== Why is this an issue?

When a ``++Serializable++`` object has a non-serializable ancestor in its inheritance chain, object deserialization (re-instantiating the object from file) starts at the first non-serializable class, and proceeds down the chain, adding the properties of each subsequent child class, until the final object has been instantiated. 


In order to create the non-serializable ancestor, its no-argument constructor is called. Therefore the non-serializable ancestor of a ``++Serializable++`` class must have a no-arg constructor. Otherwise the class is ``++Serializable++`` but not deserializable.


=== Noncompliant code example

[source,java]
----
public class Fruit {
  private Season ripe;

  public Fruit (Season ripe) {...}
  public void setRipe(Season ripe) {...}
  public Season getRipe() {...}
}

public class Raspberry extends Fruit 
        implements Serializable {  // Noncompliant; nonserializable ancestor doesn't have no-arg constructor
  private static final long serialVersionUID = 1;

  private String variety;

  public Raspberry(Season ripe, String variety) { ...}
  public void setVariety(String variety) {...}
  public String getVarity() {...}
}
----


=== Compliant solution

[source,java]
----
public class Fruit {
  private Season ripe;

  public Fruit () {...};  // Compliant; no-arg constructor added to ancestor
  public Fruit (Season ripe) {...}
  public void setRipe(Season ripe) {...}
  public Season getRipe() {...}
}

public class Raspberry extends Fruit 
        implements Serializable {
  private static final long serialVersionUID = 1;

  private String variety;

  public Raspberry(Season ripe, String variety) {...}
  public void setVariety(String variety) {...}
  public String getVarity() {...}
}
----


ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Add a no-arg constructor to "xxx".


'''
== Comments And Links
(visible only on this page)

=== on 25 Sep 2014, 08:16:23 Ann Campbell wrote:
Implementation note: see References tab for FB rule this replaces

endif::env-github,rspecator-view[]