mybatis使用步骤

0.前言

本教程是学习狂神的mybatis视频后的步骤总结，给新接触的人做为参考，之后熟悉后直接看官网文档。html

mybatis官方地址： https://mybatis.org/mybatis-3/configuration.html#mappersjava

1.建立maven项目

建立maven项目并在根pom.xml配置文件中加入如下依赖(具体版本能够根据实际状况变更)mysql

<dependencies>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.46</version>
    </dependency>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.2</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
    </dependency>
</dependencies>

为了不出现myhabits找不到资源的现象，在该pom.xml文件中加入如下配置，并刷新mavensql

<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>

2.写mybatis配置文件

根据官网的教程拷贝模板，并在其上加入本身的项目的相关配置(如数据库帐号密码等)，下面url那一行是链接数据库的配置。写完该配置文件后本例将其保存为mybatis-config.xml数据库

<?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=false&amp;
                    useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="帐号(此处根据状况写)"/>
                <property name="password" value="密码(如上)"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/kikian/dao/userMapper.xml"></mapper>
    </mappers>
</configuration>

3.写工具类

建立一个子项目并将mybatis的通用代码封装成一个工具类(最好用单例模式，将sqlSessionFactory置为static),该工具类的做用是：读取刚刚写好的mybatis-config.xml配置文件获取SqlSessionFactory对象。mybatis

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();
    }
}

4.写实体类

该实体类要与将从数据库中读取的数据要相对应，例如要从数据库读取的数据字段为id name pwd,因此设置的对象也要包含该三个变量。为了简约，此处删去了getter setter toString等代码。app

public class user {
    private int id;
    private String name;
    private String pwd;
    public user(){
    }
    public user(int id,String name,String pwd){
        setId(id);
        setName(name);
        setPwd(pwd);
    }
}

5.写接口并实现

public interface userDao {
    List<user> getUserList();
}

public class userDaoImpl implements userDao{
    public List<user> getUserList(){
        return null;
    }
}

6.写mapper配置文件

将mybatis和java代码进行映射，创建链接。maven

<?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.kikian.dao.userDao">
    <select id="getUserList" resultType="com.kikian.pojo.user">
        select * from mybatis.user
    </select>
</mapper>

namespace：命名空间，映射查询的关键参数，要和接口包名一致。 id：调就是对应的namespace中的方法名。 resultType：sql语句执行的返回值。 parameterType：传入参数的类型,以下例。工具

<select id="getUserList" parameterType="int" resultType="com.kikian.pojo.user">
        select * from mybatis.user where id = #{id};
    </select>

7.单元测试

写单元测试代码，测试项目可否跑通。单元测试

public class userDaoTest {
    @Test
    public void test(){
        SqlSession sqlSession = mybatisUtils.getSqlSession();
        userDao udao = sqlSession.getMapper(userDao.class);
        List<user> userList = udao.getUserList();
        for (user user : userList) {
            System.out.println(user);
        }
        sqlSession.close();
    }
}