeanDefinitionReader(registry);
 		this.xmlReader = new XmlBeanDefinitionReader(registry);
-		this.groovyReader = (isGroovyPresent() ? new GroovyBeanDefinitionReader(registry) : null);
+		this.groovyReader = isGroovyPresent() ? new GroovyBeanDefinitionReader(registry) : null;
 		this.scanner = new ClassPathBeanDefinitionScanner(registry);
 		this.scanner.addExcludeFilter(new ClassExcludeFilter(sources));
 	}
@@ -152,7 +153,7 @@ private void load(Object source) {
 	}
 
 	private void load(Class<?> source) {
-		if (isGroovyPresent() && GroovyBeanDefinitionSource.class.isAssignableFrom(source)) {
+		if (this.groovyReader != null && GroovyBeanDefinitionSource.class.isAssignableFrom(source)) {
 			// Any GroovyLoaders added in beans{} DSL can contribute beans here
 			GroovyBeanDefinitionSource loader = BeanUtils.instantiateClass(source, GroovyBeanDefinitionSource.class);
 			((GroovyBeanDefinitionReader) this.groovyReader).beans(loader.getBeans());
@@ -163,7 +164,9 @@ private void load(Class<?> source) {
 	}
 
 	private void load(Resource source) {
-		if (source.getFilename().endsWith(".groovy")) {
+		String filename = source.getFilename();
+		Assert.state(filename != null, "Source has no filename");
+		if (filename.endsWith(".groovy")) {
 			if (this.groovyReader == null) {
 				throw new BeanDefinitionStoreException("Cannot load Groovy beans without Groovy on classpath");
 			}
@@ -231,7 +234,7 @@ private Resource[] findResources(String source) {
 		}
 	}
 
-	private boolean isLoadCandidate(Resource resource) {
+	private boolean isLoadCandidate(@Nullable Resource resource) {
 		if (resource == null || !resource.exists()) {
 			return false;
 		}
@@ -253,7 +256,7 @@ private boolean isLoadCandidate(Resource resource) {
 		return true;
 	}
 
-	private Package findPackage(CharSequence source) {
+	private @Nullable Package findPackage(CharSequence source) {
 		Package pkg = getClass().getClassLoader().getDefinedPackage(source.toString());
 		if (pkg != null) {
 			return pkg;
@@ -264,7 +267,9 @@ private Package findPackage(CharSequence source) {
 			Resource[] resources = resolver
 				.getResources(ClassUtils.convertClassNameToResourcePath(source.toString()) + "/*.class");
 			for (Resource resource : resources) {
-				String className = StringUtils.stripFilenameExtension(resource.getFilename());
+				String filename = resource.getFilename();
+				Assert.state(filename != null, "No filename available");
+				String className = StringUtils.stripFilenameExtension(filename);
 				load(Class.forName(source + "." + className));
 				break;
 			}

core/spring-boot/src/main/java/org/springframework/boot/BootstrapContext.java

@@ -18,6 +18,8 @@
 
 import java.util.function.Supplier;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.context.ApplicationContext;
 import org.springframework.core.env.Environment;
 
@@ -41,7 +43,7 @@ public interface BootstrapContext {
 	 * @return the instance managed by the context
 	 * @throws IllegalStateException if the type has not been registered
 	 */
-	<T> T get(Class<T> type) throws IllegalStateException;
+	<T> @Nullable T get(Class<T> type) throws IllegalStateException;
 
 	/**
 	 * Return an instance from the context if the type has been registered. The instance
@@ -51,7 +53,7 @@ public interface BootstrapContext {
 	 * @param other the instance to use if the type has not been registered
 	 * @return the instance
 	 */
-	<T> T getOrElse(Class<T> type, T other);
+	<T> @Nullable T getOrElse(Class<T> type, @Nullable T other);
 
 	/**
 	 * Return an instance from the context if the type has been registered. The instance
@@ -61,7 +63,7 @@ public interface BootstrapContext {
 	 * @param other a supplier for the instance to use if the type has not been registered
 	 * @return the instance
 	 */
-	<T> T getOrElseSupply(Class<T> type, Supplier<T> other);
+	<T> @Nullable T getOrElseSupply(Class<T> type, Supplier<@Nullable T> other);
 
 	/**
 	 * Return an instance from the context if the type has been registered. The instance
@@ -74,7 +76,8 @@ public interface BootstrapContext {
 	 * @throws X if the type has not been registered
 	 * @throws IllegalStateException if the type has not been registered
 	 */
-	<T, X extends Throwable> T getOrElseThrow(Class<T> type, Supplier<? extends X> exceptionSupplier) throws X;
+	<T, X extends Throwable> @Nullable T getOrElseThrow(Class<T> type, Supplier<? extends X> exceptionSupplier)
+			throws X;
 
 	/**
 	 * Return if a registration exists for the given type.