mybatis简介

mybatis主要封装了Java对数据库的操作，是一款优秀的持久层框架，它免除了Javajdbc带来的复杂处理程序。

maven初始mybatis项目

在pom.xml文件中导入

  <!-- 导入依赖-->
    <dependencies>
        <!-- mysql驱动 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <!--mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <!--junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

在maven中创建相应目录
mybatis项目
首先创建的数据是mybatis，数据表是user。整型的id，两个String类型的namg和pwd

首先创建mybatis-config.xml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://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456789"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
          <mapper resource="com/yc/dao/UserMapper.xml"/>
    </mappers>
</configuration>

创建mybatisutils工具类。

package com.yc.utils;

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;

public class mybatisutils {

    private  static   SqlSessionFactory sqlSessionFactory;
    static {

        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }
}

创建User用户类

package com.yc.pojo;

public class User {
    private  int id;
    private  String name;
    private  String pwd;

    public User() {
    }

    public User(int id, String name, String pwd) {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", pwd='" + pwd + '\'' +
                '}';
    }
}

创建Userdao接口。

package com.yc.dao;

import com.yc.pojo.User;

import java.util.List;

public interface Userdao {
    List<User> getUserList();
}

创建UserMapper.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">

<mapper namespace="com.yc.dao.Userdao">
    <select id="getUserList" resultType="com.yc.pojo.User">
        select * from mybatis.user
    </select>
</mapper>

创建测试类test

package com.yc.dao;

import com.yc.pojo.User;
import com.yc.utils.mybatisutils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class test {
    @Test
    public void test(){
        SqlSession sqlSession= mybatisutils.getSqlSession();
        Userdao user=sqlSession.getMapper(Userdao.class);
        List<User> list=user.getUserList();
        for(User u: list) {
            System.out.println(u);
        }
        sqlSession.close();
    }
}

最终输出是发现找不到UserMapper.xml文件，因为文件没有放在配置目录下，需要导入maven资源过滤。

    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
    </build>