hibernate 并没有创建foreign key 而是单纯做

hibernate 配置如下：

<?xml version="1.0" encoding="UTF-8"?>
<!-- Course.hbm.xml -->
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="cc.sirius.bean">        
    <class name="Person">
        <id name="id" column="personId">
            <generator class="native"/>
        </id>
        
        <set name="addresses" table="PersonAddress">
            <key column="personId"/>
            <many-to-many column="addressId"
                class="Address"/>
        </set>
    </class>
    
</hibernate-mapping>

<?xml version="1.0" encoding="UTF-8"?>
<!-- Course.hbm.xml -->
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="cc.sirius.bean">        
<class name="Address">
    <id name="id" column="addressId">
        <generator class="native"/>
    </id>
    <set name="people" inverse="true" table="PersonAddress">
        <key column="addressId"/>
        <many-to-many column="personId"
            class="Person"/>
    </set>
</class
>
    
</hibernate-mapping>

运行后查看表：

mysql> show create table PersonAddress;
+---------------+----------------------------------
---------------------------------------------------
---------------------------------------------------
---------------------------------------------------
| Table         | Create Table

+---------------+----------------------------------
---------------------------------------------------
---------------------------------------------------
---------------------------------------------------
| PersonAddress | CREATE TABLE `personaddress` (
  `addressId` int(11) NOT NULL,
  `personId` bigint(20) NOT NULL,
  PRIMARY KEY (`personId`,`addressId`),
  KEY `FKA81B4EBF34EDEFEE` (`personId`),
  KEY `FKA81B4EBF4E1D97BA` (`addressId`),
) ENGINE=MyISAM DEFAULT CHARSET=utf8 |
+---------------+----------------------------------
---------------------------------------------------

经过一天多的反复研究，发现是ENGINE=MyISAM的问题。

原因：

关联的两个表中，一个或者两个表是MyISAM引擎的表。若想要使用外键约束，表必须是InnoDB引擎（实际上，如果两个表都是MyISAM 引擎的，这个错误根本不会发生，但也不会产生外键，只会建立索引）你需要检查表的引擎类型。

具体的几种不能生成外键的原因可以看一下：http://blog.csdn.net/wangpeng047/article/details/19624351

查看数据库默认的引擎：

--查看当前数据库支持的引擎列表
show engines;

--查看当前的默认引擎
show variables like '%storage_engine%';

--修改表引擎,这里不需要用到
alter table table_name engine=innodb;  

image.png

这里手动修改是不现实的，配置hibernate.cfg.xml：

<!-- 方言 -->
        <property name="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>     

这里mysql5.0以上是org.hibernate.dialect.MySQL5InnoDBDialect,以下就去掉5

然后删库，重新自动生成：

---------------------------------------------------------------+
| personaddress | CREATE TABLE `personaddress` (
  `addressId` int(11) NOT NULL,
  `personId` bigint(20) NOT NULL,
  PRIMARY KEY (`personId`,`addressId`),
  KEY `FKA81B4EBF34EDEFEE` (`personId`),
  KEY `FKA81B4EBF4E1D97BA` (`addressId`),
  CONSTRAINT `FKA81B4EBF34EDEFEE` FOREIGN KEY (`personId`) REFERENCES `person` (
`personId`),
  CONSTRAINT `FKA81B4EBF4E1D97BA` FOREIGN KEY (`addressId`) REFERENCES `address`
 (`addressId`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 |
+---------------+---------------------------------------------------------------

完成