Dagger
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 the same team that works on Guava. 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.
Documentation
You can find the dagger documentation here which has extended usage instructions and other useful information. More detailed 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
First, import the Dagger repository into your WORKSPACE
file using
http_archive
.
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.
# Top-level WORKSPACE file
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
DAGGER_TAG = "2.44.2"
DAGGER_SHA = "cbff42063bfce78a08871d5a329476eb38c96af9cf20d21f8b412fee76296181"
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.
# 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
in your top-level BUILD
file:
# 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).
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.
# 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
in your top-level BUILD
file:
# 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).
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.
# 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
in your top-level BUILD
file:
# 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).
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
:
<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>
Gradle
// 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:
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 ofapi
for better compilation performance.- See the Gradle documentation for more information on how to select appropriately, and the Android Gradle plugin documentation for Android projects.
- For Kotlin projects, use
kapt
in place ofannotationProcessor
.
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
}
}
Resources
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
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.