blocks|key|172019|text|为了在Java7中编译，您应该添加javac选项来使用源代码1.7进行编译。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|172020|您应该将javacOptions+%2B%2B=+Seq("-source",+"1.7")添加到可以在/project文件夹中找到的SBT构建配置中。|offset|length|style|CODE|172021|下面是来自SBT的引用：http://www.scala-sbt.org/release/docs/Detailed-Topics/Java-Sources.html|172022|entityMap|0|LINK|mutability|MUTABLE|url|http://www.scala-sbt.org/release/docs/Detailed-Topics/Java-Sources.html^0|0|4|12|0|C|1Z|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@$D|T|E|U|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|V|8|@]|9|@$D|W|E|X|1|Y]]|A|$]]|$1|J|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|K|$L|$5|M|N|O|A|$P|Q]]]]

In order to compile in Java 7, you should add the javac option to compile with source 1.7.

You should add <code>javacOptions ++= Seq("-source", "1.7")</code> to your SBT build config that can be found in the /project folder.

Here's the reference from SBT:
<a href="http://www.scala-sbt.org/release/docs/Detailed-Topics/Java-Sources.html" rel="nofollow">http://www.scala-sbt.org/release/docs/Detailed-Topics/Java-Sources.html</a>

blocks|key|2777812|text|作为Scala代码，您可以将断言放在构建定义中。sbt将initialize定义为执行此类操作的通用位置，但您可以使用任何设置，包括自定义设置。例如,|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2777813|initialize+:=+{
+++val+_+=+initialize.value+//+run+the+previous+initialization
+++val+classVersion+=+sys.props("java.class.version")
+++val+specVersion+=+sys.props("java.specification.version")
+++assert(...,+"Java+N+or+above+required")
}|code-block|syntax|javascript|2777814|entityMap^0|S|A|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Being Scala code, you can put assertions in the build definition. sbt defines the <code>initialize</code> as a common place for things like this, but you can use any setting, including a custom one. For example,

<pre><code>initialize := {
 val _ = initialize.value // run the previous initialization
 val classVersion = sys.props("java.class.version")
 val specVersion = sys.props("java.specification.version")
 assert(..., "Java N or above required")
}
</code></pre>

blocks|key|2777820|text|如果你没有javacOptions+%2B%2B=+Seq("-source",+"1.7",+"-target",+"1.7")源代码，使用Java是行不通的。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2777821|但是您可以在build.sbt或Build.scala中为Scala编译器设置目标JVM：|2777822|scalacOptions+%2B=+"-target:jvm-1.7"|code-block|syntax|javascript|2777823|因此，它在JDK+6上打印：|2777824|$+sbt+clean+run
[info]+Set+current+project+to+default-cd5534+(in+build+file:/tmp/so/)
[success]+Total+time:+0+s,+completed+27.10.2013+14:31:43
[info]+Updating+{file:/tmp/so/}default-cd5534...
[info]+Resolving+org.fusesource.jansi#jansi;1.4+...
[info]+Done+updating.
[info]+Compiling+1+Scala+source+to+/tmp/so/target/scala-2.10/classes...
[info]+Running+Main+
[error]+(run-main)+java.lang.UnsupportedClassVersionError:+Main+:+Unsupported+major.minor+version+51.0
java.lang.UnsupportedClassVersionError:+Main+:+Unsupported+major.minor+version+51.0
++++++++at+java.lang.ClassLoader.defineClass1(Native+Method)
++++++++at+java.lang.ClassLoader.defineClass(ClassLoader.java:634)
++++++++at+java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
++++++++at+java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
++++++++at+java.net.URLClassLoader.access$000(URLClassLoader.java:73)
++++++++at+java.net.URLClassLoader$1.run(URLClassLoader.java:212)
++++++++at+java.security.AccessController.doPrivileged(Native+Method)
++++++++at+java.net.URLClassLoader.findClass(URLClassLoader.java:205)
++++++++at+java.lang.ClassLoader.loadClass(ClassLoader.java:321)
++++++++at+java.lang.ClassLoader.loadClass(ClassLoader.java:314)
[trace]+Stack+trace+suppressed:+run+last+compile:run+for+the+full+output.
java.lang.RuntimeException:+Nonzero+exit+code:+1
++++++++at+scala.sys.package$.error(package.scala:27)
[trace]+Stack+trace+suppressed:+run+last+compile:run+for+the+full+output.
[error]+(compile:run)+Nonzero+exit+code:+1
[error]+Total+time:+4+s,+completed+27.10.2013+14:31:47|2777825|注意:也许它只适用于最新的SBT/Scalac版本。|2777826|entityMap^0|5|1K|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|X|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|Y|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|Z|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|10|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|11|8|@]|D|@]|E|$]]|$1|S|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|T|$]]

Using <code>javacOptions ++= Seq("-source", "1.7", "-target", "1.7")</code> does not work if you have no Java sources.

