SER09-J. Do not invoke overridable methods from the readObject method

Invoking overridable methods from the readObject() method can allow the overriding method to read the state of the subclass before it is fully constructed, since the base class is deserialized first, followed by the subclass. As a result, readObject() must not call any overridable methods.

Also see the related rule MET06-J. Do not invoke overridable methods in clone().

Noncompliant Code Example

This noncompliant code example invokes an overridable method from the readObject() method.

private void readObject(final ObjectInputStream stream) throws 
    IOException, ClassNotFoundException {
  overridableMethod(); 
  stream.defaultReadObject();
}

public void overridableMethod() {
  // ...
}

Compliant Solution

This compliant solution removes the call to the overridable method. When removing such calls is infeasible, ensure that the overridable method is declared private or final.

private void readObject(final ObjectInputStream stream) throws 
    IOException, ClassNotFoundException {
  stream.defaultReadObject();
}

Exceptions

SER09-EX1: "The readObject methods will often call java.io.ObjectInputStream.defaultReadObject, which is an overridable method" [[SCG 2009]]. Such calls are permitted.

Risk Assessment

Invoking overridable methods from the readObject() method can lead to initialization errors.

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Bibliography

      16. Serialization (SER)