MyBatis 初探

轩辕阁

　　话说很早以前就知道ibatis是一个ORM—对象关系映射框架，以前一直使用的是hibernate，所以也没去实际感受一下他的魅力之所在~~现在有个项目用到了MyBatis，所以就特来感受一番。

@@需要准备的jar包：mybatis-3.0.5.jar和sqljdbc.jar


下面开始我们的项目：
1、第一步：建立数据库studentDB，建表StudentInfo，具体的建表语句就不写了，比较简单。

2、第二步：创建工程
　　3、第三步：导入jar包（mybatis-3.0.5.jar和sqljdbc.jar）
　　4、第四步：编写MyBatis主配置文件—可以自定义名字。我在这里延续ibatis的传统使用SqlMapConfig.xml（类似于hibernate中的hibernate.cfg.xml文件），具体代码如下：


<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<typeAliases>
<typeAlias type="com.up.StudentInfo" alias="StudentInfo"/>
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.microsoft.sqlserver.jdbc.SQLServerDriver"/>
<property name="url" value="jdbc:sqlserver://localhost:1433;databasename=studentDB"/>
<property name="username" value="sa"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="studentMapper.xml"/>
</mappers>
</configuration>
　　5、第五步：配置数据库表映射文件：studentMapper.xml（类似于hiberante中的.hbm.xml文件）


<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--这里namespace必须配置为StudentMapper接口的路径，否则运行时会报“is not known to the MapperRegistry”
-->
<mapper namespace="com.up.StudentMapper">
<!-- 这里必须配置resultMap，否则在selectBoy中，将报null错误，无法将数据库中的值注入到StudentInfo类中-->
<resultMap type="StudentInfo" id="boys">
<id property="stuid" column="stuid"/>
<result property="stuname" column="stuname" />
<result property="stusex" column="stusex" />
<result property="stuscore" column="stuscore" />
<result property="stuage" column="stuage" />
</resultMap>
<select id="selectBoy" parameterType="string" resultMap="boys" resultType="arraylist">
select * from StudentInfo where stusex = #{stusex}
</select>
<!--这里的id必须配置和StudentMapper中的方法一样，否则也会报错。下面也一样道理-->
<select id="selectByID" parameterType="int" resultType="StudentInfo">
select * from StudentInfo where stuid = #{stuid}
</select>
<insert id="addStudent" parameterType="StudentInfo" useGeneratedKeys="true">
insert into StudentInfo(stuname,stusex,stuscore,stuage)
values(#{stuname},#{stusex},#{stuscore},#{stuage})
</insert>
<update id="updateStudent" parameterType="StudentInfo">
update StudentInfo
set stuname=#{stuname},stusex=#{stusex},stuscore=#{stuscore}
where stuid=#{stuid}
</update>
<delete id="deleteStudent" parameterType="int">
delete from StudentInfo where stuid = #{stuid}
</delete>
</mapper>
　　
6、第六步：编写java代码

　　StudentInfo实体类的代码如下：


package com.up;
public class StudentInfo {
private int stuid;
private String stuname;
private String stusex;
private double stuscore;
private int stuage;
public StudentInfo(){
super();
}
public StudentInfo(int stuid,String stuname,String stusex,double stuscore,int stuage){
super();
this.stuid = stuid;
this.stuname = stuname;
this.stusex = stusex;
this.stuscore = stuscore;
this.stuage = stuage;
}
public void setStuid(int stuid) {
this.stuid = stuid;
}
public int getStuid() {
return stuid;
}
public int getStuage() {
return stuage;
}
public String getStuname() {
return stuname;
}
public double getStuscore() {
return stuscore;
}
public String getStusex() {
return stusex;
}
public void setStuage(int stuage) {
this.stuage = stuage;
}
public void setStuname(String stuname) {
this.stuname = stuname;
}
public void setStuscore(double stuscore) {
this.stuscore = stuscore;
}
public void setStusex(String stusex) {
this.stusex = stusex;
}
public String toString(){
return "学号："+this.getStuid()+" 姓名："+this.getStuname()+" 性别："+this.getStusex()+
" 年龄："+this.getStuage()+" 分数："+this.getStuscore();
}
}
　　 StudentInfo实体的映射器取名为：StudentMapper(接口)，其代码如下：


