java - 如何使用 Google Guava 的 Throwables.propagateIfInstanceOf()？

Question

The javadoc example

  try {
    someMethodThatCouldThrowAnything();
  } catch (IKnowWhatToDoWithThisException e) {
    handle(e);
  } catch (Throwable t) {
    Throwables.propagateIfInstanceOf(t, IOException.class);
    Throwables.propagateIfInstanceOf(t, SQLException.class);
    throw Throwables.propagate(t);
  }

不是很具体。一个真正的程序会是什么样子？我真的不明白这些方法的目的 Throwables.propagateIfInstanceOf(Throwable, Class) , 传播(), 传播IfPossible()。我什么时候使用它们？

Answer 1

这些方法的目的是提供一种方便的方法来处理已检查的异常。

Throwables.propagate() 是将已检查异常包装到未检查异常中的常见用法的简写(以避免在方法的 throws 子句中声明它)。

Throwables.propagateIfInstanceOf() 用于在方法的 throws 子句中声明类型时按原样追溯已检查的异常。

换句话说，有问题的代码

public void doSomething() 
    throws IOException, SQLException {

    try {
        someMethodThatCouldThrowAnything();
    } catch (IKnowWhatToDoWithThisException e) {
        handle(e);
    } catch (Throwable t) {
        Throwables.propagateIfInstanceOf(t, IOException.class);
        Throwables.propagateIfInstanceOf(t, SQLException.class);
        throw Throwables.propagate(t);
    }  
}

是以下代码的简写:

public void doSomething() 
    throws IOException, SQLException {

    try {
        someMethodThatCouldThrowAnything();
    } catch (IKnowWhatToDoWithThisException e) {
        handle(e);
    } catch (SQLException ex) {
        throw ex;
    } catch (IOException ex) {
        throw ex;
    } catch (Throwable t) {
        throw new RuntimeException(t);
    }  
}

另请参阅:

• Checked versus unchecked exceptions
• The case against checked exceptions