1.5.4 (Nov 6, 2021)
Dec 20, 2015
Apr 20, 2022 (Retired)
Vyacheslav Rusakov (xvik)
Tobias Preuss (johnjohndoe)
Vyacheslav Rusakov (xvik)
Andres Almiray (aalmiray)
BJ Hargrave (bjhargrave)
Shaishav Gandhi (ShaishavGandhi)
H90 (h908714124)
Source code




Gradle AnimalSniffer plugin for Java or Groovy projects. AnimalSniffer is used to check compatibility with lower Java versions (when compiling with a newer Java version) or Android (SDK version).

It is implemented the same way as core Gradle quality plugins (Checkstyle, PMD etc): A task is registered for each source set (animalsnifferMain, animalsnifferTest) and attached to the check task.

Advanced features:


If you're using JDK 9 or above then you can use the --release flag instead of the plugin:

compileJava {
  options.compilerArgs.addAll(['--release', '7'])

Direct release option support available in gradle 6.6 (feature discussion).

The plugin could still be useful:

  • For Android projects to check API compatibility (because Android API signatures are published).
  • To check strong compatibility with some library: you'll need to generate signatures for this library and will be able to use them to check project compatibility (on API level, ofc) with older library versions.
  • Configuration extensions:
    • animalsniffer - check configuration
    • animalsnifferSignature - signature build configuration (optional)
  • Tasks:
    • check[Main] - check source set task
    • animalsnifferSignature - build signature (active when animalsnifferSignature configuration declared)
    • type:BuildSignatureTask - custom signature build task may be used to merge signatures
    • type:SignatureInfoTask - view signature "contents"
  • Dependencies configuration: signature - signatures for check


buildscript {
    repositories {
    dependencies {
        classpath 'ru.vyarus:gradle-animalsniffer-plugin:1.5.4'
apply plugin: 'ru.vyarus.animalsniffer'


plugins {
    id 'ru.vyarus.animalsniffer' version '1.5.4'


IMPORTANT: The plugin only works when the java (or java-library) or groovy plugin is enabled, otherwise nothing will be registered. There is no support for the Android plugin (the java plugin must be used to perform the animalsniffer check).

The plugin is compiled for Java 8, and is compatible with Java 11.

Gradle Version
5-6 1.5.4
4.x 1.4.6


Additional tasks will be assigned to the check task. So animalsniffer checks will be executed during:

$ gradlew check


AnimalSniffer requires a signature file to check against. To define a signature (or multiple signatures) use the signature configuration.

To check Java version compatibility:

repositories { mavenCentral() }
dependencies {
    signature 'org.codehaus.mojo.signature:java16:1.1@signature'

Java signatures

To check Android compatibility:

repositories { mavenCentral() }
dependencies {
    signature 'net.sf.androidscents.signature:android-api-level-14:4.0_r4@signature'

Android signatures

To check both Java version and Android compatibility:

dependencies {
    signature 'org.codehaus.mojo.signature:java16:1.1@signature'
    signature 'net.sf.androidscents.signature:android-api-level-14:4.0_r4@signature'

In the last case animalsniffer will run 2 times for each signature. You may see the same errors two times if a class/method is absent in both signatures. Each error message in the log (and file) will also contain the signature name to avoid confusion.

When no signatures are defined animalsniffer tasks will always pass.

You can also use custom libraries signatures to check version compatibility.


All project dependencies are excluded from the analysis: only classes from your source set are checked.

By default, all source sets are checked. To only check main sources:

animalsniffer {
    sourceSets = [sourceSets.main]


Violations are always printed to the console. Example output:

2 AnimalSniffer violations were found in 1 files. See the report at: file:///myproject/build/reports/animalsniffer/main.text

[Undefined reference] invalid.(
  >> int, boolean)

[Undefined reference] invalid.(
  >> java.nio.file.Path java.nio.file.Paths.get(String, String[])

NOTE: text report file will contain simplified report (error per line):

invalid.Sample:9  Undefined reference: int, boolean)
invalid.Sample:14  Undefined reference: java.nio.file.Path java.nio.file.Paths.get(String, String[])

NOTE: when multiple signatures are used, output will contain the signature name in the error message to avoid confusion.

Suppress violations

An annotation could be used to suppress violations: examples

Default annotation

Add dependency on the annotation artifact:

implementation "org.codehaus.mojo:animal-sniffer-annotations:1.16"

Use provided scope if you can. Annotation is configured by default, so you can simply use annotation to suppress violation:

private Optional param;
Custom annotation

You can define your own annotation:

package com.mycompany

@Target({ElementType.METHOD, ElementType.CONSTRUCTOR, ElementType.TYPE})
public @interface SuppressSignatureCheck {}

Configure annotation:

animalsniffer {
    annotation = 'com.mycompany.SuppressSignatureCheck'

Now check will skip blocks annotated with your annotation:

private Optional param;

Extend signature

Your project could target multiple Java versions and so reference classes, not present in a signature.

For example, your implementation could try to use Java 7 Paths and if the class is not available, fall back to the Java 6 implementation. In this case Paths could be added to the ignored classes:

animalsniffer {
    ignore 'java.nio.file.Paths'

Now usages of Paths will not cause warnings.

Multiple ignored classes could be defined:

animalsniffer {
    ignore 'java.nio.file.Paths', 'some.other.Class'


animalsniffer {
    ignore 'java.nio.file.Paths'
    ignore 'some.other.Class'

Or by directly assigning collection:

animalsniffer {
    ignore  = ['java.nio.file.Paths', 'some.other.Class']

Entire packages could be ignored using asterisk:

animalsniffer {
    ignore 'some.pkg.*'

See more info in the documentation.


Configuration example:

animalsniffer {
    toolVersion = '1.20'
    sourceSets = [sourceSets.main]
    ignoreFailures = true
    reportsDir = file("$project.buildDir/animalsnifferReports")
    annotation = 'com.mypackage.MyAnnotation'
    ignore = ['java.nio.file.Paths']

There are no required configurations - the plugin will generate defaults for all of them.

Property Description Default value
toolVersion AnimalSniffer version 1.20
sourceSets Source sets to check all source sets
ignoreFailures False to stop build when violations found, true to continue false
reportsDir Reports directory file("$project.buildDir/reports/animalsniffer")
annotation Annotation class to avoid check under annotated block
ignore Ignore usage of classes, not mentioned in signature
signatures Signatures to use for check configurations.signature
excludeJars Patterns to exclude jar names from classpath. Required for library signatures usage
cache Cache configuration By default, cache disabled

NOTE: ignore does not exclude your classes from check, it allows you to use classes not mentioned in the signature. See more details above.


The animalsniffer task is registered for each source set:

  • animalsnifferMain - run AnimalAniffer for compiled main classes
  • animalsnifferTest - run AnimalSniffer for compiled test classes
  • animalsnifferSourceSet - run AnimalSniffer for compiled SourceSet classes

The check task will depend only on tasks from configured in animalsniffer.sourceSets source sets.

Tasks support text report, enabled by default.

To disable reports for a task:

animalsnifferMain.reports.text.enabled = false

or for all tasks:

tasks.withType(AnimalSniffer) {
    reports.text.enabled = false

Animalsniffer task is a SourceTask and may be configured to include/exclude classes from check.

NOTE: The task operates on compiled classes and not sources! Be careful when defining patterns.

For example, to exclude classes in a 'invalid' subpackage from check:

animalsnifferMain {

Advanced features

Read wiki for advanced features:

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