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gradle-download-task

Download files in your Gradle build script with style progress and in parallel


Actions Status codecov Apache License, Version 2.0



This is a download task for Gradle. It displays progress information just like Gradle does when it retrieves an artifact from a repository. It is also able to download multiple files in parallel and supports concurrent execution with other tasks.

The plugin has been successfully tested with Gradle 5.0 up to 8.3. It should work with newer versions as well.

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Usage

First, apply the plugin configuration:

plugins {
    id "de.undercouch.download" version "5.5.0"
}

Then, use the Download task as follows:

task downloadFile(type: Download) {
    src 'http://www.example.com/index.html'
    dest layout.buildDirectory
}

By default, the plugin always performs a download even if the destination file already exists. If you want to prevent files from being downloaded again, use the overwrite flag (see description below).

task downloadFile(type: Download) {
    src 'http://www.example.com/index.html'
    dest layout.buildDirectory
    overwrite false
}

As an alternative to the Download task, you may also use the download extension to retrieve a file anywhere in your build script:

task myTask {
    doLast {
        // do something ...
        // ... then download a file
        download.run {
            src 'http://www.example.com/index.html'
            dest layout.buildDirectory
            overwrite false
        }
        // ... do something else
    }
}

Note that the download extension also has a runAsync method that downloads a file asynchronously. It returns a CompletableFuture that either completes successfully or exceptionally depending on whether the download has finished successfully or if it has failed. Make sure to always wait for the result of the CompletableFuture. Otherwise, errors might get lost.

Minimum requirements

The plugin requires:

  • Gradle 5.x or higher
  • Java 8 or higher

If you need to run the plugin with Gradle 2.x up to 4.x or Java 7, use gradle-download-task version 4.1.2.

Examples

Only download a file if it has been modified on the server

task downloadFile(type: Download) {
    src 'http://www.example.com/index.html'
    dest layout.buildDirectory
    onlyIfModified true
}

Note that this example only works if the server supports the If-Modified-Since request header and provides a Last-Modified timestamp in its response. If the server supports entity tags (ETags) you may use onlyIfModified together with useETag.

Concurrently download a list of files to a directory

task downloadMultipleFiles(type: Download) {
    src([
        'http://www.example.com/index.html',
        'http://www.example.com/test.html'
    ])
    dest layout.buildDirectory
}

Please note that you have to specify a directory as destination if you download multiple files. Otherwise, the plugin will fail.

Download files from a directory

If you want to download all files from a directory and the server provides a simple directory listing, you can use the following code:

task downloadDirectory {
    doLast {
        def dir = 'http://central.maven.org/maven2/de/undercouch/gradle-download-task/1.0/'
        def urlLister = new org.apache.ivy.util.url.ApacheURLLister()
        def files = urlLister.listFiles(new URL(dir))
        download.run {
           src files
           dest layout.buildDirectory
        }
    }
}

Download and extract a ZIP file

To download and unpack a ZIP file, you can combine the download task plugin with Gradle's built-in support for ZIP files:

task downloadZipFile(type: Download) {
    src 'https://github.com/michel-kraemer/gradle-download-task/archive/refs/tags/5.5.0.zip'
    dest layout.buildDirectory.file('5.5.0.zip')
}

task downloadAndUnzipFile(dependsOn: downloadZipFile, type: Copy) {
    from zipTree(downloadZipFile.dest)
    into layout.buildDirectory
}

More examples

Please have a look at the examples directory for more code samples. You can also read my blog post about common recipes for gradle-download-task.

Download task

The download task and the extension support the following properties.

General

src
The URL from which to retrieve the file. Can be a list of URLs if multiple files should be downloaded. (required)
dest
The file or directory where to store the file (required)
quiet
true if progress information should not be displayed (default: false)
overwrite
true if existing files should be overwritten (default: true)
onlyIfModified (alias: onlyIfNewer)
true if the file should only be downloaded if it has been modified on the server since the last download (default: false)
eachFile
If multiple download sources are specified, this method adds an action to be applied to each source URL before it is downloaded. The action is called with a DownloadDetails object and can modify some aspects of the target file in the destination directory (e.g. the filename or relative path). If only one download source has been given, adding an eachFile action will make the plugin fail.

Tip! You may provide Groovy Closures or Kotlin Lambdas to the src and dest properties to calculate their value at runtime.

Connection

acceptAnyCertificate
true if HTTPS certificate verification errors should be ignored and any certificate (even an invalid one) should be accepted. (default: false)
compress
true if compression should be used during download (default: true)
header
The name and value of a request header to set when making the download request (optional)
headers
A map of request headers to set when making the download request (optional)
connectTimeout
The maximum number of milliseconds to wait until a connection is established. A value of 0 (zero) means infinite timeout. Negative values are not allowed. (default: 30 seconds)
readTimeout
The maximum time in milliseconds to wait for data from the server. A value of 0 (zero) means infinite timeout. Negative values are not allowed. (default: 30 seconds)
retries
Specifies the maximum number of retry attempts if a request has failed. By default, requests are never retried and the task fails immediately if the first request does not succeed. If the value is greater than 0, failed requests are retried regardless of the actual error. This includes failed connection attempts and file-not-found errors (404). A negative value means infinite retries. (default: 0)

