Module java.base
Package java.util.jar

Class JarFile

java.lang.Object
java.util.zip.ZipFile
java.util.jar.JarFile
All Implemented Interfaces:
Closeable, AutoCloseable
public class JarFile
extends ZipFile
The JarFile class is used to read the contents of a jar file from any file that can be opened with java.io.RandomAccessFile. It extends the class java.util.zip.ZipFile with support for reading an optional Manifest entry, and support for processing multi-release jar files. The Manifest can be used to specify meta-information about the jar file and its entries.

A multi-release jar file is a jar file that contains a manifest with a main attribute named "Multi-Release", a set of "base" entries, some of which are public classes with public or protected methods that comprise the public interface of the jar file, and a set of "versioned" entries contained in subdirectories of the "META-INF/versions" directory. The versioned entries are partitioned by the major version of the Java platform. A versioned entry, with a version n, 8 < n, in the "META-INF/versions/{n}" directory overrides the base entry as well as any entry with a version number i where 8 < i < n.

By default, a JarFile for a multi-release jar file is configured to process the multi-release jar file as if it were a plain (unversioned) jar file, and as such an entry name is associated with at most one base entry. The JarFile may be configured to process a multi-release jar file by creating the JarFile with the JarFile(File, boolean, int, Runtime.Version) constructor. The Runtime.Version object sets a maximum version used when searching for versioned entries. When so configured, an entry name can correspond with at most one base entry and zero or more versioned entries. A search is required to associate the entry name with the latest versioned entry whose version is less than or equal to the maximum version (see getEntry(String)).

Class loaders that utilize JarFile to load classes from the contents of JarFile entries should construct the JarFile by invoking the JarFile(File, boolean, int, Runtime.Version) constructor with the value Runtime.version() assigned to the last argument. This assures that classes compatible with the major version of the running JVM are loaded from multi-release jar files.

If the verify flag is on when opening a signed jar file, the content of the jar entry is verified against the signature embedded inside the manifest that is associated with its path name. For a multi-release jar file, the content of a versioned entry is verfieid against its own signature and JarEntry.getCodeSigners() returns its own signers. Please note that the verification process does not include validating the signer's certificate. A caller should inspect the return value of JarEntry.getCodeSigners() to further determine if the signature can be trusted.

Unless otherwise noted, passing a null argument to a constructor or method in this class will cause a NullPointerException to be thrown.

Implementation Note:
If the API can not be used to configure a JarFile (e.g. to override the configuration of a compiled application or library), two System properties are available.
  • jdk.util.jar.version can be assigned a value that is the String representation of a non-negative integer <= Runtime.version().feature(). The value is used to set the effective runtime version to something other than the default value obtained by evaluating Runtime.version().feature(). The effective runtime version is the version that the JarFile(File, boolean, int, Runtime.Version) constructor uses when the value of the last argument is JarFile.runtimeVersion().
  • jdk.util.jar.enableMultiRelease can be assigned one of the three String values true, false, or force. The value true, the default value, enables multi-release jar file processing. The value false disables multi-release jar processing, ignoring the "Multi-Release" manifest attribute, and the versioned directories in a multi-release jar file if they exist. Furthermore, the method isMultiRelease() returns false. The value force causes the JarFile to be initialized to runtime versioning after construction. It effectively does the same as this code: (new JarFile(File, boolean, int, JarFile.runtimeVersion()).
Since:
1.2
See Also:
Manifest, ZipFile, JarEntry

  • Field Details

  • Constructor Details

    • JarFile

      public JarFile​(String name) throws IOException
      Creates a new JarFile to read from the specified file name. The JarFile will be verified if it is signed.
      Parameters:
      name - the name of the jar file to be opened for reading
      Throws:
      IOException - if an I/O error has occurred
      SecurityException - if access to the file is denied by the SecurityManager

