OpenJDK 27 · java.util.jar.JarInputStream · APIdia, the JavaDoc alternative

The JarInputStream class, which extends ZipInputStream, is used to read the contents of a JAR file from an input stream. It provides support for reading an optional Manifest entry. The Manifest can be used to store meta-information about the JAR file and its entries.

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

Accessing the Manifest

The getManifest method is used to return the Manifest from the entry META-INF/MANIFEST.MF when it is the first entry in the stream (or the second entry if the first entry in the stream is META-INF/ and the second entry is META-INF/MANIFEST.MF).

The getNextJarEntry() and getNextEntry() methods are used to read JAR file entries from the stream. These methods skip over the Manifest (META-INF/MANIFEST.MF) when it is at the beginning of the stream. In other words, these methods do not return an entry for the Manifest when the Manifest is the first entry in the stream. If the first entry is META-INF/ and the second entry is the Manifest then both are skipped over by these methods. Whether these methods skip over the Manifest when it appears later in the stream is not specified.

Signed JAR Files

A JarInputStream verifies the signatures of entries in a Signed JAR file when:

The Manifest is the first entry in the stream (or the second entry if the first entry in the stream is META-INF/ and the second entry is META-INF/MANIFEST.MF).
All signature-related entries immediately follow the Manifest

Once the JarEntry has been completely verified, which is done by reading until the end of the entry's input stream, JarEntry#getCertificates() may be called to obtain the certificates for this entry and JarEntry#getCodeSigners() may be called to obtain the signers.

It is important to 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.

Field Summary

Modifier and Type	Field and Description
private final boolean	doVerify
private JarEntry	first
private JarVerifier	jv
private Manifest	man
private ManifestEntryVerifier	mev
private boolean	tryManifest

Constructor Summary

Access	Constructor and Description
public	JarInputStream(InputStream the actual input stream in) Creates a new `JarInputStream` and reads the optional manifest.
public	JarInputStream(InputStream the actual input stream in, boolean whether or not to verify the JarInputStream if it is signed. verify) Creates a new `JarInputStream` and reads the optional manifest.

Method Summary

Modifier and Type	Method and Description
private JarEntry	checkManifest(JarEntry e)
protected ZipEntry	Returns: the `JarEntry` object just created createZipEntry(String the name of the JAR/ZIP file entry name) Overrides java.util.zip.ZipInputStream.createZipEntry. Creates a new `JarEntry` (`ZipEntry`) for the specified JAR file entry name.
public Manifest	Returns: the `Manifest` for this JAR file, or `null` otherwise. getManifest() Returns the `Manifest` for this JAR file when it is the first entry in the stream (or the second entry if the first entry in the stream is `META-INF/` and the second entry is `META-INF/MANIFEST.MF`), or `null` otherwise.
public ZipEntry	getNextEntry() Overrides java.util.zip.ZipInputStream.getNextEntry. Reads the next ZIP file entry and positions the stream at the beginning of the entry data.
public JarEntry	Returns: the next JAR file entry, or null if there are no more entries getNextJarEntry() Reads the next JAR file entry and positions the stream at the beginning of the entry data.
public int	Returns: the actual number of bytes read, or -1 if the end of the entry is reached read(byte[] the buffer into which the data is read b, int the start offset in the destination array `b` off, int the maximum number of bytes to read len) Overrides java.util.zip.ZipInputStream.read. Reads from the current JAR entry into an array of bytes, returning the number of inflated bytes.

Inherited from java.util.zip.ZipInputStream:: available close closeEntry read readAllBytes readNBytes readNBytes skip skipNBytes transferTo

Field Detail

doVerify	back to summary
private final boolean doVerify

first	back to summary
private JarEntry first

jv	back to summary
private JarVerifier jv

man	back to summary
private Manifest man

mev	back to summary
private ManifestEntryVerifier mev

tryManifest	back to summary
private boolean tryManifest

Constructor Detail

JarInputStream back to summary

JarInputStream	back to summary
public JarInputStream(InputStream in) throws IOException Creates a new `JarInputStream` and reads the optional manifest. If a manifest is present, also attempts to verify the signatures if the JarInputStream is signed. Parameters in:InputStream the actual input stream Exceptions IOException: if an I/O error has occurred

public JarInputStream(InputStream in) throws IOException

Creates a new JarInputStream and reads the optional manifest. If a manifest is present, also attempts to verify the signatures if the JarInputStream is signed.

Parameters

in:InputStream: the actual input stream

Exceptions

IOException:: if an I/O error has occurred

JarInputStream back to summary

JarInputStream	back to summary
public JarInputStream(InputStream in, boolean verify) throws IOException Creates a new `JarInputStream` and reads the optional manifest. If a manifest is present and verify is true, also attempts to verify the signatures if the JarInputStream is signed. Parameters in:InputStream the actual input stream verify:boolean whether or not to verify the JarInputStream if it is signed. Annotations @SuppressWarnings:this-escape Exceptions IOException: if an I/O error has occurred

public JarInputStream(InputStream in, boolean verify) throws IOException

Creates a new JarInputStream and reads the optional manifest. If a manifest is present and verify is true, also attempts to verify the signatures if the JarInputStream is signed.

Parameters

in:InputStream: the actual input stream
verify:boolean: whether or not to verify the JarInputStream if it is signed.

Annotations

@SuppressWarnings:this-escape

Exceptions

IOException:: if an I/O error has occurred

Method Detail

checkManifest	back to summary
private JarEntry checkManifest(JarEntry e) throws IOException

createZipEntry back to summary

createZipEntry	back to summary
protected ZipEntry createZipEntry(String name) Overrides java.util.zip.ZipInputStream.createZipEntry. Creates a new `JarEntry` (`ZipEntry`) for the specified JAR file entry name. The manifest attributes of the specified JAR file entry name will be copied to the new `JarEntry`. Parameters name:String the name of the JAR/ZIP file entry Returns:ZipEntry the `JarEntry` object just created

protected ZipEntry createZipEntry(String name)

Overrides java.util.zip.ZipInputStream.createZipEntry.

