io.github.lukehutch.fastclasspathscanner.utils

Class NestedJarHandler

java.lang.Object

io.github.lukehutch.fastclasspathscanner.utils.NestedJarHandler

public class NestedJarHandler
extends Object

Unzip a jarfile within a jarfile to a temporary file on disk. Also handles the download of jars from http(s) URLs to temp files.

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.

Field Summary

Fields

Modifier and Type	Field and Description
static String	TEMP_FILENAME_LEAF_SEPARATOR

Constructor Summary

Constructors

Constructor and Description
NestedJarHandler(InterruptionChecker interruptionChecker, LogNode log)

Method Summary

Modifier and Type	Method and Description
void	close(LogNode log) Delete temporary files and release other resources.
Map.Entry<File,Set<String>>	getInnermostNestedJar(String nestedJarPath, LogNode log) 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, LogNode log) Get a ZipFile recycler given the (non-nested) canonical path of a jarfile.

Methods inherited from class java.lang.Object

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

Field Detail

TEMP_FILENAME_LEAF_SEPARATOR

public static final String TEMP_FILENAME_LEAF_SEPARATOR

See Also:

Constant Field Values

Constructor Detail

NestedJarHandler

public NestedJarHandler(InterruptionChecker interruptionChecker,
                        LogNode log)

Method Detail

getZipFileRecycler

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

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

Returns:

The ZipFile recycler.

Throws:

Exception

getInnermostNestedJar

public Map.Entry<File,Set<String>> getInnermostNestedJar(String nestedJarPath,
                                                         LogNode log)
                                                  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:

An Entry<File, Set<String>>, where the File is the innermost jar, and the Set<String> is the set of all relative paths of scanning roots within the innermost jar (may be empty, or may contain strings like "target/classes" or similar). If there was an issue with the path, returns null.

Throws:

Exception

close

public void close(LogNode log)

Delete temporary files and release other resources.