# Configuring the Build Environment

version 9.0.0

Configuring the build environment is a powerful way to customize the build process. There are many mechanisms available. By leveraging these mechanisms, you can make your Gradle builds more flexible and adaptable to different environments and requirements.

## Available mechanisms

Gradle provides multiple mechanisms for configuring the behavior of Gradle itself and specific projects:

Mechanism | Information | Example
--- | --- | ---
Command line interface | Flags that configure build behavior and Gradle features | `--rerun`
Project properties | Properties specific to your Gradle project | `TestFilter::isFailOnNoMatchingTests=false`
System properties | Properties that are passed to the Gradle runtime (JVM) | `http.proxyHost=somehost.org`
Gradle properties | Properties that configure Gradle settings and the Java process that executes your build | `org.gradle.logging.level=quiet`
Environment variables | Properties that configure build behavior based on the environment | `JAVA_HOME`

## Priority for configurations

When configuring Gradle behavior, you can use these methods, but you must consider their priority.

The following table lists these methods in order of highest to lowest precedence (the first one wins):

Priority | Method | Location | Notes
--- | --- | --- | ---
1 | Command-line | > Command line | Flags have precedence over properties and environment variables
2 | System properties | > Project Root Dir | Stored in a `gradle.properties` file
3 | Gradle properties | > `GRADLE_USER_HOME` > Project Root Dir > `GRADLE_HOME` | Stored in a `gradle.properties` file
4 | Environment variables | > Environment | Sourced by the environment that executes Gradle

Here are all possible configurations of specifying the JDK installation directory in order of priority:

1. Command Line

       $ ./gradlew exampleTask -Dorg.gradle.java.home=/path/to/your/java/home --scan

2. Gradle Properties File

   gradle.properties

       org.gradle.java.home=/path/to/your/java/home

3. Environment Variable

       $ export JAVA_HOME=/path/to/your/java/home

## The `gradle.properties` file

Gradle properties, system properties, and project properties can be found in the `gradle.properties` file:

gradle.properties

    # Gradle properties
    org.gradle.parallel=true
    org.gradle.caching=true
    org.gradle.jvmargs=-Duser.language=en -Duser.country=US -Dfile.encoding=UTF-8

    # System properties
    systemProp.pts.enabled=true
    systemProp.log4j2.disableJmx=true
    systemProp.file.encoding = UTF-8

    # Project properties
    kotlin.code.style=official
    android.nonTransitiveRClass=false
    spring-boot.version = 2.2.1.RELEASE

You can place the `gradle.properties` file in the root directory of your project, the Gradle user home directory (`GRADLE_USER_HOME`), or the directory where Gradle is optionally installed (`GRADLE_HOME`).

When resolving properties, Gradle first looks in the user-level `gradle.properties` file located in `GRADLE_USER_HOME`, then in the project-level `gradle.properties` file, and finally in the `gradle.properties` file located in `GRADLE_HOME`, with user-level properties taking precedence over project-level and installation-level properties.

## Project properties

Project properties are specific to your Gradle project, they can be used to customize your build. Project properties can be accessed in your build files and get passed in from an external source when your build is executed. Project properties can be retrieved in build scripts lazily using `providers.gradleProperty()`.

### Setting a project property

You have four options to add project properties, listed in order of priority:

1. Command Line: You can add project properties directly to your Project object via the `-P` command line option.

       $ ./gradlew build -PmyProperty='Hi, world'

2. System Property: Gradle creates specially-named system properties for project properties which you can set using the `-D` command line flag or `gradle.properties` file. For the project property `myProperty`, the system property created is called `org.gradle.project.myProperty`.

       $ ./gradlew build -Dorg.gradle.project.myProperty='Hi, world'

   gradle.properties

       org.gradle.project.myProperty='Hi, world'

3. Gradle Properties File: You can also set project properties in `gradle.properties` files.

   gradle.properties

       myProperty='Hi, world'

4. Environment Variables: You can set project properties with environment variables. If the environment variable name looks like `ORG_GRADLE_PROJECT_myProperty='Hi, world'`, then Gradle will set a `myProperty` property on your project object, with the value of `Hi, world`.

       $ export ORG_GRADLE_PROJECT_myProperty='Hi, world'

   This is typically the preferred method for supplying project properties, especially secrets, to unattended builds like those running on CI servers.

