如何為 gradle 自定義 Java 任務輸入指定默認值？

Question

作為 Gradle 插件的一部分，我在 Java 中編寫了一個自定義 Gradle 任務，如下所示：

public abstract class MyTask extends DefaultTask {

    private static final String DEFAULT_SERVICE_VERSION = "NO VERSION";
    private String serviceVersion;

    @Option(option = "serviceVersion", description = "Configures the service version.")
    public void setServiceVersion(String serviceVersion) {
        this.serviceVersion = serviceVersion;
    }

    @Input
    public String getServiceVersion() {
        return serviceVersion;
    }


    @TaskAction
    public void myTask() {
        String serviceVersionCurrent = getServiceVersion() != null ? getServiceVersion() : DEFAULT_SERVICE_VERSION;

這允許我使用serviceVersion作為參數調用任務，如下所示：

gradle myTask --serviceVersion="0.1"

我想以某種方式使 serviceVersion 可選，如果未指定值，則默認為DEFAULT_SERVICE_VERSION

就像現在一樣，它失敗了：

> gradle myTask
> Task :myTask FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Some problems were found with the configuration of task ':myTask' (type 'MyTask').
> No value has been specified for property 'serviceVersion'.

如果沒有指定，我應該如何注釋我的屬性以使其默認為某個值？

Answer 1

只需在變量初始化時分配默認值：

public class GreetingTask extends DefaultTask {
  private String serviceVersion = "v1.0";

  @Option(option = "serviceVersion", description = "Configure service version")
  public void setServiceVersion(String serviceVersion) {
    this.serviceVersion = serviceVersion;
  }

  @Input
  public String getServiceVersion() {
    return this.serviceVersion;
  }

  @TaskAction
  public void task() {
    System.out.println(this.serviceVersion);
  }
}

output 將是：

$ ./gradlew greeting

> Task :greeting
v1.0

BUILD SUCCESSFUL in 2s
3 actionable tasks: 3 executed

$ ./gradlew greeting --serviceVersion=v2.0

> Task :greeting
v2.0

BUILD SUCCESSFUL in 1s
3 actionable tasks: 1 executed, 2 up-to-date