Gradleでの実装とコンパイルの違いは何ですか？

Androidのメーカー3.0にアップデートすると、新しいプロジェクトを作成した後、私は中にいることに気づいたbuild.gradleのではなく、新しい依存関係を追加するための新しい方法がありますcompileがありimplementation、代わりのtestCompile存在ですtestImplementation。

例：

 implementation 'com.android.support:appcompat-v7:25.0.0'
 testImplementation 'junit:junit:4.12'

の代わりに

 compile 'com.android.support:appcompat-v7:25.0.0'
 testCompile 'junit:junit:4.12'

それらの違いは何ですか？私は何を使うべきですか？

tl; dr

交換するだけです：

• compileimplementation（あなたが推移性を必要としない場合）、またはapi（あなたが推移性を必要とする場合）
• testCompile と testImplementation
• debugCompile と debugImplementation
• androidTestCompile と androidTestImplementation
• compileOnlyまだ有効です。コンパイルではなく提供されたものを置き換えるために3.0で追加されました。（providedGradleにそのユースケースの構成名がなく、Mavenが提供するスコープにちなんで名前を付けたときに導入されました。）

これは、GoogleがIO17で発表したAndroidGradleプラグイン3.0に伴う重大な変更の1つです。

compile設定がされて廃止とで交換する必要がありますimplementationかapi

Gradleのドキュメントから：

dependencies {
    api 'commons-httpclient:commons-httpclient:3.1'
    implementation 'org.apache.commons:commons-lang3:3.5'
}

api構成に表示される依存関係は、ライブラリのコンシューマーに推移的に公開されるため、コンシューマーのコンパイルクラスパスに表示されます。

implementation一方、構成で見つかった依存関係はコンシューマーに公開されないため、コンシューマーのコンパイルクラスパスにリークすることはありません。これにはいくつかの利点があります。

• 依存関係がコンシューマーのコンパイルクラスパスにリークすることがなくなったため、推移的な依存関係に誤って依存することはありません。
• クラスパスサイズの縮小によるコンパイルの高速化
• 実装の依存関係が変更された場合の再コンパイルが少なくなる：コンシューマーを再コンパイルする必要がない
• よりクリーンな公開：新しいmaven-publishプラグインと組み合わせて使用​​すると、Javaライブラリは、ライブラリに対してコンパイルするために必要なものと、実行時にライブラリを使用するために必要なものを正確に区別するPOMファイルを生成します（つまり、しないでください）。ライブラリ自体をコンパイルするために必要なものと、ライブラリに対してコンパイルするために必要なものを混合します）。

コンパイル構成はまだ存在apiしimplementationますが、および構成が提供する保証を提供しないため、使用しないでください。

注：アプリモジュールでライブラリのみを使用している場合（一般的なケース）、違いに気付くことはありません。
モジュールが相互に依存している複雑なプロジェクトがある場合、またはライブラリを作成している場合にのみ、違いがわかります。

この答えは、違いを実証するimplementation、apiとcompileのプロジェクトに。

3つのGradleモジュールを含むプロジェクトがあるとしましょう。

• アプリ（Androidアプリケーション）
• myandroidlibrary（Androidライブラリ）
• myjavalibrary（Javaライブラリ）

app持っているmyandroidlibrary依存関係として。myandroidlibrary持っているmyjavalibrary 依存関係として。

myjavalibrary持っているMySecretクラスを

public class MySecret {

    public static String getSecret() {
        return "Money";
    }
}

myandroidlibrary持っているMyAndroidComponentから値を操作するクラスMySecretクラスを。

public class MyAndroidComponent {

    private static String component = MySecret.getSecret();

    public static String getComponent() {
        return "My component: " + component;
    }    
}

最後に、appからの値にのみ関心がありますmyandroidlibrary

TextView tvHelloWorld = findViewById(R.id.tv_hello_world);
tvHelloWorld.setText(MyAndroidComponent.getComponent());

それでは、依存関係について話しましょう...

app消費する必要がある:myandroidlibraryため、appbuild.gradleではを使用しますimplementation。

(Note: You can use api/compile too. But hold that thought for a moment.)

dependencies {
    implementation project(':myandroidlibrary')      
}

What do you think myandroidlibrary build.gradle should look like? Which scope we should use?

