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The readObject() method must not call any overridable methods. Invoking overridable methods from the readObject() method can cause provide the overriding method with access to read the object's state of the subclass before it is fixedfully initialized. This premature access is possible because the base class is deserialized first, followed by the subclass. Also see the related guideline MET07, in deserialization, readObject plays the role of object constructor and therefore object initialization is not complete until readObject exits (see also MET06-J. Do not invoke overridable methods on the clone under constructionin clone()).

Noncompliant Code Example

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

private void readObject(final ObjectInputStream stream) throws 

                        throws IOException, ClassNotFoundException {
  overridableMethod(); 
  stream.defaultReadObject();
}

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

Compliant Solution

This compliant solution removes the call to the overridable method. If this cannot be done, ensure that the overridable method is declared When removing such calls is infeasible, declare the method private or final.

private void readObject(final ObjectInputStream stream) throws 

                        throws IOException, ClassNotFoundException {
  stream.defaultReadObject();
}

Exceptions

unmigratedSER09-wiki-markup*SER11-EX1:* "The {{readObject}} methods will usually call {{J-EX0: The readObject() method may invoke the overridable methods defaultReadObject() and readFields() in class java.io.ObjectInputStream.defaultReadObject}}, which is an overridable method" \ [[SCG 2009|AA. Bibliography#SCG 09]\].

Risk Assessment

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

Automated Detection

TODO

Related Vulnerabilities

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

Bibliography

\[[API 2006|AA. Bibliography#API 06]\] 
\[[SCG 2009|AA. Bibliography#SCG 09]\] Guideline 4-4 Prevent constructors from calling methods that can be overridden
\[[Bloch 2008|AA. Bibliography#Bloch 08]\] Item 17: "Design and document for inheritance or else prohibit it"

Related Guidelines

Bibliography

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Image Added Image Added Image AddedSER10-J. Do not serialize direct handles to system resources      18. Serialization (SER)      SER12-J. Avoid memory and resource leaks during serialization