Encountering this issue today made me realize that Thymeleaf lacks a straightforward solution for it. One way to address it is by setting parent references to null before passing them to Thymeleaf, but this approach may not be the most aesthetically pleasing.
Upon delving into Thymeleaf's source code, I discovered its use of Introspector to access property information. This led me to the idea of concealing certain properties by implementing a custom BeanInfo. The simplest method involves creating a class within the same package as your bean, appending BeanInfo to its name. By extending SimpleBeanInfo and only implementing the required methods (such as getPropertyDescriptors), you can effectively hide properties from Thymeleaf.
To illustrate, consider the following example:
public class InventoryItemBeanInfo extends SimpleBeanInfo {
@Override
public PropertyDescriptor[] getPropertyDescriptors() {
try {
PropertyDescriptor id = new PropertyDescriptor("id", InventoryItem.class);
PropertyDescriptor[] descriptors = {id};
return descriptors;
} catch (IntrospectionException e) {
throw new Error(e.toString());
}
}
}
This technique ensures that Thymeleaf does not encounter the problematic recursion with the Player property.
A drawback of this solution is the need to manually update the BeanInfo whenever modifications are made to the attributes of your InventoryItem bean.
An alternative solution I devised is slightly more complex but offers easier maintenance once configured.
Starting with an annotation to signify hidden properties—let’s call it HiddenProperty:
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface HiddenProperty {}
We can then create a generic BeanInfo class that leverages reflection to inspect a bean's properties, checking for our annotation to exclude specific methods:
public class HiddenPropertyAwareBeanInfo extends SimpleBeanInfo {
// Implementation details as mentioned above...
}
The final step involves creating a specialized BeanInfo that extends the aforementioned class:
public class InventoryItemBeanInfo extends HiddenPropertyAwareBeanInfo {
// Implementation details as mentioned above...
}
By annotating getters of properties to be hidden, such as Player, within your bean class, you can ensure these properties remain obscured from Thymeleaf:
@Entity
@Table(name = "inventory_item")
public class InventoryItem {
// Entity details...
@HiddenProperty
public Player getPlayer() {
return this.player;
}
// Additional getters and setters...
}
With this setup, alterations to your properties will not expose the Player property to Thymeleaf.
It should be noted that while this solution deviates from Java Beans specifications in some aspects, further enhancements can be explored by studying the Introspector's source code.
In conclusion, although effective, these workarounds underscore a potential improvement opportunity within Thymeleaf to simplify handling such scenarios without intricate solutions.