java.lang.IllegalStateException：流已在junit中操作或关闭

Question

我是Mockito的新手，并且我尝试在list为null时抛出NullPoinerException（），在这种情况下，我在下面的代码中进行了测试，但我遇到了异常 java.lang.IllegalStateException：流已被操作或关闭

原始

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

错误来自您的方法，与测试无关。

filterList是stream时，一旦过滤操作终止，它就会关闭。
以后再进行收集将不起作用。

您可以通过将其更改为以下方法来修复该方法：

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;
}

我也建议您不要扔NullPointerException。那只是不好的样式，请改用更适当的异常（或简单地返回一个空列表）。