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https://github.com/google/dagger

A fast dependency injector for Android and Java.
https://github.com/google/dagger

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A fast dependency injector for Android and Java.

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# Dagger



[![Maven Central][mavenbadge-svg]][mavencentral]



A fast dependency injector for Java and Android.



Dagger is a compile-time framework for dependency injection. It uses no

reflection or runtime bytecode generation, does all its analysis at

compile-time, and generates plain Java source code.



Dagger is actively maintained by Google.  Snapshot releases are auto-deployed to

Sonatype's central Maven repository on every clean build with the version

`HEAD-SNAPSHOT`. The current version builds upon previous work done at [Square][square].



## Documentation



You can [find the dagger documentation here][website] which has extended usage

instructions and other useful information. More detailed information can be

found in the [API documentation][latestapi].



You can also learn more from [the original proposal][proposal],

[this talk by Greg Kick][gaktalk], and on the [email protected]

mailing list.



## Installation



### Bazel



First, import the Dagger repository into your `WORKSPACE` file using

[`http_archive`][bazel-external-deps].



Note: The `http_archive` must point to a tagged release of Dagger, not just any

commit. The version of the Dagger artifacts will match the version of the tagged

release.



```python

# Top-level WORKSPACE file



load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")



DAGGER_TAG = "2.52"

DAGGER_SHA = "4062fa2cda8dab32d1961fb10ed50f40aca759149efb64dd5a08077a6fcb2fbc"

http_archive(

    name = "dagger",

    strip_prefix = "dagger-dagger-%s" % DAGGER_TAG,

    sha256 = DAGGER_SHA,

    urls = ["https://github.com/google/dagger/archive/dagger-%s.zip" % DAGGER_TAG],

)

```



Next you will need to setup targets that export the proper dependencies

and plugins. Follow the sections below to setup the dependencies you need.



#### Dagger Setup



First, load the Dagger artifacts and repositories, and add them to your list of

[`maven_install`] artifacts.



```python

# Top-level WORKSPACE file



load("@dagger//:workspace_defs.bzl", "DAGGER_ARTIFACTS", "DAGGER_REPOSITORIES")



maven_install(

    artifacts = DAGGER_ARTIFACTS + [...],

    repositories = DAGGER_REPOSITORIES + [...],

)

```



Next, load and call [`dagger_rules`](https://github.com/google/dagger/blob/master/workspace_defs.bzl)

in your top-level `BUILD` file:



```python

# Top-level BUILD file



load("@dagger//:workspace_defs.bzl", "dagger_rules")



dagger_rules()

```



This will add the following Dagger build targets:

(Note that these targets already export all of the dependencies and processors

they need).



```python

deps = [

    ":dagger",                  # For Dagger

    ":dagger-spi",              # For Dagger SPI

    ":dagger-producers",        # For Dagger Producers

]

```



#### Dagger Android Setup



First, load the Dagger Android artifacts and repositories, and add them to your

list of [`maven_install`] artifacts.



```python

# Top-level WORKSPACE file



load(

    "@dagger//:workspace_defs.bzl",

    "DAGGER_ANDROID_ARTIFACTS",

    "DAGGER_ANDROID_REPOSITORIES"

)



maven_install(

    artifacts = DAGGER_ANDROID_ARTIFACTS + [...],

    repositories = DAGGER_ANDROID_REPOSITORIES + [...],

)

```



Next, load and call [`dagger_android_rules`](https://github.com/google/dagger/blob/master/workspace_defs.bzl)

in your top-level `BUILD` file:



```python

# Top-level BUILD file



load("@dagger//:workspace_defs.bzl", "dagger_android_rules")



dagger_android_rules()

```



This will add the following Dagger Android build targets:

(Note that these targets already export all of the dependencies and processors

they need).



```python

deps = [

    ":dagger-android",          # For Dagger Android

    ":dagger-android-support",  # For Dagger Android (Support)

]

```



#### Hilt Android Setup



First, load the Hilt Android artifacts and repositories, and add them to your

list of [`maven_install`] artifacts.



```python

# Top-level WORKSPACE file



load(

    "@dagger//:workspace_defs.bzl",

    "HILT_ANDROID_ARTIFACTS",

    "HILT_ANDROID_REPOSITORIES"

)



maven_install(

    artifacts = HILT_ANDROID_ARTIFACTS + [...],

    repositories = HILT_ANDROID_REPOSITORIES + [...],

)

```



Next, load and call [`hilt_android_rules`](https://github.com/google/dagger/blob/master/workspace_defs.bzl)

in your top-level `BUILD` file:



```python

# Top-level BUILD file



load("@dagger//:workspace_defs.bzl", "hilt_android_rules")



hilt_android_rules()

```



This will add the following Hilt Android build targets:

(Note that these targets already export all of the dependencies and processors

they need).



```python

deps = [

    ":hilt-android",            # For Hilt Android

    ":hilt-android-testing",    # For Hilt Android Testing

]

```



### Other build systems



You will need to include the `dagger-2.x.jar` in your application's runtime.

