测试中使用ConfigurationProperties触发空指针异常问题求助

嘿，我一眼就看出问题出在哪了——你的测试里ApplicationProperties根本没被正确初始化！

你用@Autowired注入它，但如果测试类没加载Spring上下文（比如没加@SpringBootTest），这个对象就是null；就算加载了上下文，要是配置文件里没填application.bebusiness.end-point-provider，调用getBebusiness()返回的也是null，最后调用getEndPointProvider()的时候自然就触发空指针了。而你换成具体URL后，跳过了对ApplicationProperties的调用，当然就不会碰到这个问题啦。

下面给你几个实用的修复方案，按需选就行：

方案1：用Mockito模拟配置对象（推荐单元测试用） #

纯Mockito模拟依赖，不用加载Spring上下文，速度快还能隔离外部影响：

public class ProviderServiceTest {
    // 把ApplicationProperties和它内部的Bebusiness都mock掉
    @Mock
    private ApplicationProperties applicationProperties;
    @Mock
    private ApplicationProperties.Bebusiness bebusinessMock; // 假设你的内部类叫Bebusiness
    @Mock
    private RestTemplate restTemplate;
    
    @InjectMocks
    private ProviderServiceImpl providerService;
    
    @Rule
    public MockitoRule mockitoRule = MockitoJUnit.rule();

    @Test
    public void givenMockingIsDoneByMockito_whenGetIsCalled_shouldReturnMockedObject() {
        // 先给mock对象设好返回值
        String testUrl = "http://mock-bebusiness-url/api/providers";
        when(applicationProperties.getBebusiness()).thenReturn(bebusinessMock);
        when(bebusinessMock.getEndPointProvider()).thenReturn(testUrl);
        
        // 再模拟RestTemplate的返回
        String provider = providerInit.buildProviderDTOWithIdFromBebusiness();
        ResponseEntity<String> responseEntity = new ResponseEntity<>(provider, HttpStatus.OK);
        when(restTemplate.getForEntity(
                anyString(), 
                ArgumentMatchers.any(Class.class)
        )).thenReturn(responseEntity);
        
        // 执行测试
        List<ProviderDTO> result = providerService.getAllProviderFromBebusiness();
        
        // 断言结果，还可以顺便验证RestTemplate的调用参数对不对
        assertEquals(HttpStatus.OK.value(), responseEntity.getStatusCodeValue());
        verify(restTemplate).getForEntity(
                eq(testUrl + "&amp;page=0&amp;size=" + Integer.MAX_VALUE), 
                eq(String.class)
        );
    }
}

方案2：加载Spring上下文用真实配置（适合集成测试） #

如果需要验证配置是否正确加载，可以加@SpringBootTest让Spring帮你读配置文件：

@SpringBootTest // 加载Spring上下文，读取application.properties/yaml里的配置
public class ProviderServiceTest {
    @Autowired
    private ApplicationProperties applicationProperties;
    
    @MockBean // 替换容器里的RestTemplate为mock对象
    private RestTemplate restTemplate;
    
    @Autowired
    private ProviderServiceImpl providerService;

    @Test
    public void givenMockingIsDoneByMockito_whenGetIsCalled_shouldReturnMockedObject() {
        // 模拟RestTemplate返回
        String provider = providerInit.buildProviderDTOWithIdFromBebusiness();
        ResponseEntity<String> responseEntity = new ResponseEntity<>(provider, HttpStatus.OK);
        when(restTemplate.getForEntity(
                anyString(), 
                ArgumentMatchers.any(Class.class)
        )).thenReturn(responseEntity);
        
        List<ProviderDTO> result = providerService.getAllProviderFromBebusiness();
        
        assertEquals(HttpStatus.OK.value(), responseEntity.getStatusCodeValue());
    }
}

这种方式会加载完整Spring上下文，测试速度会慢一点，适合需要验证配置和服务集成的场景。

方案3：手动初始化配置对象 #

不想用Mockito的话，也可以手动创建并初始化ApplicationProperties：

public class ProviderServiceTest {
    private ApplicationProperties applicationProperties;
    @Mock
    private RestTemplate restTemplate;
    
    private ProviderServiceImpl providerService;
    
    @Rule
    public MockitoRule mockitoRule = MockitoJUnit.rule();

    @Before
    public void setUp() {
        // 手动创建配置对象和内部的Bebusiness实例
        applicationProperties = new ApplicationProperties();
        ApplicationProperties.Bebusiness bebusiness = new ApplicationProperties.Bebusiness();
        bebusiness.setEndPointProvider("http://test-url/api/providers");
        applicationProperties.setBebusiness(bebusiness);
        
        // 直接构造服务对象，把依赖传进去
        providerService = new ProviderServiceImpl(applicationProperties, restTemplate);
    }

    @Test
    public void givenMockingIsDoneByMockito_whenGetIsCalled_shouldReturnMockedObject() {
        // 模拟RestTemplate返回
        String provider = providerInit.buildProviderDTOWithIdFromBebusiness();
        ResponseEntity<String> responseEntity = new ResponseEntity<>(provider, HttpStatus.OK);
        when(restTemplate.getForEntity(anyString(), ArgumentMatchers.any(Class.class)))
                .thenReturn(responseEntity);
        
        List<ProviderDTO> result = providerService.getAllProviderFromBebusiness();
        
        assertEquals(HttpStatus.OK.value(), responseEntity.getStatusCodeValue());
    }
}

别忘了你的ApplicationProperties内部的Bebusiness类得有对应的getter和setter方法，不然不管是Spring注入还是手动初始化都没法给它赋值哦。

内容的提问来源于stack exchange，提问作者Aymen Kanzari