Gradle Ultimate Guide

1. Core Concepts

• Project: The basic unit of a Gradle build. One build consists of one or more projects.
• Task: The smallest executable unit. Examples: compiling code, running tests, generating documentation.
• Build Script: A file that defines projects and tasks. Typically build.gradle (Groovy) or build.gradle.kts (Kotlin).
• Gradle Wrapper (gradlew): The Gradle-recommended way to execute builds. It automatically downloads and installs the appropriate Gradle version, ensuring all team members develop in the same environment.

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2. Key Basic Commands

It is always recommended to use the Gradle Wrapper (gradlew) for commands.

Information Retrieval

• ./gradlew tasks: Displays all executable tasks.
• ./gradlew help --task <name>: Displays detailed help for a specific task.
• ./gradlew properties: Displays all project properties.
• ./gradlew projects: Displays the project structure (useful for multi-module projects).

Build and Compile

• ./gradlew build: Executes a full project build (compile, test, package).
• ./gradlew clean: Deletes the build directory and cleans up previous build artifacts.
• ./gradlew assemble: Executes compilation and packaging only, without running tests.
• ./gradlew compileJava: Executes compilation of Java source code only.
• ./gradlew classes: Compiles source code and processes resource files.

Testing

• ./gradlew test: Runs all unit tests.
• ./gradlew test --tests "com.example.MyTest": Runs only a specific test class.
• ./gradlew test --debug-jvm: Runs tests in debug mode.

Run and Install

• ./gradlew run: Runs the application (requires the application plugin).
• ./gradlew install: Installs the generated Jar/War files into the local repository.

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3. Advanced Build Options (Common Arguments)

Options to control the Gradle build process and enhance efficiency.

• Parallel Execution: -parallel
  • Builds modules in parallel using all available CPU cores.
• Configure-on-demand: --configure-on-demand
  • Configures only relevant modules in large multi-project builds.
• Continuous Mode: -t or --continuous
  • Monitors file changes and automatically re-executes tasks when code is modified.
• Skip Tests: -x test
  • Builds without executing test tasks.
• Offline Mode: --offline
  • Uses only dependencies found in the local cache, without connecting to the network.
• Verbose Logging: -i (info), -d (debug), -s (stacktrace)
  • Used for debugging build scripts or viewing detailed output.
• Daemon: --daemon / --no-daemon
  • Gradle uses a daemon process by default to speed up builds.

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4. Dependency Management Techniques

• Display Dependency Tree: ./gradlew dependencies
  • A powerful command for resolving dependency conflicts (Dependency Hell).
• Display Dependencies for a Specific Module: ./gradlew :app:dependencies
• Refresh Dependency Cache: --refresh-dependencies
  • Forces a check and download of the latest Snapshot versions or missing dependencies.

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5. Multi-Project Builds

When operating from the root directory:

• Build all subprojects: ./gradlew build
• Execute a task for a specific subproject: ./gradlew :sub-project:taskName
  • Example: ./gradlew :services:api:build

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6. Build Performance Improvement Tips

1. Always use Gradle Wrapper: Avoids issues due to version mismatches.
2. Enable Build Cache: Add org.gradle.caching=true to gradle.properties.
3. Increase Memory Limit: Set org.gradle.jvmargs=-Xmx2048m -Dfile.encoding=UTF-8 in gradle.properties.
4. Keep Gradle Up-to-Date: Significant performance improvements are often made with each major update.