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Note, however, that none of the above issues apply to static member classes. Consequently, serialization of static member classes is permitted.

Noncompliant Code Example

In this noncompliant code example, the fields contained within the outer class are also serialized when the inner class is serialized.

Code Block
bgColor#FFcccc
public class OuterSer implements Serializable {
  private int rank;
  class InnerSer implements Serializable {
    protected String name;
    //...
  }
}

Compliant Solution

This compliant solution omits implementation of the Serializable interface in the InnerSer class.

Code Block
bgColor#ccccff
public class OuterSer implements Serializable {
  private int rank;
  class InnerSer {
    protected String name;
    //...
  }
}

Compliant Solution

It is allowable to declare the inner class as static to prevent its serialization. It is also permissible for a static inner class to implement Serializable.

Code Block
bgColor#ccccff
public class OuterSer implements Serializable {
  private int rank;
  static class InnerSer implements Serializable {
    protected String name;
    //...
  }
}

Risk Assessment

Attempts to serialize inner classes can introduce platform dependencies and can cause serialization of instances of the outer class.

Rule

Severity

Likelihood

Remediation Cost

Priority

Level

SER06-J

medium

likely

low

P18

L1

Automated Detection

Detection of inner classes that implement serialization appears to be straightforward.

Related Vulnerabilities

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

Bibliography

<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="00be74d2142489b5-f45fa201-4f0a416f-9a44baee-8f08a4a96b6092f49822ece0"><ac:plain-text-body><![CDATA[

[[API 2006

AA. Bibliography#API 06]]

 

]]></ac:plain-text-body></ac:structured-macro>

<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="eb937fbad8246545-211eaf48-46bf4067-a84b827f-b37261c36886f0d9cbf217e5"><ac:plain-text-body><![CDATA[

[[Bloch 2008

AA. Bibliography#Bloch 08]]

Item 74: "Implement serialization judiciously"

]]></ac:plain-text-body></ac:structured-macro>

<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="a5c58bea4319beae-29582e56-413c4e0f-8b699c26-60f5016267eba541ea6d78b4"><ac:plain-text-body><![CDATA[

[[JLS 2005

AA. Bibliography#JLS 05]]

[Section 8.1.3, Inner Classes and Enclosing Instances

http://java.sun.com/docs/books/jls/third_edition/html/classes.html]

]]></ac:plain-text-body></ac:structured-macro>

<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="09d9e9d070fa33e8-c753d2d4-44a34e28-b4d6b115-3fafe6e7dd43380edd74131f"><ac:plain-text-body><![CDATA[

[[Sun 2006

AA. Bibliography#Sun 06]]

"Serialization specification"

]]></ac:plain-text-body></ac:structured-macro>

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