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  1. JDK
  2. JDK-8217698

Annotation to mark serial-related fields and methods



    • Type: CSR
    • Status: Closed
    • Priority: P3
    • Resolution: Approved
    • Fix Version/s: 14
    • Component/s: core-libs
    • Labels:
    • Subcomponent:
    • Compatibility Risk:
    • Interface Kind:
      Java API
    • Scope:



      Add a java.io.Serial annotation type to help mark serialization-related fields and methods for better compile-time checking.


      Mis-declaring a serialization-related field or method can silently lead to unexpected and incorrect behavior.


      Add a new annotation to the java.io package, where other serialization-related types reside.


      package java.io;
      import java.lang.annotation.*;
       * Indicates that an annotated field or method is part of the {@linkplain
       * Serializable serialization mechanism} defined by the
       * <cite>Java Object Serialization Specification</cite>. This
       * annotation type is intended to allow compile-time checking of
       * serialization-related declarations, analogous to the checking
       * enabled by the {@link java.lang.Override} annotation type to
       * validate method overriding. {@code Serializable} classes are encouraged to
       * use <code>&#64;Serial</code> annotations to help a compiler catch
       * mis-declared serialization-related fields and methods,
       * mis-declarations that may otherwise be difficult to detect.
       * <p>Specifically, annotations of this type should be
       * applied to serialization-related methods and fields in classes
       * declared to be {@code Serializable}. The five serialization-related
       * methods are:
       * <ul>
       * <li>{@code private void writeObject(java.io.ObjectOutputStream stream) throws IOException}
       * <li>{@code private void readObject(java.io.ObjectInputStream stream) throws IOException, ClassNotFoundException}
       * <li>{@code private void readObjectNoData() throws ObjectStreamException}
       * <li><i>ANY-ACCESS-MODIFIER</i> {@code Object writeReplace() throws ObjectStreamException}
       * <li><i>ANY-ACCESS-MODIFIER</i> {@code Object readResolve() throws ObjectStreamException} 
       * </ul>
       * The two serialization-related fields are:
       * <ul>
       * <li>{@code private static final ObjectStreamField[] serialPersistentFields}
       * <li>{@code private static final long serialVersionUID}
       * </ul>
       * Compilers are encouraged to validate that a method or field marked with a 
       * <code>&#64;Serial</code> annotation is one of the defined serialization-related
       * methods or fields declared in a meaningful context and issue a warning
       * if that is not the case.
       * <p>It is a semantic error to apply this annotation to other fields or methods, including:
       * <ul>
       * <li>fields or methods in a class that is not {@code Serializable}
       * <li>fields or methods of the proper structural declaration, but in
       * a type where they are ineffectual. For example, {@code enum} types
       * are defined to have a {@code serialVersionUID} of {@code 0L} so a
       * {@code serialVersionUID} field declared in an {@code enum} type is
       * ignored. The five serialization-related methods identified above
       * are likewise ignored for an {@code enum} type.
       * <li>in a class that is {@code Externalizable}:
       * <ul>
       *   <li> method declarations of {@code writeObject}, {@code
       *   readObject}, and {@code readObjectNoData}
       *  <li>a field declaration for {@code serialPersistentFields}
       * </ul>
       * While the {@code Externalizable} interface extends {@code
       * Serializable}, the three methods and one field above are
       * <em>not</em> used for externalizable classes.
       * </ul>
       * Note that serialization mechanism accesses its designated fields
       * and methods reflectively and those fields and methods may appear
       * otherwise unused in a {@code Serializable} class.
       * @see Serializable
       * @see Externalizable
      @Target({ElementType.METHOD, ElementType.FIELD})
      public @interface Serial {}


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              darcy Joe Darcy
              darcy Joe Darcy
              Reviewed By:
              Chris Hegarty, Roger Riggs
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