It is possible to change the behavior of a task based on project properties specified at invocation time. Suppose you’d like to ensure release builds are only triggered by CI. A simple way to handle this is through an `isCI` project property:

build.gradle.kts

    tasks.register("performRelease") {
        val isCI = providers.gradleProperty("isCI")
        doLast {
            if (isCI.isPresent) {
                println("Performing release actions")
            } else {
                throw InvalidUserDataException("Cannot perform release outside of CI")
            }
        }
    }

build.gradle

    tasks.register('performRelease') {
        def isCI = providers.gradleProperty("isCI")
        doLast {
            if (isCI.present) {
                println("Performing release actions")
            } else {
                throw new InvalidUserDataException("Cannot perform release outside of CI")
            }
        }
    }

    $ ./gradlew performRelease -PisCI=true --quiet
    Performing release actions

Note that running `./gradlew performRelease` yields the same results as long as your `gradle.properties` file includes `isCI=true`:

gradle.properties

    isCI=true

    $ ./gradlew performRelease --quiet
    Performing release actions

## Command-line flags

The command line interface and the available flags are described in its own section.

## System properties

System properties are variables set at the JVM level and accessible to the Gradle build process. System properties can be retrieved in build scripts lazily using `providers.systemProperty()`.

### Setting a system property

You have two options to add system properties listed in order of priority:

1. Command Line: Using the `-D` command-line option, you can pass a system property to the JVM, which runs Gradle. The `-D` option of the `gradle` command has the same effect as the `-D` option of the `java` command.

       $ ./gradlew build -Dgradle.wrapperUser=myuser

2. Gradle Properties File: You can also set system properties in `gradle.properties` files with the prefix `systemProp`.

   gradle.properties

       systemProp.gradle.wrapperUser=myuser

### System properties reference

For a quick reference, the following are common system properties:

`gradle.wrapperUser=(myuser)`

  Specify username to download Gradle distributions from servers using HTTP Basic Authentication.

`gradle.wrapperPassword=(mypassword)`

  Specify password for downloading a Gradle distribution using the Gradle wrapper.

`gradle.user.home=(path to directory)`

  Specify the `GRADLE_USER_HOME` directory.

`https.protocols`

  Specify the supported TLS versions in a comma-separated format. e.g., `TLSv1.2,TLSv1.3`.

Additional Java system properties are listed here.

In a multi-project build, `systemProp` properties set in any project except the root will be ignored. Only the root project’s `gradle.properties` file will be checked for properties that begin with `systemProp`.

## Gradle properties

Gradle properties configure Gradle itself and usually have the name `org.gradle.\*`. Gradle properties should not be used in build logic, their values should not be read/retrieved in build scripts.

### Setting a Gradle property

You have two options to add Gradle properties listed in order of priority:

1. Command Line: Using the `-D` command-line option, you can pass a Gradle property:

       $ ./gradlew build -Dorg.gradle.caching.debug=false

2. Gradle Properties File: Place these settings into a `gradle.properties` file and commit it to your version control system.

   gradle.properties

       org.gradle.caching.debug=false

The final configuration considered by Gradle is a combination of all Gradle properties set on the command line and your `gradle.properties` files. If an option is configured in multiple locations, the first one found in any of these locations wins:

Priority | Method | Location | Details
--- | --- | --- | ---
1 | Command line interface | . | In the command line using `-D`.
2 | `gradle.properties` file | `GRADLE_USER_HOME` | Stored in a `gradle.properties` file in the `GRADLE_USER_HOME`.
3 | `gradle.properties` file | Project Root Dir | Stored in a `gradle.properties` file in a project directory, then its parent project’s directory up to the project’s root directory.
4 | `gradle.properties` file | `GRADLE_HOME` | Stored in a `gradle.properties` file in the `GRADLE_HOME`, the optional Gradle installation directory.

| The location of the `GRADLE_USER_HOME` may have been changed beforehand via the `-Dgradle.user.home` system property passed on the command line.

### Gradle properties reference

For reference, the following properties are common Gradle properties:

`org.gradle.caching=(true,false)`

  When set to `true`, Gradle will reuse task outputs from any previous build when possible, resulting in much faster builds.

  Default is `false`; the build cache is not enabled.

`org.gradle.caching.debug=(true,false)`

  When set to `true`, individual input property hashes and the build cache key for each task are logged on the console.

  Default is `false`.

`org.gradle.configuration-cache=(true,false)`

  Enables configuration caching. Gradle will try to reuse the build configuration from previous builds.

  Default is `false`.

`org.gradle.configureondemand=(true,false)`

  Enables incubating configuration-on-demand, where Gradle will attempt to configure only necessary projects.

  Default is `false`.

`org.gradle.console=(auto,plain,rich,verbose)`

  Customize console output coloring or verbosity.

  Default depends on how Gradle is invoked.

`org.gradle.continue=(true,false)`

  If enabled, continue task execution after a task failure, else stop task execution after a task failure.

  Default is `false`.

`org.gradle.daemon=(true,false)`

  When set to `true` the Gradle Daemon is used to run the build.

  Default is `true`.

`org.gradle.daemon.idletimeout=(# of idle millis)`

  Gradle Daemon will terminate itself after a specified number of idle milliseconds.

  Default is `10800000` (3 hours).

