如何使用結構化並發運行 JDK 19？

Question

我想嘗試在JEP 428: Structured Concurrency (Incubator)中定義的新Project Loom功能

我的 pom.xml

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-compiler-plugin</artifactId>
  <version>3.10.1</version>
  <configuration>
    <compilerArgs>--source 19</compilerArgs>
    <compilerArgs>--enable-preview</compilerArgs>
    <compilerArgs>--add-modules jdk.incubator.concurrent</compilerArgs>
    <compilerVersion>19</compilerVersion>
    <source>19</source>
    <target>19</target>
  </configuration>
</plugin>

但是當我嘗試通過mvn compile構建時，我得到了

[ERROR] /C:/Users/ERIC/Documents/git/loom-lab/laboratory/src/main/java/net/kolotyluk/loom/Structures.java:[3,21] package jdk.incubator.concurrent is not visible
  (package jdk.incubator.concurrent is declared in module jdk.incubator.concurrent, which is not in the module graph)

有沒有我想念的秘方？

$ mvn -version
Apache Maven 3.6.0 (97c98ec64a1fdfee7767ce5ffb20918da4f719f3; 2018-10-24T11:41:47-07:00)
Maven home: C:\Program Files (Open)\Apache\apache-maven-3.6.0
Java version: 19-ea, vendor: Oracle Corporation, runtime: C:\Program Files (Open)\jdk-19
Default locale: en_CA, platform encoding: UTF-8
OS name: "windows 10", version: "10.0", arch: "amd64", family: "windows"

Answer 1

我不了解所有活動部件，但我確實成功訪問了 Java 19 中正在孵化和預覽的新 Project Loom 功能。

這是我的main方法。

record Event( UUID id , Instant when , Integer reading ) {}

try ( var scope = new StructuredTaskScope.ShutdownOnFailure() )
{
    Future < UUID > futureId = scope.fork( ( ) -> UUID.randomUUID() );
    Future < Instant > futureWhen = scope.fork( ( ) -> Instant.now() );
    Future < Integer > futureReading = scope.fork( ( ) -> ThreadLocalRandom.current().nextInt( 1 , 10 ) );

    scope.join();           // Join both forks
    scope.throwIfFailed();  // ... and propagate errors
    Event event = new Event( futureId.get() , futureWhen.get() , futureReading.get() );
    System.out.println( event );
}
catch ( InterruptedException e )
{
    throw new RuntimeException( e );
}
catch ( ExecutionException e )
{
    throw new RuntimeException( e );
}

該代碼使用這些輸入：

import java.time.Instant;
import java.util.UUID;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadLocalRandom;

運行時：

事件[id=de316aca-10b1-41ed-bfc6-732c4e184566, when=2022-08-07T03:04:48.207650Z, reading=9]

我在src/main/java的 package 層次結構之外添加了一個module-info.java文件。

還有我的POM 。 我從 Apache Maven 快速入門工件開始。 然后我將所有版本號更新到最新。

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns = "http://maven.apache.org/POM/4.0.0"
         xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation = "http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>work.basil.example</groupId>
    <artifactId>Loom</artifactId>
    <version>1.0-SNAPSHOT</version>

    <name>Loom</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.release>19</maven.compiler.release>
    </properties>

    <dependencies>

        <!-- https://mvnrepository.com/artifact/org.junit.jupiter/junit-jupiter -->
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter</artifactId>
            <version>5.9.0</version>
            <scope>test</scope>
        </dependency>


    </dependencies>

    <build>
        <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (maybe moved to parent pom) -->
            <plugins>
                <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
                <plugin>
                    <artifactId>maven-clean-plugin</artifactId>
                    <version>3.2.0</version>
                </plugin>
                <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
                <plugin>
                    <artifactId>maven-resources-plugin</artifactId>
                    <version>3.3.0</version>
                </plugin>
                <plugin>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.10.1</version>
                    <configuration>
                        <!--<compilerVersion>19</compilerVersion>-->
                        <release>19</release>
                        <!--<compilerArgs>&#45;&#45;source 19</compilerArgs>-->
                        <compilerArgs>--enable-preview</compilerArgs>
                        <!--<compilerArgs>&#45;&#45;add-modules jdk.incubator.concurrent</compilerArgs>-->
                    </configuration>
                </plugin>
                <plugin>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>3.0.0-M7</version>
                </plugin>
                <plugin>
                    <artifactId>maven-jar-plugin</artifactId>
                    <version>3.2.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-install-plugin</artifactId>
                    <version>3.0.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-deploy-plugin</artifactId>
                    <version>3.0.0</version>
                </plugin>
                <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
                <plugin>
                    <artifactId>maven-site-plugin</artifactId>
                    <version>4.0.0-M3</version>
                </plugin>
                <plugin>
                    <artifactId>maven-project-info-reports-plugin</artifactId>
                    <version>3.4.0</version>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>
</project>

Answer 2

@BasilBourque 的一個小補充很好的答案。 對於那些可能不使用 Maven 或模塊的人，您不需要將您的應用程序設為模塊。 所有啟動器都需要--enable-preview --add-modules jdk.incubator.concurrent的參數，無論是直接啟動還是通過 Maven。

