Planned lessonMID-010-L03

Reflection and opens

On This Lesson 4 topics

This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.

In this lesson

explain why frameworks need opens.

exports allows compile-time and runtime access to public types; it does not allow deep reflection on private members.
opens allows reflective access at runtime (including setAccessible) to a package.
open module opens everything; opens ... to targets specific modules.
Frameworks such as Spring, Hibernate, and Jackson reflect on your classes and need them opened.
Symptom: InaccessibleObjectException at startup.

Draft outline details

java

module com.shop.core {
    exports com.shop.core.api;
    opens com.shop.core.model to com.fasterxml.jackson.databind;
}

Which keyword fixes an InaccessibleObjectException caused by reflection?

Show answer

opens.

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