Java.lang.NullPointerException what's wrong

Question

It says error in this method a null pointer Exception

   @Test
     public void showBookListPage() throws Exception {

         List<Book> expectedBookList =  bookService.findAll();
                 BookService bookService = mock(BookService.class);

            when( bookService.findAll()).thenReturn(expectedBookList);

         BookController bookController = new BookController(bookService);
         MockMvc mockMvc = standaloneSetup(bookController).build();

         mockMvc.perform(get(" /book/bookList"))
         .andExpect(view().name("bookList"))
         .andExpect(model().attributeExists("bookList"))
         .andExpect(model().attribute("bookList", hasItems(expectedBookList.toArray())));
     }
}

Other than that everything seems to be correct

This is the error I got after mocking the book service first before call

java.lang.IllegalStateException: missing behavior definition for the preceding method call:
BookService.findAll()
Usage is: expect(a.foo()).andXXX()

    at org.easymock.internal.MockInvocationHandler.invoke(MockInvocationHandler.java:42)
    at org.easymock.internal.ObjectMethodsFilter.invoke(ObjectMethodsFilter.java:94)
    at com.sun.proxy.$Proxy134.findAll(Unknown Source)
    at com.admintest.controller.BookControllerTest.showBookListPage(BookControllerTest.java:101)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.springf

And this is my edit to the test method @Test public void showBookListPage() throws Exception {

        BookService bookService = mock(BookService.class);
        List<Book> expectedBookList = bookService.findAll();
        when(bookService.findAll()).thenReturn(expectedBookList);

        BookController bookController = new BookController(bookService);
        MockMvc mockMvc = standaloneSetup(bookController).build();

        mockMvc.perform(get(" /book/bookList"))
                .andExpect(view().name("bookList"))
                .andExpect(model().attributeExists("bookList"))
                .andExpect(model().attribute("bookList", hasItems(expectedBookList.toArray())));
}

And by the way this is the controller

 @RequestMapping("/bookList")
    public String bookList(Model model) {
        List<Book> bookList = bookService.findAll();
        model.addAttribute("bookList", bookList);
        return "bookList";

    }

Should we guess where this NullPointerException is thrown? Please post also a stack trace for the exception. For me the very first line can throw a NullPointerException, as you are trying to call findAll() method on bookService that is mocked after that call. — Kamil, Oct 08 '17 at 20:17
Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Kamil, Oct 08 '17 at 20:18

score 0 · Accepted Answer · answered Oct 08 '17 at 20:18

0

You have to mock the bookService before using it. Not after it's usage. So do the mocking of bookService in @BeforeMethod

answered Oct 08 '17 at 20:18

pavan

16
2

As the exception says, you need to add the behaviour before. Means, when() statement should be defined before using bookService.findall() – pavan Oct 08 '17 at 20:44
but the value I am returning expected Book list is found in the book service .find All there by giving an error because I'm using it before initialization @pavan – valik Oct 08 '17 at 20:57

Java.lang.NullPointerException what's wrong

1 Answers1