`org.gradle.debug=(true,false)`

  When set to `true`, Gradle will run the build with remote debugging enabled, listening on port 5005. Note that this is equivalent to adding `-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005` to the JVM command line and will suspend the virtual machine until a debugger is attached.

  Default is `false`.

`org.gradle.java.home=(path to JDK home)`

  Specifies the Java home for the Gradle build process. The value can be set to either a `jdk` or `jre` location; however, using a JDK is safer depending on what your build does. This does not affect the version of Java used to launch the Gradle client VM.

  You can also control the JVM used to run Gradle itself using the Daemon JVM criteria.

  Default is derived from your environment (`JAVA_HOME` or the path to `java`) if the setting is unspecified.

`org.gradle.jvmargs=(JVM arguments)`

  Specifies the JVM arguments used for the Gradle Daemon. The setting is particularly useful for configuring JVM memory settings for build performance. This does not affect the JVM settings for the Gradle client VM.

  Default is `-Xmx512m "-XX:MaxMetaspaceSize=384m"`.

`org.gradle.logging.level=(quiet,warn,lifecycle,info,debug)`

  When set to quiet, warn, info, or debug, Gradle will use this log level. The values are not case-sensitive.

  Default is `lifecycle` level.

`org.gradle.parallel=(true,false)`

  When configured, Gradle will fork up to `org.gradle.workers.max` JVMs to execute projects in parallel.

  Default is `false`.

`org.gradle.priority=(low,normal)`

  Specifies the scheduling priority for the Gradle daemon and all processes launched by it.

  Default is `normal`.

`org.gradle.projectcachedir=(directory)`

  Specify the project-specific cache directory. Defaults to `.gradle` in the root project directory."

  Default is `.gradle`.

`org.gradle.problems.report=(true|false)`

  Enable (`true`) or disable (`false`) the generation of `build/reports/problems-report.html`. `true` is the default. The report is generated with problems provided to the Problems API.

`org.gradle.unsafe.isolated-projects=(true,false)`

  Enables project isolation, which enables configuration caching.

  Default is `false`.

`org.gradle.vfs.verbose=(true,false)`

  Configures verbose logging when watching the file system.

  Default is `false`.

`org.gradle.vfs.watch=(true,false)`

  Toggles watching the file system. When enabled, Gradle reuses information it collects about the file system between builds.

  Default is `true` on operating systems where Gradle supports this feature.

`org.gradle.warning.mode=(all,fail,summary,none)`

  When set to `all`, `summary`, or `none`, Gradle will use different warning type display.

  Default is `summary`.

`org.gradle.workers.max=(max # of worker processes)`

  When configured, Gradle will use a maximum of the given number of workers.

  Default is the number of CPU processors.

## Environment variables

Gradle provides a number of environment variables, which are listed below. Environment variables can be retrieved in build scripts lazily using `providers.environmentVariable()`.

### Setting environment variables

Let’s take an example that sets the $JAVA_HOME environment variable:

    $ set JAVA_HOME=C:\Path\To\Your\Java\Home   // Windows
    $ export JAVA_HOME=/path/to/your/java/home  // Mac/Linux

You can access environment variables as properties in the build script using the `System.getenv()` method:

    task printEnvVariables {
        doLast {
            println "JAVA_HOME: ${System.getenv('JAVA_HOME')}"
        }
    }

### Environment variables reference

The following environment variables are available for the `gradle` command:

`GRADLE_HOME`

  Installation directory for Gradle.

  Can be used to specify a local Gradle version instead of using the wrapper.

  You can add `GRADLE_HOME/bin` to your `PATH` for specific applications and use cases (such as testing an early release for Gradle).

`JAVA_OPTS`

  Used to pass JVM options and custom settings to the JVM.

  `export JAVA_OPTS="-Xmx18928m -XX:+HeapDumpOnOutOfMemoryError -Dfile.encoding=UTF-8 -Djava.awt.headless=true -Dkotlin.daemon.jvm.options=-Xmx6309m"`

`GRADLE_OPTS`

  Specifies JVM arguments to use when starting the Gradle client VM.

  The client VM only handles command line input/output, so one would rarely need to change its VM options.

  The actual build is run by the Gradle daemon, which is not affected by this environment variable.

`GRADLE_USER_HOME`

  Specifies the `GRADLE_USER_HOME` directory for Gradle to store its global configuration properties, initialization scripts, caches, log files and more.

  Defaults to `USER_HOME/.gradle` if not set.

`JAVA_HOME`

  Specifies the JDK installation directory to use for the client VM.

  This VM is also used for the daemon unless a different one is specified in a Gradle properties file with `org.gradle.java.home` or using the Daemon JVM criteria.

`GRADLE_LIBS_REPO_OVERRIDE`

  Overrides for the default Gradle library repository.

  Can be used to specify a default Gradle repository URL in `org.gradle.plugins.ide.internal.resolver`.

  Useful override to specify an internally hosted repository if your company uses a firewall/proxy.