初步了解mybatis

初步了解MyBatis
            
需要导入 mybatis-x.x.x.jar;
连接数据库为mysql   导入对应数据库的 mysql-connector-java-5.1.18-bin.jar

数据库表 t_user  里面字段：id（主键、自增） name   passwod  age  qq
Model层里面对应的类：User
package nie.wei.qing.model;

public class User {

private int age;
private int id;
private String name;
private String password;
private String qq;
//补充getter  and  setter
}
Dao层，一个对数据操作的接口： UserDao
package nie.wei.qing.dao;

import java.util.List;

import nie.wei.qing.model.User;

public interface UserDao {

public User selectById(int id);   //按id查找用户
public List<User> findAll();    //查找所有用户
public void update(User user);  //更新用户
public void insert(User user);  //插入新的用户
public void deleteById(int id);  //按照id来删除对应的用户
}

配置文件 mybatis-congig.xml

<?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://localhost:3306/nie" />
<property name="username" value="root" />
<property name="password" value="root" />
</dataSource>
</environment>
</environments>
<mappers>
       <!-- 对应的路径 -->
<mapper resource="MybatisUserDao.xml" />
</mappers>
</configuration>


对MySql操作的配置  MyBaitsUserDao.xml

<?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="nie.wei.qing.dao.UserDao">

<select id="selectById" parameterType="int" resultType="nie.wei.qing.model.User"> <!-- 根据用户id查找用户 -->
select * from t_user where id=#{id}
</select>

<select id="findAll" resultType="nie.wei.qing.model.User"> <!-- 查找所有用户 -->
select * from t_user
</select>

<update id="update" parameterType="nie.wei.qing.model.User">     <!-- 更新库中的用户 -->
update t_user set
name=#{name},password=#{password},age=#{age},qq=#{qq} where id=#{id}
</update>

<insert id="insert" parameterType="nie.wei.qing.model.User">    <!-- 向数据库中插入用户 -->
insert into t_user(name,password,age,qq)
values(#{name},#{password},#{age},#{qq})
</insert>

<delete id="deleteById" parameterType="int">    <!-- 删除用户 -->
delete from t_user where id=#{id}
</delete>
</mapper>
   Junit测试代码：
String resource = "mybatis-config.xml";    //mybatis配置文件的路径
        Reader reader = Resources.getResourceAsReader(resource);
        SqlSessionFactoryBuilder builfer = new SqlSessionFactoryBuilder();
        SqlSessionFactory factory = builfer.build(reader);
        SqlSession session = factory.openSession();
        //前面的操作是得到对应的session  有点像hibernate的操作；
        //根据配置文件得到UserDao的一个实例
        UserDao userDao = session.getMapper(UserDao.class);
        //查找对应的id来得到一个user
        User user=userDao.selectById(1);
        System.out.println(user.getName());
        //得到所有的用户
        List<User> users=userDao.findAll();
        for(int i=0;i<users.size();i++){
        System.out.println("id号是："+users.get(i).getId()+"  name is :"+users.get(i).getName());
        }
        user.setPassword("99999");
        userDao.update(user);//更新相应的User
        User u=new User();
        u.setName("h");
        u.setPassword("d");
        u.setAge(23);
        u.setQq("1111");
        userDao.insert(u);//插入新用户
        userDao.deleteById(4);//根据id删除对应的用户
        session.commit();
        session.close();