IT忍者神龟之Hibernat持久化对象-数据表映射配置回顾
1.持久化对象POJO编写规则： 1） 有空参public构造器； 2） 提供标识属性，映射数据表主键； 3） 属性提供setter和getter方法； 4） 属性使用基本数据类型的包装类型。基本类型在数据库中不能区分null和0； 5） 不使用final修饰。如果使用final则无法生成代
1.持久化对象POJO编写规则：
1） 有空参public构造器；
2） 提供标识属性，映射数据表主键；
3） 属性提供setter和getter方法；
4） 属性使用基本数据类型的包装类型。基本类型在数据库中不能区分null和0；
5） 不使用final修饰。如果使用final则无法生成代理对象；当使用了final，load查询将如同get查询。
2.POJO的OID：
OID是持久化类与数据表主键对应的属性，用来唯一区分持久化对象。
自然主键：采用数据库中有意义的列的值作为主键（有意义）
代理主键：采用自动生成的流水号、UUID作为主键（无意义，推荐）
3.数据类型：
基本类型无法区分null和0，开发中POJO属性都使用包装类型。
4.持久化类配置POJO.hbm.xml：
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | <code class="xml keyword">xml <code class="xml color1"> version<code class="xml plain">=<code class="xml string">"1.0" <code class="xml color1"> encoding<code class="xml plain">=<code class="xml string">"UTF-8"<code class="xml plain">?> <code class="xml plain">DOCTYPE <code class="xml plain"> hibernate-mapping PUBLIC <code class="xml spaces"> <code class="xml plain">"-//Hibernate/Hibernate Mapping DTD 3.0//EN" <code class="xml spaces"> <code class="xml plain">"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <code class="xml comments"><!-- package="POJO所在包" --> <code class="xml plain">hibernate-mapping <code class="xml color1"> package<code class="xml plain">=<code class="xml string">"cn.cvu.domain"<code class="xml plain">> <code class="xml spaces"> <code class="xml comments"><!-- name="POJO类" table="数据库中的表单" catalog="数据库，对应项目的hibernate核心配置文件中<property name='hibernate.connection.url'>jdbc:mysql:///数据库</property> " --> <code class="xml spaces"> <code class="xml plain">class <code class="xml color1"> name<code class="xml plain">=<code class="xml string">"User" <code class="xml color1"> table<code class="xml plain">=<code class="xml string">"table_user" <code class="xml color1"> catalog<code class="xml plain">=<code class="xml string">"db_hibernate"<code class="xml plain">> <code class="xml spaces"> <code class="xml comments"><!-- name="POJO对应的属性" column="表单的主键 列" type="POJO属性的数据类型" --> <code class="xml spaces"> <code class="xml plain">id <code class="xml color1"> name<code class="xml plain">=<code class="xml string">"id" <code class="xml color1"> column<code class="xml plain">=<code class="xml string">"id" <code class="xml color1"> type<code class="xml plain">=<code class="xml string">"int"<code class="xml plain">> <code class="xml spaces"> <code class="xml comments"><!-- class="主键生成策略" --> <code class="xml spaces"> <code class="xml plain">generator <code class="xml color1"> class<code class="xml plain">=<code class="xml string">"native"<code class="xml plain">><code class="xml keyword">generator<code class="xml plain">> <code class="xml spaces"> <code class="xml comments"><!-- 常用策略：increment、identity、sequence、native、uuid、assigned --> <code class="xml spaces"> <code class="xml plain"><code class="xml keyword">id<code class="xml plain">> <code class="xml spaces"> <code class="xml comments"><!-- name="POJO中对应属性" colunm="表单中的 列" type="POJO数据类型" --> <code class="xml plain"> <code class="xml spaces"> <code class="xml plain">property <code class="xml color1"> name<code class="xml plain">=<code class="xml string">"name" <code class="xml color1"> column<code class="xml plain">=<code class="xml string">"name" <code class="xml color1"> type<code class="xml plain">=<code class="xml string">"string"<code class="xml plain">><code class="xml keyword">property<code class="xml plain">> <code class="xml plain"> <code class="xml spaces"> <code class="xml plain">property <code class="xml color1"> name<code class="xml plain">=<code class="xml string">"age" <code class="xml color1"> column<code class="xml plain">=<code class="xml string">"age" <code class="xml color1"> type<code class="xml plain">=<code class="xml string">"int" <code class="xml plain"> ><code class="xml keyword">property<code class="xml plain">> <code class="xml plain"> <code class="xml spaces"> <code class="xml plain">property <code class="xml color1"> name<code class="xml plain">=<code class="xml string">"city" <code class="xml color1"> column<code class="xml plain">=<code class="xml string">"city" <code class="xml color1"> sql-type<code class="xml plain">=<code class="xml string">"string"<code class="xml plain">><code class="xml keyword">property<code class="xml plain">> <code class="xml spaces"> <code class="xml comments"><!-- 常用属性：length：列值长度、not-null：非空true/false、unique：唯一true/false --> <code class="xml spaces"> <code class="xml plain"><code class="xml keyword">class<code class="xml plain">> <code class="xml plain"><code class="xml keyword">hibernate-mapping<code class="xml plain">> |
