Maybatis的一些总结（二：基本使用过程）

理清一下使用需要做的步骤

• 建项目，导入mybatis(3.5.2)和mysql(5.1.47)进pom.xml
• pom.xml需配置build时过滤器，否则会出现xml文件导出不了的问题
• resources文件夹下配置mybatis-config.xml，这是mybatis的核心配置文件。主要配置有数据库的连接信息，mapper.xml。
• utils文件夹下新建MybatisUtilis工具类。作用：读取mybatis-config.xml，用SqlSessionFactoryBuilder读取配置文件，build出一个sqlSessionFactory。并搞一个方法用于Factory打开一个session。（工具类，大家都照抄就行）
• ----------------以下是实际需要编写的DAO层代码------------------------------
• 创建POJO文件夹下的实体类，这里名字是User
• 创建DAO文件夹下的Mapper接口（如果返回数据返回类型就是类似List<User>这种）
• 仍然是DAO文件夹下，接口的实现转变为一个UserMapper.xml，在其中先绑定一个Mapper接口，再绑定Mapper接口中的方法为sql语句。
• -----------------以下是测试或者使用时的代码-----------------------------
• 通过工具类获得sqlsession对象
• 通过sqlsession.getmapper获得一个Usermapper接口的实例。
• 然后调用usermapper其中的方法就能获得List<User>类型的数据了。
• 最后关闭这个sqlsession

项目配置部分详细代码：

    <dependencies>
        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/junit/junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
    </dependencies>

pom依赖

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

过滤器

<?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?useUnicode=true&amp;characterEncoding=UTF-8&amp;useSSL=true"/>
                <property name="username" value="root"/>
                <property name="password" value="你的数据库密码"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/ou/dao/UserMapper.xml"/>
    </mappers>
</configuration>

mybatis-config.xml

package com.ou.utilis;

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 MybatisUtilis {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        String resource = "mybatis-config.xml";
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
            e.printStackTrace();
        }
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }

    public static SqlSession getsqlsession()
    {
        return sqlSessionFactory.openSession();
    }

}

MybatisUtilis

DAO部分详细代码：

package com.ou.pojo;

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

    public User() {
    }

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

    public int getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

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

    public String getPwd() {
        return pwd;
    }

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

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

pojo类

package com.ou.dao;

import com.ou.pojo.User;

import java.util.List;
import java.util.Map;

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

UserMapper接口

<?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.ou.dao.UserMapper">
    <select id="getUserList" resultType="com.ou.pojo.User">
       SELECT * FROM mybatis.user
    </select>
</mapper>

UserMapper.xml

测试部分代码：

    @Test
    public void test()
    {
        SqlSession sqlSession = MybatisUtilis.getsqlsession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);//不懂这一步
        List<User> userList = userMapper.getUserList();

        for(User user:userList)
        {
            System.out.println(user.toString());
        }
        sqlSession.close();
    }

测试

补充项目结构：