GH-2334 - Fix compiler and IDE warnings where appropriate.

Went through all the compiler and IDE warnings and fixed all compiler warnings and in the process setting the build to fail if any new one appears.
Most of them are unchecked conversions, which we cannot avoid in all places. Those have been surpressed.

This closes #2334.

Author: michael-simons

pom.xml

@@ -720,6 +720,23 @@
 					</execution>
 				</executions>
 			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<executions>
+					<execution>
+						<goals>
+							<goal>compile</goal>
+						</goals>
+						<configuration combine.self="append">
+							<compilerArgs>
+								<arg>-Xlint:all,-options,-path</arg>
+								<arg>-Werror</arg>
+							</compilerArgs>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
 		</plugins>
 
 	</build>

src/main/java/org/springframework/data/neo4j/config/Neo4jCdiConfigurationSupport.java

@@ -72,19 +72,19 @@ public Neo4jOperations neo4jOperations(
 	}
 
 	@Produces @Singleton
-	public Neo4jClient neo4jClient(Driver driver) {
+	public Neo4jClient neo4jClient(@SuppressWarnings("CdiInjectionPointsInspection") Driver driver) {
 		return Neo4jClient.create(driver);
 	}
 
 	@Produces @Singleton
-	public Neo4jMappingContext neo4jMappingContext(Driver driver, @Any Instance<Neo4jConversions> neo4JConversions) {
+	public Neo4jMappingContext neo4jMappingContext(@SuppressWarnings("CdiInjectionPointsInspection") Driver driver, @Any Instance<Neo4jConversions> neo4JConversions) {
 
 		return new Neo4jMappingContext(resolve(neo4JConversions), driver.defaultTypeSystem());
 	}
 
 	@Produces @Singleton
 	public PlatformTransactionManager transactionManager(
-			Driver driver, @Any Instance<DatabaseSelectionProvider> databaseNameProvider) {
+			@SuppressWarnings("CdiInjectionPointsInspection") Driver driver, @Any Instance<DatabaseSelectionProvider> databaseNameProvider) {
 
 		return new Neo4jTransactionManager(driver, resolve(databaseNameProvider));
 	}

src/main/java/org/springframework/data/neo4j/config/Neo4jCdiExtension.java

@@ -17,7 +17,6 @@
 
 import java.lang.annotation.Annotation;
 import java.util.Map;
-import java.util.Optional;
 import java.util.Set;
 
 import javax.enterprise.event.Observes;
@@ -81,8 +80,7 @@ void addNeo4jBeansProducer(@Observes BeforeBeanDiscovery event) {
 
 	void registerRepositoryFactoryBeanPerRepositoryType(@Observes AfterBeanDiscovery event, BeanManager beanManager) {
 
-		Optional<CustomRepositoryImplementationDetector> optionalCustomRepositoryImplementationDetector =
-				Optional.ofNullable(getCustomImplementationDetector());
+		CustomRepositoryImplementationDetector optionalCustomRepositoryImplementationDetector = getCustomImplementationDetector();
 
 		for (Map.Entry<Class<?>, Set<Annotation>> entry : getRepositoryTypes()) {
 

src/main/java/org/springframework/data/neo4j/config/Neo4jEntityScanner.java

@@ -74,8 +74,7 @@ private Neo4jEntityScanner(@Nullable ResourceLoader resourceLoader) {
 	 * @return a set of entity classes
 	 * @throws ClassNotFoundException if an entity class cannot be loaded
 	 */
-	@SafeVarargs
-	public final Set<Class<?>> scan(String... basePackages) throws ClassNotFoundException {
+	public Set<Class<?>> scan(String... basePackages) throws ClassNotFoundException {
 		return scan(Arrays.stream(basePackages).collect(Collectors.toList()));
 	}
 
@@ -105,7 +104,10 @@ public Set<Class<?>> scan(Collection<String> packages) throws ClassNotFoundExcep
 		for (String basePackage : packages) {
 			if (StringUtils.hasText(basePackage)) {
 				for (BeanDefinition candidate : scanner.findCandidateComponents(basePackage)) {
-					entitySet.add(ClassUtils.forName(candidate.getBeanClassName(), classLoader));
+					String beanClassName = candidate.getBeanClassName();
+					if (beanClassName != null) {
+						entitySet.add(ClassUtils.forName(beanClassName, classLoader));
+					}
 				}
 			}
 		}
@@ -120,7 +122,7 @@ public Set<Class<?>> scan(Collection<String> packages) throws ClassNotFoundExcep
 	 * @return a {@link ClassPathScanningCandidateComponentProvider} suitable to scan for Neo4j entities
 	 */
 	private static ClassPathScanningCandidateComponentProvider createClassPathScanningCandidateComponentProvider(
-			ResourceLoader resourceLoader) {
+			@Nullable ResourceLoader resourceLoader) {
 
