Grid Application Toolkit A simple API for Grid Applications

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File.java Go to the documentation of this file. package org.gridlab.gat.io; import java.io.IOException; import java.io.Serializable; import java.net.URI; import org.gridlab.gat.GATContext; import org.gridlab.gat.Preferences; import org.gridlab.gat.engine.GATEngine; import org.gridlab.gat.io.cpi.FileCpi; import org.gridlab.gat.monitoring.Monitorable; import org.gridlab.gat.net.RemoteException; /** * 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 File extends java.io.File implements Monitorable, Serializable { protected URI location; 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 File(GATContext gatContext, Preferences preferences, URI location) { super(location); this.location = location; 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 File create(GATContext gatContext, URI location) { return create(gatContext, null, location); } /** * 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 File create(GATContext gatContext, Preferences preferences, URI location) { // Make life a bit easier for the programmer: // If the URI does not have a scheme part, just consider it a local file. // The ctor of java.io.file does not accept this. URI tmpLocation = location; if(tmpLocation.getScheme() == null) { java.io.File tmp = new java.io.File(tmpLocation.toString()); tmpLocation = tmp.toURI(); } GATEngine gatEngine = GATEngine.getGATEngine(); Object[] array = new Object[1]; array[0] = tmpLocation; FileCpi f = (FileCpi) gatEngine.getAdaptor(FileCpi.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.File)) return false; org.gridlab.gat.io.File file = (org.gridlab.gat.io.File) object; return location.equals(file.getURI()); } /** * This method returns the URI of this File * * @return The URI of this File */ public URI getURI() { return location; } /** * This method copies the physical file represented by this File instance to * a physical file identified by the passed URI. * * @param loc * The new location * @throws java.rmi.RemoteException * Thrown upon problems accessing the remote instance * @throws java.io.IOException * Upon non-remote IO problem */ public abstract void copy(URI loc) throws IOException, RemoteException; /** * This method moves the physical file represented by this File instance to * a physical file identified by the passed URI. * * @param location * The URI to which to move the physical file corresponding * to this File instance * @throws java.rmi.RemoteException * Thrown upon problems accessing the remote instance * @throws java.io.IOException * Upon non-remote IO problem */ public void move(URI location) throws IOException { // Step 1: Copy the original file copy(location); // Step 2: Delete the original file delete(); // Step 3: Update location this.location = location; } }