Error when trying to convert Java object to JSON string using GSON

Question

I have an object MobilePhone with fields (String brand and name, int ram and rom) that I want to convert to a Json string. I try doing so like this

public static void main(String[] args) {
    MobilePhone mp = new MobilePhone();
    mp.setBrand("iPhone");
    mp.setName("X");
    mp.setRam(4);
    mp.setRom(1);
    
    Gson json = new Gson();
    String object = json.toJson(mp);
    System.out.println(object);
}

I get the following errors:

Exception in thread "main" java.lang.reflect.InaccessibleObjectException: Unable to make public (package name).MobilePhone() accessible: module (project name) does not "exports (package name)" to module gson at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:349) at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:289) at java.base/java.lang.reflect.Constructor.checkCanSetAccessible(Constructor.java:189) at java.base/java.lang.reflect.Constructor.setAccessible(Constructor.java:182) at [email protected]/com.google.gson.internal.ConstructorConstructor.newDefaultConstructor(ConstructorConstructor.java:101) at [email protected]/com.google.gson.internal.ConstructorConstructor.get(ConstructorConstructor.java:83) at [email protected]/com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:99) at [email protected]/com.google.gson.Gson.getAdapter(Gson.java:423) at [email protected]/com.google.gson.Gson.toJson(Gson.java:661) at [email protected]/com.google.gson.Gson.toJson(Gson.java:648) at [email protected]/com.google.gson.Gson.toJson(Gson.java:603) at [email protected]/com.google.gson.Gson.toJson(Gson.java:583) at IAssessment/application.AddData.main(AddData.java:23) - this is line String object = json.toJson(mp);

Pls help

polo-language · Accepted Answer · 2021-12-30 12:32:31Z

2

As the error indicates, the module containing the MobilePhone class does not export the package containing MobilePhone, so it is not visible outside of its own module. (Or if it is exported, it is only exported to some modules other than gson.) In general this means that you must add an exports directive to the module descriptor file, like so:

exports <pkg-name> to gson;

But since gson uses reflection extensively, probably you need to go a step further and provide private and reflective access of the package to gson. To do this, add an opens directive to the module descriptor file:

opens <pkg-name> to gson;

answered Dec 30, 2021 at 12:32

polo-language

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4 Comments

Tomislav Over a year ago

How do I open the module descriptor file? I'm not sure what that is. Sorry for the basic and or dumb questions, I'm quite t he novice in java and I am just now learning software development

polo-language Over a year ago

Start with a tutorial or check out the Project Jigsaw page.

Tomislav Over a year ago

Nevermind, I figured it out. You're the 🐐

Elated Coder Over a year ago

Fantastic. It works!

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