Spring Boot Controller Test, Null Pointer Exception

Question

I'm learning to makes APIs. I'm trying to run a test on my Get request, but keep getting a Null Pointer Exception in my test class. What did I miss?

I'm using Spring Boot/Maven/Java 11. This is a very basic setup (as far as I know) as I have just begun to dip my toe into the world of Spring Boot.

Please see code below:

Controller Test Class:

package ControllerTest;

import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.ResultMatcher;
import org.springframework.test.web.servlet.request.MockHttpServletRequestBuilder;
import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
import org.springframework.test.web.servlet.result.MockMvcResultMatchers;

public class StatControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @Test
    public void testGetResponse()
            throws Exception {

        MockHttpServletRequestBuilder builder = MockMvcRequestBuilders
                .get("/get");

        ResultMatcher contentMatcher = MockMvcResultMatchers.content()
                .string("GET Response");

        mockMvc.perform(builder).andExpect(contentMatcher).andExpect(MockMvcResultMatchers.status().isOk());
    }
}

Controller Class:

package apiPackage;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

@RestController
public class StatController {

    @RequestMapping("/")
    public String index(){
        return "Welcome to the SilverSnacks Stat Sheet!";
    }

    @GetMapping("/get")
    public @ResponseBody ResponseEntity<String> get(){
        return new ResponseEntity<String>("GET Response", HttpStatus.OK);
    }

    @GetMapping("/get/{id}")
    public @ResponseBody ResponseEntity<String> getById(@PathVariable String id){
        return new ResponseEntity<String>("GET Response:" + id, HttpStatus.OK);
    }

    @PutMapping("/put")
    public @ResponseBody ResponseEntity<String> put(){
        return new ResponseEntity<String>("PUT Response", HttpStatus.OK);
    }

    @PostMapping("/post")
    public @ResponseBody ResponseEntity<String> post(){
        return new ResponseEntity<String>("POST Response", HttpStatus.OK);
    }

    @DeleteMapping("/delete")
    public @ResponseBody ResponseEntity<String> delete(){
        return new ResponseEntity<String>("DELETE Response", HttpStatus.OK);
    }

    @PatchMapping("/patch")
    public @ResponseBody ResponseEntity<String> patch(){
        return new ResponseEntity<String>("PATCH Response", HttpStatus.OK);
    }
}

Error Output:

java.lang.NullPointerException
    at ControllerTest.StatControllerTest.testGetResponse(StatControllerTest.java:26)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    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.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

does test class has @RunWith and @WebMvcTest annotations? — Ryuzaki L
– Ryuzaki L, Commented Oct 8, 2019 at 16:13
No, I did not add those annotations at first. However, a comment below asked me to do. I did, and got another error. I did add the WebMvcTest annotation, and got yet another error. "Configuration error: found multiple declarations of @BootstrapWith for test class". Any idea why? — Brodiman
– Brodiman, Commented Oct 8, 2019 at 20:34

shahaf · Accepted Answer · 2019-10-08 16:14:15Z

3

try to add the following annotation to the StatControllerTest

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
public class StatControllerTest {

    @Autowired
    private MockMvc mockMvc;
....
}

answered Oct 8, 2019 at 16:14

shahaf

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2 Comments

Brodiman Over a year ago

I've added your suggested annotations, however I got yet another error. "Unable to find a @SpringBootConfiguration". Any idea why this is happening?

Brodiman Over a year ago

Ok, did a little more research and found that your answer was correct, but was missing one piece. "@SpringBootTest(classes = Application.class)". I needed to tell it where to find SpringBootConfiguration. Thanks for pointing me in the right direction.

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