您應該能夠使用以下源代碼啟動器或 javac/java 從命令行使用標准類路徑和沒有 module-info.java 運行他提供的並發示例：

%JAVAHOME%/bin/java --source 19 --enable-preview --add-modules jdk.incubator.concurrent ConcurrencyEx.java

或者編譯然后運行它：

%JAVAHOME%/bin/javac --source 19 --enable-preview --add-modules jdk.incubator.concurrent -d ../build ConcurrencyEx.java

%JAVAHOME%/bin/java --enable-preview --add-modules jdk.incubator.concurrent -cp ../build ConcurrencyEx

顯然，只需將%JAVAHOME%替換$JAVAHOME即可在 Linux 而不是 Windows 上運行。

源代碼：

import java.util.UUID;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadLocalRandom;
import jdk.incubator.concurrent.*;

public class ConcurrencyEx {
    
    // main as from @BasilBourque answer
    public static void main(String[] args) throws InterruptedException, ExecutionException {
        record Event( UUID id , Instant when , Integer reading ) {}

        try ( var scope = new StructuredTaskScope.ShutdownOnFailure() ) {
            Future < UUID > futureId = scope.fork( ( ) -> UUID.randomUUID() );
            Future < Instant > futureWhen = scope.fork( ( ) -> Instant.now() );
            Future < Integer > futureReading = scope.fork( ( ) -> ThreadLocalRandom.current().nextInt( 1 , 10 ) );

            scope.join();           // Join both forks
            scope.throwIfFailed();  // ... and propagate errors
            Event event = new Event( futureId.get() , futureWhen.get() , futureReading.get() );
            System.out.println( event );
        }
    }
}

Answer 3

我設法讓它與 Maven 一起工作，而不需要module-info.java文件。 我的 POM 和你的 POM 之間的主要區別似乎是我如何設置編譯器 arguments。 而不是你所擁有的：

<configuration>
  <compilerArgs>--source 19</compilerArgs>
  <compilerArgs>--enable-preview</compilerArgs>
  <compilerArgs>--add-modules jdk.incubator.concurrent</compilerArgs>
  <compilerVersion>19</compilerVersion>
  <source>19</source>
  <target>19</target>
</configuration>

我有：

<configuration>
  <compilerArgs>
    <arg>--add-modules=jdk.incubator.concurrent</arg>
  </compilerArgs>
</configuration>

注意我有嵌套在<compilerArgs>中的<arg>元素。 我在--add-modules參數中也有= ，但我不知道這是否是絕對必要的。 似乎只有在運行時才需要--enable-preview ，而不是編譯時。 您擁有的其他 arguments 我設置了不同的方式（例如， <properties>元素）。

---

例子

這是一個示例，其中JAVA_HOME設置為 JDK 19 安裝。

源/構建文件

App.java：

package sample;

import jdk.incubator.concurrent.StructuredTaskScope;

public class App {
  public static void main( String[] args ) throws Exception {
    try (var scope = new StructuredTaskScope<Void>()) {
      scope.fork(() -> delayPrint(1000, "Hello,"));
      scope.fork(() -> delayPrint(2000, "World!"));
      scope.join();
    }
    System.out.println("Done!");
  }

  private static Void delayPrint(long delay, String message) throws Exception {
    Thread.sleep(delay);
    System.out.println(message);
    return null;
  }
}

pom.xml ：

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example</groupId>
  <artifactId>sample</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>sample</name>
  <url>http://maven.apache.org</url>
  
  <properties>
    <maven.compiler.source>19</maven.compiler.source>
    <maven.compiler.target>19</maven.compiler.target>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <build>

    <plugins>

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.10.1</version>
        <configuration>
          <compilerArgs>
            <arg>--add-modules=jdk.incubator.concurrent</arg>
          </compilerArgs>
        </configuration>
      </plugin>

      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>exec-maven-plugin</artifactId>
        <version>3.1.0</version>
        <configuration>
          <executable>${java.home}/bin/java</executable>
          <arguments>
            <argument>--add-modules=jdk.incubator.concurrent</argument>
            <argument>--enable-preview</argument>
            <argument>--class-path</argument>
            <classpath/>
            <argument>sample.App</argument>
          </arguments>
        </configuration>
      </plugin>

    </plugins>
  </build>

</project>

Output

編譯：

> mvn compile

[INFO] Scanning for projects...
[INFO]
[INFO] -------------------------< com.example:sample >-------------------------
[INFO] Building sample 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ sample ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory C:\Users\***\Desktop\structured_concurrency\sample\src\main\resources
[INFO]
[INFO] --- maven-compiler-plugin:3.10.1:compile (default-compile) @ sample ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to C:\Users\***\Desktop\structured_concurrency\sample\target\classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.439 s
[INFO] Finished at: 2022-08-08T01:01:26-06:00
[INFO] ------------------------------------------------------------------------

執行：

> mvn exec:exec

[INFO] Scanning for projects...
[INFO]
[INFO] -------------------------< com.example:sample >-------------------------
[INFO] Building sample 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- exec-maven-plugin:3.1.0:exec (default-cli) @ sample ---
WARNING: Using incubator modules: jdk.incubator.concurrent
Hello,
World!
Done!
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  2.610 s
[INFO] Finished at: 2022-08-08T01:02:42-06:00
[INFO] ------------------------------------------------------------------------