java - 在 Kotlin 项目中包含使用 Java9 或 Java10 构建的 Maven 依赖项

Question

是否可以包含 Java9(或 10)依赖项？由于 Kotlin 目前只能编译为 Java 8。我收到一个 java.lang.UnsupportedClassVersionError 错误，显然表明我包含的 JAR/依赖项中的一个类已由更新版本的 Java 运行时编译。但是我不能指定一个更新的 JDK，它能够运行用旧版本编译的类(Kotlin 的东西？)。

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-compiler-plugin</artifactId>
  <version>3.7.0</version>
  <configuration>
    <release>9</release>
    <source>${maven.compiler.source}</source>
    <target>${maven.compiler.target}</target>
    <encoding>${project.build.sourceEncoding}</encoding>
  </configuration>
  <dependencies>
    <dependency>
      <groupId>org.ow2.asm</groupId>
      <artifactId>asm</artifactId>
      <version>6.1</version> <!-- Use newer version of ASM -->
    </dependency>
  </dependencies>
</plugin>

具有属性

<maven.compiler.source>9</maven.compiler.source>
<maven.compiler.target>9</maven.compiler.target>

但是现在我得到了错误:“错误:Kotlin:未知 JVM 目标版本:1.9
支持的版本:1.6、1.8"

Kotlin 版本是 1.2.41，到目前为止我总是可以切换到最新版本，直到它发布...

下面的 XML 片段没问题。但是 java.lang.UnsupportedClassVersionError 的问题仍然存在。

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.5.1</version>
            <configuration>
                <source>9</source>
                <target>9</target>
            </configuration>
            <executions>
                <!-- Replacing default-compile as it is treated specially by maven -->
                <execution>
                    <id>default-compile</id>
                    <phase>none</phase>
                </execution>
                <!-- Replacing default-testCompile as it is treated specially by maven -->
                <execution>
                    <id>default-testCompile</id>
                    <phase>none</phase>
                </execution>
                <execution>
                    <id>java-compile</id>
                    <phase>compile</phase>
                    <goals> <goal>compile</goal> </goals>
                </execution>
                <execution>
                    <id>java-test-compile</id>
                    <phase>test-compile</phase>
                    <goals> <goal>testCompile</goal> </goals>
                </execution>
            </executions>
        </plugin>

我正在尝试为我的(当前)Java9 项目构建 Kotlin 模块/maven 包。

Maven-Kotlin 插件配置为:

      <plugin>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-maven-plugin</artifactId>
            <version>${kotlin.version}</version>
            <configuration>
                <jvmTarget>1.8</jvmTarget>
            </configuration>
            <executions>
                <execution>
                    <id>compile</id>
                    <phase>compile</phase>
                    <goals>
                        <goal>compile</goal>
                    </goals>
                    <configuration>
                        <sourceDirs>
                            <source>src/main/java</source>
                            <source>src/main/kotlin</source>
                        </sourceDirs>
                    </configuration>
                </execution>
                <execution>
                    <id>test-compile</id>
                    <phase>test-compile</phase>
                    <goals>
                        <goal>test-compile</goal>
                    </goals>
                    <configuration>
                        <sourceDirs>
                            <source>src/test/java</source>
                            <source>src/test/kotlin</source>
                        </sourceDirs>
                    </configuration>
                </execution>
            </executions>
        </plugin>

我的整个 pom.xml:

