mybatis 实现oracle主键自增机制的教程，mybatisoracle
mybatis 实现oracle主键自增的机制教程
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
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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
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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
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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
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CREATE SEQUENCE student_sequence
INCREMENT BY 1
NOMAXVALUE
NOCYCLE
CACHE 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
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create or replace trigger student_trigger
before insert on student
for each row
begin
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
[sql] view plain copy
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
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username=go
password=go
url=jdbc:oracle:thin:@127.0.0.1:1521:orcl
driver=oracle.jdbc.driver.OracleDriver
mybatis-config.xml文件
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<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
https://blog.csdn.net/thepeakofmountain/article/details/17173715
对应的Student.xml文件
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<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
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public class TestMybatis {
@Test
public 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();
}
}
@Test
public 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 exception
e.printStackTrace();
}
}
/*@Test
public 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();
}
}*/
@Test
public 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);
}
}
@Test
public 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
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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。