org.sadun.util
Class BaseObjectWithId

java.lang.Object
  org.sadun.util.BaseObjectWithId

All Implemented Interfaces:

ObjectWithId, java.io.Serializable

public abstract class BaseObjectWithId

extends java.lang.Object

implements java.io.Serializable, ObjectWithId

A base implementation of ObjectWithId.

This partial implementation stores the object id in the protected field #id, and can be used both for classes requiring id based equality only or requring also type-equality.

It also provides a default ObjectWithIdMetadata in #metadata, defininig:

• the metadata (that is, a string with which every id must start) by
  • creating an acronym of the unqualified class name, keeping only the uppercase letters;
    for example, foo.MyClass has MC as acronym;

  • if the acronym built with the rule above is the empty string, the first three letters (or less if there are less available) of the unqualified className are used.

  Subclasses may set #metadata independently in a static intializer; if the id prefix is set to null, no check is made on the id pattern when a new object is constructed.

  Author:

  Cristiano Sadun

  See Also:

  Serialized Form

  Field Summary

  protected java.lang.String	objectId The id of the object.
  protected static java.util.Map	objectWithIdMetadataMap

  Constructor Summary

  protected	BaseObjectWithId(java.lang.String id) Create an instance with the given id and which will equate only to object of the same type.
  protected	BaseObjectWithId(java.lang.String id, boolean requireSameTypeForEquality) Create an instance of the class with the given id which will or will not perform a type comparison in the equals(Object) method, depending on the value of the requireSameTypeForEquality parameter.

  Method Summary

  protected void	checkPrefix(java.lang.String id, ObjectWithIdMetadata metadata) This method is used at construction to verify whether the given id is suitable for the object, and shoud throw an IllegalArgumentException if it not.
  protected void	clearModified() Subclasses may use this method to set the "modified" status of the object to true.
  boolean	equals(java.lang.Object obj) Verifies if two object are the same, by comparing their ids.
  protected boolean	equalWithNoObjectWithId(java.lang.Object obj) Subclasses may override this method to implement an equality check with some other type than ObjectWithId.
  java.lang.String	getId() Return the unique id of the object.
  ObjectWithIdMetadata	getMetadata() Return the value of the #metadata field.
  int	hashCode() Return an hash code for the object, obtained by its id.
  boolean	isModified() This method return true if the object "modified" status has been set by setModified().
  protected void	setModified() Subclasses may use this method to set the "modified" status of the object to true.

  Methods inherited from class java.lang.Object

  clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

  Field Detail

  objectWithIdMetadataMap

  protected static transient java.util.Map objectWithIdMetadataMap

  objectId

  protected java.lang.String objectId

  The id of the object.

  Constructor Detail

  BaseObjectWithId

  protected BaseObjectWithId(java.lang.String id,
                             boolean requireSameTypeForEquality)

  Create an instance of the class with the given id which will or will not perform a type comparison in the equals(Object) method, depending on the value of the requireSameTypeForEquality parameter.

  Unless #metadata returns a null id prefix, the constructor also checks that the given id matches the class (see class comment).

  Parameters:

  id - the unique id of the object

  requireSameTypeForEquality - if true, equals(Object) will perform also a type comparsino besides an id comparison.

  BaseObjectWithId

  protected BaseObjectWithId(java.lang.String id)

  Create an instance with the given id and which will equate only to object of the same type.

  Unless #metadata is null, the constructor also checks that the given id matches the class id prefix (see class comment).

  Parameters:

  id - the unique id of the object

  Method Detail

  checkPrefix

  protected void checkPrefix(java.lang.String id,
                             ObjectWithIdMetadata metadata)

  This method is used at construction to verify whether the given id is suitable for the object, and shoud throw an IllegalArgumentException if it not.

  This method can be overridden by subclasses.

  This implementation accepts only prefixes which start with the id prefix specified by the metadata.

  Parameters:

  metadata - the metadata for the object

  Throws:

  java.lang.IllegalArgumentException - if the id is invalid.

  getId

  public java.lang.String getId()

  Return the unique id of the object.

  Specified by:

  getId in interface ObjectWithId

  Returns:

  an id for an object.

  See Also:

  ObjectWithId.getId()

  equals

  public final boolean equals(java.lang.Object obj)

  Verifies if two object are the same, by comparing their ids. Depending on the at construction parameter requireSameTypeForEquality, the comparison may also require that the compared object has the same class as this object.

  Parameters:

  obj - the object to compare

  Returns:

  if the given object is equalt to this object

  equalWithNoObjectWithId

  protected boolean equalWithNoObjectWithId(java.lang.Object obj)

  Subclasses may override this method to implement an equality check with some other type than ObjectWithId.

  This implementation returns false.

  Parameters:

  obj - the object to compare (which is not an ObjectWithId.

  Returns:

  false.

  hashCode

  public final int hashCode()

  Return an hash code for the object, obtained by its id.

  Returns:

  an hash code for the object, obtained by its id.

  getMetadata

  public ObjectWithIdMetadata getMetadata()

  Return the value of the #metadata field. The metadata is set on a per-class basis.

  Specified by:

  getMetadata in interface ObjectWithId

  Returns:

  the metadatafor the object.

  See Also:

  ObjectWithId.getMetadata()

  setModified

  protected final void setModified()

  Subclasses may use this method to set the "modified" status of the object to true.

  Typically this is done in setters.

  clearModified

  protected final void clearModified()

  Subclasses may use this method to set the "modified" status of the object to true.

  isModified

  public final boolean isModified()

  This method return true if the object "modified" status has been set by setModified().

  Returns: