Fix deriving DataSources from custom type

Eliminate the unsupported datasource property exception thrown
when trying to derive a datasource from an unknown datasource type.

See gh-27453

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/jdbc/DataSourceBuilder.java

@@ -281,17 +281,22 @@ public String toString() {
 		}
 
 		Method findSetter(Class<?> type) {
-			return extracted("set", type);
+			return extracted("set", type, true);
 		}
 
 		Method findGetter(Class<?> type) {
-			return extracted("get", type);
+			return extracted("get", type, false);
 		}
 
-		private Method extracted(String prefix, Class<?> type) {
+		private Method extracted(String prefix, Class<?> type, boolean hasParameter) {
 			for (String candidate : this.names) {
-				Method method = ReflectionUtils.findMethod(type, prefix + StringUtils.capitalize(candidate),
-						String.class);
+				Method method;
+				if (hasParameter) {
+					method = ReflectionUtils.findMethod(type, prefix + StringUtils.capitalize(candidate), String.class);
+				}
+				else {
+					method = ReflectionUtils.findMethod(type, prefix + StringUtils.capitalize(candidate));
+				}
 				if (method != null) {
 					return method;
 				}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/jdbc/DataSourceBuilderTests.java

@@ -331,6 +331,19 @@ void buildWhenDerivedFromExistingDatabaseWithTypeChange() {
 		assertThat(built.getUrl()).isEqualTo("jdbc:postgresql://localhost:5432/postgres");
 	}
 
+	@Test // gh -27295
+	void buildWhenDerivedFromCustomTypeSpecifiedReturnsDataSource() {
+		CustomDataSource dataSource = new CustomDataSource();
+		dataSource.setUsername("test");
+		dataSource.setPassword("secret");
+		dataSource.setUrl("jdbc:postgresql://localhost:5432/postgres");
+		DataSourceBuilder<?> builder = DataSourceBuilder.derivedFrom(dataSource).type(SimpleDriverDataSource.class);
+		SimpleDriverDataSource testSource = (SimpleDriverDataSource) builder.build();
+		assertThat(testSource.getUsername()).isEqualTo("test");
+		assertThat(testSource.getUrl()).isEqualTo("jdbc:postgresql://localhost:5432/postgres");
+		assertThat(testSource.getPassword()).isEqualTo("secret");
+	}
+
 	final class HidePackagesClassLoader extends URLClassLoader {
 
 		private final String[] hiddenPackages;