io.github.lukehutch.fastclasspathscanner.utils

Class NestedJarHandler

java.lang.Object

io.github.lukehutch.fastclasspathscanner.utils.NestedJarHandler

All Implemented Interfaces:

AutoCloseable

public class NestedJarHandler
extends Object
implements AutoCloseable

Unzip a jarfile within a jarfile to a temporary file on disk. Somewhat paradoxically, the fastest way to support scanning zipfiles-within-zipfiles is to unzip the inner zipfile to a temporary file on disk, because the inner zipfile can only be read using ZipInputStream, not ZipFile (the ZipFile constructors only take a File argument). ZipInputStream doesn't have methods for reading the zip directory at the beginning of the stream, so using ZipInputStream rather than ZipFile, you have to decompress the entire zipfile to read all the directory entries. However, there may be many non-whitelisted entries in the zipfile, so this could be a lot of wasted work. FastClasspathScanner makes two passes, one to read the zipfile directory, which whitelist and blacklist criteria are applied to (this is a fast operation when using ZipFile), and then an additional pass to read only whitelisted (non-blacklisted) entries. Therefore, in the general case, the ZipFile API is always going to be faster than ZipInputStream. Therefore, decompressing the inner zipfile to disk is the only efficient option.

Constructor Summary

Constructors

Constructor and Description
NestedJarHandler(InterruptionChecker interruptionChecker, LogNode log)

Method Summary

Modifier and Type	Method and Description
void	close() Delete temporary files and release other resources.
File	getInnermostNestedJar(String nestedJarPath) Given a nested jar path consisting of jar names separated by '!', decompress each nested jarfile to a temporary file, and return the File reference for the innermost jarfile.
File	getNestedJarfile(String nestedJarfilePath) Get a File for a given (possibly nested) jarfile path, unzipping the first N-1 segments of an N-segment '!'-delimited path to temporary files, then returning the N-th temporary file.
Recycler<ZipFile,IOException>	getZipFileRecycler(String canonicalPath) Get a ZipFile recycler given the (non-nested) canonical path of a jarfile.
File	unzipToTempFile(ZipFile zipFile, ZipEntry zipEntry) Unzip a ZipEntry to a temporary file, then return the temporary file.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

NestedJarHandler

public NestedJarHandler(InterruptionChecker interruptionChecker,
                        LogNode log)

Method Detail

getNestedJarfile

public File getNestedJarfile(String nestedJarfilePath)

Get a File for a given (possibly nested) jarfile path, unzipping the first N-1 segments of an N-segment '!'-delimited path to temporary files, then returning the N-th temporary file. If the path does not contain '!', returns the file represented by the path. All path segments should end in a jarfile extension, e.g. ".jar" or ".zip".

Returns:

the File for the innermost jar, or null if any path segment does not exist, or if an exception was thrown during singleton creation, or the operation was interrupted.

getZipFileRecycler

public Recycler<ZipFile,IOException> getZipFileRecycler(String canonicalPath)

Get a ZipFile recycler given the (non-nested) canonical path of a jarfile.

Returns:

The ZipFile recycler, or null if an exception was thrown during singleton creation, or if the thread was interrupted.

getInnermostNestedJar

public File getInnermostNestedJar(String nestedJarPath)

Given a nested jar path consisting of jar names separated by '!', decompress each nested jarfile to a temporary file, and return the File reference for the innermost jarfile.

Returns:

null if any of the nested jars don't exist, or if an exception was thrown during singleton creation, or if the thread was interrupted.

unzipToTempFile

public File unzipToTempFile(ZipFile zipFile,
                            ZipEntry zipEntry)
                     throws IOException

Unzip a ZipEntry to a temporary file, then return the temporary file.

Throws:

IOException

close

public void close()

Delete temporary files and release other resources.

Specified by:

close in interface AutoCloseable