Gradle Wrapper Reference

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The recommended way to execute any Gradle build is with the help of the Gradle Wrapper (referred to as "Wrapper").

The Wrapper is a script that invokes a declared version of Gradle, downloading it beforehand if necessary. As a result, developers can get up and running with a Gradle project quickly.

Provisioning the Gradle version for different users is done with a simple Wrapper definition change.

Provisioning the Gradle version for different execution environments (e.g., IDEs or Continuous Integration servers) is done with a simple Wrapper definition change.

Generating the Wrapper files requires an installed version of the Gradle runtime on your machine as described in Installation . Thankfully, generating the initial Wrapper files is a one-time process.

Every vanilla Gradle build comes with a built-in task called wrapper . The task is listed under the group "Build Setup tasks" when listing the tasks .

Executing the wrapper task generates the necessary Wrapper files in the project directory:

$ gradle wrapper

To make the Wrapper files available to other developers and execution environments, you need to check them into version control. Wrapper files, including the JAR file, are small. Adding the JAR file to version control is expected. Some organizations do not allow projects to submit binary files to version control, and there is no workaround available.

The type of Gradle distribution . By default, the -bin distribution contains only the runtime but no sample code and documentation.

The Gradle version used for executing the build. By default, the wrapper task picks the same Gradle version used to generate the Wrapper files.

Optionally, a timeout in ms used when downloading the Gradle distribution.

Optionally, a boolean to set the validation of the distribution URL.

The Gradle version used for downloading and executing the Wrapper. The resulting distribution URL is validated before it is written to the properties file.

The following labels are allowed:

The Gradle distribution type used for the Wrapper. Available options are bin and all . The default value is bin .


    --gradle-distribution-url

The full URL pointing to the Gradle distribution ZIP file. This option makes --gradle-version and --distribution-type obsolete, as the URL already contains this information. This option is valuable if you want to host the Gradle distribution inside your company’s network. The URL is validated before it is written to the properties file.


    --gradle-distribution-sha256-sum

The SHA256 hash sum used for verifying the downloaded Gradle distribution .


    --network-timeout

The network timeout to use when downloading the Gradle distribution, in ms. The default value is 10000 .


    --no-validate-url

Disables the validation of the configured distribution URL.


    --validate-url

Enables the validation of the configured distribution URL. Enabled by default.

If the distribution URL is configured with --gradle-version or --gradle-distribution-url , the URL is validated by sending a HEAD request in the case of the https scheme or by checking the existence of the file in the case of the file scheme.

Let’s assume the following use-case to illustrate the use of the command line options. You would like to generate the Wrapper with version 8.6 and use the -all distribution to enable your IDE to enable code-completion and being able to navigate to the Gradle source code.

The following command-line execution captures those requirements:

$ gradle wrapper --gradle-version 8.6 --distribution-type all
> Task :wrapper
BUILD SUCCESSFUL in 0s
1 actionable task: 1 executed

As a result, you can find the desired information (the generated distribution URL) in the Wrapper properties file:

distributionUrl=https\://services.gradle.org/distributions/gradle-8.6-all.zip

Let’s have a look at the following project layout to illustrate the expected Wrapper files:

A Gradle project typically provides a settings.gradle(.kts) file and one build.gradle(.kts) file for each subproject. The Wrapper files live alongside in the gradle directory and the root directory of the project.

The following list explains their purpose:


    gradle-wrapper.jar

The Wrapper JAR file containing code for downloading the Gradle distribution.


    gradle-wrapper.properties

A properties file responsible for configuring the Wrapper runtime behavior e.g. the Gradle version compatible with this version. Note that more generic settings, like configuring the Wrapper to use a proxy , need to go into a different file .


    gradlew


    gradlew.bat

A shell script and a Windows batch script for executing the build with the Wrapper.

You can go ahead and execute the build with the Wrapper without installing the Gradle runtime. If the project you are working on does not contain those Wrapper files, you will need to generate them .

