Question

我使用scala-maven-plugin编译一个包含scala和java代码的项目。我已经将源和目标设置为1.7，但不确定为什么maven仍然使用1.5。

这是我在pom.xml中的插件

<plugin>
        <groupId>net.alchim31.maven</groupId>
        <artifactId>scala-maven-plugin</artifactId>
        <version>3.2.2</version>
        <executions>
          <execution>
            <id>eclipse-add-source</id>
            <goals>
              <goal>add-source</goal>
            </goals>
          </execution>
          <execution>
            <id>scala-compile-first</id>
            <phase>process-resources</phase>
            <goals>
              <goal>compile</goal>
            </goals>
          </execution>
          <execution>
            <id>scala-test-compile-first</id>
            <phase>process-test-resources</phase>
            <goals>
              <goal>testCompile</goal>
            </goals>
          </execution>
          <execution>
            <id>attach-scaladocs</id>
            <phase>verify</phase>
            <goals>
              <goal>doc-jar</goal>
            </goals>
          </execution>
        </executions>
        <configuration>
          <scalaVersion>${scala.version}</scalaVersion>
          <recompileMode>incremental</recompileMode>
          <useZincServer>true</useZincServer>
          <args>
            <arg>-unchecked</arg>
            <arg>-deprecation</arg>
            <arg>-feature</arg>
          </args>
          <jvmArgs>
            <jvmArg>-Xms1024m</jvmArg>
            <jvmArg>-Xmx1024m</jvmArg>
            <jvmArg>-XX:PermSize=${PermGen}</jvmArg>
            <jvmArg>-XX:MaxPermSize=${MaxPermGen}</jvmArg>
          </jvmArgs>
          <javacArgs>
            <javacArg>-source</javacArg>
            <javacArg>1.7</javacArg>
            <javacArg>-target</javacArg>
            <javacArg>1.7</javacArg>
            <javacArg>-Xlint:all,-serial,-path,-options</javacArg>
          </javacArgs>
        </configuration>
      </plugin>

这就是我看到的输出错误

[warn]   implicit def toDisplayTraversableFunctions[T <: Product](traversable: Traversable[T]): DisplayTraversableFunctions[T] = new DisplayTraversableFunctions[T](traversable)
[warn]                ^
[warn] two warnings found
[error] /Users/jzhang/github/zeppelin/spark/src/main/java/org/apache/zeppelin/spark/DepInterpreter.java:158: error: diamond operator is not supported in -source 1.5
[error]     settings.explicitParentLoader_$eq(new Some<>(Thread.currentThread()

但我相信我会使用JDK8。

java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

Maven也使用JDK8

Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=1024M; support was removed in 8.0
Apache Maven 3.3.9 (bb52d8502b132ec0a5a3f4c09453c07478323dc5; 2015-11-11T00:41:47+08:00)
Maven home: /Users/jzhang/Java/lib/apache-maven-3.3.9
Java version: 1.8.0_45, vendor: Oracle Corporation
Java home: /Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "mac os x", version: "10.11.6", arch: "x86_64", family: "mac"

Answer 1

现在设置编译器源代码和目标版本的典型方法似乎是使用这些预定义的属性：

<properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
</properties>

如您所知，这些默认为maven中的1.5。这是因为Maven总是关于“约定优于配置”，并且当Java 1.5仍然闪亮而且新的时候定义了这个默认值。不幸的是，这很难改变，因为任何仍然依赖于Java 1.5的现有项目（并且没有指定这些值）可能会破坏。

Answer 2

Maven默认会安装Java 1.5编译器。您需要在<dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-stream-kafka</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-stream</artifactId> </dependency>文件中专门分配Java 1.8。由于Maven只是各种插件的组合，我们需要添加编译器插件并通过添加以下代码段来指定Java编译器版本：

pom.xml

源值1.5的错误已过时，将在以后的版本

2 个答案: