test empty = null for settings

src/main/java/stirling/software/SPDF/config/AppConfig.java

@@ -1,5 +1,6 @@
 package stirling.software.SPDF.config;
 
+import org.springframework.beans.PropertyEditorRegistrar;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -8,6 +9,18 @@ import stirling.software.SPDF.model.ApplicationProperties;
 @Configuration
 public class AppConfig {
 
+	@Bean
+    public CustomEditorConfigurer customEditorConfigurer() {
+        return new CustomEditorConfigurer();
+    }
+
+    @Bean
+    public PropertyEditorRegistrar propertyEditorRegistrar() {
+        return registry -> {
+            registry.registerCustomEditor(String.class, new EmptyStringAsNullEditor());
+        };
+    }
+    
     @Autowired
     ApplicationProperties applicationProperties;
     

src/main/java/stirling/software/SPDF/config/CustomEditorConfigurer.java

@@ -0,0 +1,42 @@
+package stirling.software.SPDF.config;
+import java.beans.PropertyEditor;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.PropertyEditorRegistrar;
+import org.springframework.beans.PropertyEditorRegistry;
+import org.springframework.beans.factory.config.BeanPostProcessor;
+import org.springframework.validation.DataBinder;
+
+public class CustomEditorConfigurer implements BeanPostProcessor {
+
+    @Override
+    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
+        if (bean instanceof PropertyEditorRegistrar) {
+            ((PropertyEditorRegistrar) bean).registerCustomEditors(new PropertyEditorRegistry() {
+                @Override
+                public void registerCustomEditor(Class<?> requiredType, String propertyPath, java.beans.PropertyEditor propertyEditor) {
+                    DataBinder dataBinder = new DataBinder(bean);
+                    dataBinder.registerCustomEditor(requiredType, propertyPath, propertyEditor);
+                }
+
+                @Override
+                public void registerCustomEditor(Class<?> requiredType, java.beans.PropertyEditor propertyEditor) {
+                    DataBinder dataBinder = new DataBinder(bean);
+                    dataBinder.registerCustomEditor(requiredType, propertyEditor);
+                }
+
+				@Override
+				public PropertyEditor findCustomEditor(Class<?> requiredType, String propertyPath) {
+					return null;
+				}
+            });
+        }
+
+        return bean;
+    }
+
+    @Override
+    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
+        return bean;
+    }
+}

src/main/java/stirling/software/SPDF/config/EmptyStringAsNullEditor.java

@@ -0,0 +1,13 @@
+package stirling.software.SPDF.config;
+import java.beans.PropertyEditorSupport;
+
+public class EmptyStringAsNullEditor extends PropertyEditorSupport {
+    @Override
+    public void setAsText(String text) {
+        if (text != null && text.trim().isEmpty()) {
+            setValue(null);
+        } else {
+            setValue(text);
+        }
+    }
+}