org.springframework.data.redis.RedisSystemException: Unknown redis exception; nested exception is java.lang.NullPointerException at org.springframework.data.redis.FallbackExceptionTranslationStrategy.getFallback(FallbackExceptionTranslationStrategy.java:48) ~[spring-data-redis-1.6.1.RELEASE.jar:1.6.1.RELEASE] at org.springframework.data.redis.FallbackExceptionTranslationStrategy.translate(FallbackExceptionTranslationStrategy.java:38) ~[spring-data-redis-1.6.1.RELEASE.jar:1.6.1.RELEASE] at org.springframework.data.redis.connection.jedis.JedisConnection.convertJedisAccessException(JedisConnection.java:210) ~[spring-data-redis-1.6.1.RELEASE.jar:1.6.1.RELEASE] at org.springframework.data.redis.connection.jedis.JedisConnection.setEx(JedisConnection.java:1235) ~[spring-data-redis-1.6.1.RELEASE.jar:1.6.1.RELEASE] at org.springframework.data.redis.connection.DefaultStringRedisConnection.setEx(DefaultStringRedisConnection.java:742) ~[spring-data-redis-1.6.1.RELEASE.jar:1.6.1.RELEASE] at org.springframework.data.redis.core.DefaultValueOperations$11.potentiallyUsePsetEx(DefaultValueOperations.java:193) ~[spring-data-redis-1.6.1.RELEASE.jar:1.6.1.RELEASE] at org.springframework.data.redis.core.DefaultValueOperations$11.doInRedis(DefaultValueOperations.java:186) ~[spring-data-redis-1.6.1.RELEASE.jar:1.6.1.RELEASE] at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:191) ~[spring-data-redis-1.6.1.RELEASE.jar:1.6.1.RELEASE] at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:153) ~[spring-data-redis-1.6.1.RELEASE.jar:1.6.1.RELEASE] at org.springframework.data.redis.core.AbstractOperations.execute(AbstractOperations.java:86) ~[spring-data-redis-1.6.1.RELEASE.jar:1.6.1.RELEASE] at org.springframework.data.redis.core.DefaultValueOperations.set(DefaultValueOperations.java:182) ~[spring-data-redis-1.6.1.RELEASE.jar:1.6.1.RELEASE]
redis 调用set方法的时候，值是null的话 ,会报这个错