第一天mybatis学习（中）

5）在entity目录下创建StudentMapper.xml配置文件

<?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">

<mapper namespace="mynamespace">
    <insert id="add1">
        insert into students(id,name,sal) values(1,'哈哈',7000)
    </insert>
    <insert id="add2" parameterType="cn.itcast.javaee.mybatis.app05.Student">
        insert into students(id,name,sal) values(#{id},#{name},#{sal})
    </insert>
</mapper>

6）在src目录下创建mybatis.xml配置文件

<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/> 
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/mybatis"/>  
                <property name="username" value="root"/>    
                <property name="password" value="root"/>    
            </dataSource>
        </environment>  
    </environments>
    <mappers>
        <mapper resource="cn/itcast/javaee/mybatis/app05/StudentMapper.xml"/>
    </mappers>
</configuration>

7）在util目录下创建MyBatisUtil.java类，并测试与数据库是否能连接
/**
* MyBatis工具类
* @author AdminTC
*/
public class MyBatisUtil {
private static ThreadLocal threadLocal = new ThreadLocal();
private static SqlSessionFactory sqlSessionFactory;
static{
try {
Reader reader = Resources.getResourceAsReader(“mybatis.xml”);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
} catch (IOException e) {
e.printStackTrace();
throw new RuntimeException(e);
}
}
private MyBatisUtil(){}
public static SqlSession getSqlSession(){
SqlSession sqlSession = threadLocal.get();
if(sqlSession == null){
sqlSession = sqlSessionFactory.openSession();
threadLocal.set(sqlSession);
}
return sqlSession;
}
public static void closeSqlSession(){
SqlSession sqlSession = threadLocal.get();
if(sqlSession != null){
sqlSession.close();
threadLocal.remove();
}
}
public static void main(String[] args) {
Connection conn = MyBatisUtil.getSqlSession().getConnection();
System.out.println(conn!=null?”连接成功”:”连接失败”);
}
}
8）在dao目录下创建StudentDao.java类并测试
/**
* 持久层
* @author AdminTC
*/
public class StudentDao {
/**
* 增加学生（无参）
*/
public void add1() throws Exception{
SqlSession sqlSession = MyBatisUtil.getSqlSession();
try{
sqlSession.insert(“mynamespace.add1”);
}catch(Exception e){
e.printStackTrace();
sqlSession.rollback();
throw e;
}finally{
sqlSession.commit();
}
MyBatisUtil.closeSqlSession();
}
/**
* 增加学生（有参）
*/
public void add2(Student student) throws Exception{
SqlSession sqlSession = MyBatisUtil.getSqlSession();
try{
sqlSession.insert(“mynamespace.add2”,student);
}catch(Exception e){
e.printStackTrace();
sqlSession.rollback();
throw e;
}finally{
sqlSession.commit();
}
MyBatisUtil.closeSqlSession();
}
public static void main(String[] args) throws Exception{
StudentDao dao = new StudentDao();
dao.add1();
dao.add2(new Student(2,”呵呵”,8000D));
}
}
四.mybatis工作流程(注意理解，代码依据工作流程实现 )
1）通过Reader对象读取src目录下的mybatis.xml配置文件(该文本的位置和名字可任意)
2）通过SqlSessionFactoryBuilder对象创建SqlSessionFactory对象
3）从当前线程中获取SqlSession对象
4）事务开始，在mybatis中默认
5）通过SqlSession对象读取StudentMapper.xml映射文件中的操作编号，从而读取sql语句
6）事务提交，必写
7）关闭SqlSession对象，并且分开当前线程与SqlSession对象，让GC尽早回收

第一天mybatis学习（中）

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