java.lang.IllegalStateException：流已经在junit中被操作或关闭

Question

我是 Mockito 的新手，我正在尝试在列表为 null 时抛出 NullPoinerException()，对于这种情况，我使用下面的代码进行测试，但我得到异常 java.lang.IllegalStateException: 流已经被操作或关闭

原创

public List<Employee>getEmployeesListStartWithA(){

        List<Employee>list = new ArrayList<>();
        list.add(new Employee(1, "ram", "ram@gmail.com"));
        list.add(new Employee(2, "santhosh", "santhosh@gmail.com"));
        list.add(new Employee(3, "rita", "rita@gmail.com"));
        list.add(new Employee(4, "ramesh", "ramesh@gmail.com"));
        Stream<Employee>filterList = list.stream().filter(item->{
            return item.getName().startsWith("r");
        });

        if(filterList==null || filterList.collect(Collectors.toList()).size()==0){
           throw new NullPointerException();
        }

        return filterList.collect(Collectors.toList());
    }

测试：

@Test
public void getEmployeesListStartWithATest(){
    List<Employee>list = new ArrayList<>();
    list.add(new Employee(1, "ram", "ram@gmail.com"));
    list.add(new Employee(3, "rita", "rita@gmail.com"));
    list.add(new Employee(4, "ramesh", "ramesh@gmail.com"));
doReturn(null).when(configurationClass).getEmployeesListStartWithA();
    doThrow(new NullPointerException()).when(configurationClass).getEmployeesListStartWithA();

}

Answer 1

错误来自你的方法，与测试无关。

虽然filterList 是stream，但一旦过滤操作终止，它就会关闭。
稍后对其进行收集将无法正常工作。

您可以通过将其更改为以下方式来修复该方法：

public List<Employee> getEmployeesListStartWithA() {

    List<Employee>list = new ArrayList<>();
    list.add(new Employee(1, "ram", "ram@gmail.com"));
    list.add(new Employee(2, "santhosh", "santhosh@gmail.com"));
    list.add(new Employee(3, "rita", "rita@gmail.com"));
    list.add(new Employee(4, "ramesh", "ramesh@gmail.com"));
    List<Employee>filterList = list.stream().filter(item->{
        return item.getName().startsWith("r");
    }).collect(Collectors.toList());

    if(filterList==null || filterList.size()==0){
       throw new NullPointerException();
    }

    return filterList;
}

另外我建议你不要抛出NullPointerException。这只是一种糟糕的风格，请改用更合适的异常（或简单地返回一个空列表）。