package com.up;
import java.util.ArrayList;
public interface StudentMapper {
//这里的方法对应了studentMapper.xml中的select,update,delete语句
public ArrayList<StudentInfo> selectBoy(String male);
public StudentInfo selectByID(int id);
public void addStudent(StudentInfo student);
public void updateStudent(StudentInfo student);
public void deleteStudent(int id);
}
　　注意： 该接口类似于hibernate中的dao层接口，只是该接口只需要声明，不需要实现。
　　据我所知：在MyBatis中不声明该接口也是可以的。也许这是一个约定俗成的东西。所以最好定义一下。
　　加载配置文件得到SqlSessionFactory工具类代码：


package com.up;
import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
public class MyBatisUtil {
private static final SqlSessionFactory factory;
static {
String resource = "SqlMapConfig.xml";
Reader reader = null;
try {
reader = Resources.getResourceAsReader(resource);
} catch (Exception e) {
e.printStackTrace();
}
factory = new SqlSessionFactoryBuilder().build(reader);
}
public static SqlSessionFactory getSqlSessionFactory(){
return factory;
}
}
　　主要的测试类，该类只是用于测试，所以各方法定义的不是那么灵活，可扩展。

package com.up;
import java.io.Reader;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
/**
* 在该类中，主要定义了几个方法，用来测试XML文件中的insert,update,delete,select语句
* addStudent()方法对应了studentMapper.xml中的addStudent操作
* getBoys()方法对应了studentMapper.xml中的selectBoy操作
* getStudent()方法对应了studentMapper.xml中的selectByID操作
* delStudent()方法对应了studentMapper.xml中的deleteStudent操作
* updateStudent()方法对应了studentMapper.xml中的updateStudent操作
*
* @author 小小虾
*
*/
public class TestMybatis {
private static SqlSessionFactory factory = null;
static {
factory = MyBatisUtil.getSqlSessionFactory();
}
public void addStudent(){
SqlSession session = factory.openSession();
StudentInfo student = new StudentInfo();
student.setStuname("王王王");
student.setStuid(00001);
student.setStusex("男");
student.setStuscore(88);
student.setStuage(19);
try {
session.selectOne("StudentMapper.addStudent", student);
session.commit();
} finally {
session.close();
}
}
public void getBoys(){
SqlSession session = factory.openSession();
try {
StudentMapper mapper = session.getMapper(StudentMapper.class);
ArrayList list = mapper.selectBoy("男");
for(int i=0;i<list.size();i++){
StudentInfo stu = (StudentInfo)list.get(i);
System.out.println(stu);
}
} finally {
session.close();
}
}
public void getStudent(){
SqlSession session = factory.openSession();
try {
StudentMapper mapper = session.getMapper(StudentMapper.class);
StudentInfo stu = mapper.selectByID(10018);
System.out.println("信息："+stu);
} finally {
session.close();
}
}
public void delStudent(){
SqlSession session = factory.openSession();
try {
StudentMapper mapper = session.getMapper(StudentMapper.class);
mapper.deleteStudent(10018);
session.commit();
} finally {
session.close();
}
}
public void updateStudent(){
SqlSession session = factory.openSession();
StudentInfo student = new StudentInfo();
student.setStuname("swu");
student.setStuid(10006);
student.setStusex("女");
student.setStuscore(111);
student.setStuage(100);
try {
StudentMapper mapper = session.getMapper(StudentMapper.class);
mapper.updateStudent(student);
session.commit();
} finally {
session.close();
}
}
public static void main(String[] args) {
TestMybatis m = new TestMybatis();
m.delStudent();
m.getStudent();
}
}
　　注意：


try {
StudentMapper mapper = session.getMapper(StudentMapper.class);
mapper.addStudent(student);
} finally {
session.close();
}
　　session必须在finally中关闭。

　　至此，我的MyBatis初探就告一段落了，在此，要感谢网络上各位大侠。