1）主键生成策略increment：顶层递增：
由hibernate自动完成，原理：先查询最大值，再插入此值加一。OID必须为long、int或short类型。
优点：跨数据库。
缺点：多线程并发访问问题。
2）主键生成策略identity：底层递增：
由数据库自动完成，要求数据库必须支持自增主键。mysql支持，oracle不支持。OID必须为long、int或short类型。
优点：无并发访问问题。
3）主键生成策略sequence：序列：
由数据库自动完成递增，要求数据库必须支持序列。mysql不支持，oracle支持。OID必须为long、int或short类型。
Oracle：
1创建序列：create sequence myseq;
2调用序列：insert into customer values (myseq.nextval); #序列加一
4）主键生成策略native：本地：
采用数据库支持的自增策略。 mysql：identity，oracle：sequence。OID必须为long、int或short类型。
优点：跨数据库平台。
5）主键生成策略uuid：标识符：
由数据库自动创建。 uuid是32位唯一字符串，表单主键使用varchar类型，POJO对应属性是String类型。
6）主键生成策略assigned：手动指定：
在调用hibernate时手动指定主键的值，用于自然主键（有意义的）。
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 | public <code class="java keyword"> void <code class="java plain"> testInsertAssigned() { <code class="java spaces"> <code class="java plain">Session session = UtilGetSesstion.openSession(); <code class="java spaces"> <code class="java plain">Transaction transaction = session.beginTransaction(); <code class="java spaces"> <code class="java spaces"> <code class="java plain">User user = <code class="java keyword">new <code class="java plain"> User(); <code class="java spaces"> <code class="java plain">user.setId(<code class="java value">20130124<code class="java plain">); <code class="java comments">//手动设置主键 <code class="java spaces"> <code class="java plain">user.setName(<code class="java string">"EminemXXX"<code class="java plain">); <code class="java spaces"> <code class="java plain">user.setAge(<code class="java value">42<code class="java plain">); <code class="java spaces"> <code class="java plain">user.setCity(<code class="java string">"NewYorkXXX"<code class="java plain">); <code class="java spaces"> <code class="java plain">session.save(user); <code class="java spaces"> <code class="java spaces"> <code class="java plain">transaction.commit(); <code class="java spaces"> <code class="java plain">session.close(); <code class="java spaces"> <code class="java plain">} |
7）主键生成策略：复合主键：
（1）编写POJO类 Person.java：
| 1 2 3 4 5 6 7 8 9 10 11 | package <code class="java plain"> cn.cvu.domain; <code class="java keyword">import <code class="java plain"> java.io.Serializable; <code class="java comments">//务必事先序列化接口 <code class="java keyword">public <code class="java keyword"> class <code class="java plain"> Person <code class="java keyword">implements <code class="java plain"> Serializable { <code class="java spaces"> <code class="java keyword">private <code class="java plain"> String firstName; <code class="java comments">//对应表单的复合主键 <code class="java spaces"> <code class="java keyword">private <code class="java plain"> String secondName; <code class="java comments">//对应表单的复合主键 <code class="java spaces"> <code class="java keyword">private <code class="java plain"> String address; <code class="java spaces"> <code class="java spaces"> <code class="java comments">//get/set <code class="java spaces"> <code class="java comments">//toString <code class="java plain">} |
（2）配置POJO.hbm.xml:
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | <code class="xml keyword">xml <code class="xml color1"> version<code class="xml plain">=<code class="xml string">"1.0" <code class="xml color1"> encoding<code class="xml plain">=<code class="xml string">"UTF-8"<code class="xml plain">?> <code class="xml plain">DOCTYPE <code class="xml plain"> hibernate-mapping PUBLIC <code class="xml spaces"> <code class="xml plain">"-//Hibernate/Hibernate Mapping DTD 3.0//EN" <code class="xml spaces"> <code class="xml plain">"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <code class="xml plain">hibernate-mapping <code class="xml color1"> package<code class="xml plain">=<code class="xml string">"cn.cvu.domain"<code class="xml plain">> <code class="xml spaces"> <code class="xml plain">class <code class="xml color1"> name<code class="xml plain">=<code class="xml string">"Person" <code class="xml color1"> table<code class="xml plain">=<code class="xml string">"table_person" <code class="xml color1"> catalog<code class="xml plain">=<code class="xml string">"db_hibernate"<code class="xml plain">> <code class="xml spaces"> <code class="xml comments"><!