Creates a new JarEntry (ZipEntry) for the specified JAR file entry name. The manifest attributes of the specified JAR file entry name will be copied to the new JarEntry.

Parameters

name:String: the name of the JAR/ZIP file entry

Returns:ZipEntry

the JarEntry object just created

getManifest back to summary

getManifest	back to summary
public Manifest getManifest() Returns the `Manifest` for this JAR file when it is the first entry in the stream (or the second entry if the first entry in the stream is `META-INF/` and the second entry is `META-INF/MANIFEST.MF`), or `null` otherwise. Returns:Manifest the `Manifest` for this JAR file, or `null` otherwise.

public Manifest getManifest()

Returns the Manifest for this JAR file when it is the first entry in the stream (or the second entry if the first entry in the stream is META-INF/ and the second entry is META-INF/MANIFEST.MF), or null otherwise.

Returns:Manifest: the Manifest for this JAR file, or null otherwise.

getNextEntry	back to summary
public ZipEntry getNextEntry() throws IOException Overrides java.util.zip.ZipInputStream.getNextEntry. Reads the next ZIP file entry and positions the stream at the beginning of the entry data. If verification has been enabled, any invalid signature detected while positioning the stream for the next entry will result in an exception. Exceptions IOException: if an I/O error has occurred ZipException: if a ZIP file error has occurred SecurityException: if any of the jar file entries are incorrectly signed.

getNextEntry

back to summary

public ZipEntry getNextEntry() throws IOException

Overrides java.util.zip.ZipInputStream.getNextEntry.

Reads the next ZIP file entry and positions the stream at the beginning of the entry data. If verification has been enabled, any invalid signature detected while positioning the stream for the next entry will result in an exception.

Exceptions

IOException:: if an I/O error has occurred
ZipException:: if a ZIP file error has occurred
SecurityException:: if any of the jar file entries are incorrectly signed.

getNextJarEntry	back to summary
public JarEntry getNextJarEntry() throws IOException Reads the next JAR file entry and positions the stream at the beginning of the entry data. If verification has been enabled, any invalid signature detected while positioning the stream for the next entry will result in an exception. Returns:JarEntry the next JAR file entry, or null if there are no more entries Exceptions IOException: if an I/O error has occurred ZipException: if a ZIP file error has occurred SecurityException: if any of the jar file entries are incorrectly signed.

getNextJarEntry

back to summary

public JarEntry getNextJarEntry() throws IOException

Reads the next JAR file entry and positions the stream at the beginning of the entry data. If verification has been enabled, any invalid signature detected while positioning the stream for the next entry will result in an exception.

Returns:JarEntry

the next JAR file entry, or null if there are no more entries

Exceptions

IOException:: if an I/O error has occurred
ZipException:: if a ZIP file error has occurred
SecurityException:: if any of the jar file entries are incorrectly signed.

read back to summary

read	back to summary
public int read(byte[] b, int off, int len) throws IOException Overrides java.util.zip.ZipInputStream.read. Reads from the current JAR entry into an array of bytes, returning the number of inflated bytes. If `len` is not zero, the method blocks until some input is available; otherwise, no bytes are read and `0` is returned. If the current entry is compressed and this method returns a nonzero integer n then `buf[off]` through `buf[off+`n`-1]` contain the uncompressed data. The content of elements `buf[off+`n`]` through `buf[off+`len`-1]` is undefined, contrary to the specification of the `InputStream` superclass, so an implementation is free to modify these elements during the inflate operation. If this method returns `-1` or throws an exception then the content of `buf[off]` through `buf[off+`len`-1]` is undefined. If verification has been enabled, any invalid signature on the current entry will be reported at some point before the end of the entry is reached. Parameters b:byte[] the buffer into which the data is read off:int the start offset in the destination array `b` len:int the maximum number of bytes to read Returns:int the actual number of bytes read, or -1 if the end of the entry is reached Exceptions IOException: if an I/O error has occurred IndexOutOfBoundsException: If `off` is negative, `len` is negative, or `len` is greater than `b.length - off` ZipException: if a ZIP file error has occurred SecurityException: if any of the jar file entries are incorrectly signed.

public int read(byte[] b, int off, int len) throws IOException

Overrides java.util.zip.ZipInputStream.read.

Reads from the current JAR entry into an array of bytes, returning the number of inflated bytes. If len is not zero, the method blocks until some input is available; otherwise, no bytes are read and 0 is returned.

If the current entry is compressed and this method returns a nonzero integer n then buf[off] through buf[off+n-1] contain the uncompressed data. The content of elements buf[off+n] through buf[off+len-1] is undefined, contrary to the specification of the InputStream superclass, so an implementation is free to modify these elements during the inflate operation. If this method returns -1 or throws an exception then the content of buf[off] through buf[off+len-1] is undefined.

If verification has been enabled, any invalid signature on the current entry will be reported at some point before the end of the entry is reached.

Parameters

b:byte[]: the buffer into which the data is read
off:int: the start offset in the destination array b
len:int: the maximum number of bytes to read

Returns:int

the actual number of bytes read, or -1 if the end of the entry is reached

Exceptions

IOException:: if an I/O error has occurred
IndexOutOfBoundsException:: If off is negative, len is negative, or len is greater than b.length - off
ZipException:: if a ZIP file error has occurred
SecurityException:: if any of the jar file entries are incorrectly signed.

public Class JarInputStream

Accessing the Manifest

Signed JAR Files

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail