密封特征/对象案例类字节代码从2.9.1更改。到2.9.2？

Question

两个目录中的相同源文件

我在Errors.scala中有以下密封特征，我想在Java类中引用它。在Scala 2.9.1中，我能够从Java引用Errors.TooBig作为错误$ TooBig $在2.9.2中不再编译。

Errors.scala

package com.abc

sealed trait Error

object Errors {
  case object TooBig extends Error
}

JavaTest.java

import com.abc.Errors$TooBig$;
public class JavaTest {
}

我在两个不同的目录（2.9.1 / 2.9.2）中有相同的源文件。我能够使用2.9.1编译源代码，但不能编译2.9.2。

>2.9.1$ brew switch scala 2.9.1
>2.9.1$ scalac Errors.scala
>2.9.1$ javac -classpath .:/usr/local/Cellar/scala/2.9.1/libexec/lib/scala-library.jar JavaTest.java
>2.9.1$
>2.9.1$ cd ../2.9.2
>2.9.2$ brew switch scala 2.9.2
>2.9.2$ scalac Errors.scala
>2.9.2$ javac -classpath .:/usr/local/Cellar/scala/2.9.2/libexec/lib/scala-library.jar JavaTest.java
JavaTest.java:1: cannot find symbol
symbol  : class Errors$TooBig$
location: package com.abc
import com.abc.Errors$TooBig$;
              ^
1 error
}
}

以下是com.abc.Errors $ TooBig $ class文件的javap转储的差异：

mhughes:~/scalatest$ diff 2.9.1/TooBig.txt 2.9.2/TooBig.txt 
2c2
< public final class com.abc.Errors$TooBig$ extends java.lang.Object implements com.abc.Error,scala.ScalaObject,scala.Product,scala.Serializable
---
> public final class com.abc.Errors$TooBig$ extends java.lang.Object implements com.abc.Error,scala.Product,scala.Serializable
5a6,7
>   InnerClass: 
>    public final #68= #9 of #67; //TooBig$=class com/abc/Errors$TooBig$ of class com/abc/Errors
73,80c75,84
< const #65 = Asciz com/abc/Error;
< const #66 = class #65;    //  com/abc/Error
< const #67 = Asciz scala/ScalaObject;
< const #68 = class #67;    //  scala/ScalaObject
< const #69 = Asciz scala/Product;
< const #70 = class #69;    //  scala/Product
< const #71 = Asciz scala/Serializable;
< const #72 = class #71;    //  scala/Serializable
---
> const #65 = Asciz InnerClasses;
> const #66 = Asciz com/abc/Errors;
> const #67 = class #66;    //  com/abc/Errors
> const #68 = Asciz TooBig$;
> const #69 = Asciz com/abc/Error;
> const #70 = class #69;    //  com/abc/Error
> const #71 = Asciz scala/Product;
> const #72 = class #71;    //  scala/Product
> const #73 = Asciz scala/Serializable;
> const #74 = class #73;    //  scala/Serializable

你可以看到2.9.1和2.9.2都有一个名为'Errors $ TooBig $'的类。

Answer 1

您不应该依赖类名来从Java检索scala对象。您可以编写一个旨在从Java调用的静态工厂：

package com.abc

sealed trait Error

object Errors {
  case object TooBig extends Error

  //Java API
  def getTooBig(): Error = TooBig
}

然后，用Java调用它：

import com.abc.*;

Error tooBig = Errors.getTooBig();