code: public void setFetchSize(@Nullable Integer size) {
          if (size != null && size < 0)
              throw new IllegalArgumentException("Illegal fetch size " + size + ". Fetch size must be null or >= 0");
          this.fetchSize = size;
      }
docs: A non-null fetch size will be set as the fetch size for the statements executed from this query.
  If the fetch size specified is zero, the JDBC driver ignores the value and makes its own best guess of the fetch size.
  
  @param size fetch size in rows or null
  @throws IllegalArgumentException if size is < 0