Java 8 流中的 JUnit 断言
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JUnit assertions within in Java 8 stream
提问by user1660256
Say I have three objects that I save to the database and set the db generated ID into. I don't know the order of the objects returned from the method saveToDb. But I want to junit test that those generated IDs are there. How do I do that within in stream? I want to do something like this:
假设我将三个对象保存到数据库中并将数据库生成的 ID 设置到其中。我不知道从方法返回的对象的顺序saveToDb。但我想 junit 测试那些生成的 ID 是否在那里。我如何在流中做到这一点？我想做这样的事情：
List<MyObject> myObjects = getObjects();
numRecords = saveToDb(myObjects); // numRecords=3
List<Integer> intArray = Arrays.asList(1, 2, 3);
intArray.stream()
.forEach(it -> myObjects.stream()
.filter(it2 -> it2.getId().equals(it))
.????
But I'm not sure where my assertEquals()would go in a statement like this. Or is my approach all wrong? I know I could use a simple for-loop, but I like the elegance of streams. Additionally, is there a way to dynamically create the intArray, in case I have more than 3 myObjects?
但我不确定在assertEquals()这样的声明中我会去哪里。还是我的方法全错了？我知道我可以使用简单的 for 循环，但我喜欢流的优雅。另外，如果我有 3 个以上的 myObjects，有没有办法动态创建 intArray？
采纳答案by Eugene
It seems (if i understood correctly), how about something like this:
看起来（如果我理解正确的话），这样的事情怎么样：
boolean result = Arrays.asList(1, 2, 3).stream()
.allMatch(i -> objects
.stream()
.map(MyObject::getId)
.filter(j -> j == i).findAny().isPresent());
Assert.assertTrue(result);
回答by shizhz
Just a little supplement for your additional question:
只是对您的其他问题的一点补充：
Additionally, is there a way to dynamically create the intArray, in case I have more than 3 myObjects?
另外，如果我有 3 个以上的 myObjects，有没有办法动态创建 intArray？
Yes you can use IntStreamto create a stream based on the size of your objects like:
是的，您可以IntStream根据对象的大小创建流，例如：
IntStream.rangeClosed(1, objects.size()) // both start and end inclusive
and there's also a method IntStream.range(int start, int end)which endis exclusive.
也有一个方法，IntStream.range(int start, int end)这end是唯一的。
回答by skombijohn
So you basically want to check whether a MyObject instance was assigned an ID? Is the equalness to the IDs in the array from any importance?
所以你基本上想检查一个 MyObject 实例是否被分配了一个 ID？与数组中的 ID 相等是否有任何重要性？
If not:
如果不：
List<MyObject> objects = getObjects();
saveToDb(objects);
objects.stream().map(MyObject::getId).forEach(Assert::assertNotNull);
Assuming there is a "getId" Method on MyObject of course.
当然，假设 MyObject 上有一个“getId”方法。
