How to Fix Java 9's InaccessibleObjectException: JDK and Application Code Solutions?

How to Resolve InaccessibleObjectException on Java 9

When using Java 9, developers may encounter the InaccessibleObjectException. It arises due to the Java Platform Module System's implementation of strong encapsulation.

Exception Message Breakdown:

Unable to make {member} accessible: module {A} does not "opens {package}" to {B}

Main Scenarios Causing the Exception:

1. Reflective Call Into JDK

• {A} is a JDK module (e.g., java.base)
• {member} and {package} belong to the JDK API
• {B} is a library/framework/application module (often unnamed module @...)

2. Reflection Over Application Code

• {A} is an application module
• {member} and {package} belong to the application code
• {B} is a framework module or unnamed module @...

1. Solution for Reflective Call Into JDK:

Use the following command-line flag to open the specified package for reflection:

java --add-opens java.base/java.lang=ALL-UNNAMED

Replace ALL-UNNAMED with the name of the named module if applicable.

2. Solution for Reflection Over Application Code:

Edit module {A} to open the internal package using one of the following options within its module descriptor:

• exports {package} (makes it publicly accessible)
• exports {package} to {B} (makes it accessible only to B)
• opens {package} (makes it accessible at runtime to all code)
• opens {package} to {B} (makes it accessible at runtime to only B)
• open module {A} { ... } (makes the entire module accessible to all code at runtime)

The above is the detailed content of How to Fix Java 9's InaccessibleObjectException: JDK and Application Code Solutions?. For more information, please follow other related articles on the PHP Chinese website!