It is always recommended to execute a build with the Wrapper to ensure a reliable, controlled, and standardized execution of the build. Using the Wrapper looks like running the build with a Gradle installation. Depending on the operating system you either run gradlew or gradlew.bat instead of the gradle command.

The following console output demonstrates the use of the Wrapper on a Windows machine for a Java-based project:

$ gradlew.bat build
Downloading https://services.gradle.org/distributions/gradle-5.0-all.zip
.....................................................................................
Unzipping C:\Documents and Settings\Claudia\.gradle\wrapper\dists\gradle-5.0-all\ac27o8rbd0ic8ih41or9l32mv\gradle-5.0-all.zip to C:\Documents and Settings\Claudia\.gradle\wrapper\dists\gradle-5.0-al\ac27o8rbd0ic8ih41or9l32mv
Set executable permissions for: C:\Documents and Settings\Claudia\.gradle\wrapper\dists\gradle-5.0-all\ac27o8rbd0ic8ih41or9l32mv\gradle-5.0\bin\gradle
BUILD SUCCESSFUL in 12s
1 actionable task: 1 executed

If the Gradle distribution is unavailable on the machine, the Wrapper will download it and store it in the local file system. Any subsequent build invocation will reuse the existing local distribution as long as the distribution URL in the Gradle properties doesn’t change.

Projects typically want to keep up with the times and upgrade their Gradle version to benefit from new features and improvements.

One way to upgrade the Gradle version is by manually changing the distributionUrl property in the Wrapper’s gradle-wrapper.properties file.

The better and recommended option is to run the wrapper task and provide the target Gradle version as described in Adding the Gradle Wrapper . Using the wrapper task ensures that any optimizations made to the Wrapper shell script or batch file with that specific Gradle version are applied to the project.

As usual, you should commit the changes to the Wrapper files to version control.

Note that running the wrapper task once will update gradle-wrapper.properties only, but leave the wrapper itself in gradle-wrapper.jar untouched. This is usually fine as new versions of Gradle can be run even with older wrapper files.

Once you have upgraded the wrapper, you can check that it’s the version you expected by executing ./gradlew --version .

Don’t forget to run the wrapper task again to download the Gradle distribution binaries (if needed) and update the gradlew and gradle.bat files.

Most users of Gradle are happy with the default runtime behavior of the Wrapper. However, organizational policies, security constraints or personal preferences might require you to dive deeper into customizing the Wrapper.

Thankfully, the built-in wrapper task exposes numerous options to bend the runtime behavior to your needs. Most configuration options are exposed by the underlying task type Wrapper .

Let’s assume you grew tired of defining the -all distribution type on the command line every time you upgrade the Wrapper. You can save yourself some keyboard strokes by re-configuring the wrapper task.

Check out the API documentation for a more detailed description of the available configuration options. You can also find various samples for configuring the Wrapper in the Gradle distribution.

Authenticated Gradle distribution download

The Gradle Wrapper can download Gradle distributions from servers using HTTP Basic Authentication. This enables you to host the Gradle distribution on a private protected server.

You can specify a username and password in two different ways depending on your use case: as system properties or directly embedded in the distributionUrl . Credentials in system properties take precedence over the ones embedded in distributionUrl .

System properties can be specified in the .gradle/gradle.properties file in the user’s home directory or by other means .

To specify the HTTP Basic Authentication credentials, add the following lines to the system properties file:

systemProp.gradle.wrapperUser=username
systemProp.gradle.wrapperPassword=password

Embedding credentials in the distributionUrl in the gradle/wrapper/gradle-wrapper.properties file also works. Please note that this file is to be committed into your source control system.

Verification of downloaded Gradle distributions

The Gradle Wrapper allows for verification of the downloaded Gradle distribution via SHA-256 hash sum comparison. This increases security against targeted attacks by preventing a man-in-the-middle attacker from tampering with the downloaded Gradle distribution.

To enable this feature, download the .sha256 file associated with the Gradle distribution you want to verify.

