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RandomAccessFile.java Go to the documentation of this file. package org.gridlab.gat.io; import java.io.FileNotFoundException; import org.gridlab.gat.GATContext; import org.gridlab.gat.Preferences; import org.gridlab.gat.engine.GATEngine; import org.gridlab.gat.io.cpi.RandomAccessFileCpi; import org.gridlab.gat.monitoring.Monitorable; /** * An abstract representation of a physical file. * <p> * An instance of this class presents an abstract, system-independent view of a * physical file. User interfaces and operating systems use system-dependent * pathname strings to identify physical files. GAT, however, uses an operating * system independent pathname string to identify a physical file. A physical * file in GAT is identified by a URI. * <p> * An instance of this File class allows for various high-level operations to be * preformed on a physical file. For example, one can, with a single API call, * copy a physical file from one location to a second location, move a physical * file from one location to a second location, delete a physical file, and * preform various other operations on a physical file. The utility of this * high-level view of a physical file is multi-fold. The client of an instance * of this class does not have to concern themselves with the details of reading * every single byte of a physical file when all they wish to do is copy the * physical file to a new location. Similarly, a client does not have to deal * with all the various error states that can occur when moving a physical file ( * Have all the various bytes been read correctly? Have all the various bytes * been saved correctly? Did the deletion of the original file proceed * correctly? ); the client simply has to call a single API call and the * physical file is moved. */ public abstract class RandomAccessFile extends java.io.RandomAccessFile implements Monitorable, java.io.Serializable { protected File file; protected String mode; protected GATContext gatContext; protected Preferences preferences; /** * Constructs a File instance which corresponds to the physical file * identified by the passed URI and whose access rights are determined by * the passed GATContext. * * @param location * A URI which represents the URI corresponding to the physical * file. * @param gatContext * A GATContext which is used to determine the access rights for * this File. * @param preferences * A Preferences which is used to determine the user's * preferences for this File. * @throws java.lang.Exception * Thrown upon creation problems */ protected RandomAccessFile(GATContext gatContext, Preferences preferences, File file, String mode) throws FileNotFoundException { super(file, mode); this.file = file; this.mode = mode; this.gatContext = gatContext; this.preferences = preferences; } /** * Constructs a File instance which corresponds to the physical file * identified by the passed URI and whose access rights are determined by * the passed GATContext. * * @param location * A URI which represents the URI corresponding to the physical * file. * @param gatContext * A GATContext which is used to determine the access rights for * this File. * @throws java.lang.Exception * Thrown upon creation problems */ public static RandomAccessFile create(GATContext gatContext, File file, String mode) throws FileNotFoundException { return create(gatContext, null, file, mode); } /** * Constructs a File instance which corresponds to the physical file * identified by the passed URI and whose access rights are determined by * the passed GATContext. * * @param location * A URI which represents the URI corresponding to the physical * file. * @param gatContext * A GATContext which is used to determine the access rights for * this File. * @param preferences * A Preferences which is used to determine the user's * preferences for this File. * @throws java.lang.Exception * Thrown upon creation problems */ public static RandomAccessFile create(GATContext gatContext, Preferences preferences, File file, String mode) throws FileNotFoundException { GATEngine gatEngine = GATEngine.getGATEngine(); Object[] array = new Object[2]; array[0] = file; array[1] = mode; RandomAccessFileCpi f = (RandomAccessFileCpi) gatEngine.getAdaptor( RandomAccessFileCpi.class, gatContext, preferences, array); return f; } /** * Tests this File for equality with the passed Object. * <p> * If the given object is not a File, then this method immediately returns * false. * <p> * If the given object is a File, then it is deemed equal to this instance * if a URI object constructed from this File's location and a URI object * constructed from the passed File's URI are equal as determined by the * Equals method of URI. * * @param object * The Object to test for equality * @return A boolean indicating equality */ public boolean equals(Object object) { if (!(object instanceof org.gridlab.gat.io.RandomAccessFile)) return false; org.gridlab.gat.io.RandomAccessFile other = (org.gridlab.gat.io.RandomAccessFile) object; return file.equals(other.file); } }