In order to activate code generation and generate implementations to manage

your graph you will need to include `dagger-compiler-2.x.jar` in your build

at compile time.



#### Maven



In a Maven project, include the `dagger` artifact in the dependencies section

of your `pom.xml` and the `dagger-compiler` artifact as an

`annotationProcessorPaths` value of the `maven-compiler-plugin`:



```xml



  

    com.google.dagger

    dagger

    2.x

  



  

    

      org.apache.maven.plugins

      maven-compiler-plugin

      3.6.1

      

        

          

            com.google.dagger

            dagger-compiler

            2.x

          

        

      

    

  



```



If you are using a version of the `maven-compiler-plugin` lower than `3.5`, add

the `dagger-compiler` artifact with the `provided` scope:



```xml



  

    com.google.dagger

    dagger

    2.x

  

  

    com.google.dagger

    dagger-compiler

    2.x

    provided

  



```



If you use the beta `dagger-producers` extension (which supplies

parallelizable execution graphs), then add this to your maven configuration:



```xml



  

    com.google.dagger

    dagger-producers

    2.x

  



```



#### Gradle

```groovy

// Add Dagger dependencies

dependencies {

  implementation 'com.google.dagger:dagger:2.x'

  annotationProcessor 'com.google.dagger:dagger-compiler:2.x'

}

```



If you're using classes in `dagger.android` you'll also want to include:



```groovy

implementation 'com.google.dagger:dagger-android:2.x'

implementation 'com.google.dagger:dagger-android-support:2.x' // if you use the support libraries

annotationProcessor 'com.google.dagger:dagger-android-processor:2.x'

```



Notes:



-   We use `implementation` instead of `api` for better compilation performance.

    -   See the [Gradle documentation][gradle-api-implementation] for more

        information on how to select appropriately, and the [Android Gradle

        plugin documentation][gradle-api-implementation-android] for Android

        projects.

-   For Kotlin projects, use [`kapt`] in place of `annotationProcessor`.



If you're using the [Android Databinding library][databinding], you may want to

increase the number of errors that `javac` will print. When Dagger prints an

error, databinding compilation will halt and sometimes print more than 100

errors, which is the default amount for `javac`. For more information, see

[Issue 306](https://github.com/google/dagger/issues/306).



```groovy

gradle.projectsEvaluated {

  tasks.withType(JavaCompile) {

    options.compilerArgs << "-Xmaxerrs" << "500" // or whatever number you want

  }

}

```



### Resources



*   [Documentation][website]

*   [Javadocs][latestapi]

*   [GitHub Issues]



If you do not use maven, gradle, ivy, or other build systems that consume

maven-style binary artifacts, they can be downloaded directly via the

[Maven Central Repository][mavencentral].



Developer snapshots are available from Sonatype's

[snapshot repository][dagger-snap], and are built on a clean build of

the GitHub project's master branch.



## Building Dagger



See [the CONTRIBUTING.md docs][Building Dagger].



## License



    Copyright 2012 The Dagger Authors



    Licensed under the Apache License, Version 2.0 (the "License");

    you may not use this file except in compliance with the License.

    You may obtain a copy of the License at



       http://www.apache.org/licenses/LICENSE-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.



[`bazel`]: https://bazel.build

[bazel-external-deps]: https://docs.bazel.build/versions/master/external.html#depending-on-other-bazel-projects

[`maven_install`]: https://github.com/bazelbuild/rules_jvm_external#exporting-and-consuming-artifacts-from-external-repositories

[Building Dagger]: CONTRIBUTING.md#building-dagger

[dagger-snap]: https://oss.sonatype.org/content/repositories/snapshots/com/google/dagger/

[databinding]: https://developer.android.com/topic/libraries/data-binding/

[gaktalk]: https://www.youtube.com/watch?v=oK_XtfXPkqw

[GitHub Issues]: https://github.com/google/dagger/issues

[gradle-api-implementation]: https://docs.gradle.org/current/userguide/java_library_plugin.html#sec:java_library_separation

[gradle-api-implementation-android]: https://developer.android.com/studio/build/dependencies#dependency_configurations

[`kapt`]: https://kotlinlang.org/docs/reference/kapt.html

[latestapi]: https://dagger.dev/api/latest/

[mavenbadge-svg]: https://maven-badges.herokuapp.com/maven-central/com.google.dagger/dagger/badge.svg

[mavencentral]: https://search.maven.org/artifact/com.google.dagger/dagger

[project]: http://github.com/google/dagger/

[proposal]: https://github.com/square/dagger/issues/366

[square]: http://github.com/square/dagger/

[website]: https://dagger.dev