问题描述
我有一个需要几个参数的方法.其中之一是某个类的 List，null 是该参数的可接受值.
I have a method that takes a few parameters. One of them is a List of some class, and null is an acceptable value for this parameter.
public void doStuff(String string, @Nullable List<SomeClass> list) {
...
}
我想编写一个测试，使用 Mockito 来验证该方法是否以 null 作为参数调用.我尝试使用 isNull(List.class):
I want to write a test that uses Mockito to verify the method was called with null as a parameter. I tried using isNull(List.class):
MyClass myClass = ...
verify(myClass).doStuff(any(String.class), isNull(List.class));
但这会产生警告:
未经检查的转换
需要:java.util.List
com.package.SomeClass>
找到:java.util.List
unchecked conversion
required: java.util.List< com.package.SomeClass>
found: java.util.List
如果列表不为空，我可以看到如何修复此警告:
I can see how to fix this warning in the event that the list is not null:
// this generates the same warning
verify(myClass).doStuff(any(String.class), any(List.class));
// this does not generate the warning
verify(myClass).doStuff(any(String.class), Matchers.anyListOf(SomeClass.class)));
但是，我似乎找不到将这两种方法结合在一起的方法.或者找到一种替代方法来完成我想做的事情.(除了用注释来抑制警告)
However, I can't seem to find a way to combine these two approaches together. Or find an alternate approach that accomplishes what I am trying to do. (Other than suppressing the warning with an annotation)
推荐答案
一般的答案是使用显式的泛型方法参数.
The general answer is to use an explicit generic method argument.
verify(myClass).doStuff(any(String.class), Matchers.<List<SomeClass>>isNull());
补充说明:
- 实际上，警告并不能保护您免受任何伤害；
null是null，并且通过类型擦除，所有这些形式都将编译为相同的字节码. - Java 8 可以从方法参数推断泛型类型，因此
isNull()就足够了. - Mockito 1.x 调用类
org.mockito.Matchers，而 Mockito 2.x 弃用该类以支持org.mockito.ArgumentMatchers.在这两种情况下，匹配器方法都可以通过org.mockito.Mockito看到，但 static-methods-via-inheritance 在语义上很弱，可能会导致这些方法不显示在 IDE 中. 如果没有将
Matchers作为静态参数，则无法指定<List<SomeClass>>isNull().你可以做什么，如果你需要做很多，就是提取一个本地静态方法......
- In practice, the warning isn't protecting you from anything;
nullisnull, and with type erasure all of these forms will compile to the same bytecode anyway. - Java 8 can infer generic types from method arguments, so
isNull()is sufficient there without cleverness. - Mockito 1.x calls the class
org.mockito.Matcherswhereas Mockito 2.x deprecates that class in favor oforg.mockito.ArgumentMatchers. In both cases the matcher methods are visible throughorg.mockito.Mockito, but static-methods-via-inheritance is semantically weak and can cause those methods not to show up in IDEs. There's no way to specify
<List<SomeClass>>isNull()without theMatchersas a static argument. What you can do, if you need to do this a lot, is to extract a local static method...
private static List<SomeClass> nullSomeClassList() {
return isNull(); // Return value types can be inferred before Java 8.
}
// elsewhere
verify(myClass).doStuff(any(String.class), nullSomeClassList());
...但无论你做什么，不要提取到字段.副作用在这里很重要.
...but whatever you do, don't extract to a field instead. The side effects are what matters here.
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