Eclipse中没有出现的try-with-resources中的异常自我抑制错误

Question

我遇到了一个令人不安的情况,我希望Java抱怨(通过IllegalArgumentExceptionfrom Throwable.addSuppressed)两次抛出相同的异常,一次来自try-with-resources块,一次来自AutoCloseable类的close()例程.我在下面创建了一个简单的测试用例,突出了问题.

我使用以下代码运行JDK 1.7.0_65:

public class TestDoubleThrow {
    public static void main(String[] args) {
        class TestA implements AutoCloseable {
            RuntimeException e;
            public TestA(RuntimeException e) { this.e = e; }
            @Override public void close() { throw e; }
        }

        RuntimeException e = new RuntimeException("My Exception");
        try (TestA A = new TestA(e)) {
            throw e;
        }
    }
}

当我通过命令行编译并运行上面的代码时,我得到了预期的结果,这个错误表明我试图自我抑制和异常:

[coreys terminal]$ java TestDoubleThrow.java ; java TestDoubleThrow
Exception in thread "main" java.lang.IllegalArgumentException: Self-suppression not permitted
    at java.lang.Throwable.addSuppressed(Throwable.java:1043)
    at TestDoubleThrow.main(TestDoubleThrow.java:12)
Caused by: java.lang.RuntimeException: My Exception
    at TestDoubleThrow.main(TestDoubleThrow.java:9)

但是,当我从Eclipse构建并运行相同的代码时,我得不到相同的结果,我得到以下内容:

Exception in thread "main" java.lang.RuntimeException: My Exception
    at TestDoubleThrow.main(TestDoubleThrow.java:9)

我从命令行构建后删除了.class路径,以确保Eclipse重建它.从调试器运行我注意到从Eclipse开始,代码永远不会进入java.lang.Throwable.addSuppressed().

有趣的是,如果我从Eclipse构建类,那么从命令行运行它我不会看到自我抑制错误.类似地,如果我从命令行构建类并从Eclipse运行它(无需从Eclipse构建),那么我会看到错误.这表明eclipse如何构建课程是有趣的.

我想知道如何确保Eclipse能够以这样的方式构建类,以便我得到错误,因为出于我的目的,这是一个错误,我希望能够在从Eclipse构建和运行时检测它.

Answer 1

Eclipse 有它自己的编译器并产生不同的输出。Eclipse 编译的代码在调用Throwable.addSuppressed之前检查受抑制的异常是否等于其自身。您可以使用javap工具看到这一点。

请参阅if_acmpeqEclipse 编译器输出中的行。

JDK 的行为更严格地遵循规范中的示例。您可以向 Eclipse 团队提出缺陷。

JDK/javac 输出：

  public static void main(java.lang.String[]);
    Code:
       0: new           #2                  // class java/lang/RuntimeException
       3: dup           
       4: ldc           #3                  // String My Exception
       6: invokespecial #4                  // Method java/lang/RuntimeException."<init>":(Ljava/lang/String;)V
       9: astore_1      
      10: new           #5                  // class TestDoubleThrow$1TestA
      13: dup           
      14: aload_1       
      15: invokespecial #6                  // Method TestDoubleThrow$1TestA."<init>":(Ljava/lang/RuntimeException;)V
      18: astore_2      
      19: aconst_null   
      20: astore_3      
      21: aload_1       
      22: athrow        
      23: astore        4
      25: aload         4
      27: astore_3      
      28: aload         4
      30: athrow        
      31: astore        5
      33: aload_2       
      34: ifnull        63
      37: aload_3       
      38: ifnull        59
      41: aload_2       
      42: invokevirtual #8                  // Method TestDoubleThrow$1TestA.close:()V
      45: goto          63
      48: astore        6
      50: aload_3       
      51: aload         6
      53: invokevirtual #9                  // Method java/lang/Throwable.addSuppressed:(Ljava/lang/Throwable;)V
      56: goto          63
      59: aload_2       
      60: invokevirtual #8                  // Method TestDoubleThrow$1TestA.close:()V
      63: aload         5
      65: athrow        
    Exception table:
       from    to  target type
          21    23    23   Class java/lang/Throwable
          41    45    48   Class java/lang/Throwable
          21    33    31   any

日食输出：

  public static void main(java.lang.String[]);
    Code:
       0: new           #16                 // class java/lang/RuntimeException
       3: dup           
       4: ldc           #18                 // String My Exception
       6: invokespecial #20                 // Method java/lang/RuntimeException."<init>":(Ljava/lang/String;)V
       9: astore_1      
      10: aconst_null   
      11: astore_2      
      12: aconst_null   
      13: astore_3      
      14: new           #23                 // class TestDoubleThrow$1TestA
      17: dup           
      18: aload_1       
      19: invokespecial #25                 // Method TestDoubleThrow$1TestA."<init>":(Ljava/lang/RuntimeException;)V
      22: astore        4
      24: aload_1       
      25: athrow        
      26: astore_2      
      27: aload         4
      29: ifnull        37
      32: aload         4
      34: invokevirtual #28                 // Method TestDoubleThrow$1TestA.close:()V
      37: aload_2       
      38: athrow        
      39: astore_3      
      40: aload_2       
      41: ifnonnull     49
      44: aload_3       
      45: astore_2      
      46: goto          59
      49: aload_2       
      50: aload_3       
      51: if_acmpeq     59
      54: aload_2       
      55: aload_3       
      56: invokevirtual #31                 // Method java/lang/Throwable.addSuppressed:(Ljava/lang/Throwable;)V
      59: aload_2       
      60: athrow        
    Exception table:
       from    to  target type
          24    26    26   any
          14    39    39   any

我使用 JDK 8 和 Eclipse 4.4。