5.Hibernate级联操作

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Hibernate级联操作

JPA中的级联操作一共包括

ALL,PERSIST,MERGE,REMOVE,REFRESH,DETACH

具体可以在javax.persistence.CascadeType中查看；Hibernate扩展了JPA中的级联关系，添加了

DELETE,SAVE_UPDATE,REPLICATE,LOCK

具体可以在org.hibernate.annotations.CascadeType中查看

测试用的对象

public class Order implements Serializable {    private static final long serialVersionUID = 6072861571390551559L;    @Id    @GeneratedValue(strategy = GenerationType.IDENTITY)    private long id;    private String orderNumber;    private double price;    @ManyToOne(fetch = FetchType.LAZY)    @JoinColumn(name = "customID")    private Custom custom;}

public class Custom implements Serializable {    private static final long serialVersionUID = -518200003900734931L;    @Id    @GeneratedValue(strategy = GenerationType.IDENTITY)    @GenericGenerator(name = "userID", strategy = "uuid", parameters = {@Parameter(name = "property", value = "user")})    private long id;    private String name;    private int age;}

使用了单向一对多关联

默认级联关系

默认情况下，是没有设置级联关系的

Custom custom = new Custom("custom 01", 25);Order order = new Order("order 01", 5.36);order.setCustom(custom);session.persist(order);

由于custom对象还是处于游离状态下，测试代码在运行时，会抛出异常，无法插入数据库中，添加session.persist(custom);后顺利运行

CascadeType.PERSIST

修改Order类

@ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.PERSIST)

运行测试代码后，保存成功。

2017-01-08 19:13:25 DEBUG insert into t_custom (age, name) values (?, ?)2017-01-08 19:13:25 DEBUG insert into t_order (customID, orderNumber, price) values (?, ?, ?)

同样的，如果添加CascadeType.MERGE,CascadeType.REMOVE,CascadeType.REFRESH,CascadeType.DETACH，会在对象更新，删除，刷新时对关联对象做同样的操作

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