We have three options:

dependencies {
    // Option #1
    implementation project(':myjavalibrary') 
    // Option #2
    compile project(':myjavalibrary')      
    // Option #3
    api project(':myjavalibrary')           
}

What's the difference between them and what should I be using?

Compile or Api (option #2 or #3)

If you're using compile or api. Our Android Application now able to access myandroidcomponent dependency, which is a MySecret class.

TextView textView = findViewById(R.id.text_view);
textView.setText(MyAndroidComponent.getComponent());
// You can access MySecret
textView.setText(MySecret.getSecret());

Implementation (option #1)

If you're using implementation configuration, MySecret is not exposed.

TextView textView = findViewById(R.id.text_view);
textView.setText(MyAndroidComponent.getComponent());
// You can NOT access MySecret
textView.setText(MySecret.getSecret()); // Won't even compile

So, which configuration you should choose? That really depends on your requirement.

If you want to expose dependencies use api or compile.

If you don't want to expose dependencies (hiding your internal module) then use implementation.

Note:

This is just a gist of Gradle configurations, refer to Table 49.1. Java Library plugin - configurations used to declare dependencies for more detailed explanation.

The sample project for this answer is available on https://github.com/aldoKelvianto/ImplementationVsCompile

Compile configuration was deprecated and should be replaced by implementation or api.

You can read the docs at https://docs.gradle.org/current/userguide/java_library_plugin.html#sec:java_library_separation.

The brief part being-

The key difference between the standard Java plugin and the Java Library plugin is that the latter introduces the concept of an API exposed to consumers. A library is a Java component meant to be consumed by other components. It's a very common use case in multi-project builds, but also as soon as you have external dependencies.

The plugin exposes two configurations that can be used to declare dependencies: api and implementation. The api configuration should be used to declare dependencies which are exported by the library API, whereas the implementation configuration should be used to declare dependencies which are internal to the component.

For further explanation refer to this image.

Brief Solution:

The better approach is to replace all compile dependencies with implementation dependencies. And only where you leak a module’s interface, you should use api. That should cause a lot less recompilation.

 dependencies {
         implementation fileTree(dir: 'libs', include: ['*.jar'])
 
         implementation 'com.android.support:appcompat-v7:25.4.0'
         implementation 'com.android.support.constraint:constraint-layout:1.0.2'
         // …
 
         testImplementation 'junit:junit:4.12'
         androidTestImplementation('com.android.support.test.espresso:espresso-core:2.2.2', {
             exclude group: 'com.android.support', module: 'support-annotations'
         })
 }

Explain More:

Before Android Gradle plugin 3.0: we had a big problem which is one code change causes all modules to be recompiled. The root cause for this is that Gradle doesn’t know if you leak the interface of a module through another one or not.

After Android Gradle plugin 3.0: the latest Android Gradle plugin now requires you to explicitly define if you leak a module’s interface. Based on that it can make the right choice on what it should recompile.

As such the compile dependency has been deprecated and replaced by two new ones:

• api: you leak the interface of this module through your own interface, meaning exactly the same as the old compile dependency

• implementation: you only use this module internally and does not leak it through your interface

So now you can explicitly tell Gradle to recompile a module if the interface of a used module changes or not.