 		ClassPathScanningCandidateComponentProvider delegate = new ClassPathScanningCandidateComponentProvider(false);
 		if (resourceLoader != null) {

src/main/java/org/springframework/data/neo4j/core/DefaultNeo4jClient.java

@@ -99,6 +99,7 @@ static class AutoCloseableQueryRunnerHandler implements InvocationHandler {
 			this.target = target;
 		}
 
+		@Nullable
 		@Override
 		public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
 
@@ -143,7 +144,7 @@ public DatabaseSelectionProvider getDatabaseSelectionProvider() {
 	 * Basically a holder of a cypher template supplier and a set of named parameters. It's main purpose is to orchestrate
 	 * the running of things with a bit of logging.
 	 */
-	class RunnableStatement {
+	static class RunnableStatement {
 
 		RunnableStatement(Supplier<String> cypherSupplier) {
 			this(cypherSupplier, new NamedParameters());
@@ -179,7 +180,7 @@ protected final Result runWith(AutoCloseableQueryRunner statementRunner) {
 	 *
 	 * @param ex                  the exception to translate
 	 * @param exceptionTranslator the {@link PersistenceExceptionTranslator} to be used for translation
-	 * @return
+	 * @return Any translated exception
 	 */
 	private static RuntimeException potentiallyConvertRuntimeException(RuntimeException ex,
 			PersistenceExceptionTranslator exceptionTranslator) {
@@ -189,12 +190,12 @@ private static RuntimeException potentiallyConvertRuntimeException(RuntimeExcept
 
 	class DefaultRunnableSpec implements RunnableSpec {
 
-		private RunnableStatement runnableStatement;
+		private final RunnableStatement runnableStatement;
 
 		private String targetDatabase;
 
 		DefaultRunnableSpec(Supplier<String> cypherSupplier) {
-			this.targetDatabase = Neo4jClient.verifyDatabaseName(resolveTargetDatabaseName(targetDatabase));
+			this.targetDatabase = Neo4jClient.verifyDatabaseName(resolveTargetDatabaseName(null));
 			this.runnableStatement = new RunnableStatement(cypherSupplier);
 		}
 
@@ -230,8 +231,8 @@ public RunnableSpecTightToDatabase with(Function<T, Map<String, Object>> binder)
 		}
 
 		@Override
-		public OngoingBindSpec<?, RunnableSpecTightToDatabase> bind(@Nullable Object value) {
-			return new DefaultOngoingBindSpec(value);
+		public <T> OngoingBindSpec<T, RunnableSpecTightToDatabase> bind(T value) {
+			return new DefaultOngoingBindSpec<>(value);
 		}
 
 		@Override
@@ -243,8 +244,8 @@ public RunnableSpecTightToDatabase bindAll(Map<String, Object> newParameters) {
 		@Override
 		public <T> MappingSpec<T> fetchAs(Class<T> targetClass) {
 
-			return new DefaultRecordFetchSpec(this.targetDatabase, this.runnableStatement,
-					new SingleValueMappingFunction(conversionService, targetClass));
+			return new DefaultRecordFetchSpec<>(this.targetDatabase, this.runnableStatement,
+					new SingleValueMappingFunction<>(conversionService, targetClass));
 		}
 
 		@Override
@@ -368,7 +369,7 @@ class DefaultRunnableDelegation<T> implements RunnableDelegation<T>, OngoingDele
 		}
 
 		@Override
-		public RunnableDelegation in(@Nullable @SuppressWarnings("HiddenField") String targetDatabase) {
+		public RunnableDelegation<T> in(@Nullable @SuppressWarnings("HiddenField") String targetDatabase) {
 
 			this.targetDatabase = Neo4jClient.verifyDatabaseName(targetDatabase);
 			return this;

src/main/java/org/springframework/data/neo4j/core/DefaultReactiveNeo4jClient.java

@@ -154,8 +154,8 @@ public RunnableSpecTightToDatabase with(Function<T, Map<String, Object>> binder)
 		}
 
 		@Override
-		public Neo4jClient.OngoingBindSpec<?, RunnableSpecTightToDatabase> bind(@Nullable Object value) {
-			return new DefaultOngoingBindSpec(value);
+		public <T> Neo4jClient.OngoingBindSpec<T, RunnableSpecTightToDatabase> bind(T value) {
+			return new DefaultOngoingBindSpec<>(value);
 		}
 
 		@Override
@@ -168,7 +168,7 @@ public RunnableSpecTightToDatabase bindAll(Map<String, Object> newParameters) {
 		public <R> MappingSpec<R> fetchAs(Class<R> targetClass) {
 
 			return new DefaultRecordFetchSpec<>(this.targetDatabase, this.cypherSupplier, this.parameters,
-					new SingleValueMappingFunction(conversionService, targetClass));
+					new SingleValueMappingFunction<>(conversionService, targetClass));
 		}
 
