MacマシンにJDK10をインストールしただけです。バージョンを確認しました:-
localhost:Java-10 vinayprajapati$ Java -version
Java version "10" 2018-03-20
Java(TM) SE Runtime Environment 18.3 (build 10+46)
Java HotSpot(TM) 64-Bit Server VM 18.3 (build 10+46, mixed mode)
使用するコンパイラも同じバージョンであることを確認するために、以下を実行しました:-
localhost:Java-10 vinayprajapati$ javac -version
javac 10
次の構造の単純なMavenプロジェクトを作成しました:-
localhost:Java-10 vinayprajapati$ tree
.
├── pom.xml
├── src
│ ├── main
│ │ └── Java
│ │ └── com
│ │ └── practice
│ │ └── Java_10
│ │ └── App.Java
│ └── test
│ └── Java
│ └── com
│ └── practice
│ └── Java_10
│ └── AppTest.Java
└── target
私のpom.xmlは:-
<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>com.practice</groupId>
<artifactId>Java-10</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>Java-10</name>
<url>http://maven.Apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.Apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<configuration>
<release>10</release>
</configuration>
<dependencies>
<dependency>
<groupId>org.ow2.asm</groupId>
<artifactId>asm</artifactId>
<version>6.1</version> <!-- Use newer version of ASM -->
</dependency>
</dependencies>
</plugin>
</plugins>
</build>
</project>
私のApp.Javaファイルは次のとおりです。-
package com.practice.Java_10;
import Java.util.ArrayList;
public class App {
public static void main(String[] args) {
var list = new ArrayList<String>();
System.out.println("Hello Java 10! Shall I welcome you?");
}
}
私は走ったmvn compile
およびmvn install
そして両方ともうまくいきました。以下の証明:-
localhost:Java-10 vinayprajapati$ mvn compile
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------< com.practice:Java-10 >------------------------
[INFO] Building Java-10 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ Java-10 ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /Users/vinayprajapati/Desktop/project/Java-10/Java-10/src/main/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.7.0:compile (default-compile) @ Java-10 ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to /Users/vinayprajapati/Desktop/project/Java-10/Java-10/target/classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.823 s
[INFO] Finished at: 2018-03-23T01:49:13+05:30
[INFO] ------------------------------------------------------------------------
localhost:Java-10 vinayprajapati$ mvn install
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------< com.practice:Java-10 >------------------------
[INFO] Building Java-10 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ Java-10 ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /Users/vinayprajapati/Desktop/project/Java-10/Java-10/src/main/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.7.0:compile (default-compile) @ Java-10 ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ Java-10 ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /Users/vinayprajapati/Desktop/project/Java-10/Java-10/src/test/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.7.0:testCompile (default-testCompile) @ Java-10 ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to /Users/vinayprajapati/Desktop/project/Java-10/Java-10/target/test-classes
[INFO]
[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ Java-10 ---
[INFO] Surefire report directory: /Users/vinayprajapati/Desktop/project/Java-10/Java-10/target/surefire-reports
-------------------------------------------------------
T E S T S
-------------------------------------------------------
Running com.practice.Java_10.AppTest
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.029 sec
Results :
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
[INFO]
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ Java-10 ---
[INFO] Building jar: /Users/vinayprajapati/Desktop/project/Java-10/Java-10/target/Java-10-0.0.1-SNAPSHOT.jar
[INFO] META-INF/maven/com.practice/Java-10/pom.xml already added, skipping
[INFO] META-INF/maven/com.practice/Java-10/pom.properties already added, skipping
[INFO]
[INFO] --- maven-install-plugin:2.4:install (default-install) @ Java-10 ---
[INFO] Installing /Users/vinayprajapati/Desktop/project/Java-10/Java-10/target/Java-10-0.0.1-SNAPSHOT.jar to /Users/vinayprajapati/.m2/repository/com/practice/Java-10/0.0.1-SNAPSHOT/Java-10-0.0.1-SNAPSHOT.jar
[INFO] Installing /Users/vinayprajapati/Desktop/project/Java-10/Java-10/pom.xml to /Users/vinayprajapati/.m2/repository/com/practice/Java-10/0.0.1-SNAPSHOT/Java-10-0.0.1-SNAPSHOT.pom
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.157 s
[INFO] Finished at: 2018-03-23T01:49:22+05:30
[INFO] ------------------------------------------------------------------------
実行されたときmvn exec:Java -Dexec.mainClass="com.practice.Java_10.App"
、以下のようなエラーが発生しました:-
localhost:Java-10 vinayprajapati$ mvn exec:Java -Dexec.mainClass="com.practice.Java_10.App"
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------< com.practice:Java-10 >------------------------
[INFO] Building Java-10 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- exec-maven-plugin:1.6.0:Java (default-cli) @ Java-10 ---
[WARNING]
Java.lang.Error: Unresolved compilation problem:
var cannot be resolved to a type
at com.practice.Java_10.App.main (App.Java:11)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.Java:62)
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.Java:43)
at Java.lang.reflect.Method.invoke (Method.Java:564)
at org.codehaus.mojo.exec.ExecJavaMojo$1.run (ExecJavaMojo.Java:282)
at Java.lang.Thread.run (Thread.Java:844)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.019 s
[INFO] Finished at: 2018-03-23T01:51:02+05:30
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.6.0:Java (default-cli) on project Java-10: An exception occured while executing the Java class. Unresolved compilation problem:
[ERROR] var cannot be resolved to a type
[ERROR]
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.Apache.org/confluence/display/MAVEN/MojoExecutionException
なぜこのエラーが発生するのかわかりません。どんな考えでも大歓迎です。その間、根本原因を探してみます。
ランタイムプラグインをJava 10にも設定するか、ルート構成に設定する必要があります。現在はコンパイラーのみです。