    • JarFile

      public JarFile​(String name, boolean verify) throws IOException
      Creates a new JarFile to read from the specified file name.
      Parameters:
      name - the name of the jar file to be opened for reading
      verify - whether or not to verify the jar file if it is signed.
      Throws:
      IOException - if an I/O error has occurred
      SecurityException - if access to the file is denied by the SecurityManager

    • JarFile

      public JarFile​(File file) throws IOException
      Creates a new JarFile to read from the specified File object. The JarFile will be verified if it is signed.
      Parameters:
      file - the jar file to be opened for reading
      Throws:
      IOException - if an I/O error has occurred
      SecurityException - if access to the file is denied by the SecurityManager

    • JarFile

      public JarFile​(File file, boolean verify) throws IOException
      Creates a new JarFile to read from the specified File object.
      Parameters:
      file - the jar file to be opened for reading
      verify - whether or not to verify the jar file if it is signed.
      Throws:
      IOException - if an I/O error has occurred
      SecurityException - if access to the file is denied by the SecurityManager.

    • JarFile

      public JarFile​(File file, boolean verify, int mode) throws IOException
      Creates a new JarFile to read from the specified File object in the specified mode. The mode argument must be either OPEN_READ or OPEN_READ | OPEN_DELETE.
      Parameters:
      file - the jar file to be opened for reading
      verify - whether or not to verify the jar file if it is signed.
      mode - the mode in which the file is to be opened
      Throws:
      IOException - if an I/O error has occurred
      IllegalArgumentException - if the mode argument is invalid
      SecurityException - if access to the file is denied by the SecurityManager
      Since:
      1.3

    • JarFile

      public JarFile​(File file, boolean verify, int mode, Runtime.Version version) throws IOException
      Creates a new JarFile to read from the specified File object in the specified mode. The mode argument must be either OPEN_READ or OPEN_READ | OPEN_DELETE. The version argument, after being converted to a canonical form, is used to configure the JarFile for processing multi-release jar files.

      The canonical form derived from the version parameter is Runtime.Version.parse(Integer.toString(n)) where n is Math.max(version.feature(), JarFile.baseVersion().feature()).

      Parameters:
      file - the jar file to be opened for reading
      verify - whether or not to verify the jar file if it is signed.
      mode - the mode in which the file is to be opened
      version - specifies the release version for a multi-release jar file
      Throws:
      IOException - if an I/O error has occurred
      IllegalArgumentException - if the mode argument is invalid
      SecurityException - if access to the file is denied by the SecurityManager
      NullPointerException - if version is null
      Since:
      9

  • Method Details

    • baseVersion

      public static Runtime.Version baseVersion()
      Returns the version that represents the unversioned configuration of a multi-release jar file.
      Returns:
      the version that represents the unversioned configuration
      Since:
      9

    • runtimeVersion

      public static Runtime.Version runtimeVersion()
      Returns the version that represents the effective runtime versioned configuration of a multi-release jar file.

      By default the feature version number of the returned Version will be equal to the feature version number of Runtime.version(). However, if the jdk.util.jar.version property is set, the returned Version is derived from that property and feature version numbers may not be equal.

      Returns:
      the version that represents the runtime versioned configuration
      Since:
      9

    • getVersion

      public final Runtime.Version getVersion()
      Returns the maximum version used when searching for versioned entries.

      If this JarFile is not a multi-release jar file or is not configured to be processed as such, then the version returned will be the same as that returned from baseVersion().

      Returns:
      the maximum version
      Since:
      9

    • isMultiRelease

      public final boolean isMultiRelease()
      Indicates whether or not this jar file is a multi-release jar file.
      Returns:
      true if this JarFile is a multi-release jar file
      Since:
      9

    • getManifest

      public Manifest getManifest() throws IOException
      Returns the jar file manifest, or null if none.
      Returns:
      the jar file manifest, or null if none
      Throws:
      IllegalStateException - may be thrown if the jar file has been closed
      IOException - if an I/O error has occurred

    • getJarEntry

      public JarEntry getJarEntry​(String name)
      Returns the JarEntry for the given base entry name or null if not found.

