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package oracle.toplink.essentials.internal.identitymaps;
import java.util.*;
import java.io.*;
import oracle.toplink.essentials.internal.helper.*;
/**
* <p><b>Purpose</b>: Caches objects, and allows their retrieval by their primary key.
* <p><b>Responsibilities</b>:<ul>
* <li> Store CacheKeys containing objects and possibly writeLockValues
* <li> Insert & retrieve objects from the cache
* <li> Allow retrieval and modification of writeLockValue for a cached object.
* </ul>
* @see CacheKey
* @since TOPLink/Java 1.0
*/
public abstract class IdentityMap implements Serializable, Cloneable {
/** The innitial or maximum size of the cache depending upon the concrete implementation */
protected int maxSize;
/** Used to optimize get through avoiding recreation of the cache key each time. */
protected CacheKey searchKey;
/**
* Instantiate an new IdentityMap with it's maximum size.<p>
* <b>NOTE</b>: Subclasses may provide different behaviour for maxSize.
* @param anInteger is the maximum size to be allocated for the recevier.
*/
public IdentityMap(int size) {
maxSize = size;
searchKey = new CacheKey(new Vector(1), null, null);
}
/**
* Acquire the deferred lock
*/
public CacheKey acquireDeferredLock(Vector primaryKey) {
//check if the key is already in the hashtable
CacheKey key = null;
//cache key should not be changed in other threads during the lock acquire operation
synchronized (this) {
// bug 3094912 get must be synchronized as well
key = getCacheKey(primaryKey);
if (key == null) {
//create a chachKey and lock the object
CacheKey cacheKey = createCacheKey(primaryKey, null, null);
cacheKey.acquireDeferredLock();
put(cacheKey);
return cacheKey;
}
}
// code removed as key will never be null here, either one will be found or one created
key.acquireDeferredLock();
return key;
}
/**
* Set an exclusive lock on an object in the IdentityMap. This is provided so that when the object is being read from the database
* the reader can lock the object while it builds and caches the new object. This will prevent other threads
* from accessing this objects but will not stop other threads from inserting other objects into this IdentityMap.
*/
public CacheKey acquireLock(Vector primaryKey, boolean forMerge) {
//check if the key is already in the hashtable
CacheKey key = null;
//cache key should not be changed in other threads during the lock acquire operation
synchronized (this) {
// bug 3094912 get must be synchronized as well
key = getCacheKey(primaryKey);
if (key == null) {
//create a chachKey and lock the object
CacheKey cacheKey = createCacheKey(primaryKey, null, null);
cacheKey.acquire(forMerge);
put(cacheKey);
return cacheKey;
}
}
// code removed as key will never be null here, either one will be found or one created
key.acquire();
return key;
}
/**
* INTERNAL:
* Used to print all the Locks in every identity map in this session.
* The output of this method will go to log passed in as a parameter.
*/
public abstract void collectLocks(HashMap threadList);
/**
* Set an exclusive lock on an object in the IdentityMap. This is provided so that when the object is being read from the database
* the reader can lock the object while it builds and caches the new object. This will prevent other threads
* from accessing this objects but will not stop other threads from inserting other objects into this IdentityMap.
*/
public CacheKey acquireLockNoWait(Vector primaryKey, boolean forMerge) {
//check if the key is already in the hashtable
CacheKey key = null;
//cache key should not be changed in other threads during the lock acquire operation
synchronized (this) {
key = getCacheKey(primaryKey);
if (key == null) {
//create a chachKey and lock the object
CacheKey cacheKey = createCacheKey(primaryKey, null, null);
cacheKey.acquire(forMerge);
put(cacheKey);
return cacheKey;
}
}
//find the key in the hashtable, lock the object
if (key != null) {
//couldn't acquire the key so do not return it
if (!key.acquireNoWait(forMerge)) {
key = null;
}
}
return key;
}
/**
* INTERNAL:
* Find the cachekey for the provided primary key and place a readlock on it.
