/**
* Helper method for subclasses to implement getFooAttribute(String attributeName), as such:
*
* <pre>
* public class User
* {
* private final Set<UserAttribute> userAttributes = new HashSet<UserAttribute>();
*
* public String getUserAttribute(String attributeName)
* {
* return PersistentAttribute.getAttribute(userAttributes, attributeName);
* }
* }
* </pre>
*
* @param attributeSet the set of objects derived from PersistentAttribute to turn into a
* Map<String,String>
* @param attributeName the name of the desired attribute
* @return the attribute value or null if the attribute does not exist
*/
public static <OwnerClass, AttributeClass extends PersistentAttribute<OwnerClass>>
String getAttribute(Set<AttributeClass> attributeSet, String attributeName) {
for (AttributeClass attribute : attributeSet) {
if (attribute.getName().equals(attributeName)) return attribute.getValue();
}
return null;
}
/**
* Helper method for subclasses to implement getFooAttributes(), as such:
*
* <pre>
* public class User
* {
* private final Set<UserAttribute> userAttributes = new HashSet<UserAttribute>();
*
* public Map<String,String> getUserAttributes()
* {
* return PersistentAttribute.buildMap(userAttributes);
* }
* }
* </pre>
*
* @param attributeSet the set of objects derived from PersistentAttribute to turn into a
* Map<String,String>
* @return an unmodifiable Map representing the attributes attached to the object
*/
public static <OwnerClass, AttributeClass extends PersistentAttribute<OwnerClass>>
Map<String, String> buildMap(Set<AttributeClass> attributeSet) {
Map<String, String> map = new HashMap<String, String>(attributeSet.size());
for (AttributeClass attribute : attributeSet) {
map.put(attribute.getName(), attribute.getValue());
}
return Collections.unmodifiableMap(map);
}
/**
* Helper method for subclasses to implement removeFooAttribute(), as such:
*
* <pre>
* public class User
* {
* private final Set<UserAttribute> userAttributes = new HashSet<UserAttribute>();
*
* public void removeUserAttribute(String name)
* {
* PersistentAttribute.clearAttribute(userAttributes, name);
* }
* }
* </pre>
*
* @param attributeSet the set to modify by removing the target attribute
* @param name the attribute name
*/
public static <OwnerClass, AttributeClass extends PersistentAttribute<OwnerClass>>
void clearAttribute(Set<AttributeClass> attributeSet, String name) {
validateNotNull(attributeSet, "clearExistingAttribute.attributeSet must be non-null");
validateNotNull(name, "clearExistingAttribute.name must be non-null");
for (AttributeClass existingAttribute : attributeSet) {
if (existingAttribute.getName().equals(name)) {
attributeSet.remove(existingAttribute);
existingAttribute.setOwner(null);
return;
}
}
}
/**
* Helper method for subclasses to implement setFooAttribute(), as such:
*
* <pre>
* public class User
* {
* private final Set<UserAttribute> userAttributes = new HashSet<UserAttribute>();
*
* public void setUserAttribute(String name, String value)
* {
* PersistentAttribute.setAttribute(this, userAttributes, name, value, UserAttribute.class);
* }
* }
* </pre>
*
* This function will overwrite any existing attribute of the same name.
*
* @param owner the owner of the attribute collection (usually the <code>this</code> pointer of
* the caller
* @param attributeSet the set to modify by adding or replacing the target attribute
* @param name the attribute name
* @param value the attribute value
* @param attributeClass the Class of the PersistentAttribute subclass
* @return the newly created attribute object (already stored in the attributeSet)
*/
public static <OwnerClass, AttributeClass extends PersistentAttribute<OwnerClass>>
AttributeClass setAttribute(
OwnerClass owner,
Set<AttributeClass> attributeSet,
String name,
String value,
Class<? extends AttributeClass> attributeClass) {
validateNotNull(attributeSet, "setAttribute.attributeSet must be non-null");
validateNotNull(name, "clearExistingAttribute.name must be non-null");
validateNotNull(value, "clearExistingAttribute.value must be non-null");
validateNotNull(attributeClass, "clearExistingAttribute.attributeClass must be non-null");
for (AttributeClass existingAttribute : attributeSet) {
if (existingAttribute.getName().equals(name)) {
// we must remove/re-add the existing attribute when changing its
// value so that it gets filed in the correct hash bucket
attributeSet.remove(existingAttribute);
existingAttribute.setValue(value);
attributeSet.add(existingAttribute);
return existingAttribute;
}
}
AttributeClass attribute;
try {
Constructor<? extends AttributeClass> constructor =
attributeClass.getConstructor(String.class, String.class);
attribute = constructor.newInstance(name, value);
} catch (Exception e) {
throw new IllegalArgumentException("can't instantiate class: " + attributeClass.getName(), e);
}
attributeSet.add(attribute);
attribute.setOwner(owner);
return attribute;
}