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bug 59166: suggest alternative implementations for TempFileCreationStrategy

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git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1751190 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Javen O'Neal 2016-07-04 01:07:52 +00:00
parent 569db169dd
commit f972e1c6e4
3 changed files with 64 additions and 8 deletions
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26
src/java/org/apache/poi/util/DefaultTempFileCreationStrategy.java
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@ -9,13 +9,25 @@ import java.security.SecureRandom;
* Files are collected into one directory and by default are deleted on exit from the VM.
* Files may be manually deleted by user prior to JVM exit.
* Files can be kept by defining the system property {@link #KEEP_FILES}.
*
* Each file is registered for deletion with the JVM and the temporary directory is not deleted
* after the JVM exits. Files that are created in the poifiles directory outside
* the control of DefaultTempFileCreationStrategy are not deleted.
* See {@link TempFileCreationStrategy} for better strategies for long-running
* processes or limited temporary storage.
*/
public class DefaultTempFileCreationStrategy implements TempFileCreationStrategy {
/** Define a constant for this property as it is sometimes mistypes as "tempdir" otherwise */
/** Define a constant for this property as it is sometimes mistypes as "tempdir" otherwise
* This is private to avoid having two public-visible constants ({@link TempFile#JAVA_IO_TMPDIR}). */
private static final String JAVA_IO_TMPDIR = TempFile.JAVA_IO_TMPDIR;
/*package*/ static final String POIFILES = "poifiles";
/** To keep files after JVM exit, set the <code>-Dpoi.keep.tmp.files</code> JVM property */
public static final String KEEP_FILES = "poi.keep.tmp.files";
/** random number generator to generate unique filenames */
private static final SecureRandom random = new SecureRandom();
/** The directory where the temporary files will be created (<code>null</code> to use the default directory). */
private File dir;
@ -47,12 +59,18 @@ public class DefaultTempFileCreationStrategy implements TempFileCreationStrategy
if (tmpDir == null) {
throw new IOException("Systems temporary directory not defined - set the -D"+JAVA_IO_TMPDIR+" jvm property!");
}
dir = new File(tmpDir, "poifiles");
dir = new File(tmpDir, POIFILES);
}
createTempDirectory(dir);
}
/**
* Attempt to create a directory
*
* @param directory
* @throws IOException
*/
private void createTempDirectory(File directory) throws IOException {
if (!(directory.exists() || directory.mkdirs()) || !directory.isDirectory()) {
throw new IOException("Could not create temporary directory '" + directory + "'");
@ -75,8 +93,8 @@ public class DefaultTempFileCreationStrategy implements TempFileCreationStrategy
// All done
return newFile;
}
private static final SecureRandom random = new SecureRandom();
/* (non-JavaDoc) Created directory path is <JAVA_IO_TMPDIR>/poifiles/prefix0123456789 */
@Override
public File createTempDirectory(String prefix) throws IOException {
// Identify and create our temp dir, if needed

39
src/java/org/apache/poi/util/TempFileCreationStrategy.java
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@ -22,6 +22,43 @@ import java.io.IOException;
/**
* Interface used by the {@link TempFile} utility class to create temporary files.
*
* Classes that implement a TempFileCreationStrategy attempt to handle the cleanup
* of temporary files.
*
* Examples include:
* <ul>
* <li>{@link DefaultTempFileCreationStrategy} deletes temporary files when
* the JVM exits.
* This may not be suitable for long-running applications that never
* shut down the JVM since the list of registered files and disk space
* usage would grow for as long as the JVM is running.
* You may wish to implement your own strategy that meets the needs of
* your situation.
* </li>
* <li>A strategy that keeps the <code>n</code> most-recent files, discarding
* older files on a first-in, first-out basis.
* A java.util.Deque or org.apache.commons.collections4.queue.CircularFifoQueue
* may be helpful for achieving this.
* </li>
* <li>A strategy that keeps track of every temporary file that has been
* created by the class or instance and provides a method to explicitly
* delete the temporary files in the reverse order that they were created.
* This is the same as DefaultTempFileCreationStrategy, except the strategy
* class would maintain the list of files to delete rather than or in
* addition to {@link java.io.DeleteOnExitHook} maintaining the list, and
* the files could be deleted before the JVM exit.
* </li>
* <li>A strategy that creates a directory that is deleted on JVM exit.
* Any files inside the directory do not need to be registered since the
* entire directory will be deleted at exit.
* This could be dangerous if files were added to the temporary directory
* outside of this TempFileCreationStrategy's control.
* This could be accomplished with {@link #createTempDirectory(String)} and
* creating regular (unregistered) files in the temp directory.
* </li>
* </ul>
*
*/
public interface TempFileCreationStrategy {
/**
@ -44,6 +81,8 @@ public interface TempFileCreationStrategy {
* @return The path to the newly created and empty temporary directory.
*
* @throws IOException If no temporary directory could be created.
*
* @since POI 3.15 beta 3.
*/
File createTempDirectory(String prefix) throws IOException;
}

7
src/testcases/org/apache/poi/util/TestTempFile.java
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@ -20,7 +20,6 @@ import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;
import java.io.File;
import java.io.FileOutputStream;
@ -57,7 +56,7 @@ public class TestTempFile {
String[] files = tempDir.list();
// can have the "poifiles" subdir
if(files.length == 1) {
assertEquals("Had: " + Arrays.toString(files), "poifiles", files[0]);
assertEquals("Had: " + Arrays.toString(files), DefaultTempFileCreationStrategy.POIFILES, files[0]);
files = new File(tempDir, files[0]).list();
assertEquals("Had: " + Arrays.toString(files), 0, files.length);
} else {
@ -96,7 +95,7 @@ public class TestTempFile {
assertTrue("temp file's name should end with .txt",
tempFile.getName().endsWith(".txt"));
assertEquals("temp file is saved in poifiles directory",
"poifiles", tempFile.getParentFile().getName());
DefaultTempFileCreationStrategy.POIFILES, tempFile.getParentFile().getName());
// Can't think of a good way to check whether a file is actually deleted since it would require the VM to stop.
// Solution: set TempFileCreationStrategy to something that the unit test can trigger a deletion"
@ -119,7 +118,7 @@ public class TestTempFile {
assertTrue("testDir's name starts with testDir",
tempDir.getName().startsWith("testDir"));
assertEquals("tempDir is saved in poifiles directory",
"poifiles", tempDir.getParentFile().getName());
DefaultTempFileCreationStrategy.POIFILES, tempDir.getParentFile().getName());
// Can't think of a good way to check whether a directory is actually deleted since it would require the VM to stop.
// Solution: set TempFileCreationStrategy to something that the unit test can trigger a deletion"