      If this JarFile is a multi-release jar file and is configured to be processed as such, then a search is performed to find and return a JarEntry that is the latest versioned entry associated with the given entry name. The returned JarEntry is the versioned entry corresponding to the given base entry name prefixed with the string "META-INF/versions/{n}/", for the largest value of n for which an entry exists. If such a versioned entry does not exist, then the JarEntry for the base entry is returned, otherwise null is returned if no entries are found. The initial value for the version n is the maximum version as returned by the method getVersion().

      Implementation Requirements:
      This implementation invokes getEntry(String).
      Parameters:
      name - the jar file entry name
      Returns:
      the JarEntry for the given entry name, or the versioned entry name, or null if not found
      Throws:
      IllegalStateException - may be thrown if the jar file has been closed
      See Also:
      JarEntry

    • getEntry

      public ZipEntry getEntry​(String name)
      Returns the ZipEntry for the given base entry name or null if not found.

      If this JarFile is a multi-release jar file and is configured to be processed as such, then a search is performed to find and return a ZipEntry that is the latest versioned entry associated with the given entry name. The returned ZipEntry is the versioned entry corresponding to the given base entry name prefixed with the string "META-INF/versions/{n}/", for the largest value of n for which an entry exists. If such a versioned entry does not exist, then the ZipEntry for the base entry is returned, otherwise null is returned if no entries are found. The initial value for the version n is the maximum version as returned by the method getVersion().

      Overrides:
      getEntry in class ZipFile
      Implementation Requirements:
      This implementation may return a versioned entry for the requested name even if there is not a corresponding base entry. This can occur if there is a private or package-private versioned entry that matches. If a subclass overrides this method, assure that the override method invokes super.getEntry(name) to obtain all versioned entries.
      Parameters:
      name - the jar file entry name
      Returns:
      the ZipEntry for the given entry name or the versioned entry name or null if not found
      Throws:
      IllegalStateException - may be thrown if the jar file has been closed
      See Also:
      ZipEntry

    • entries

      public Enumeration<JarEntry> entries()
      Returns an enumeration of the jar file entries.
      Overrides:
      entries in class ZipFile
      Returns:
      an enumeration of the jar file entries
      Throws:
      IllegalStateException - may be thrown if the jar file has been closed

    • stream

      public Stream<JarEntry> stream()
      Returns an ordered Stream over the jar file entries. Entries appear in the Stream in the order they appear in the central directory of the jar file.
      Overrides:
      stream in class ZipFile
      Returns:
      an ordered Stream of entries in this jar file
      Throws:
      IllegalStateException - if the jar file has been closed
      Since:
      1.8

    • versionedStream

      public Stream<JarEntry> versionedStream()
      Returns a Stream of the versioned jar file entries.

      If this JarFile is a multi-release jar file and is configured to be processed as such, then an entry in the stream is the latest versioned entry associated with the corresponding base entry name. The maximum version of the latest versioned entry is the version returned by getVersion(). The returned stream may include an entry that only exists as a versioned entry. If the jar file is not a multi-release jar file or the JarFile is not configured for processing a multi-release jar file, this method returns the same stream that stream() returns.

      Returns:
      stream of versioned entries
      Since:
      10

    • getInputStream

      public InputStream getInputStream​(ZipEntry ze) throws IOException
      Returns an input stream for reading the contents of the specified zip file entry.
      Overrides:
      getInputStream in class ZipFile
      Parameters:
      ze - the zip file entry
      Returns:
      an input stream for reading the contents of the specified zip file entry
      Throws:
      ZipException - if a zip file format error has occurred
      IOException - if an I/O error has occurred
      SecurityException - if any of the jar file entries are incorrectly signed.
      IllegalStateException - may be thrown if the jar file has been closed