Why Does Spring Boot Return Null from Redis? Understanding Template Mismatches

Basic Spring Boot Redis Integration

Add the starter dependency to pom.xml:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

Configure connection properties in application.yml (or application.properties), for example:

spring:
  redis:
    host: 127.0.0.1
    port: 6379
    database: 1
    password: 123456
    timeout: 5000

Inject RedisTemplate (or StringRedisTemplate) and use it in a test class:

@SpringBootTest
@RunWith(SpringRunner.class)
public class TokenTest {

    @Autowired
    private RedisTemplate redisTemplate;

    @Test
    public void getValue() {
        Object value = redisTemplate.opsForValue().get("1");
        System.out.println("value:" + value);
    }
}

Root Cause of Null Reads

Spring Boot’s RedisAutoConfiguration defines two beans:

@Configuration
public class RedisAutoConfiguration {

    @Bean
    @ConditionalOnMissingBean(name = {"redisTemplate"})
    public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory cf) {
        RedisTemplate<Object, Object> template = new RedisTemplate<>();
        template.setConnectionFactory(cf);
        return template;
    }

    @Bean
    @ConditionalOnMissingBean
    public StringRedisTemplate stringRedisTemplate(RedisConnectionFactory cf) {
        StringRedisTemplate template = new StringRedisTemplate();
        template.setConnectionFactory(cf);
        return template;
    }
}

The first bean ( redisTemplate) works with Object keys/values; the second ( stringRedisTemplate) works with String keys/values. If data is stored with one template and read with the other, the differing serializers cause the read to return null.

Impact of @Resource vs @Autowired

@Resource

resolves by bean name first, then by type. @Autowired resolves solely by type.

In the example, the storing component uses:

@Autowired
private RedisTemplate<String, String> redisTemplate;

while the retrieving component uses:

@Resource
private RedisTemplate<String, String> redisTemplate;

@Resource

matches the bean named redisTemplate, which is the RedisTemplate<Object, Object> instance. @Autowired matches the StringRedisTemplate bean. The mismatch leads to null values.

Resolution Strategies

Replace @Resource with @Autowired so both injections are type‑based.

Specify the bean name in @Resource as stringRedisTemplate to explicitly request the correct bean.

Standardize on a single template throughout the project—either always use RedisTemplate<Object, Object> or always use StringRedisTemplate.

Key Takeaway

Spring Boot’s auto‑configuration simplifies Redis usage, but the presence of two default RedisTemplate beans and the differing injection semantics of @Resource and @Autowired can cause hard‑to‑detect null reads. Consistent injection practices and awareness of which template is used prevent this issue.