Bryan's Column

A common model is to have a dependent object share the primary key of its parent. In the case of a OneToOne the childs primary key is the same as the parent, and in the case of a ManyToOne the child

Table 1-1 JPA Annotations by CategoryCategoryDescriptionAnnotationsEntityBy default, TopLink JPA assumes that a Java class is non-persistent and not eligible for JPA servic

JPQL就是一种查询语言，具有与SQL 相类似的特征，JPQL是完全面向对象的，具备继承、多态和关联等特性，和hibernate HQL很相似。 查询语句的参数JPQL语句支持两种方式的参数定义方式: 命名参数和位置参数。。在同一个查询语句中只允许使用一种参数定义方式。 命令参数的格式为：“: +参数名”例：Query query = em.createQuery("s

Java Persistence/Identity and Sequencing Common Problemsnull is inserted into the database, or error on insert.This typically occurs because the @Id was not configured to use an @GeneratedVa

今天用JPA生成数据表，虽然在Entity上已经配置好了一对多和多对一的关系，总是奇怪不能生成外键索引。后来发现是MySQL的 storage engine 的问题。默认的MyISAM是不支持外键的。只有改成 InnoDB才支持外键修改方法，找到 my.ini（在Linux中是my.cnf） 在里面添加或修改（如果有的话）default-storage-engine = Inn