* This will allow multiple users to read the same object but prevent writes to
* the object while the read lock is held.
*/
public CacheKey acquireReadLockOnCacheKey(Vector primaryKey) {
//check if the key is already in the hashtable
CacheKey key = null;
//cache key should not be changed in other threads during the lock acquire operation
synchronized (this) {
key = getCacheKey(primaryKey);
if (key == null) {
//create a chachKey and lock the object
CacheKey cacheKey = createCacheKey(primaryKey, null, null);
//lets create one but not put it in the cache, as we are only reading
// should not be writing to the identitymap
cacheKey.acquireReadLock();
return cacheKey;
}
}
key.acquireReadLock();
return key;
}
/**
* INTERNAL:
* Find the cachekey for the provided primary key and place a readlock on it.
* This will allow multiple users to read the same object but prevent writes to
* the object while the read lock is held.
* If no readlock can be acquired then do not wait but return null.
*/
public CacheKey acquireReadLockOnCacheKeyNoWait(Vector primaryKey) {
//check if the key is already in the hashtable
CacheKey key = null;
//cache key should not be changed in other threads during the lock acquire operation
synchronized (this) {
key = getCacheKey(primaryKey);
if (key == null) {
//create a chachKey and lock the object
CacheKey cacheKey = createCacheKey(primaryKey, null, null);
cacheKey.acquireReadLock();
//lets create one but not put it in the cache, as we are only reading
// should not be writing to the identitymap
return cacheKey;
}
}
//find the key in the hashtable, lock the object
if (key != null) {
//couldn't acquire the key so do not return it
if (!key.acquireReadLockNoWait()) {
key = null;
}
}
return key;
}
/**
* INTERNAL:
* Clones itself.
*/
public Object clone() {
Object object = null;
try {
object = super.clone();
} catch (Exception e) {
;
}
return object;
}
/**
* Return true if an object is indexed in the recevier at the primary key <aVector>
* @param aVector is the primary key for the object to search for.
*/
public boolean containsKey(Vector primaryKey) {
CacheKey wrapper = getCacheKeyWithReadLock(primaryKey);
if (wrapper == null) {
return false;
} else {
return true;
}
}
public CacheKey createCacheKey(Vector primaryKey, Object object, Object writeLockValue) {
return createCacheKey(primaryKey, object, writeLockValue, 0);
}
public CacheKey createCacheKey(Vector primaryKey, Object object, Object writeLockValue, long readTime) {
return new CacheKey(primaryKey, object, writeLockValue, readTime);
}
/**
* Allow for the cache to be iterated on.
*/
public abstract Enumeration elements();
/**
* Return the object cached in the identity map or null if it could not be found.
*/
public Object get(Vector primaryKey) {
CacheKey cacheKey = getCacheKeyWithReadLock(primaryKey);
if (cacheKey == null) {
return null;
}
return cacheKey.getObject();
}
/**
* Get the cache key (with object) for the primary key.
* This reuses the same instance of cache key (searchKey) for all of the get to improve performance.
*/
protected CacheKey getCacheKey(Vector primaryKey) {
CacheKey key = null;
synchronized (this) {
getSearchKey().setKey(primaryKey);
key = getCacheKey(getSearchKey());
}
return key;
}
/**
* Return the cache key (with object) matching the cache key wrapper of the primary key.
*/
protected abstract CacheKey getCacheKey(CacheKey cacheKey);
/**
* Get the cache key (with object) for the primary key with read lock.
*/
protected CacheKey getCacheKeyWithReadLock(Vector primaryKey) {
CacheKey key = getCacheKey(primaryKey);
if (key != null) {
key.acquireReadLock();
key.releaseReadLock();
}
return key;
}
/**
* INTERNAL:
* Returns the class which should be used as an identity map. For JDK1.1.x
* FullIdentityMap is the default, for JDK1.2 it is SoftCacheWeakIdentityMap.