 		@Override
@@ -280,7 +280,7 @@ Mono<ResultSummary> run() {
 	 * exception if the conversation failed. Thus allows safe re-throwing of the return value.
 	 *
 	 * @param ex the exception to translate
-	 * @return
+	 * @return Any translated exception
 	 */
 	private RuntimeException potentiallyConvertRuntimeException(RuntimeException ex) {
 		RuntimeException resolved = persistenceExceptionTranslator.translateExceptionIfPossible(ex);
@@ -303,7 +303,7 @@ class DefaultRunnableDelegation<T> implements RunnableDelegation<T>, OngoingDele
 		}
 
 		@Override
-		public RunnableDelegation in(@Nullable @SuppressWarnings("HiddenField") String targetDatabase) {
+		public RunnableDelegation<T> in(@Nullable @SuppressWarnings("HiddenField") String targetDatabase) {
 
 			this.targetDatabase = Neo4jClient.verifyDatabaseName(targetDatabase);
 			return this;
@@ -317,7 +317,7 @@ public Mono<T> run() {
 		}
 	}
 
-	final class RxStatementRunnerHolder {
+	static final class RxStatementRunnerHolder {
 		private final RxQueryRunner rxQueryRunner;
 
 		private final Publisher<Void> commit;

src/main/java/org/springframework/data/neo4j/core/NamedParameters.java

@@ -23,6 +23,7 @@
 
 import org.apiguardian.api.API;
 import org.neo4j.cypherdsl.core.Cypher;
+import org.springframework.lang.Nullable;
 
 /**
  * @author Michael J. Simons
@@ -52,7 +53,7 @@ void addAll(Map<String, Object> newParameters) {
 	 * @param value The value of the new parameter
 	 * @throws IllegalStateException when a parameter with the given name already exists
 	 */
-	void add(String name, Object value) {
+	void add(String name, @Nullable Object value) {
 
 		if (this.parameters.containsKey(name)) {
 			Object previousValue = this.parameters.get(name);
@@ -80,7 +81,8 @@ public String toString() {
 				.collect(Collectors.joining(", ", ":params {", "}"));
 	}
 
-	private static Object formatValue(Object value) {
+	@Nullable
+	private static String formatValue(@Nullable Object value) {
 		if (value == null) {
 			return null;
 		} else if (value instanceof String) {
@@ -90,7 +92,7 @@ private static Object formatValue(Object value) {
 					.map(e -> String.format("%s: %s", e.getKey(), formatValue(e.getValue()))).collect(
 							Collectors.joining(", ", "{", "}"));
 		} else if (value instanceof Collection) {
-			return ((Collection) value).stream().map(NamedParameters::formatValue).collect(
+			return ((Collection<?>) value).stream().map(NamedParameters::formatValue).collect(
 					Collectors.joining(", ", "[", "]"));
 		}
 

src/main/java/org/springframework/data/neo4j/core/Neo4jClient.java

@@ -269,7 +269,8 @@ interface RunnableDelegation<T> {
 	 * @return A possibly trimmed name of the database.
 	 * @throws IllegalArgumentException when the database name is not allowed with the underlying driver.
 	 */
-	static String verifyDatabaseName(String databaseName) {
+	@Nullable
+	static String verifyDatabaseName(@Nullable String databaseName) {
 
 		String newTargetDatabase = databaseName == null ? null : databaseName.trim();
 		if (newTargetDatabase != null && newTargetDatabase.isEmpty()) {

src/main/java/org/springframework/data/neo4j/core/Neo4jOperations.java

@@ -25,6 +25,7 @@
 import org.springframework.data.neo4j.core.mapping.Neo4jPersistentProperty;
 import org.springframework.data.neo4j.repository.NoResultException;
 import org.springframework.data.neo4j.repository.query.QueryFragmentsAndParameters;
+import org.springframework.lang.Nullable;
 
 /**
  * Specifies operations one can perform on a database, based on an <em>Domain Type</em>.
@@ -224,7 +225,7 @@ default <T, R> List<R> saveAllAs(Iterable<T> instances, Class<R> resultType) {
 	 */
 	<T> void deleteById(Object id, Class<T> domainType);
 
-	<T> void deleteByIdWithVersion(Object id, Class<T> domainType, Neo4jPersistentProperty versionProperty, Object versionValue);
+	<T> void deleteByIdWithVersion(Object id, Class<T> domainType, Neo4jPersistentProperty versionProperty, @Nullable Object versionValue);
 
 	/**
 	 * Deletes all entities with one of the given ids, including all entities related to that entity.