Dagger 2

A fast dependency injector for Android and Java.

About Google's Fork

Dagger 2 is a compile-time evolution approach to dependency injection. Taking the approach started in Dagger 1.x to its ultimate conclusion, Dagger 2.x eliminates all reflection, and improves code clarity by removing the traditional ObjectGraph/Injector in favor of user-specified @Component interfaces.

This github project represents the Dagger 2 development stream. The earlier project page (Square, Inc's repository) represents the earlier 1.0 development stream. Both versions have benefitted from strong involvement from Square, Google, and other contributors.

Dagger is currently in active development, primarily internally at Google, with regular pushes to the open-source community. Snapshot releases are auto-deployed to sonatype's central maven repository on every clean build with the version HEAD-SNAPSHOT.

Dagger 2's main documentation website can be found here.

Documentation

You can find the dagger documentation here which has extended usage instructions and other useful information. Substantial usage information can be found in the API documentation.

You can also learn more from the original proposal, this talk by Greg Kick, and on the dagger-discuss@googlegroups.com mailing list.

Installation

Bazel

If you build with bazel, follow the bazel documentation for referencing external projects to include Dagger in your build.

Given the following WORKSPACE definition, you can reference dagger via @com_google_dagger//:dagger_with_compiler in your deps.

http_archive(
    name = "com_google_dagger"
    urls = ["https://github.com/google/dagger/archive/dagger-<version>.zip"],
)

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:

<dependencies>
  <dependency>
    <groupId>com.google.dagger</groupId>
    <artifactId>dagger</artifactId>
    <version>2.x</version>
  </dependency>
</dependencies>
<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-compiler-plugin</artifactId>
      <version>3.6.1</version>
      <configuration>
        <annotationProcessorPaths>
          <path>
            <groupId>com.google.dagger</groupId>
            <artifactId>dagger-compiler</artifactId>
            <version>2.x</version>
          </path>
        </annotationProcessorPaths>
      </configuration>
    </plugin>
  </plugins>
</build>

If you are using a version of the maven-compiler-plugin lower than 3.5, add the dagger-compiler artifact with the provided scope:

<dependencies>
  <dependency>
    <groupId>com.google.dagger</groupId>
    <artifactId>dagger</artifactId>
    <version>2.x</version>
  </dependency>
  <dependency>
    <groupId>com.google.dagger</groupId>
    <artifactId>dagger-compiler</artifactId>
    <version>2.x</version>
    <scope>provided</scope>
  </dependency>
</dependencies>

If you use the beta dagger-producers extension (which supplies parallelizable execution graphs), then add this to your maven configuration:

<dependencies>
  <dependency>
    <groupId>com.google.dagger</groupId>
    <artifactId>dagger-producers</artifactId>
    <version>2.x</version>
  </dependency>
</dependencies>

Java Gradle

// Add plugin https://plugins.gradle.org/plugin/net.ltgt.apt
plugins {
  id "net.ltgt.apt" version "0.10"
}

// Add Dagger dependencies
dependencies {
  compile 'com.google.dagger:dagger:2.x'
  apt 'com.google.dagger:dagger-compiler:2.x'
}

Android Gradle

// Add Dagger dependencies
dependencies {
  compile '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:

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

If you're using a version of the Android gradle plugin below 2.2, see https://bitbucket.org/hvisser/android-apt.

If you're using the Android Databinding library, 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.

gradle.projectsEvaluated {
  tasks.withType(JavaCompile) {
    options.compilerArgs << "-Xmaxerrs" << "500" // or whatever number you want
  }
}

Download

• 2.x (google/dagger)
  • Dagger 2.0 Documentation
  • Dagger 2.0 Javadocs
  • Dagger development Javadocs (from the master branch on GitHub)
  • Google's Dagger project site on GitHub
  • Google+ Dagger Project Page
  • Google+ Dagger Users Community
• 1.x (square/dagger)
  • Square's original Dagger project site on GitHub
  • Square Open Source Community

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.

Developer snapshots are available from Sonatype's snapshot repository, and are built on a clean build of the GitHub project's master branch.

Building Dagger

Dagger is built with [bazel]. The tests can be run with bazel test //.... util/install-local-snapshot.sh will build all of the Dagger libraries and install a copy in your local maven repository with the version LOCAL-SNAPSHOT.

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.