Junit with MockMVC - Error - java.lang.IllegalArgumentException: Entity must not be null

Question

I have created a simple get and post rest service for bookstore. I am new in Junit. When using Mockito post call I am getting error.

BookRepository.java

public interface BookRepository extends MongoRepository<Book, BigInteger> {

}

BookController.java


@RestController
public class BookController {

    @Autowired
    BookRepository bookRepository;

    @GetMapping("/books")
    public ResponseEntity<List<Book>> get(){
        return new ResponseEntity<List<Book>>(bookRepository.findAll(), HttpStatus.OK);
    }

    @PostMapping("/book")
    public ResponseEntity<Book> create(@RequestBody Book book){
        return new ResponseEntity<Book>(bookRepository.save(book), HttpStatus.CREATED);
    }

}

Book.java

@Document(collection="book")
public class Book {

    @Id
    private BigInteger id;
    private String bookname;
    private String author;
    private BigDecimal price;
    //getter and setter
}

JunitApplicationTests.java

@SpringBootTest
@AutoConfigureMockMvc
class JunitApplicationTests {

    @Autowired
    private MockMvc mockMvc;

    @Autowired
    private BookRepository bookRepository;

    @Test
    public void get() throws Exception {
        mockMvc.perform(MockMvcRequestBuilders.get("/books")).andExpect(MockMvcResultMatchers.status().isOk());
    }

    @Test
    public void create() throws Exception{
        Book book=createBook();
        Mockito.when(bookRepository.save(Mockito.any(Book.class))).thenReturn(book);//here I am getting error
        mockMvc.perform(MockMvcRequestBuilders.post("/book")).andExpect(MockMvcResultMatchers.status().isCreated());
    }

    public Book createBook() {
        Book book=new Book();
        book.setId(new BigInteger("102"));
        book.setBookname("Java Concept");
        book.setAuthor("James K");
        book.setPrice(new BigDecimal("205.50"));
        return book;
    }
}

I am getting below error

java.lang.IllegalArgumentException: Entity must not be null!
    at org.springframework.util.Assert.notNull(Assert.java:198)
    at org.springframework.data.mongodb.repository.support.SimpleMongoRepository.save(SimpleMongoRepository.java:81)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.springframework.data.repository.core.support.RepositoryComposition$RepositoryFragments.invoke(RepositoryComposition.java:371)
    at org.springframework.data.repository.core.support.RepositoryComposition.invoke(RepositoryComposition.java:204)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$ImplementationMethodExecutionInterceptor.invoke(RepositoryFactorySupport.java:657)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:621)
    at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:605)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.data.projection.DefaultMethodInvokingMethodInterceptor.invoke(DefaultMethodInvokingMethodInterceptor.java:80)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:95)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
    at com.sun.proxy.$Proxy82.save(Unknown Source)
    at com.example.demo.JunitApplicationTests.create(JunitApplicationTests.java:33)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:675)
    at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:125)
    at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:132)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:124)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:74)
    at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:104)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:62)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:43)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:35)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:202)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:198)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:135)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:69)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:135)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
    at java.util.ArrayList.forEach(Unknown Source)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
    at java.util.ArrayList.forEach(Unknown Source)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:220)
    at org.junit.platform.launcher.core.DefaultLauncher.lambda$execute$6(DefaultLauncher.java:188)
    at org.junit.platform.launcher.core.DefaultLauncher.withInterceptedStreams(DefaultLauncher.java:202)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:181)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:128)
    at org.eclipse.jdt.internal.junit5.runner.JUnit5TestReference.run(JUnit5TestReference.java:89)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)

I have created a simple get and post rest service for bookstore. I am new in Junit. When using Mockito post call I am getting error.

You use `@Autowired` BookRepository, I think it should be `@MockBean` instead? — Chaffy, Feb 27 '20 at 21:36
Thanks for your suggestion. It worked. But when I am executing the Junit test case the create book test is actually creating record in database. I think it should not be. Can you please suggest. — Randhir, Feb 27 '20 at 22:00
if you used @MockBean annotation on the bookRepository field, it shouldn't create any record in the database, as it doesn't call the actual save() method of it. Could you please share the piece of test code that causes the record to go straight to the database? — Chaffy, Feb 27 '20 at 22:09
I had used ```@Mock``` instead ```@MockBean```, and it was creating record in database, now I have used ```@MockBean```, and record is not creating. But I am surprised why ```@Mock``` is creating record and ```@MockBean``` is not, What is the difference between both. — Randhir, Feb 27 '20 at 22:28
I'd use @Mock when the project is not a SpringBoot project with SpringBootTests in it : ) Here is a good explanation of how they are different: https://stackoverflow.com/questions/44200720/difference-between-mock-mockbean-and-mockito-mock — Chaffy, Feb 27 '20 at 22:37

score 0 · Answer 1 · answered Feb 28 '20 at 08:11

0

Problem in test create(). You are doing post without body. Add .content() and .contentType():

mockMvc.perform(MockMvcRequestBuilders.post("/book"))
   .contentType(MediaType.APPLICATION_JSON_UTF8)
   .content(bookJson)
   .andExpect(MockMvcResultMatchers.status().isCreated());

answered Feb 28 '20 at 08:11

Misha Lemko

591
4
9

Good things to point out, however that wasn't an issue. If it were, it would throw 400 (Bad Request) and not NPE : ) NPE happened because BookRepository was autowired and not mocked. So, the save() method was an actual call. Spring asserted that the entity is null and reacted accordingly, as `any(Book.class)` will return null. – Chaffy Mar 04 '20 at 20:33

Junit with MockMVC - Error - java.lang.IllegalArgumentException: Entity must not be null

I have created a simple get and post rest service for bookstore. I am new in Junit. When using Mockito post call I am getting error.

I have created a simple get and post rest service for bookstore. I am new in Junit. When using Mockito post call I am getting error.

1 Answers1