Can teaclave support the persistence operation, such as h2database

基于samples/springboot项目，在common和enclave模块增加h2db的crud操作，目前程序能正常运行，save操作没有报错。
但涉及到读数据的接口，返回内容就是null，即使不是返回数据库中的内容。

**service**：

**controller**：（返回null）

Start with the samples/springboot project and inspect the CRUD paths in the common and enclave modules, comparing the working save operation with the read interfaces shown in the issue. Reproduce the read requests and trace their returned values; done means the read endpoints return the expected persisted data rather than null.

Written by the indexing model from the issue text.