Downloading the SHA-256 file

You can download the .sha256 file from the stable releases or release candidate and nightly releases . The format of the file is a single line of text that is the SHA-256 hash of the corresponding zip file.

You can also reference the list of Gradle distribution checksums .

Configuring checksum verification

Add the downloaded (SHA-256 checksum) hash sum to gradle-wrapper.properties using the distributionSha256Sum property or use --gradle-distribution-sha256-sum on the command-line:

distributionSha256Sum=371cb9fbebbe9880d147f59bab36d61eee122854ef8c9ee1ecf12b82368bcf10

Gradle will report a build failure if the configured checksum does not match the checksum found on the server hosting the distribution. Checksum verification is only performed if the configured Wrapper distribution hasn’t been downloaded yet.

The


   Wrapper

task fails if


   gradle-wrapper.properties

contains


   distributionSha256Sum

, but the task configuration does not define a sum. Executing the


   Wrapper

task preserves the


   distributionSha256Sum

configuration when the Gradle version does not change.

The Wrapper JAR is a binary file that will be executed on the computers of developers and build servers. As with all such files, you should ensure it’s trustworthy before executing it.

Since the Wrapper JAR is usually checked into a project’s version control system, there is the potential for a malicious actor to replace the original JAR with a modified one by submitting a pull request that only upgrades the Gradle version.

To verify the integrity of the Wrapper JAR, Gradle has created a GitHub Action that automatically checks Wrapper JARs in pull requests against a list of known good checksums.

Gradle also publishes the checksums of all releases (except for version 3.3 to 4.0.2, which did not generate reproducible JARs), so you can manually verify the integrity of the Wrapper JAR.

Automatically verifying the Gradle Wrapper JAR on GitHub

The GitHub Action is released separately from Gradle, so please check its documentation for how to apply it to your project.

Manually verifying the Gradle Wrapper JAR

You can manually verify the checksum of the Wrapper JAR to ensure that it has not been tampered with by running the following commands on one of the major operating systems.

Manually verifying the checksum of the Wrapper JAR on Linux:

$ cd gradle/wrapper

Troubleshooting a checksum mismatch

If the checksum does not match the one you expected, chances are the wrapper task wasn’t executed with the upgraded Gradle distribution.

You should first check whether the actual checksum matches a different Gradle version.

Here are the commands you can run on the major operating systems to generate the actual checksum of the Wrapper JAR.

Generating the checksum of the Wrapper JAR on Linux:

$ sha256sum gradle/wrapper/gradle-wrapper.jar
d81e0f23ade952b35e55333dd5f1821585e887c6d24305aeea2fbc8dad564b95 gradle/wrapper/gradle-wrapper.jar

Generating the actual checksum of the Wrapper JAR on macOS:

$ shasum --algorithm=256 gradle/wrapper/gradle-wrapper.jar
d81e0f23ade952b35e55333dd5f1821585e887c6d24305aeea2fbc8dad564b95 gradle/wrapper/gradle-wrapper.jar

Generating the actual checksum of the Wrapper JAR on Windows (using PowerShell):

> (Get-FileHash gradle\wrapper\gradle-wrapper.jar -Algorithm SHA256).Hash.ToLower()
d81e0f23ade952b35e55333dd5f1821585e887c6d24305aeea2fbc8dad564b95

Once you know the actual checksum, check whether it’s listed on https://gradle.org/release-checksums/ . If it is listed, you have verified the integrity of the Wrapper JAR. If the version of Gradle that generated the Wrapper JAR doesn’t match the version in gradle/wrapper/gradle-wrapper.properties , it’s safe to run the wrapper task again to update the Wrapper JAR.

If the checksum is not listed on the page, the Wrapper JAR might be from a milestone, release candidate, or nightly build or may have been generated by Gradle 3.3 to 4.0.2. Try to find out how it was generated but treat it as untrustworthy until proven otherwise. If you think the Wrapper JAR was compromised, please let the Gradle team know by sending an email to [email protected] .

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