How to resolve “java.lang.IllegalAccessError” OR “unnamed module cannot access class” Error in java 17

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After Java 17 upgrade some of you might have face this “java.lang.IllegalAccessError” or “unnamed module cannot access class” error and you might have try to use --illegal-access=permit or --illegal-access=warn but after Java 16 release, it will no longer be possible for end users to use the --illegal-access option to enable access to internal elements of the JDK. let’s see how to solve this error.

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First approach:

Understand how the Java Platform Module System works. In JPMS, classes belong to modules, and access to classes from other modules is controlled by module descriptors (module-info.java). then ensure that your module declarations (module-info.java) are correctly specifying the necessary exports and opens directives to allow other modules to access the required packages and classes.

If you’re using third-party libraries or frameworks, ensure that their modules are accessible to your module. You may need to add dependencies in your module-info.java file using requires.

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If you are in hurry second approach might be for you,

Second approach:

Easiest way to use --add-exports and --add-opens Flags in Java options.

The --add-exports option enables access to the public types of a specified package.

syntax: --add-exports=<source-module>/<package>=<target-module>

It is sometimes necessary to go further and enable access to all non-public elements. This is were the --add-opens option can be used, at run time, to do this. It has the same syntax as the --add-exports option:

syntax: --add-opens=<source-module>/<package>=<target-module>

where <source-module> and <target-module> are module names and <package> is the name of a package.

Example: if the <target-module> is ALL-UNNAMED then the source package will be exported to all unnamed modules, whether they exist initially or are created later on. Thus access to the sun.management package of the java.management module can be granted to all code on the class path via the option --add-exports=java.management/sun.management=ALL-UNNAMED

finally it will looks like this,

java --add-exports=java.management/sun.management=ALL-UNNAMED

if you wants your java code to take this option from environment variable and append it to existing options. you can use

export JAVA_OPTS= --add-exports=java.management/sun.management=ALL-UNNAMED

The --add-exports and --add-opens options must be used with great care. You can use them to gain access to an internal API of a library module, or even of the JDK itself, but you do so at your own risk: If that internal API is changed or removed then your library or application will fail.

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