| 1 | package de.uka.ipd.sdq.sensorframework.dao.file; |
| 2 | |
| 3 | import java.util.Collection; |
| 4 | import java.util.Collections; |
| 5 | import java.util.HashMap; |
| 6 | |
| 7 | import de.uka.ipd.sdq.sensorframework.dao.file.entities.SerializableEntity; |
| 8 | import de.uka.ipd.sdq.sensorframework.entities.dao.IDAOFactory; |
| 9 | |
| 10 | /** |
| 11 | * An abstract implementation of a file DAO. The DAO is based on the following principle. All entities |
| 12 | * are stored in a hashmap which hashes IDs to entities. The hashmap is fully loaded from the background |
| 13 | * storage at startup, manipulated in memory, and finally stored back on request or when the DAO is disposed. |
| 14 | * |
| 15 | * @author Steffen Becker |
| 16 | * |
| 17 | * @param <T> The type of the entities this DAO is able to handle |
| 18 | */ |
| 19 | public abstract class AbstractFileDAO<T> { |
| 20 | |
| 21 | /** |
| 22 | * Interface to other DAOs |
| 23 | */ |
| 24 | protected FileDAOFactory factory = null; |
| 25 | |
| 26 | /** |
| 27 | * Prefix of the file which stores the elements controlled by this DAO |
| 28 | */ |
| 29 | private String myPrefix; |
| 30 | |
| 31 | /** |
| 32 | * ID Generator instance. Used by subclasses to create IDs of new elements |
| 33 | */ |
| 34 | protected IDGenerator idGen; |
| 35 | |
| 36 | /** |
| 37 | * A cache/storage for elements in this DAO |
| 38 | */ |
| 39 | private HashMap<Long, T> entitiesCache = null;//why not a sorted map? |
| 40 | |
| 41 | |
| 42 | /** Constructor of this DAO |
| 43 | * @param factory Interface to other DAOs |
| 44 | * @param idGen Identifier Generator used for new elements |
| 45 | * @param prefix Filename prefix for the filename used to persist the elements controlled by this DAO |
| 46 | */ |
| 47 | public AbstractFileDAO(IDAOFactory factory, IDGenerator idGen, String prefix) { |
| 48 | this.factory = (FileDAOFactory)factory; |
| 49 | this.idGen = idGen; |
| 50 | this.myPrefix = prefix; |
| 51 | loadDataFromStorage(); |
| 52 | } |
| 53 | |
| 54 | /** |
| 55 | * Load all elements controlled by this DAO into memory. Called on startup to initialise this DAO |
| 56 | */ |
| 57 | @SuppressWarnings("unchecked") |
| 58 | private void loadDataFromStorage() { |
| 59 | this.entitiesCache = (HashMap<Long, T>) this.factory.getFileManager().deserializeFromFile(this.myPrefix); |
| 60 | if (this.entitiesCache == null) { |
| 61 | this.entitiesCache = new HashMap<Long, T>(); |
| 62 | } else { |
| 63 | for (T value : this.entitiesCache.values()) { |
| 64 | SerializableEntity serializable = (SerializableEntity) value; |
| 65 | serializable.setFactory(this.factory); |
| 66 | } |
| 67 | } |
| 68 | } |
| 69 | |
| 70 | /** |
| 71 | * Stores all elements controlled by this DAO on the persistent storage |
| 72 | */ |
| 73 | public void storeAll() { |
| 74 | factory.getFileManager().serializeToFile(this.myPrefix,entitiesCache); |
| 75 | } |
| 76 | |
| 77 | /** Get entity with given ID from DAO |
| 78 | * @param id ID of the element to retrieve. The element with ID id has to exist otherwise an |
| 79 | * IllegalArguementException is thrown |
| 80 | * @return The requested element |
| 81 | */ |
| 82 | public T get(long id) { |
| 83 | if (!entitiesCache.containsKey(id)) |
| 84 | throw new IllegalArgumentException("Entity with ID "+id+" not found in DAO"); |
| 85 | return entitiesCache.get(id); |
| 86 | } |
| 87 | |
| 88 | /** |
| 89 | * Store a new element in this DAO. Used by subclasses to register newly created elements |
| 90 | * @param entity A new element. The element must not be controlled by the DAO already |
| 91 | */ |
| 92 | protected void putEntity(T entity) { |
| 93 | SerializableEntity serialisable = (SerializableEntity) entity; |
| 94 | if (entitiesCache.containsKey(serialisable.getID())) |
| 95 | throw new IllegalArgumentException("Entity with ID "+serialisable.getID()+" already exists in this DAO"); |
| 96 | this.entitiesCache.put(serialisable.getID(), entity); |
| 97 | } |
| 98 | |
| 99 | /** Returns a list of all entities stored in this DAO |
| 100 | * @return A list of all entities stored in this DAO |
| 101 | */ |
| 102 | protected Collection<T> getAllEntities() { |
| 103 | return Collections.unmodifiableCollection(entitiesCache.values()); |
| 104 | } |
| 105 | |
| 106 | /** Remove the given entity from this DAO's control |
| 107 | * @param entity The entity to remove |
| 108 | * @param doCascade If true, all entities which depend on the passed entity are deleted as well |
| 109 | */ |
| 110 | public void removeEntity(T entity, boolean doCascade) { |
| 111 | if (entity == null) |
| 112 | throw new IllegalArgumentException("Entity can not be null"); |
| 113 | if (!entitiesCache.containsValue(entity)) |
| 114 | throw new IllegalArgumentException("Entity not controlled by this DAO"); |
| 115 | |
| 116 | if (doCascade == true) { |
| 117 | throw new UnsupportedOperationException(); |
| 118 | } |
| 119 | |
| 120 | entitiesCache.remove(((SerializableEntity)entity).getID()); |
| 121 | } |
| 122 | |
| 123 | /** |
| 124 | * Disposes this DAO. This includes persisting all changes to the background storage |
| 125 | */ |
| 126 | public void dispose() { |
| 127 | this.storeAll(); |
| 128 | this.entitiesCache.clear(); |
| 129 | } |
| 130 | } |