MyBatis入门配置

mybatis-config,db.properties pom.xml(日志单独写在另一篇)

1、导包

pom.xml

过滤器的作用，编译时候，resources下的*.propertise和*.xml没法编译到target里，所以这里添加过滤

<dependencies>
     <!--mysql驱动-->
     <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
     <dependency>
         <groupId>mysql</groupId>
         <artifactId>mysql-connector-java</artifactId>
         <version>5.1.26</version>
     </dependency>
     <!--mybatis-->
     <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
     <dependency>
         <groupId>org.mybatis</groupId>
         <artifactId>mybatis</artifactId>
         <version>3.5.6</version>
     </dependency>
     <!--junit-->
     <!-- https://mvnrepository.com/artifact/junit/junit -->
     <dependency>
         <groupId>junit</groupId>
         <artifactId>junit</artifactId>
         <version>4.12</version>
         <scope>test</scope>
     </dependency>
 </dependencies>
 <build>
     <resources>
         <resource>
             <directory>src/main/resources</directory>
             <includes>
                 <include>**/*.properties
                 **/*.xml</include>
             </includes>
             <filtering>true</filtering>
         </resource>
         <resource>
             <directory>src/main/java</directory>
             <includes>
                 <include>**/*.properties
                 **/*.xml</include>
             </includes>
             <filtering>true</filtering>
         </resource>
     </resources>
 </build>

db.properties

配置数据库资源

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/test?useSSL=true&useUnicode=true&characterEncoding=UTF-8
username=root
password=sz@mysql

mybatis-config.xml

1、引入properties文件
2、配置扫描的包（作用纯粹扫描xml,否则找不到对应的mapper.xml文件）

<mappers>****.xmlmappers>

如果是注解开发 需要在mapper里绑定接口 （这里我测试了不能同时扫描包和绑定接口，这就意味着 不能同时使用注解和xml开发，spring是可以的。也有可能是我搞错了吧）

<mappers>
	<mapper class="com.mybatis.dao.UserMapper"/>
mappers>

3、设置别名

<typeAliases>******typeAliases>

这里如果不配置，那么mapper.xml的每个类都要写全路径，并且不配置的话， 没法使用注解开发（虽然不常用）。比如

配置前
<select id="getUserList" resultType="com.mybatis.pojo.User">
配置后
<select id="getUserList" resultType="User">

设置数据库环境(可以是多个 但是只能用一个)和要扫描的mapper（扫描某个文件或包下所有mapper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>
    <properties resource="db.properties"/>
    <typeAliases>
        <package name="com.mybatis.pojo"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
        <environment id="development1">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/test?useSSL=true&useUnicode=true&characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="sz@mysql"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
    	<!--将接口绑定到配置-->
    	<!--方法1-->
        <!--<mapper resource="com/mybatis/dao/UserMapper.xml"/>-->
    	<!--方法2-->
        <!--<mapper resource="com/mybatis/dao/*.xml"/>-->
        <!--方法3-->
        <package name="com.mybatis.dao"/>
    </mappers>
</configuration>

db.properties和在xml配置的数据库url 里面区别在于要不要转义符 &

创建pojo

package com.mybatis.pojo;
public class User {
    private int id;
    private String name;
    private String sex;
    private int age;

    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 getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

创建接口UserMapper.java (接口名要和mapper名一致，如果不一致 要改哪里我不知道，以后知道了再补回来)

package com.mybatis.dao;

import com.mybatis.pojo.User;

import java.util.List;

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

    public void addUser(User user);

    public void updateUserById(int id);

    public void deleteUserById(int id);
}

创建UserMapper.xml

<?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.mybatis.dao.UserMapper">
    <select id="getUserList" resultType="User">
        select * from user
    </select>

    <insert id="addUser" >
        insert into user (id,name,sex,age) values(#{id},#{name},#{sex},#{age})
    </insert>
    <update id="updateUserById" parameterType="int">
        update user set name="9999" where id=#{id}
    </update>

    <delete id="deleteUserById" parameterType="int">
        delete from user where id=#{id}
    </delete>
</mapper>

编写工具包（通过xml方式，需要通过sqlSession获取mapper对象，然后执行sql方法，sqlSession通过SqlSessionFactory 工厂获取，每次都是用，所以自己创建的时候使用单例模式）

package utils;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.mapping.Environment;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
public class MybatisUtil {
    private  static SqlSessionFactory sqlSessionFactory;
    private static SqlSession sqlSession;
    static {
        try{
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    public static SqlSession getSqlSession(){
        sqlSession = sqlSessionFactory.openSession();
        return sqlSession;
    }

}

编写测试类（对于修改了数据库的方法，在执行之后要添加commit 才会真正的修改）

import com.mybatis.dao.UserMapper;
import com.mybatis.pojo.User;
import org.apache.ibatis.session.SqlSession;
import utils.MybatisUtil;
import java.util.List;
public class MyTest {
    public static void main(String[] args) {
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        /**
         * addUser
         */
//        User user = new User();
//        user.setId(9);
//        user.setName("ttt");
//        user.setSex("femal");
//        user.setAge(88);
//        mapper.addUser(user);
//        sqlSession.commit();
        /**
         * select users
         */
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user.getName());
        }
        /**
         * update user
         */
//        mapper.updateUserById(1);
//        sqlSession.commit();

        /**
         * delete user
         */
//        mapper.deleteUserById(1);
//        sqlSession.commit();
        System.out.println("end");
        sqlSession.close();
    }
}

总结：

这里单纯的mybatis，如果整合spring springboot会方便很多

不知道原理 博客真不好写 每一步为啥这么干，不这么干怎么办 不理解！！！