diff --git a/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/DataSourceBuilder.java b/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/DataSourceBuilder.java
index e57a967ad23..ecaa0296fde 100644
--- a/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/DataSourceBuilder.java
+++ b/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/DataSourceBuilder.java
@@ -93,7 +93,7 @@ public final class DataSourceBuilder<T extends DataSource> {
 
 	private final @Nullable ClassLoader classLoader;
 
-	private final Map<DataSourceProperty, String> values = new HashMap<>();
+	private final Map<DataSourceProperty, @Nullable String> values = new HashMap<>();
 
 	private @Nullable Class<T> type;
 
diff --git a/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/ClickHouseEnvironment.java b/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/ClickHouseEnvironment.java
index 0140d7dd2ac..29df912b6b6 100644
--- a/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/ClickHouseEnvironment.java
+++ b/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/ClickHouseEnvironment.java
@@ -37,9 +37,19 @@ class ClickHouseEnvironment {
 	private final String database;
 
 	ClickHouseEnvironment(Map<String, @Nullable String> env) {
-		this.username = env.getOrDefault("CLICKHOUSE_USER", "default");
+		this.username = extractUsername(env);
 		this.password = extractPassword(env);
-		this.database = env.getOrDefault("CLICKHOUSE_DB", "default");
+		this.database = extractDatabase(env);
+	}
+
+	private static String extractDatabase(Map<String, @Nullable String> env) {
+		String result = env.get("CLICKHOUSE_DB");
+		return (result != null) ? result : "default";
+	}
+
+	private static String extractUsername(Map<String, @Nullable String> env) {
+		String result = env.get("CLICKHOUSE_USER");
+		return (result != null) ? result : "default";
 	}
 
 	private String extractPassword(Map<String, @Nullable String> env) {
diff --git a/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/MariaDbEnvironment.java b/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/MariaDbEnvironment.java
index c4ed44db513..4225926950c 100644
--- a/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/MariaDbEnvironment.java
+++ b/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/MariaDbEnvironment.java
@@ -47,7 +47,10 @@ class MariaDbEnvironment {
 
 	private String extractUsername(Map<String, @Nullable String> env) {
 		String user = env.get("MARIADB_USER");
-		return (user != null) ? user : env.getOrDefault("MYSQL_USER", "root");
+		if (user == null) {
+			user = env.get("MYSQL_USER");
+		}
+		return (user != null) ? user : "root";
 	}
 
 	private String extractPassword(Map<String, @Nullable String> env) {
diff --git a/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/MySqlEnvironment.java b/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/MySqlEnvironment.java
index af478601cd2..026f7005b46 100644
--- a/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/MySqlEnvironment.java
+++ b/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/MySqlEnvironment.java
@@ -40,11 +40,16 @@ class MySqlEnvironment {
 	private final String database;
 
 	MySqlEnvironment(Map<String, @Nullable String> env) {
-		this.username = env.getOrDefault("MYSQL_USER", "root");
+		this.username = extractUsername(env);
 		this.password = extractPassword(env);
 		this.database = extractDatabase(env);
 	}
 
+	private static String extractUsername(Map<String, @Nullable String> env) {
+		String result = env.get("MYSQL_USER");
+		return (result != null) ? result : "root";
+	}
+
 	private String extractPassword(Map<String, @Nullable String> env) {
 		Assert.state(!env.containsKey("MYSQL_RANDOM_ROOT_PASSWORD"), "MYSQL_RANDOM_ROOT_PASSWORD is not supported");
 		boolean allowEmpty = env.containsKey("MYSQL_ALLOW_EMPTY_PASSWORD") || env.containsKey("ALLOW_EMPTY_PASSWORD");
diff --git a/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/OracleEnvironment.java b/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/OracleEnvironment.java
index bf61f3bbea9..5d23f66397b 100644
--- a/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/OracleEnvironment.java
+++ b/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/OracleEnvironment.java
@@ -37,9 +37,19 @@ class OracleEnvironment {
 	private final String database;
 
 	OracleEnvironment(Map<String, @Nullable String> env, String defaultDatabase) {
-		this.username = env.getOrDefault("APP_USER", "system");
+		this.username = extractUsername(env);
 		this.password = extractPassword(env);
-		this.database = env.getOrDefault("ORACLE_DATABASE", defaultDatabase);
+		this.database = extractDatabase(env, defaultDatabase);
+	}
+
+	private static String extractDatabase(Map<String, @Nullable String> env, String defaultDatabase) {
+		String result = env.get("ORACLE_DATABASE");
+		return (result != null) ? result : defaultDatabase;
+	}
+
+	private static String extractUsername(Map<String, @Nullable String> env) {
+		String result = env.get("APP_USER");
+		return (result != null) ? result : "system";
 	}
 
 	private String extractPassword(Map<String, @Nullable String> env) {
diff --git a/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/PostgresEnvironment.java b/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/PostgresEnvironment.java
index 74fcb336f0e..70cfeaa86d5 100644
--- a/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/PostgresEnvironment.java
+++ b/module/spring-boot-jdbc/src/main/java/org/springframework/boot/jdbc/docker/compose/PostgresEnvironment.java
@@ -57,8 +57,9 @@ class PostgresEnvironment {
 
 	private String extract(Map<String, @Nullable String> env, String[] keys, String defaultValue) {
 		for (String key : keys) {
-			if (env.containsKey(key)) {
-				return env.get(key);
+			String value = env.get(key);
+			if (value != null) {
+				return value;
 			}
 		}
 		return defaultValue;