*
* @return java.lang.Class
*/
public static Class getDefaultIdentityMapClass() {
return ClassConstants.SoftCacheWeakIdentityMap_Class;
}
/**
* @return The maxSize for the IdentityMap (NOTE: some subclasses may use this differently).
*/
public int getMaxSize() {
if (maxSize == -1) {
maxSize = 100;
}
return maxSize;
}
protected CacheKey getSearchKey() {
return searchKey;
}
/**
* Return the number of objects in the receiver.
*/
public abstract int getSize();
/**
* Return the number of actual objects of type myClass in the IdentityMap.
* Recurse = true will include subclasses of myClass in the count.
*/
public abstract int getSize(Class myClass, boolean recurse);
/**
* Get the wrapper object from the cache key associated with the given primary key,
* this is used for EJB.
*/
public Object getWrapper(Vector primaryKey) {
CacheKey cacheKey = getCacheKeyWithReadLock(primaryKey);
if (cacheKey == null) {
return null;
} else {
return cacheKey.getWrapper();
}
}
/**
* Get the write lock value from the cache key associated to the primarykey
*/
public Object getWriteLockValue(Vector primaryKey) {
CacheKey cacheKey = getCacheKeyWithReadLock(primaryKey);
if (cacheKey == null) {
return null;
} else {
return cacheKey.getWriteLockValue();
}
}
/**
* Initialize the newly allocated instance of this class. This method must be called in order for
* the IdentityMap to be functional.
* @param anInteger is the maximum size to be allocated for the recevier.
*/
public void initialize(int size) {
setMaxSize(size);
}
/**
* Allow for the cache keys to be iterated on.
*/
public abstract Enumeration keys();
/**
* Store the object in the cache at its primary key.
* @param primaryKey is the primary key for the object.
* @param object is the domain object to cache.
* @param writeLockValue is the current write lock value of object, if null the version is ignored.
* @param readTime the read time of the object to be stored in the cache
*/
public abstract CacheKey put(Vector primaryKey, Object object, Object writeLockValue, long readTime);
/**
* Store the object in the cache with the cache key.
* Should be overide by the sub-class
*/
protected abstract void put(CacheKey cacheKey);
/**
* Remove the primary key from the cache.
*/
public Object remove(Vector primaryKey) {
CacheKey key = getCacheKey(primaryKey);
return remove(key);
}
/**
* Remove the cache key from the cache.
*/
public abstract Object remove(CacheKey cacheKey);
/**
* Set the maximum size for the recevier.
* @param anInteger is the new maximum size.
*/
protected void setMaxSize(int size) {
maxSize = size;
}
/**
* INTERNAL:
* This method will be used to update the max cache size, any objects exceeding the max cache size will
* be remove from the cache. Please note that this does not remove the object from the identityMap, except in
* the case of the CacheIdentityMap.
*/
public synchronized void updateMaxSize(int maxSize) {
setMaxSize(maxSize);
}
protected void setSearchKey(CacheKey searchKey) {
this.searchKey = searchKey;
}
/**
* Update the wrapper object the cache key associated with the given primary key,
* this is used for EJB.
*/
public void setWrapper(Vector primaryKey, Object wrapper) {
CacheKey cacheKey = getCacheKey(primaryKey);
if (cacheKey != null) {
cacheKey.setWrapper(wrapper);
}
}
/**
* Update the write lock value of the cache key associated with the given primary key,
*/
public void setWriteLockValue(Vector primaryKey, Object writeLockValue) {
CacheKey cacheKey = getCacheKey(primaryKey);
if (cacheKey != null) {
//lock/release the cache key during the lock value updating
cacheKey.acquire();
cacheKey.setWriteLockValue(writeLockValue);
cacheKey.release();
}
}
public String toString() {
return oracle.toplink.essentials.internal.helper.Helper.getShortClassName(getClass()) + "[" + getSize() + "]";
}
/**
* This is used to notify the identity map of a locked keys modification to allow updating of weak refs.
*/
public void updateCacheKey(CacheKey cacheKey) {
return;
}
}
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