-- 复合id --> <code class="xml spaces"> <code class="xml plain">composite-id<code class="xml plain">> <code class="xml spaces"> <code class="xml comments"><!-- 主键列 name="POJO属性" column="表单列名" --> <code class="xml spaces"> <code class="xml plain">key-property <code class="xml color1"> name<code class="xml plain">=<code class="xml string">"firstName" <code class="xml color1"> column<code class="xml plain">=<code class="xml string">"nameFirst"<code class="xml plain">><code class="xml keyword">key-property<code class="xml plain">> <code class="xml spaces"> <code class="xml plain">key-property <code class="xml color1"> name<code class="xml plain">=<code class="xml string">"secondName" <code class="xml color1"> column<code class="xml plain">=<code class="xml string">"nameFirst"<code class="xml plain">><code class="xml keyword">key-property<code class="xml plain">> <code class="xml spaces"> <code class="xml plain"><code class="xml keyword">composite-id<code class="xml plain">> <code class="xml spaces"> <code class="xml comments"><!-- 普通列 name="POJO属性" column="表单列名" type="数据类型" --> <code class="xml spaces"> <code class="xml plain">property <code class="xml color1"> name<code class="xml plain">=<code class="xml string">"address" <code class="xml color1"> column<code class="xml plain">=<code class="xml string">"addr" <code class="xml color1"> type<code class="xml plain">=<code class="xml string">"string"<code class="xml plain">><code class="xml keyword">property<code class="xml plain">> <code class="xml spaces"> <code class="xml plain"><code class="xml keyword">class<code class="xml plain">> <code class="xml plain"><code class="xml keyword">hibernate-mapping<code class="xml plain">> |
（3）配置hibernate.cfg.xml，加载Person.hbm.xml文件:
（4）操作类的方法：
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | public <code class="java keyword"> void <code class="java plain"> testInsert() { <code class="java spaces"> <code class="java plain">Configuration configuration = <code class="java keyword">new <code class="java plain"> Configuration().configure(); <code class="java spaces"> <code class="java plain">SessionFactory sessionFactory = configuration.buildSessionFactory(); <code class="java spaces"> <code class="java plain">Session session = sessionFactory.openSession(); <code class="java spaces"> <code class="java plain">Transaction transaction = session.beginTransaction(); <code class="java spaces"> <code class="java spaces"> <code class="java plain">Person person = <code class="java keyword">new <code class="java plain"> Person(); <code class="java spaces"> <code class="java plain">person.setFirstName(<code class="java string">"C"<code class="java plain">); <code class="java spaces"> <code class="java plain">person.setSecondName(<code class="java string">"Vigiles"<code class="java plain">); <code class="java spaces"> <code class="java plain">person.setAddress(<code class="java string">"Beijng"<code class="java plain">); <code class="java spaces"> <code class="java plain">session.save(person); <code class="java spaces"> <code class="java spaces"> <code class="java plain">transaction.commit(); <code class="java spaces"> <code class="java plain">session.close(); <code class="java spaces"> <code class="java plain">sessionFactory.close(); <code class="java spaces"> <code class="java plain">} |
（5）结果：
INFO: HHH000262: Table not found: tb_person
2013-11-5 10:07:12 org.hibernate.tool.hbm2ddl.SchemaUpdate execute
ERROR: HHH000388: Unsuccessful: create table db_hibernate.tb_person (namef varchar(255) not null, names varchar(255) not null, age integer, city varchar(255), primary key (namef, names)) type=InnoDB
2013-11-5 10:07:12 org.hibernate.tool.hbm2ddl.SchemaUpdate execute
ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'type=InnoDB' at line 7
2013-11-5 10:07:12 org.hibernate.tool.hbm2ddl.SchemaUpdate execute
INFO: HHH000232: Schema update complete
| 1 2 3 | <!-- 方言-指定数据库为5.1版本之后的SQL语言 --> <code class="xml spaces"> <code class="xml plain">property <code class="xml color1"> name<code class="xml plain">=<code class="xml string">"hibernate.dialect"<code class="xml plain">> <code class="xml plain"> org.hibernate.dialect.MySQL5InnoDBDialect<code class="xml keyword">property<code class="xml plain">> |
-end
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