Courtesy of Jeroen Mols blog

+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| Name               | Role                 | Consumable? | Resolveable? | Description                             |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| api                | Declaring            |      no     |      no      | This is where you should declare        |
|                    | API                  |             |              | dependencies which are transitively     |
|                    | dependencies         |             |              | exported to consumers, for compile.     |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| implementation     | Declaring            |      no     |      no      | This is where you should                |
|                    | implementation       |             |              | declare dependencies which are          |
|                    | dependencies         |             |              | purely internal and not                 |
|                    |                      |             |              | meant to be exposed to consumers.       |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| compileOnly        | Declaring compile    |     yes     |      yes     | This is where you should                |
|                    | only                 |             |              | declare dependencies                    |
|                    | dependencies         |             |              | which are only required                 |
|                    |                      |             |              | at compile time, but should             |
|                    |                      |             |              | not leak into the runtime.              |
|                    |                      |             |              | This typically includes dependencies    |
|                    |                      |             |              | which are shaded when found at runtime. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| runtimeOnly        | Declaring            |      no     |      no      | This is where you should                |
|                    | runtime              |             |              | declare dependencies which              |
|                    | dependencies         |             |              | are only required at runtime,           |
|                    |                      |             |              | and not at compile time.                |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| testImplementation | Test dependencies    |      no     |      no      | This is where you                       |
|                    |                      |             |              | should declare dependencies             |
|                    |                      |             |              | which are used to compile tests.        |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| testCompileOnly    | Declaring test       |     yes     |      yes     | This is where you should                |
|                    | compile only         |             |              | declare dependencies                    |
|                    | dependencies         |             |              | which are only required                 |
|                    |                      |             |              | at test compile time,                   |
|                    |                      |             |              | but should not leak into the runtime.   |
|                    |                      |             |              | This typically includes dependencies    |
|                    |                      |             |              | which are shaded when found at runtime. |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+
| testRuntimeOnly    | Declaring test       |      no     |      no      | This is where you should                |
|                    | runtime dependencies |             |              | declare dependencies which              |
|                    |                      |             |              | are only required at test               |
|                    |                      |             |              | runtime, and not at test compile time.  |
+--------------------+----------------------+-------------+--------------+-----------------------------------------+

Gradle 3.0 introduced next changes:

• compile -> api

  api keyword is the same as deprecated compile

• compile -> implementation

  Is preferable way because has some advantages. implementation expose dependency only for one level up at build time (the dependency is available at runtime). As a result you have a faster build(no need to recompile consumers which are higher then 1 level up)

• provided -> compileOnly

  This dependency is available only in compile time(the dependency is not available at runtime). This dependency can not be transitive and be .aar. It can be used with compile time annotation processor and allows you to reduce a final output file

• compile -> annotationProcessor

  Very similar to compileOnly but also guarantees that transitive dependency are not visible for consumer

• apk -> runtimeOnly

  Dependency is not available in compile time but available at runtime.

[POM dependency type]

The brief difference in layman's term is:

• If you are working on an interface or module that provides support to other modules by exposing the members of the stated dependency you should be using 'api'.
• If you are making an application or module that is going to implement or use the stated dependency internally, use 'implementation'.
• 'compile' worked same as 'api', however, if you are only implementing or using any library, 'implementation' will work better and save you resources.

read the answer by @aldok for a comprehensive example.

Since version 5.6.3 Gradle documentation provides simple rules of thumb to identify whether an old compile dependency (or a new one) should be replaced with an implementation or an api dependency:

• Prefer the implementation configuration over api when possible

This keeps the dependencies off of the consumer’s compilation classpath. In addition, the consumers will immediately fail to compile if any implementation types accidentally leak into the public API.

So when should you use the api configuration? An API dependency is one that contains at least one type that is exposed in the library binary interface, often referred to as its ABI (Application Binary Interface). This includes, but is not limited to:

• types used in super classes or interfaces
• types used in public method parameters, including generic parameter types (where public is something that is visible to compilers. I.e. , public, protected and package private members in the Java world)
• types used in public fields
• public annotation types

By contrast, any type that is used in the following list is irrelevant to the ABI, and therefore should be declared as an implementation dependency:

• types exclusively used in method bodies
• types exclusively used in private members
• types exclusively found in internal classes (future versions of Gradle will let you declare which packages belong to the public API)

• implementation: mostly we use implementation configuration. It hides the internal dependency of the module to its consumer to avoid accidental use of any transitive dependency, hence faster compilation and less recompilation.

• api: must be used very carefully, since it leaks the to consumer’s compile classpath, hence misusing of api could lead to dependency pollution.

• compileOnly: when we don’t need any dependency at runtime, since compileOnly dependency won’t become the part of the final build. we will get a smaller build size.

• runtimeOnly: when we want to change or swap the behaviour of the library at runtime (in final build).

I have created a post with an in-depth understanding of each one with Working Example: source code

https://medium.com/@gauraw.negi/how-gradle-dependency-configurations-work-underhood-e934906752e5