mybatis操作oracle数据库主键自增(触发器)

上一篇文章介绍了hibernate 实现oracle主机自增的机制，本篇文章将研究mybatis 实现oracle主键自增的机制

首先我们看对于同一张student表，对于mysql，sql server，oracle中它们都是怎样创建主键的

在mysql中

create table Student( Student_ID  int(6) NOT NULL PRIMARY KEY AUTO_INCREMENT, Student_Name varchar(10) NOT NULL, Student_Age int(2) NOT NULL);insert into student(student_name,student_age) values('zhangsan',20);

在sql server中

create table Student( Student_ID  int primary key identity(1,1), Student_Name varchar2(10) NOT NULL, Student_Age number(2) NOT NULL);insert into student(student_name,student_age) values('zhangsan',20);

在oracle中

create table Student( Student_ID  number(6) NOT NULL PRIMARY KEY, Student_Name varchar2(10) NOT NULL, Student_Age number(2) NOT NULL);

而oracle如果想设置主键自增长，则需要创建序列

CREATE SEQUENCE student_sequence INCREMENT BY 1NOMAXVALUENOCYCLECACHE 10;insert into Student values(student_sequence.nextval,'aa',20);

如果使用了触发器的话，就更简单了

create or replace trigger student_trigger  before insert on student    for each rowbegin  select student_sequence.nextval into :new.student_id from dual;end student_trigger;/

此时插入的时候触发器会帮你插入id

insert into student(student_name,student_age) values('wangwu',20);

至此，mysql，sql server，oracle中怎样创建表中的自增长主键都已完成。看一看出oracle的主键自增较mysql和sql sever要复杂些，mysql，sqlserver配置好主键之后，插入时，字段和值一一对应即可，数据库就会完成你想做的，但是在oracle由于多了序列的概念，那么oracle怎样实现主键自增呢？且看下文

首先是mybatis框架的配置文件

jdbc.properties文件

username=gopassword=gourl=jdbc:oracle:thin:@127.0.0.1:1521:orcldriver=oracle.jdbc.driver.OracleDriver

mybatis-config.xml文件

<configuration><properties resource="jdbc.properties"/><typeAliases><package name="com.bean"/></typeAliases><environments default="development"><environment id="development"><transactionManager type="JDBC" /><dataSource type="POOLED"><property name="driver" value="${driver}" /><property name="url" value="${url}" /><property name="username" value="${username}" /><property name="password" value="${password}" /></dataSource></environment></environments><!-- 将mapper文件加入到配置文件中 --><mappers><mapper resource="com/bean/Student.xml" /></mappers></configuration>

对应的实体类Student无变化，参考hibernate操作oracle数据库 主键自增

http://blog.csdn.net/thepeakofmountain/article/details/17173715

对应的Student.xml文件

<mapper namespace="com.bean.Student"><insert id="add" parameterType="Student">    <!--<selectKey keyProperty="student_id" resultType="int" order="BEFORE">      select student_sequence.nextval from dual    </selectKey>如果未使用触发器，请保留该注释--!>     insert into student(student_id,student_name,student_age) values(#{student_id},#{student_name},#{student_age})    </insert><select id="load" parameterType="int" resultType="Student">select * from student where student_id=#{student_id}</select><select id="delete" parameterType="int" resultType="int">delete from student where student_id=#{student_id}</select><update id="update" parameterType="Student">update student set student_name=#{student_name},student_age=#{student_age} where student_id=#{student_id}</update><select id="list" resultType="Student">select * from student</select></mapper>

测试类

public class TestMybatis {@Testpublic  void testAdd() {   //为原始的获取配置文件，自己创建session，一步一步走的try {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);SqlSession session = factory.openSession();Student u = new Student();u.setStudent_name("sunwukong");u.setStudent_age(50);session.insert("com.bean.Student.add", u);session.commit();session.close();} catch (IOException e) {e.printStackTrace();}}@Testpublic void testUpdate(){SqlSession session = null;try {session = MyBatisUtil.createSession();Student stu = new Student();stu.setStudent_id(11);stu.setStudent_name("bajie");stu.setStudent_age(20);session.update(Student.class.getName()+".update", stu);session.commit();session.close();} catch (Exception e) {// TODO: handle exceptione.printStackTrace();}}/*@Testpublic void testDelete() {SqlSession session= null;try {session = MyBatisUtil.createSession();session.delete(Student.class.getName()+".delete",105);session.commit();session.close();} catch (IOException e) {e.printStackTrace();}}*/@Testpublic void testLoad() {SqlSession session = null;try{session = MyBatisUtil.createSession();Student u = (Student)session.selectOne(Student.class.getName()+".load", 11);System.out.println(u.getStudent_name());} finally {MyBatisUtil.closeSession(session);}}@Testpublic void testList() {SqlSession session = null;try{session = MyBatisUtil.createSession();List<Student> us = session.selectList(Student.class.getName()+".list", null);System.out.println(us.size());} finally {MyBatisUtil.closeSession(session);}}}

工厂类MyBatisUtil

public class MyBatisUtil {public static SqlSessionFactory factory;static {try {InputStream is = Resources.getResourceAsStream("mybatis-config.xml");factory = new SqlSessionFactoryBuilder().build(is);} catch (IOException e) {e.printStackTrace();}}public static SqlSession createSession() {return factory.openSession();}public static void closeSession(SqlSession session) {if(session!=null) session.close();}}

小结：mybatis+oracle主键自增实现的核心，就插入来说，就是先从序列中查找一个序列值，然后插入到对应的表中，也就是分两步走

先select student_sequence.nextval from dual

后insert into student(student_id,student_name,student_age) values(#{student_id},#{student_name},#{student_age})

比较hibernate和mybatis，实现oracle主键自增都是需要两步，而在hibernate中无论是注解版还是非注解版，都需要将id字段映射到创建的序列名上。

补充：mybatis框架导入的jar包为mybatis-3.3.2.jar版本，junit为junit-4.5.jar，连接oracle的jar包ojdbc14.jar，其中MyBatisUtil.java文件其实是一个创建简单工厂模式，如果有兴趣，可以看看设计模式方面的书

对于我来说，还是喜欢用sql语句，感觉更原始，更清楚的知道自己在干什么，当然越底层，效率的话，肯定是mybatis高一些，但是现在还是hibernate用的多吧，当然只是我一家之言，欢迎与各路朋友探讨相关问题。

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