<?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>restful-web</groupId>
    <artifactId>restful-web</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <kotlin.version>1.2.41</kotlin.version>
        <kotlin.compiler.jvmTarget>1.8</kotlin.compiler.jvmTarget>
        <sirix.version>0.8.9-SNAPSHOT</sirix.version>
        <main.verticle>org.sirix.rest.SirixVerticle</main.verticle>
        <maven.compiler.source>9</maven.compiler.source>
        <maven.compiler.target>9</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>io.vertx</groupId>
            <artifactId>vertx-core</artifactId>
            <version>3.5.1</version>
        </dependency>
        <dependency>
            <groupId>io.vertx</groupId>
            <artifactId>vertx-web</artifactId>
            <version>3.5.1</version>
        </dependency>
        <dependency>
            <groupId>io.vertx</groupId>
            <artifactId>vertx-lang-kotlin</artifactId>
            <version>3.5.1</version>
        </dependency>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-stdlib-jdk8</artifactId>
            <version>${kotlin.version}</version>
        </dependency>
        <dependency>
            <groupId>com.github.sirixdb.sirix</groupId>
            <artifactId>sirix-core</artifactId>
            <version>${sirix.version}</version>
        </dependency>
        <dependency>
            <groupId>com.github.sirixdb.sirix</groupId>
            <artifactId>sirix-xquery</artifactId>
            <version>${sirix.version}</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>
                <configuration>
                    <source>${maven.compiler.source}</source>
                    <target>${maven.compiler.target}</target>
                </configuration>
                <executions>
                    <!-- Replacing default-compile as it is treated specially by maven -->
                    <execution>
                        <id>default-compile</id>
                        <phase>none</phase>
                    </execution>
                    <!-- Replacing default-testCompile as it is treated specially by maven -->
                    <execution>
                        <id>default-testCompile</id>
                        <phase>none</phase>
                    </execution>
                    <execution>
                        <id>java-compile</id>
                        <phase>compile</phase>
                        <goals> <goal>compile</goal> </goals>
                    </execution>
                    <execution>
                        <id>java-test-compile</id>
                        <phase>test-compile</phase>
                        <goals> <goal>testCompile</goal> </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>2.3</version>
                <executions>
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <transformers>
                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                    <manifestEntries>
                                        <Main-Class>io.vertx.core.Launcher</Main-Class>
                                        <Main-Verticle>${main.verticle}</Main-Verticle>
                                    </manifestEntries>
                                </transformer>
                                <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                                    <resource>META-INF/services/io.vertx.core.spi.VerticleFactory</resource>
                                </transformer>
                            </transformers>
                            <artifactSet>
                            </artifactSet>
                            <outputFile>${project.build.directory}/${project.artifactId}-${project.version}-fat.jar</outputFile>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.jetbrains.kotlin</groupId>
                <artifactId>kotlin-maven-plugin</artifactId>
                <version>${kotlin.version}</version>
                <configuration>
                    <jvmTarget>1.8</jvmTarget>
                </configuration>
                <executions>
                    <execution>
                        <id>compile</id>
                        <phase>compile</phase>
                        <goals>
                            <goal>compile</goal>
                        </goals>
                        <configuration>
                            <sourceDirs>
                                <source>src/main/java</source>
                                <source>src/main/kotlin</source>
                            </sourceDirs>
                        </configuration>
                    </execution>
                    <execution>
                        <id>test-compile</id>
                        <phase>test-compile</phase>
                        <goals>
                            <goal>test-compile</goal>
                        </goals>
                        <configuration>
                            <sourceDirs>
                                <source>src/test/java</source>
                                <source>src/test/kotlin</source>
                            </sourceDirs>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

    <pluginRepositories>
        <pluginRepository>
            <id>kotlin-bintray</id>
            <name>Kotlin Bintray</name>
            <url>http://dl.bintray.com/kotlin/kotlin-dev</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </pluginRepository>
    </pluginRepositories>

    <repositories>
        <repository>
            <id>sonatype-nexus-snapshots</id>
            <name>Sonatype Nexus Snapshots</name>
            <url>https://oss.sonatype.org/content/repositories/snapshots</url>
            <releases>
                <enabled>false</enabled>
            </releases>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
    </repositories>

</project>

堆栈跟踪的错误消息/相关部分是:

java.lang.UnsupportedClassVersionError: org/sirix/access/conf/DatabaseConfiguration 已由较新版本的 Java 运行时(类文件版本 53.0)编译，此版本的 Java 运行时仅识别类文件版本高达 52.0

Answer 1

我怀疑问题出在 Kotlin Maven 插件中，它直接从 maven.compiler.source/maven 推断出 -jvm-target 参数值.compiler.target 属性，没有考虑 Kotlin 编译器只支持 1.6 和 1.8 版本的事实。解决方法是将 JVM 字节码目标版本明确指定为 1.8，例如(请注意，以 1.8 为目标的字节码将在 Java 9 上运行得很好):

<plugin>
    <artifactId>kotlin-maven-plugin</artifactId>
    <groupId>org.jetbrains.kotlin</groupId>
    <version>${kotlin.version}</version>
    ...
    <configuration>
        <jvmTarget>1.8</jvmTarget>
    </configuration>
</plugin>

也就是说，我无法在小型示例项目中重现您的问题，所以如果您有时间，请在 https://kotl.in/issue 报告问题，我们将不胜感激。