Java Gradle Project
This is just a super simple java project to show some of the basics of gradle.
This project was generated by running gradle init followed by selecting
application, Java, Groovy, JUnit 4 for a test framework, the default
project, name, and a source package name (com.maker2413.gradle in this case).
When we select application for a project type gradle will create a app
directory with the apporpriate folder structure for the project language
selected. Let's run tree to see the directory structure of a Java project
after running gradle init with the above inputs:
tree .
Outputs:
. ├── app │ ├── build.gradle │ └── src │ ├── main │ │ ├── java │ │ │ └── com │ │ │ └── maker2413 │ │ │ └── gradle │ │ │ └── App.java │ │ └── resources │ └── test │ ├── java │ │ └── com │ │ └── maker2413 │ │ └── gradle │ │ └── AppTest.java │ └── resources ├── gradle │ └── wrapper │ ├── gradle-wrapper.jar │ └── gradle-wrapper.properties ├── gradlew ├── gradlew.bat ├── README.org └── settings.gradle 16 directories, 9 files
You will notice that this time we have the app directory mentioned above and
it contains both our source code and our test code which in this case will be
JUnit 4 format. You will also notice that if we cat our App.java it even
created a simple beginning Java Application for us:
cat app/src/main/java/com/maker2413/gradle/App.java
Outputs:
/*
* This Java source file was generated by the Gradle 'init' task.
*/
package com.maker2413.gradle;
public class App {
public String getGreeting() {
return "Hello World!";
}
public static void main(String[] args) {
System.out.println(new App().getGreeting());
}
}
It also generated a simple test for our java application:
cat app/src/test/java/com/maker2413/gradle/AppTest.java
Outputs:
/*
* This Java source file was generated by the Gradle 'init' task.
*/
package com.maker2413.gradle;
import org.junit.Test;
import static org.junit.Assert.*;
public class AppTest {
@Test public void testAppHasAGreeting() {
App classUnderTest = new App();
assertNotNull("app should have a greeting", classUnderTest.getGreeting());
}
}
The other thing that gradle went ahead and did for us is that it made some extra tasks that we can take advantage of:
./gradlew tasks --all
Outputs:
Downloading https://services.gradle.org/distributions/gradle-7.0.2-bin.zip ..........10%...........20%...........30%..........40%...........50%...........60%..........70%...........80%...........90%..........100% > Task :tasks ------------------------------------------------------------ Tasks runnable from root project 'JavaProject' ------------------------------------------------------------ Application tasks ----------------- app:run - Runs this project as a JVM application Build tasks ----------- app:assemble - Assembles the outputs of this project. app:build - Assembles and tests this project. app:buildDependents - Assembles and tests this project and all projects that depend on it. app:buildNeeded - Assembles and tests this project and all projects it depends on. app:classes - Assembles main classes. app:clean - Deletes the build directory. app:jar - Assembles a jar archive containing the main classes. app:testClasses - Assembles test classes. Build Setup tasks ----------------- init - Initializes a new Gradle build. wrapper - Generates Gradle wrapper files. Distribution tasks ------------------ app:assembleDist - Assembles the main distributions app:distTar - Bundles the project as a distribution. app:distZip - Bundles the project as a distribution. app:installDist - Installs the project as a distribution as-is. Documentation tasks ------------------- app:javadoc - Generates Javadoc API documentation for the main source code. Help tasks ---------- buildEnvironment - Displays all buildscript dependencies declared in root project 'JavaProject'. app:buildEnvironment - Displays all buildscript dependencies declared in project ':app'. dependencies - Displays all dependencies declared in root project 'JavaProject'. app:dependencies - Displays all dependencies declared in project ':app'. dependencyInsight - Displays the insight into a specific dependency in root project 'JavaProject'. app:dependencyInsight - Displays the insight into a specific dependency in project ':app'. help - Displays a help message. app:help - Displays a help message. javaToolchains - Displays the detected java toolchains. app:javaToolchains - Displays the detected java toolchains. outgoingVariants - Displays the outgoing variants of root project 'JavaProject'. app:outgoingVariants - Displays the outgoing variants of project ':app'. projects - Displays the sub-projects of root project 'JavaProject'. app:projects - Displays the sub-projects of project ':app'. properties - Displays the properties of root project 'JavaProject'. app:properties - Displays the properties of project ':app'. tasks - Displays the tasks runnable from root project 'JavaProject' (some of the displayed tasks may belong to subprojects). app:tasks - Displays the tasks runnable from project ':app'. Verification tasks ------------------ app:check - Runs all checks. app:test - Runs the unit tests. Other tasks ----------- app:compileJava - Compiles main Java source. app:compileTestJava - Compiles test Java source. components - Displays the components produced by root project 'JavaProject'. [deprecated] app:components - Displays the components produced by project ':app'. [deprecated] dependentComponents - Displays the dependent components of components in root project 'JavaProject'. [deprecated] app:dependentComponents - Displays the dependent components of components in project ':app'. [deprecated] model - Displays the configuration model of root project 'JavaProject'. [deprecated] app:model - Displays the configuration model of project ':app'. [deprecated] prepareKotlinBuildScriptModel app:processResources - Processes main resources. app:processTestResources - Processes test resources. app:startScripts - Creates OS specific scripts to run the project as a JVM application. BUILD SUCCESSFUL in 35s 1 actionable task: 1 executed
These tasks can be found in the build.gradle and are being provided by the application plugin. Lets try one of the these tasks right now:
./gradlew compileJava
Outputs:
: > Task :app:compileJava UP-TO-DATE : : BUILD SUCCESSFUL in 551ms : 1 actionable task: 1 up-to-date
Now if we look in the app directory:
ls app/
Outputs:
: build : build.gradle : src
We can see that gradle has compiled our java code and put it in a build
directory in app. Now lets see what it created for us:
tree app/build/
Outputs:
app/build/
├── classes
│ └── java
│ └── main
│ └── com
│ └── maker2413
│ └── gradle
│ └── App.class
├── generated
│ └── sources
│ ├── annotationProcessor
│ │ └── java
│ │ └── main
│ └── headers
│ └── java
│ └── main
└── tmp
└── compileJava
└── source-classes-mapping.txt
16 directories, 2 files
We also have a task that will clean up the build directory for us:
./gradlew clean
Outputs:
: > Task :app:clean : : BUILD SUCCESSFUL in 507ms : 1 actionable task: 1 executed
Lets see if it worked:
ls app/
Outputs:
: build.gradle : src
Lets try one final task:
./gradlew test
Outputs:
> Task :app:compileJava > Task :app:processResources NO-SOURCE > Task :app:classes > Task :app:compileTestJava > Task :app:processTestResources NO-SOURCE > Task :app:testClasses > Task :app:test BUILD SUCCESSFUL in 1s 3 actionable tasks: 3 executed
This will run the test we have defined in the test directory. It even
generates a report in html format that we can open in a browser of our choice
to see the results:
tree app/build/reports/
Outputs:
app/build/reports/
└── tests
└── test
├── classes
│ └── com.maker2413.gradle.AppTest.html
├── css
│ ├── base-style.css
│ └── style.css
├── index.html
├── js
│ └── report.js
└── packages
└── com.maker2413.gradle.html
6 directories, 6 files
Opening the index.html would display a site like this:
Feel free to play around with more of the tasks provided by the application plugin. Here are some other notable tasks that we have available to us:
gradle jar- Will compile our code and create a jar file for us.
gradle run- Will compile and run our code.
--rerun-tasks- It is important to know that adding
--rerun-tasksto any gradle command will ignore any existing artifacts and run it from scratch.