1.5.0 (Feb 5, 2019)
Dec 20, 2015
Dec 22, 2019
Vyacheslav Rusakov (xvik)
Vyacheslav Rusakov (xvik)
Andres Almiray (aalmiray)
Shaishav Gandhi (ShaishavGandhi)
Source code

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Gradle AnimalSniffer plugin for Java or groovy projects. AnimalSniffer used to check compatibility with lower java version (when compiling with newer java) or android (sdk version).

Implemented the same way as core gradle quality plugins (checkstyle, pmd etc): task registered for each source set (animalsnifferMain, animalsnifferTest) and attached to check task


  • Plugin will use animalsniffer 1.16 by default, which is not compatible with java 9
  • Use version 1.17 (toolVersion=1.17) if you need to run on java 9, but note that 1.17 can't be used on java 8 (and that's why it is not set by default)

Advanced features:


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

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

See gradle issue about better option support.

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


Releases are published to bintray jcenter, maven central and gradle plugins portal.

buildscript {
    repositories {
    dependencies {
        classpath 'ru.vyarus:gradle-animalsniffer-plugin:1.5.0'
apply plugin: 'ru.vyarus.animalsniffer'


plugins {
    id 'ru.vyarus.animalsniffer' version '1.5.0'

IMPORTANT: plugin must be declared after java or groovy plugin, otherwise nothing will be registered.

Starting from version 1.5.0 gradle >= 5 is required. For older gradle use version 1.4.6.


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

$ gradlew check


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

Check java version compatibility:

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

Java signatures

Check android compatibility:

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

Android signatures

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 class/method is absent in both signatures. Each error message in log (and file) will also contain signature name to avoid confusion.

When no signatures defined animalsniffer tasks will always pass.

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


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

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

animalsniffer {
    sourceSets = [sourceSets.main]


Violations are always printed to 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 used, output will contain signature name in the error message to void confusion.

Suppress violations

Annotation could be used to suppress violations: examples

Default annotation

Add dependency on annotation:

compile "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

Project could target multiple java versions and so reference classes, not present in signature.

For example, implementation could try to use java 7 Paths and if class is not available, fall back to java 6 implementation. In this case Paths could be added to 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 documentation.


Configuration example:

animalsniffer {
    toolVersion = '1.16'
    sourceSets = [sourceSets.main]
    ignoreFailures = true
    reportsDir = file("$project.buildDir/animalsnifferReports")
    annotation = 'com.mypackage.MyAnnotation'
    ignore = ['java.nio.file.Paths']

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

Property Description Default value
toolVersion AnimalSniffer version 1.16
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 using classes not mentioned in signature. See more details above.


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

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 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: task operate on compiled classes and not sources! Be careful when defining patterns.

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

animalsnifferMain {

Advanced features

Read wiki for advanced features:

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