MonitoredOutputStream.java

package org.springframework.roo.process.manager.internal;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;

import org.apache.commons.codec.digest.DigestUtils;
import org.apache.commons.io.FileUtils;
import org.apache.commons.lang3.Validate;
import org.springframework.roo.file.monitor.NotifiableFileMonitorService;

/**
 * Ensures the {@link NotifiableFileMonitorService#notifyChanged(String)} method
 * is invoked when {@link #close()} is called.
 * <p>
 * This is useful for ensuring the file monitoring system is notified of all
 * changed files, even those which are changed very rapidly on disk and would
 * not normally be detected using the file system's "last updated" timestamps.
 * 
 * @author Ben Alex
 * @since 1.0
 */
public class MonitoredOutputStream extends ByteArrayOutputStream {

  private final File file;
  private final NotifiableFileMonitorService fileMonitorService;

  private final ManagedMessageRenderer managedMessageRenderer;

  /**
   * Constructs a {@link MonitoredOutputStream}.
   * 
   * @param file the file to output to (required)
   * @param managedMessageRenderer a rendered for outputting a message once
   *            the output stream is closed (required)
   * @param fileMonitorService an optional monitoring service (null is
   *            acceptable)
   * @throws FileNotFoundException if the file cannot be found
   */
  public MonitoredOutputStream(final File file,
      final ManagedMessageRenderer managedMessageRenderer,
      final NotifiableFileMonitorService fileMonitorService) throws FileNotFoundException {
    Validate.notNull(file, "File required");
    Validate.notNull(managedMessageRenderer, "Message renderer required");
    this.file = file;
    this.fileMonitorService = fileMonitorService;
    this.managedMessageRenderer = managedMessageRenderer;
  }

  @Override
  public void close() throws IOException {
    // Obtain the bytes the user is writing out
    final byte[] bytes = toByteArray();

    // Try to calculate the SHA hash code
    managedMessageRenderer.setHashCode(DigestUtils.shaHex(bytes));

    // Log that we're writing the file
    managedMessageRenderer.logManagedMessage();

    // Write the actual file out to disk
    FileUtils.writeByteArrayToFile(file, bytes);

    // Tell the FileMonitorService what happened
    String fileCanonicalPath;
    try {
      fileCanonicalPath = file.getCanonicalPath();
    } catch (final IOException ioe) {
      throw new IllegalStateException(ioe);
    }
    if (fileMonitorService != null) {
      fileMonitorService.notifyChanged(fileCanonicalPath);
    }
  }
}