But you can set the target JVM for the Scala compiler in build.sbt or Build.scala:

<pre><code>scalacOptions += "-target:jvm-1.7"
</code></pre>

As a result it prints on a JDK 6:

<pre><code>$ sbt clean run
[info] Set current project to default-cd5534 (in build file:/tmp/so/)
[success] Total time: 0 s, completed 27.10.2013 14:31:43
[info] Updating {file:/tmp/so/}default-cd5534...
[info] Resolving org.fusesource.jansi#jansi;1.4 ...
[info] Done updating.
[info] Compiling 1 Scala source to /tmp/so/target/scala-2.10/classes...
[info] Running Main 
[error] (run-main) java.lang.UnsupportedClassVersionError: Main : Unsupported major.minor version 51.0
java.lang.UnsupportedClassVersionError: Main : Unsupported major.minor version 51.0
 at java.lang.ClassLoader.defineClass1(Native Method)
 at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
 at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
 at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
 at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
 at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
 at java.security.AccessController.doPrivileged(Native Method)
 at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:314)
[trace] Stack trace suppressed: run last compile:run for the full output.
java.lang.RuntimeException: Nonzero exit code: 1
 at scala.sys.package$.error(package.scala:27)
[trace] Stack trace suppressed: run last compile:run for the full output.
[error] (compile:run) Nonzero exit code: 1
[error] Total time: 4 s, completed 27.10.2013 14:31:47
</code></pre>

Note: Maybe it works only for the latest SBT/Scalac version.

blocks|key|2777832|text|在SBT0.13.6中，有一个新的VersionNumber类和VersionNumberCompatibility特性。调整@MarkHarrah推荐的方法以使用此方法可能会执行以下操作：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2777833|initialize+:=+{
++++val+_+=+initialize.value+//+run+the+previous+initialization
++++val+required+=+VersionNumber("1.8")
++++val+curr+=+VersionNumber(sys.props("java.specification.version"))
++++assert(CompatibleJavaVersion(curr,+required),+s"Java+$required+or+above+required")
}

...
/**+Java+specification+version+compatibility+rule.+*/
object+CompatibleJavaVersion+extends+VersionNumberCompatibility+{
++++def+name+=+"Java+specification+compatibility"
++++def+isCompatible(current:+VersionNumber,+required:+VersionNumber)+=
++++++++current.numbers.zip(required.numbers).foldRight(required.numbers.size<=current.‌​numbers.size)((a,b)+=>+(a._1+>+a._2)+%7C%7C+(a._1==a._2+&&+b))
++++def+apply(current:+VersionNumber,+required:+VersionNumber)+=+isCompatible(current,+required)
}|code-block|syntax|javascript|2777834|entityMap^0|H|D|W|Q|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

In SBT 0.13.6 there is a new <code>VersionNumber</code> class and <code>VersionNumberCompatibility</code> trait. Tweaking the approach recommended by @MarkHarrah to use this one might do the following:

<pre><code>initialize := {
 val _ = initialize.value // run the previous initialization
 val required = VersionNumber("1.8")
 val curr = VersionNumber(sys.props("java.specification.version"))
 assert(CompatibleJavaVersion(curr, required), s"Java $required or above required")
}

...
/** Java specification version compatibility rule. */
object CompatibleJavaVersion extends VersionNumberCompatibility {
 def name = "Java specification compatibility"
 def isCompatible(current: VersionNumber, required: VersionNumber) =
 current.numbers.zip(required.numbers).foldRight(required.numbers.size&lt;=current.‌​numbers.size)((a,b) =&gt; (a._1 &gt; a._2) || (a._1==a._2 &amp;&amp; b))
 def apply(current: VersionNumber, required: VersionNumber) = isCompatible(current, required)
}
</code></pre>

blocks|key|174259|text|对于将来的任何人来说，这也是一个很好的方法。如果找不到正确的Java版本，它会立即停止执行：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|174260|initialize+:=+{
++val+_+=+initialize.value+//+run+the+previous+initialization
++val+required+=+"1.8"
++val+current++=+sys.props("java.specification.version")
++assert(current+==+required,+s"Unsupported+JDK:+java.specification.version+$current+!=+$required")
}|code-block|syntax|javascript|174261|你把这个放到你的build.sbt里。|offset|length|style|CODE|174262|entityMap^0|0|0|8|9|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

For anybody in the future, this is also a good way to do it. It halts execution immediately if it cannot find the right Java version:

<pre><code>initialize := {
 val _ = initialize.value // run the previous initialization
 val required = "1.8"
 val current = sys.props("java.specification.version")
 assert(current == required, s"Unsupported JDK: java.specification.version $current != $required")
}
</code></pre>

You put this in your <code>build.sbt</code>.

blocks|key|175765|text|如果您使用基于eclipse的scala-ide，请在|type|unstyled|depth|inlineStyleRanges|entityRanges|data|175766|窗口-->首选项-->+scala编译器-->标准-->目标--+>+jvm-1.7|175767|​|175768|📷|atomic|offset|length|175769|175770|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/4834de36051abca69d85310e82ce275b.png|imageAlt^0|0|0|0|0|1|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@$I|Y|J|Z|1|10]]|A|$]]|$1|K|3|E|5|6|7|11|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|M|$N|$5|O|P|Q|A|$R|S|T|-4]]]]

Just in-case if you use eclipse based scala-ide change settings in 

window --> pref -- scala compiler --> standard --> target --> jvm-1.7 

<a href="https://i.stack.imgur.com/C9f9K.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/C9f9K.png" alt="enter image description here"></a>

My scala application will only run with Java 7 as it depends on libraries that only appeared in that version of the JDK.

How do I enforce that in sbt, so that the correct error message is shown immediately to the user if she is using the wrong version of Java when starting sbt to run/compile the application?

NOTE: There is NO Java™ source code to compile here. I only have Scala source code. The Scala code requires an <code>import java.nio.file.Path</code> that's available from Java 7.

Enforcing Java version for Scala project in sbt?

编译器

Java

我的scala应用程序只能在Java 7上运行，因为它依赖于仅在JDK版本中出现的库。如何在sbt中强制执行，以便在启动sbt运行/编译应用程序时用户使用错误的Java版本时，立即向用户显示正确的错误消息？注意:这里没有要编译的 Java™源代码。I只有有Scala源代码。Scala代码需要Java7提供的import...

问在sbt中强制执行Scala项目的Java版本？
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问在sbt中强制执行Scala项目的Java版本？EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问在sbt中强制执行Scala项目的Java版本？
EN