GWT Serialization 2

GWT can serialize this class.

public MyClass  implements IsSerializable {
    public String myStr;
}

But if you change MyClass into the one below, GWT cannot serialize it and you’ll get the unhelpful error message: “Error: Type ‘foo.bar.MyClass’ was not serializable and has no concrete serializable subtypes”.

public MyClass  implements IsSerializable {
    public String myStr;
    public MyClass(String str){myStr = str;}
}

Want to know why? Because MyClass now lacks a no argument constructor.

I learned this from a thread on issue 540 at the Google Code website. The first post, which came during the GWT 1.3 time frame, rightly asks for a better error message when GWT cannot serialize something. Further down the thread, post say this problem is fixed. It seems to have been fixed before GWT 1.4. Nevertheless, the problem of the unhelpful serialization error message persists, at least when using IntelliJ IDEA 7.0.1 with the GWT Studio plugin.

The work around mentioned in the thread’s 2nd post still holds: any classe you want GWT to serialize must have a no arg constructor. GWT can serialize the class below.

public MyClass  implements IsSerializable {
    public String myStr;
    public MyClass(){}
    public MyClass(String str){  myStr = str; }
}