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/**
* Implementation of <code>IEntityNameFinder</code> for <code>IPersons</code> by
* looking up displayName from an <code>IPersonAttributeDao</code>.
* @version Revision: 1.13++
*/
public class PersonDirNameFinder
implements IEntityNameFinder {
/**
* Data Access Object backing this name finder.
*/
private IPersonAttributeDao paDao;
/** Our cache of entity names: */
private SoftHashMapMap names = new SoftHashMap();
/**
* Instantiate a PersonDirNameFinder backed by the given
* IPersonAttributeDao.
* @param pa DAO to back this PersonDirNameFinder
*/
PersonDirNameFinder (IPersonAttributeDao pa) {
this.paDao = pa;
}
public String getName (String key) {
String name = (String) this.names.get(key);
if (name == null) {
// cached name not found, get name from underlying DAO.
name = primGetName(key);
// cache the name
this.names.put(key, name);
}
return name;
}
public java.util.Map getNames (java.lang.String[] keys) {
Map selectedNames = new HashMap();
for (int i = 0; i < keys.length; i++) {
String name = getName(keys[i]);
selectedNames.put(keys[i], name);
}
return selectedNames;
}
public Class getType () {
return org.jasig.portal.security.IPerson.class;
}
/**
* Actually lookup a user name using the underlying IPersonAttributeDao.
* @param key - entity key which in this case is a unique identifier for a user
* @return the display name for the identified user
*/
private String primGetName (String key) {
String name = key;
Map userInfo = this.paDao.getUserAttributes(name);
if (userInfo != null)
{
Object displayName = userInfo.get("displayName");
String displayNameStr = "";
if (displayName != null)
{
if (displayName instanceof java.util.List)
{
List displayNameList = (List) displayName;
if (! displayNameList.isEmpty() )
{ displayNameStr = (String)displayNameList.get(0); }
}
else displayNameStr = (String)displayName;
if (! displayNameStr.trim().equals(""))
{ name = displayNameStr; }
}
}
return name;
}
/**
* Get a static singleton instance of this class backed by PersonDirectory.
* @return singleton PersonDirNameFinder backed by PersonDirectory
* @deprecated as of uP 2.5 instead use PersonDirNameFinderFactory
*/
public static IEntityNameFinder singleton () {
return new PersonDirNameFinderFactory().newFinder();
}
/**
* Returns a String that represents the value of this object.
* @return a string representation of the receiver
*/
public String toString () {
return "PersonDirNameFinder backed by " + this.paDao;
}
}
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JavaDoc comments for private members make comments available in JavaDoc generated from this code and in IDEs that use JavaDoc to provide context, e.g. Eclipse.
JavaDoc comments are not included for methods declared by the IEntityNameFinder interface. We are not re-specifying these methods, we're just implementing them, so appropriate comments in PersonDirNameFinder are comments about the implementation. By eliminating duplication of the method specifications in both IEntityNameFinder and in this class we eliminate the possibility of these comments getting out of sync.
primGetNames()
Dropped method primGetNames() because all this private method did was give us access to the private field private SoftHashMap names. The method was private and so was not providing an opportunity for anyone to extend this class and override the method to have us use some other SoftHashMap.
Thread safety
This implementation of getName wasn't threadsafe:
| Code Block | ||
|---|---|---|
| ||
/**
* Given the key, returns the entity's name.
* @param key java.lang.String
*/
public String getName (String key) throws Exception {
if (primGetNames().get(key) == null) {
primGetNames().put(key, primGetName(key));
}
return (String)primGetNames().get(key);
}
|
With suitably pathological thread switching and garbage collection, the thread could be interrupted after the if statement but before the return statement. If during that interruption the GC runs and harvests the entry we verified, then when control returns and we get the mapped value for the key, we may get and return null.
By keeping a local reference to the displayName String, we make the implementation threadsafe:
| Code Block | ||
|---|---|---|
| ||
public String getName (String key) {
String name = (String) this.names.get(key);
if (name == null) {
// cached name not found, get name from underlying DAO.
name = primGetName(key);
// cache the name
this.names.put(key, name);
}
return name;
}
|
Payoff: a testcase
Conclusion
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