【Mybatis】mybatis3入门

mybatis简介

MyBatis 是一款优秀的持久层框架，它支持定制化 SQL、存储过程以及高级映射。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以使用简单的 XML 或注解来配置和映射原生类型、接口和 Java 的 POJO（Plain Old Java Objects，普通老式 Java 对象）为数据库中的记录。

使用入门

0.新建数据库

1.导包

2.加载配置文件

注释：

启用驼峰命名法检验
<settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
</settings>
dao映射文件地址
<mappers>
        <mapper resource="com/blb/dao/UserDao-config.xml"/>
</mappers>

新建src目录下创建xml配置文件，mybatis-config.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>
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>
    <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/taobaodb"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/blb/dao/UserDao-config.xml"/>
    </mappers>
</configuration>

3.建立session

try (SqlSession session = sqlSessionFactory.openSession()) {
		代码
}

4.取dao层接口

 UserDao userDao = session.getMapper(UserDao.class);

创建以下文件

创建dao层接口

package com.blb.dao;

import com.blb.bean.User;

import java.util.List;

public interface UserDao {
    List<User> getUsers();
}

UserDao.xml映射配置文件

注释：

<mapper namespace="com.blb.dao.UserDao">
    <select id="dao接口方法名" resultType="方法返回值类型的类相对地址">
    sql语句，不加分号
  </select>
</mapper>

正文：

<?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="com.blb.dao.UserDao">
    <select id="getUsers" resultType="com.blb.bean.User">
    select * from userinfo
  </select>
</mapper>

创建User类

package com.blb.bean;

public class User {
    private int userid;
    private String username;
    private String userpwd;
    private int typeid;
    private String userstatus;

    public int getUserid() {
        return userid;
    }

    public void setUserid(int userid) {
        this.userid = userid;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getUserpwd() {
        return userpwd;
    }

    public void setUserpwd(String userpwd) {
        this.userpwd = userpwd;
    }

    public int getTypeid() {
        return typeid;
    }

    public void setTypeid(int typeid) {
        this.typeid = typeid;
    }

    @Override
    public String toString() {
        return "User{" +
                "userid=" + userid +
                ", username='" + username + '\'' +
                ", userpwd='" + userpwd + '\'' +
                ", typeid=" + typeid +
                ", userstatus='" + userstatus + '\'' +
                '}';
    }

    public String getUserstatus() {
        return userstatus;
    }

    public void setUserstatus(String userstatus) {
        this.userstatus = userstatus;
    }
}

5.操作

创建Test类

package com.blb.service;

import com.blb.bean.User;
import com.blb.dao.UserDao;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

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

public class Test {
    public static void main(String[] args) throws IOException {
        //从 XML 中构建 SqlSessionFactory
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //从 SqlSessionFactory 中获取 SqlSession
        try (SqlSession session = sqlSessionFactory.openSession()) {
            UserDao userDao = session.getMapper(UserDao.class);
            List<User> users = userDao.getUsers();
            for(User u:users){
                System.out.println(u);
            }
        }
    }
}

Mybatis开启日志，增删改查的操作，请看下篇

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