如何为 gradle 自定义 Java 任务输入指定默认值？

Question

作为 Gradle 插件的一部分，我在 Java 中编写了一个自定义 Gradle 任务，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;

这允许我使用serviceVersion作为参数调用任务，如下所示：

gradle myTask --serviceVersion="0.1"

我想以某种方式使 serviceVersion 可选，如果未指定值，则默认为DEFAULT_SERVICE_VERSION

就像现在一样，它失败了：

> 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'.

如果没有指定，我应该如何注释我的属性以使其默认为某个值？

Answer 1

只需在变量初始化时分配默认值：

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 将是：

$ ./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