Authentication

username
The username that should be used if the server requires authentication (optional)
password
The password that should be used if the server requires authentication (optional)
preemptiveAuth
true if preemptive Basic authentication should be enabled. By default, gradle-download-task automatically detects the required authentication scheme by sending two requests: one without credentials to determine the scheme based on the WWW-Authenticate header in the server's response and the actual request with credentials. This will fail if the server does not send a WWW-Authenticate header. In this case, set preemptiveAuth to true to use Basic authentication and to always send credentials in the first request. Note: Sending credentials in clear text in the first request without checking if the server actually needs them might pose a security risk. (default: false)

Advanced

downloadTaskDir
The directory where the plugin stores information that should persist between builds. It will only be created if necessary. (default: ${layout.buildDirectory}/download-task)
tempAndMove
true if the file should be downloaded to a temporary location and, upon successful execution, moved to the final location. If overwrite is set to false, this flag is useful to avoid partially downloaded files if Gradle is forcefully closed or the system crashes. Note that the plugin always deletes partial downloads on connection errors, regardless of the value of this flag. The default temporary location can be configured with the downloadTaskDir property. (default: false)
useETag
Use this flag in combination with onlyIfModified. If both flags are true, the plugin will check a file’s timestamp as well as its entity tag (ETag) and only download it if it has been modified on the server since the last download. The plugin can differentiate between strong and weak ETags. Possible values are:
false (default)
Do not use the ETag
true
Use the ETag but display a warning if it is weak
"all"
Use the ETag and do not display a warning if it is weak
"strongOnly"
Only use the ETag if it is strong
cachedETagsFile
The location of the file that keeps entity tags (ETags) received from the server. (default: ${downloadTaskDir}/etags.json)
method
The HTTP method to use (default: GET)
body
An optional request body. As gradle-download-task is meant for downloading and not for uploading, only simple strings are supported. (optional)

Verify task

The plugin also provides a Verify task that can be used to check the integrity of a downloaded file by calculating its checksum and comparing it to a pre-defined value. The task succeeds if the file’s checksum equals the given value and fails if it doesn’t.

Use the task as follows:

task verifyFile(type: Verify) {
    src layout.buildDirectory.file('file.ext')
    algorithm 'MD5'
    checksum 'ce114e4501d2f4e2dcea3e17b546f339'
}

You can combine the download task and the verify task as follows:

task downloadFile(type: Download) {
    src 'http://www.example.com/index.html'
    dest layout.buildDirectory
}

task verifyFile(type: Verify, dependsOn: downloadFile) {
    src layout.buildDirectory.file('index.html')
    algorithm 'MD5'
    checksum '09b9c392dc1f6e914cea287cb6be34b0'
}

The verify task supports the following properties:

src
The file to verify (required)
checksum
The actual checksum to verify against (required)
algorithm
The algorithm to use to compute the checksum. See the list of algorithm names for more information. (default: MD5)

DownloadDetails

If you specify an eachFile action, it will be called with an instance of the DownloadDetails class, which provides details about a download source and its target file. It can be used to change some aspects of the target file (e.g. its name or relative path).

DownloadDetails provides the following properties:

URL sourceURL (read-only)
The source URL of the file to be downloaded
String name
The name of the target file
String path
The path of the target file (including the filename), relative to download directory
RelativePath relativePath
The path of the target file (including the filename), relative to download directory

Example

eachFile { f ->
    f.name = f.name.toLowerCase()
    if (f.sourceURL.path.toLowerCase().endsWith(".jpg")) {
        f.path = "images/" + f.path
    }
}

Proxy configuration

You can configure a proxy server by setting standard JVM system properties. The plugin uses the same system properties as Gradle. You can set them in the build script directly. For example, the proxy host can be set as follows:

System.setProperty("http.proxyHost", "www.somehost.org");

Alternatively, you can set the properties in a gradle.properties file like this:

systemProp.http.proxyHost=www.somehost.org
systemProp.http.proxyPort=8080
systemProp.http.proxyUser=userid
systemProp.http.proxyPassword=password
systemProp.http.nonProxyHosts=*.nonproxyrepos.com|localhost

Put this file in your project’s root directory or in your Gradle home directory.

HTTPS is also supported:

systemProp.https.proxyHost=www.somehost.org
systemProp.https.proxyPort=8080
systemProp.https.proxyUser=userid
systemProp.https.proxyPassword=password
systemProp.https.nonProxyHosts=*.nonproxyrepos.com|localhost

Migrating from version 4.x to 5.x

gradle-download-task 5.0.0 introduces the following breaking changes:

  • The authScheme property has been removed. The plugin now automatically detects the correct scheme to use based on the server response.
  • The download extension was incompatible with Gradle 8. Also, using it from Kotlin build scripts was rather inconvenient. It is therefore now necessary to call the extension through its run method. Replace download { ... } with download.run { ... }. The same applies to the verify extension.

Migrating from version 3.x to 4.x

In gradle-download-task 4.x, we made the following breaking changes to the API:

  • The plugin now requires Gradle 2.x (or higher) and Java 7 (or higher)
  • We removed the timeout property and introduced connectTimeout and readTimeout instead. This allows you to control the individual timeouts better. Also, it improves compatibility with Gradle 5.x, where all tasks have a timeout property by default.
  • The credentials property has been removed. The same applies to the possibility to pass instances of Apache HttpClient’s AuthScheme to the authScheme property. The strings Basic and Digest are now the only accepted values. There is no replacement. If you need this functionality, please file an issue.
  • The properties requestInterceptor and responseInterceptor have been removed. There is no replacement. Again, if you need this functionality, please file an issue.

License

The plugin is licensed under the Apache License, Version 2.0.

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.