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(boolean removeTemporaryFilesAfterScan, 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) 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 File reference for 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(boolean removeTemporaryFilesAfterScan,
                        InterruptionChecker interruptionChecker,
                        LogNode log)

Method Detail

getZipFileRecycler

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

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

Returns:

The ZipFile recycler.

Throws:

Exception

getInnermostNestedJar

public File getInnermostNestedJar(String nestedJarPath)
                           throws Exception

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 File reference for 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.

Throws:

Exception

unzipToTempFile

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

Unzip a ZipEntry to a temporary file, then return the temporary file. The temporary file will be removed when NestedJarHandler#close() is called.

Throws:

IOException

close

public void close()

Delete temporary files and release other resources.

Specified by:

close in interface AutoCloseable