我正在为我的CacheService班级撰写单元测验：

public class CacheService {
    private final HashOperations<String, String, String> redisHashOps;
    private final ValueOperations<String, String> valueOps;
    private final SetOperations<String, String> setOps;


    public CacheService(StringRedisTemplate redisTemplate) {
        this.redisHashOps = redisTemplate.opsForHash();
        this.valueOps = redisTemplate.opsForValue();
        this.setOps = redisTemplate.opsForSet();
    }

单元测验：

public class CacheServiceTest {

    private CacheService cacheService;

    private HashOperations<String, String, String> redisHashOps;
    private ValueOperations<String, String> redisValueOps;
    private SetOperations<String, String> redisSetOps;

    @BeforeEach
    public void setUp() {
        final StringRedisTemplate redisTemplate = mock(StringRedisTemplate.class);

        redisValueOps = mock(ValueOperations.class);
        redisHashOps = mock(HashOperations.class);
        redisSetOps = mock(SetOperations.class);

        when(redisTemplate.opsForValue()).thenReturn(redisValueOps);
        when(redisTemplate.opsForHash()).thenReturn(redisHashOps);
        when(redisTemplate.opsForSet()).thenReturn(redisSetOps);

redisValueOps并且redisSetOps没有问题，但是对于redisHashOps，IDE 提示：

如果我构建项目将看到以下错误：

java: no suitable method found for thenReturn(org.springframework.data.redis.core.HashOperations<java.lang.String,java.lang.String,java.lang.String>)
    method org.mockito.stubbing.OngoingStubbing.thenReturn(org.springframework.data.redis.core.HashOperations<java.lang.String,java.lang.Object,java.lang.Object>) is not applicable
      (argument mismatch; org.springframework.data.redis.core.HashOperations<java.lang.String,java.lang.String,java.lang.String> cannot be converted to org.springframework.data.redis.core.HashOperations<java.lang.String,java.lang.Object,java.lang.Object>)
    method org.mockito.stubbing.OngoingStubbing.thenReturn(org.springframework.data.redis.core.HashOperations<java.lang.String,java.lang.Object,java.lang.Object>,org.springframework.data.redis.core.HashOperations<java.lang.String,java.lang.Object,java.lang.Object>...) is not applicable
      (argument mismatch; org.springframework.data.redis.core.HashOperations<java.lang.String,java.lang.String,java.lang.String> cannot be converted to org.springframework.data.redis.core.HashOperations<java.lang.String,java.lang.Object,java.lang.Object>)

查看RedisTemplate的原始码发现了opsForHash和opsForValue的区别：

public <HK, HV> HashOperations<K, HK, HV> opsForHash() ...
public ValueOperations<K, V> opsForValue() ...

如何修改单元测验以使其作业？

uj5u.com热心网友回复：

您可以doReturn改用以下方法重写您的模拟期望：

doReturn(redisHashOps).when(redisTemplate).opsForHash();

uj5u.com热心网友回复：

你发现它是正确的：

在第一种（也是最后一种）情况下<K, V>是指RedisTemplate泛型自变量（在<String, String>此处分配）。

在 的情况下<HK, HV> HashOperations<K, HK, HV>，K是“再次安全”，但是<HK, HV>是“方法泛型自变量”，编译器无法在此处推断。

解决方案：

• 正如 armandino 正确建议的那样：

  doReturn(redisHashOps).when(redisTemplate).opsForHash();
  

  我们让编译器免于猜测。
• 或通过“通用自变量”：

  when(redisTemplate.<String,String>opsForHash()).thenReturn(redisHashOps);
  

• 或“原始”/残酷的方法：

  private HashOperations<String, Object, Object> redisHashOps;
  ...
  when(redisTemplate.opsForHash()).thenReturn(redisHashOps);