j2ee development without EJB 笔记

Typical candidate concerns include:
?      Tracing and performance monitoring
?      Auditing
?      Notification (such as e-mailing an administrator when a certain exception is thrown)

 

A connection: This represents a communication session with a specific data store. Typically
connections are not thread-safe, and are thus freshly created by a connection factory for each
conversation. For JDBC, this is a Connection; for JDO, a PersistenceManager; for Hibernate,
a Session; for TopLink, a Sessionor UnitOfWork(depending on usage).

 

根据chapter 10 DAO pattern的一些总结：

Hibernate的transparent persistence为编程带来的一个改变是，DAO可以是coarse-grained,而传统的往往是fine-grained. 对于简单的系统，甚至于不需要DAO层，但是对于复杂一些的系统，有一个很薄的DAO层还是好的，好处在于：

1. easy for mock

2.  DAOs offer a clear, strongly typed persistence API for a domain: It is immediately obvious
which persistent objects are retrieved, created, or deleted. The generic API of an O/R mapping
tool allows it to apply any persistence operation to any object, which makes it hard to find out
actually available operations for a specific domain.

3. DAOs allow finder methods with domain arguments, removing the need to maintain object
query language strings in business objects.

能coarse-grained的话,最好

读书到319页 Data Access with the Spring Framework

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