edu.cornell.mannlib.vitro.webapp.filestorage.TempFileHolder.java Source code

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Here is the source code for edu.cornell.mannlib.vitro.webapp.filestorage.TempFileHolder.java

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/* $This file is distributed under the terms of the license in /doc/license.txt$ */

package edu.cornell.mannlib.vitro.webapp.filestorage;

import java.io.IOException;

import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import edu.cornell.mannlib.vitro.webapp.application.ApplicationUtils;
import edu.cornell.mannlib.vitro.webapp.filestorage.model.FileInfo;
import edu.cornell.mannlib.vitro.webapp.modules.fileStorage.FileStorage;

/**
 * Attaches an uploaded file to the session with a listener, so the file will be
 * deleted if
 * <ul>
 * <li>The session times out.</li>
 * <li>The session is invalidated.</li>
 * <li>The server is shut down.</li>
 * <li>Another file is attached to the session with the same attribute name.</li>
 * </ul>
 * To see that the file isn't deleted, remove it from the session with a call to
 * {@link TempFileHolder#remove(HttpSession, String) remove}.
 */
public class TempFileHolder implements HttpSessionBindingListener {
    private static final Log log = LogFactory.getLog(TempFileHolder.class);

    /**
     * Create a {@link TempFileHolder} holding the given {@link FileInfo}, and
     * attach it to the session with the given attribute name.
     * 
     * If an attribute with this name already exists, it is replaced.
     */
    public static void attach(HttpSession session, String attributeName, FileInfo fileInfo) {
        if (session == null) {
            throw new NullPointerException("session may not be null.");
        }
        if (attributeName == null) {
            throw new NullPointerException("attributeName may not be null.");
        }
        if (fileInfo == null) {
            throw new NullPointerException("fileInfo may not be null.");
        }
        log.debug("attach this file: " + fileInfo);
        session.setAttribute(attributeName, new TempFileHolder(fileInfo));
    }

    /**
     * Get the {@link TempFileHolder} which is stored as an attribute on this
     * session, extract the {@link FileInfo} from it, and remove it from the
     * session.
     * 
     * If there is no such attribute, of if it is not a {@link TempFileHolder},
     * return null.
     */
    public static FileInfo remove(HttpSession session, String attributeName) {
        if (session == null) {
            throw new NullPointerException("session may not be null.");
        }
        if (attributeName == null) {
            throw new NullPointerException("attributeName may not be null.");
        }
        Object attribute = session.getAttribute(attributeName);
        if (attribute instanceof TempFileHolder) {
            FileInfo fileInfo = ((TempFileHolder) attribute).extractFileInfo();
            session.removeAttribute(attributeName);
            log.debug("remove this file: " + fileInfo);
            return fileInfo;
        } else if (attribute == null) {
            return null;
        } else {
            session.removeAttribute(attributeName);
            return null;
        }
    }

    private FileInfo fileInfo;

    private TempFileHolder(FileInfo fileInfo) {
        if (fileInfo == null) {
            throw new NullPointerException("fileInfo may not be null.");
        }
        this.fileInfo = fileInfo;
    }

    /**
     * Gets the {@link FileInfo} payload, and removes it so the file won't be
     * deleted when the value is unbound.
     * 
     * @return
     */
    private FileInfo extractFileInfo() {
        FileInfo result = this.fileInfo;
        this.fileInfo = null;
        return result;
    }

    /**
     * When attached to the session, do nothing.
     * 
     * @see HttpSessionBindingListener#valueBound(HttpSessionBindingEvent)
     */
    @Override
    public void valueBound(HttpSessionBindingEvent event) {
        // Nothing to do.
    }

    /**
     * When removed from the session, if the {@link #fileInfo} is not empty,
     * delete the file. If you had wanted this file, you should have called
     * {@link #remove(HttpSession, String) remove}.
     * 
     * @see HttpSessionBindingListener#valueUnbound(HttpSessionBindingEvent)
     */
    @Override
    public void valueUnbound(HttpSessionBindingEvent event) {
        if (fileInfo == null) {
            log.trace("No file info.");
            return;
        }

        if (fileInfo.getBytestreamUri() == null) {
            log.warn("File info has no URI?");
            return;
        }

        FileStorage fs = ApplicationUtils.instance().getFileStorage();
        try {
            fs.deleteFile(fileInfo.getBytestreamUri());
            log.debug("Deleted file " + fileInfo);
        } catch (IOException e) {
            log.error("Failed to delete temp file from session: " + event, e);
        }
    }

}