Why there are multiple copies for the same version of gradle

Question

I have an android studio project, with the file gradle/wrapper/gradle-wrapper.properties configured as following.

#Wed Apr 10 15:27:10 PDT 2013
distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists
distributionUrl=https\://services.gradle.org/distributions/gradle-2.2.1-all.zip

And I have the 2.2.1-all version installed in my home directory.

.gradle/wrapper/dists/gradle-2.2.1-all/c64ydeuardnfqctvr1gm30w53/gradle-2.2.1-all.zip

When I invoke ./gradlew command to build the project. I should use the gradle-2.2.1-all.zip to build.

But it doesn't, it will download another gradle even for the same version instead. So, there are two gradles for the version 2.2.1-all. Because my internet connection is very slow, it takes too long.

.gradle/wrapper/dists/gradle-2.2.1-all/c64ydeuardnfqctvr1gm30w53/gradle-2.2.1-all.zip
.gradle/wrapper/dists/gradle-2.2.1-all/6dibv5rcnnqlfbq9klf8imrndn/gradle-2.2.1-all.zip

It's very annoying since it has to download a new one for the same version very time I invoke the command to build my project.

Why the gradle build system couldn't pick the installed one?

Answer 1

The problem occurred is because the hash policy for the download url is different between studio's gradle-wrapper.jar and latest gradle-wrapper.jar.

The gradle-wrapper.jar under my Android app directory (I guess it's copied from android-sdk-macosx/tools/templates/gradle/wrapper/gradle/wrapper/gradle-wrapper.jar) use the following method to calculate hash for the download url.

// PathAssembler.java
private String getMd5Hash(String string) {
    try {
        MessageDigest e = MessageDigest.getInstance("MD5");
        byte[] bytes = string.getBytes();
        e.update(bytes);
        return (new BigInteger(1, e.digest())).toString(32);
    } catch (Exception var4) {
        throw new RuntimeException("Could not hash input string.", var4);
    }
}

But the latest gradle-wrapper.jar use the following method to do. The radix change from 32 to 36.

private String getHash(String string) {
    try {
        MessageDigest messageDigest = MessageDigest.getInstance("MD5");
        byte[] bytes = string.getBytes();
        messageDigest.update(bytes);
        return new BigInteger(1, messageDigest.digest()).toString(36);
    } catch (Exception e) {
        throw new RuntimeException("Could not hash input string.", e);
    }
}

The magic string I found in the directory name is the md5 hash string of the download url.

For version 2.10, there is a directory name

.gradle/wrapper/dists/gradle-2.10-all/a4w5fzrkeut1ox71xslb49gst

And the a4w5fzrkeut1ox71xslb49gst is hashed from the download url.

try {
    MessageDigest messageDigest = MessageDigest.getInstance("MD5");
    messageDigest.update("https://services.gradle.org/distributions/gradle-2.10-all.zip".getBytes());
    System.out.println(new BigInteger(1, messageDigest.digest()).toString(36));
} catch (NoSuchAlgorithmException e) {
    e.printStackTrace();
}

By using the same hash method (use the same gradle-wrapper.jar) for the same download url from gradle/wrapper/gradle-wrapper.properties, there won't be multiple downloads for the same version of gradle.

This issue only exist between android studio project and other gradle project.

Answer 2

It's an Unresolved issue Why Gradle download wrapper multiple times for the same version?

Answer 3

Saw same problem and made a try. Looks like that Android Studio does not build with the grale/wrapper/gradle-wrapper.jar in your project, but instead the one within itself(Android Studio.app/Contents/plugins/android/lib/templates/gradle/wrapper/gradle/wrapper/gradle-wrapper.jar in macOS).

As mentioned by @alijandro, if the gradle-wrapper.jar in your two projects are not using the same hash policy, or not the same as the Android Studio app, it will cause the problem you saw.

To get rid of this, just copy the gradle-wrapper.jar from Android Studio app directory to your project and you're all set.