我遇到了一个在 ScriptableObject 进行一些转换。如果转换失败，代码将引发异常。这意味着像下面的代码这样的属性分配可能会导致抛出运行时异常。
aScriptable.dateOfArrival = aVar;
默认情况下，rhino 不会让脚本捕获在 [Scriptable.put][1] 期间抛出的运行时异常。因此，以下代码中的 catch 块永远不会运行：
try{
aScriptable.dateOfArrival = aVar;
}catch(e){
//will not run even if above assignment generates an exception. Script will be terminated instead
}
使用以下代码重写 ContextFactory.hasFeature() 使上述 catch 块起作用：
protected boolean hasFeature(Context cx, int featureIndex) {
if(featureIndex == Context.FEATURE_ENHANCED_JAVA_ACCESS){
return true;
}
return super.hasFeature(cx, featureIndex);
}
我的问题是，使属性分配抛出异常的设计决策是否正确或属性分配永远不应该抛出异常？
[1]: http: //www.mozilla.org/rhino/apidocs/org/mozilla/javascript/Scriptable.html#put(java.lang.String, org.mozilla.javascript.Scriptable, java.lang.Object)
I came across a design that overrides [Scriptable.put][1] in a subclass of ScriptableObject to do some conversion. If the conversion fails the code is throwing an exception. Which means that property assignments like following code can cause a runtime exception to be thrown
aScriptable.dateOfArrival = aVar;
By default rhino wouldn't let the script catch a runtime exception thrown during [Scriptable.put][1]. So catch block in following code will never run:
try{
aScriptable.dateOfArrival = aVar;
}catch(e){
//will not run even if above assignment generates an exception. Script will be terminated instead
}
Overriding ContextFactory.hasFeature() with following code makes the above catch block work:
protected boolean hasFeature(Context cx, int featureIndex) {
if(featureIndex == Context.FEATURE_ENHANCED_JAVA_ACCESS){
return true;
}
return super.hasFeature(cx, featureIndex);
}
My question is that whether the design decision to make property assignment throw exception is correct or property assignments are never supposed to throw exceptions?
[1]: http://www.mozilla.org/rhino/apidocs/org/mozilla/javascript/Scriptable.html#put(java.lang.String, org.mozilla.javascript.Scriptable, java.lang.Object)
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评论（1）
在我看来，从 JS 代码无法捕获的
put方法中设计抛出异常是没有意义的。我认为在设置属性时抛出异常是可以的，尽管并不常见。请注意，JS 代码可以使用抛出异常的自定义 setter 轻松重新配置属性（在 ECMAScript 5 中）。另一方面，我认为如果属性获取器抛出异常，那将是非常令人惊讶的。
IMO it doesn't make sense to throw an exception by design from the
putmethod that JS code can't catch. I think throwing an exception on setting a property is fine, although not that common. Note that JS code can easily reconfigure a property (in ECMAScript 5) with a custom setter that throws.On the other hand, I think it would be quite surprising if a property getter throws an exception.