Mybatis 使用redis 作为二级缓存时，无法通过cacheEnabled=false 将其关闭

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <settings>
        <!-- 是否开启二级缓存 默认为true -->
        <setting name="cacheEnabled" value="false"/>
        <!-- 是否懒加载 -->
        <setting name="lazyLoadingEnabled" value="false" />
    </settings>
</configuration>

即使如此，当我的mappler里面有<cache type="com.springbank.dao.support.cache.redis.RedisCache" />，查询这张表时，我发现mybatis仍然去查询redis

### Error querying database.  Cause: org.springframework.data.redis.RedisConnectionFailureException: Cannot get Jedis connection; nested exception is java.lang.NullPointerException
### Cause: org.springframework.data.redis.RedisConnectionFailureException: Cannot get Jedis connection; nested exception is java.lang.NullPointerException
	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:150)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:77)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:434)
	... 18 more
Caused by: org.springframework.data.redis.RedisConnectionFailureException: Cannot get Jedis connection; nested exception is java.lang.NullPointerException
	at org.springframework.data.redis.connection.jedis.JedisConnectionFactory.fetchJedisConnector(JedisConnectionFactory.java:198)
	at org.springframework.data.redis.connection.jedis.JedisConnectionFactory.getConnection(JedisConnectionFactory.java:345)
	at com.springbank.dao.support.cache.redis.RedisCache.getObject(RedisCache.java:62)
	at org.apache.ibatis.cache.decorators.LoggingCache.getObject(LoggingCache.java:57)
	at org.apache.ibatis.cache.decorators.TransactionalCache.getObject(TransactionalCache.java:68)
	at org.apache.ibatis.cache.TransactionalCacheManager.getObject(TransactionalCacheManager.java:35)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:101)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
	... 25 more
Caused by: java.lang.NullPointerException
	at redis.clients.jedis.BinaryJedis.<init>(BinaryJedis.java:101)
	at redis.clients.jedis.Jedis.<init>(Jedis.java:78)
	at org.springframework.data.redis.connection.jedis.JedisConnectionFactory.fetchJedisConnector(JedisConnectionFactory.java:193)

根据异常栈，在CachingExecutor.java:101 看到如下代码

@Override
  public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql)
      throws SQLException {
    Cache cache = ms.getCache();
    if (cache != null) {
      flushCacheIfRequired(ms);
      if (ms.isUseCache() && resultHandler == null) {
        ensureNoOutParams(ms, parameterObject, boundSql);
        @SuppressWarnings("unchecked")
        List<E> list = (List<E>) tcm.getObject(cache, key);
        if (list == null) {
          list = delegate.<E> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
          tcm.putObject(cache, key, list); // issue #578 and #116
        }
        return list;
      }
    }
    return delegate.<E> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
  }

于是我想，这里cache变量要是null就好了