Refine null-safety in the spring-jdbc module

Closes gh-34147

spring-jdbc/src/main/java/org/springframework/jdbc/core/ArgumentTypePreparedStatementSetter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -45,10 +45,8 @@ public class ArgumentTypePreparedStatementSetter implements PreparedStatementSet
 	 * @param args the arguments to set
 	 * @param argTypes the corresponding SQL types of the arguments
 	 */
-	@SuppressWarnings("NullAway")
 	public ArgumentTypePreparedStatementSetter(@Nullable Object @Nullable [] args, int @Nullable [] argTypes) {
-		if ((args != null && argTypes == null) || (args == null && argTypes != null) ||
-				(args != null && args.length != argTypes.length)) {
+		if ((args == null && argTypes != null) || (args != null && (argTypes == null || args.length != argTypes.length))) {
 			throw new InvalidDataAccessApiUsageException("args and argTypes parameters must match");
 		}
 		this.args = args;

spring-jdbc/src/main/java/org/springframework/jdbc/datasource/SingleConnectionDataSource.java

@@ -179,7 +179,7 @@ public class SingleConnectionDataSource extends DriverManagerDataSource
 
 
 	@Override
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Lazy initialization
 	public Connection getConnection() throws SQLException {
 		this.connectionLock.lock();
 		try {

spring-jdbc/src/main/java/org/springframework/jdbc/datasource/embedded/EmbeddedDatabaseFactory.java

@@ -159,7 +159,7 @@ public class EmbeddedDatabaseFactory {
 	 * Factory method that returns the {@linkplain EmbeddedDatabase embedded database}
 	 * instance, which is also a {@link DataSource}.
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Lazy initialization
 	public EmbeddedDatabase getDatabase() {
 		if (this.dataSource == null) {
 			initDatabase();

spring-jdbc/src/main/java/org/springframework/jdbc/support/incrementer/AbstractDataFieldMaxValueIncrementer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -76,7 +76,7 @@ public abstract class AbstractDataFieldMaxValueIncrementer implements DataFieldM
 	/**
 	 * Return the data source to retrieve the value from.
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Lazy initialization
 	public DataSource getDataSource() {
 		return this.dataSource;
 	}
@@ -91,7 +91,7 @@ public abstract class AbstractDataFieldMaxValueIncrementer implements DataFieldM
 	/**
 	 * Return the name of the sequence/table.
 	 */
-	@SuppressWarnings("NullAway")
+	@SuppressWarnings("NullAway") // Lazy initialization
 	public String getIncrementerName() {
 		return this.incrementerName;
 	}

spring-jdbc/src/main/java/org/springframework/jdbc/support/incrementer/AbstractIdentityColumnMaxValueIncrementer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,10 +23,13 @@ import java.sql.Statement;
 
 import javax.sql.DataSource;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.dao.DataAccessException;
 import org.springframework.dao.DataAccessResourceFailureException;
 import org.springframework.jdbc.datasource.DataSourceUtils;
 import org.springframework.jdbc.support.JdbcUtils;
+import org.springframework.util.Assert;
 
 /**
  * Abstract base class for {@link DataFieldMaxValueIncrementer} implementations
@@ -41,7 +44,7 @@ public abstract class AbstractIdentityColumnMaxValueIncrementer extends Abstract
 	private boolean deleteSpecificValues = false;
 
 	/** The current cache of values. */
-	private long[] valueCache;
+	private long @Nullable [] valueCache;
 
 	/** The next id to serve from the value cache. */
 	private int nextValueIndex = -1;
@@ -53,11 +56,9 @@ public abstract class AbstractIdentityColumnMaxValueIncrementer extends Abstract
 	 * @see #setIncrementerName
 	 * @see #setColumnName
 	 */
-	@SuppressWarnings("NullAway")
 	public AbstractIdentityColumnMaxValueIncrementer() {
 	}
 
-	@SuppressWarnings("NullAway")
 	public AbstractIdentityColumnMaxValueIncrementer(DataSource dataSource, String incrementerName, String columnName) {
 		super(dataSource, incrementerName, columnName);
 	}
@@ -120,6 +121,7 @@ public abstract class AbstractIdentityColumnMaxValueIncrementer extends Abstract
 				DataSourceUtils.releaseConnection(con, getDataSource());
 			}
 		}
+		Assert.state(this.valueCache != null, "The cache of values can't be null");
 		return this.valueCache[this.nextValueIndex++];
 	}