Mybatis入门（一）

　　半年不写后台，又给忘光了，呵呵，这次记个笔记吧，废话就此止

今天就写一个简单的mybatis demo

所需jar:

mybatis-3.2.1

mysql-connector-java-5.0.8

数据库表

demo的工程目录

 

conf.xml

mybatis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" />
            <!-- 配置数据库连接信息 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/mydb" />
                <property name="username" value="root" />
                <property name="password" value="mald123" />
            </dataSource>
        </environment>
    </environments>
</configuration>

User.java

package com.mld.domain;

public class User {
    private String userId;
    private String userName;
    private String password;
    private String sex;
    private String email;
    public String getUserId() {
        return userId;
    }
    public void setUserId(String userId) {
        this.userId = userId;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    @Override
    public String toString() {
        return "User [userId=" + userId + ", userName=" + userName
                + ", password=" + password + ", sex=" + sex + ", email="
                + email + "]";
    }
    
    
}

userMapping.xml

和每个数据库表所对应的po对应，进行表的各项操作

<?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">
<!-- 为这个mapper指定一个唯一的namespace，namespace的值习惯上设置成包名+sql映射文件名，这样就能够保证namespace的值是唯一的
例如namespace="me.gacl.mapping.userMapper"就是me.gacl.mapping(包名)+userMapper(userMapper.xml文件去除后缀)
 -->
<mapper namespace="com.mld.mapping.userMapping">  //每个mapper对应于一个表结构的操作
    <!-- 在select标签中编写查询的SQL语句， 设置select标签的id属性为getUser，id属性值必须是唯一的，不能够重复
    使用parameterType属性指明查询时使用的参数类型，resultType属性指明查询返回的结果集类型
    resultType="me.gacl.domain.User"就表示将查询结果封装成一个User类的对象返回
    User类就是users表所对应的实体类
    -->
    <!-- 
        根据id查询得到一个user对象
     -->
    <select id="getUserById" parameterType="int" resultType="com.mld.domain.User">
        select * from user where userId=#{id}
    </select>
    <!-- 查询所有 -->
    <select id="getUsers" resultType="com.mld.domain.User">
        select * from user
    </select>
</mapper>

将userMapping.xml注册到conf.xml中

conf.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" />
            <!-- 配置数据库连接信息 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/mydb" />
                <property name="username" value="root" />
                <property name="password" value="mald123" />
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
        <!-- 注册userMapper.xml文件 ,userMapper.xml位于com.mld.mapping这个包
        下，所以resource写成com/mld/mapping/userMapping.xml
        -->
        <mapper resource="com/mld/mapping/userMapping.xml"></mapper>   //此处/分割
    </mappers> 
</configuration>

test.java

package com.mld.test;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.util.List;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import com.mld.domain.User;

public class test {
    public static void main(String[] args) throws IOException{
        /*Reader reader = Resources.getResourceAsReader("com/mld/test/conf.xml");  //用mybatis提供的方法加载配置文件
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
        SqlSession session = sessionFactory.openSession();
        String statement = "com.mld.mapping.userMapping.getUserById";
        User user = session.selectOne(statement, 2);
        System.out.println(user);*/
        
        String conf = "com/mld/test/conf.xml";
        InputStream is = test.class.getClassLoader().getResourceAsStream(conf); //用类加载器加载配置文件
        SqlSessionFactory sessionfactory = new SqlSessionFactoryBuilder().build(is);
        SqlSession session = sessionfactory.openSession(true);　　//为true会自动commit，默认为false，需手动commit
        User user = session.selectOne("com.mld.mapping.userMapping.getUserById", 1);
        List<User> list = session.selectList("com.mld.mapping.userMapping.getUsers");
        System.out.println(list.size());
        System.out.println(user);
    }
}

 运行结果：

 

好了