Resolving NullPointerException in BeanCopier Caused by Lombok @Accessors(chain=true)

Problem description: MCube loads templates and during view rendering a NullPointerException occurs, with a stack trace showing cglib BeanCopier failures.

Analysis: The error originates from using Lombok @Accessors(chain=true), which changes setter methods to return the object itself instead of void. JDK Introspector only treats void‑returning set methods as write methods, so BeanCopier cannot locate a writeMethod for the property, leading to a NullPointerException in ReflectUtils.getMethodInfo .

Relevant code snippets illustrate the stack trace, the Lombok‑generated setter, and the Introspector source that filters setters based on return type.

java.lang.NullPointerException: null
  at net.sf.cglib.core.ReflectUtils.getMethodInfo(ReflectUtils.java:424) ~[cglib-3.1.jar:?]
  at net.sf.cglib.beans.BeanCopier$Generator.generateClass(BeanCopier.java:133) ~[cglib-3.1.jar:?]
  ... (stack trace omitted for brevity)

@Accessors(chain = true)
public class YourClass {
    private int a;

    @Setter
    public YourClass setA(int a) {
        this.a = a;
        return this;
    }
}

The article also examines the copyPropertiesOfList and copyProperties utilities that rely on BeanCopier, confirming that the target class lacks a proper writeMethod due to the Lombok annotation.

Solution 1: Remove the @Accessors(chain = true) annotation and use conventional void setters.

Solution 2: Keep the annotation but replace BeanCopier with a safer mapper such as MapStruct, which generates correct getters/setters at compile time and works well with Lombok.

Conclusion: Any component that depends on JDK Introspector to discover setter methods will fail for classes using Lombok's chainable setters; developers should be aware of this limitation and choose appropriate copying utilities.