Signing a jar allows users to authenticate the publisher.

Signs JAR files with the jarsigner command line tool. It will take a named file in the jar attribute, and an optional destDir or signedJar attribute. Nested paths are also supported; here only an (optional) destDir is allowed. If a destination directory or explicit JAR file name is not provided, JARs are signed in place.

Dependency rules


Attribute Description Required
jar the jar file to sign Yes, unless nested paths have been used.
alias the alias to sign under Yes.
storepass password for keystore integrity. Yes.
keystore keystore location No
storetype keystore type No
keypass password for private key (if different) No
sigfile name of .SF/.DSA file No
signedjar name of signed JAR file. This can only be set when the jar attribute is set. No.
verbose (true | false) verbose output when signing No; default false
strict (true | false) strict checking when signing.
since Ant 1.9.1.
No; default false
internalsf (true | false) include the .SF file inside the signature block No; default false
sectionsonly (true | false) don't compute hash of entire manifest No; default false
lazy flag to control whether the presence of a signature file means a JAR is signed. This is only used when the target JAR matches the source JAR No; default false
maxmemory Specifies the maximum memory the jarsigner VM will use. Specified in the style of standard java memory specs (e.g. 128m = 128 MBytes) No
preservelastmodified Give the signed files the same last modified time as the original jar files. No; default false.
tsaurl URL for a timestamp authority for timestamped JAR files in Java1.5+ No
tsacert alias in the keystore for a timestamp authority for timestamped JAR files in Java1.5+ No
executable Specify a particular jarsigner executable to use in place of the default binary (found in the same JDK as Apache Ant is running in).
Must support the same command line options as the Sun JDK jarsigner command. since Ant 1.8.0.
force Whether to force signing of the jar file even if it doesn't seem to be out of date or already signed. since Ant 1.8.0. No; default false
sigalg name of signature algorithm No
digestalg name of digest algorithm No

Parameters as nested elements

Attribute Description Required
path path of JAR files to sign. since Ant 1.7 No
fileset fileset of JAR files to sign. No
mapper A mapper to rename jar files during signing No, and only one can be supplied
sysproperty JVM system properties, with the syntax of Ant environment variables No, and only one can be supplied


For instructions on generating a code signing certificate, see the keytool documentation and/or instructions from your certificate authority.

<signjar jar="${dist}/lib/ant.jar"
alias="apache-group" storepass="secret"/>

signs the ant.jar with alias "apache-group" accessing the keystore and private key via "secret" password.

<signjar destDir="signed"
    alias="testonly" keystore="testkeystore"
    <fileset dir="dist" includes="**/*.jar" />
  <flattenmapper />

Sign all JAR files matching the dist/**/*.jar pattern, copying them to the directory "signed" afterwards. The flatten mapper means that they will all be copied to this directory, not to subdirectories.

    alias="testonly" keystore="testkeystore"
    <fileset dir="dist" includes="**/*.jar" />

Sign all the JAR files in dist/**/*.jar in-situ. Lazy signing is used, so the files will only be signed if they are not already signed.

    alias="testonly" keystore="testkeystore"
    <fileset dir="dist" includes="**/*.jar" />

Sign all the JAR files in dist/**/*.jar using the digest algorithm SHA1 and the signature algorithm MD5withRSA. This is especially useful when you want to use the JDK 7 jarsigner (which uses SHA256 and SHA256withRSA as default) to create signed jars that will be deployed on platforms not supporting SHA256 and SHA256withRSA.

About timestamp signing

Timestamps record the date and time that a signature took place, allowing the signature to be verified as of that point in time. With trusted timestamping, users can verify that signing occurred before a certificate's expiration or revocation. Without this timestamp, users can only verify the signature as of their current date.

Timestamped JAR files were introduced in Java1.5 and supported in Ant since Ant 1.7. Ant does not yet support proxy setup for this signing process.

Common public timestamp authorities include