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package com.sun.appserv.ha.spi;
import java.util.Properties;
/**
* An object that stores a given Metadata against an id. This class defines the
* set of operations that a container could perform on a store.
*
* <p>
* An instance of BackingStore is created by calling
* <code>BackingStoreFactory.createSimpleStore()</code> method.
*
* <p>
* The BackingStore instance is created and used for storing data that belongs
* to a single application or container.
*
* <p>
* The store implementation must be thread safe.
*/
public abstract class BackingStore<K extends Metadata> {
private String appId;
private Properties props;
protected Properties getProperties() {
return props;
}
protected String getAppId() {
return this.appId;
}
protected void initialize(String appId, Properties props) {
this.appId = appId;
this.props = props;
}
/**
* Load and return the daata for the given id. The store is expected to
* return the largest ever version that was saved in the stored using the
* <code>save()</code> method. Note that the return value could be null if
* Metadata was not accessed for {@link Metadata#getMaxInactiveInterval()}
*
* @param id
* the id whose value must be returned
* @return the value if this store contains it or null. The implementation
* must return the exact same type as that was passed to it in the
* save method.
*
* @throws NullPointerException
* if the id is null
* @throws BackingStoreException
* if the underlying store implementation encounters any
* exception
*/
public abstract K load(String id) throws BackingStoreException;
/**
* Save the value whose key is id.
*
* @param id
* the id
* @param value
* The Metadata to be stored
* @throws BackingStoreException
* if the underlying store implementation encounters any
* exception
*/
public abstract void save(String id, K value) throws BackingStoreException;
/**
* Update the last access time for this id.
*
* @param id
* the id for the Metadata
* @param time
* the time at which this data was last accessed
* @param version
* the new version number for the data associated with this id. A
* newly created version will have version number zero.
* @throws BackingStoreException
* if the underlying store implementation encounters any
* exception
*/
public abstract void updateLastAccessTime(String id, long time, long version)
throws BackingStoreException;
/**
* Remove the association for the id. After this call, any call to
* <code>load(id)</code> <b>must</b> return null
*
* @param id
* the id
* @return true if the id was successfully removed false otherwise
* @throws BackingStoreException
* if the underlying store implementation encounters any
* exception
*/
public abstract void remove(String id) throws BackingStoreException;
/**
* Remove all instances that are idle. The implementation of this method
* must use {@link Metadata#getLastAccessTime()} and
* {@link Metadata#getMaxInactiveInterval()} to determine if a particular
* Metadata is idle or not. A Metadata is considered idle if <code>
* (Metadata.getMaxInactiveInterval > 0)
* && ((System.currentTimeMillis() - Metadata.getLastAccessTime()) >=
* Metadata.getMaxInactiveInterval())</code>
*
* @return The number of (idle) sessions removed.
* @throws BackingStoreException
* if the underlying store implementation encounters any
* exception
*/
public abstract int removeExpired() throws BackingStoreException;
/**
* Get the current size of the store
*
* @return the number of entries in the store
* @throws BackingStoreException
* if the underlying store implementation encounters any
* exception
*/
public abstract int size() throws BackingStoreException;
/**
* Called when the store is no longer needed. Must clean up and close any
* opened resources.
*/
public abstract void destroy() throws BackingStoreException;
}
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