第一个Mybatis

思路：搭建环境-->导入Mybatis-->编写代码-->测试

1、搭建环境

新建maven工程，配置xml文件

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0"

         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>

    <artifactId>mybatis</artifactId>

    <version>1.0-SNAPSHOT</version>

    <!--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>

            <scope>test</scope>

        </dependency>

    </dependencies>

</project>

编写mybatis的核心配置文件（在resources文件夹下创建mybatis-config.xml）

Mysql8.0以上url还得设置时区setTimeZone

<?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核心配置文件-->

<configuration>

    <environments default="development">

        <environment id="development">

            <transactionManager type="JDBC"/>

            <!--数据源-->

            <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;characterEncode=UTF-8"/>

                <property name="username" value="root"/>

                <property name="password" value="123456"/>

            </dataSource>

        </environment>

    </environments>

    <!--每一个Mapper.xml都需要在mybatis核心配置文件中注册！-->

    <mappers>

        <mapper resource="org/mybatis/example/UserDaoMapper.xml"/>

    </mappers>

</configuration>

2、编写代码

实体类

package com.spong.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 + '\'' +

                '}';

    }

}

Mapper接口

public interface UserMapper {

    List<User> getUserList();

}

接口实现类由原来的UserDaoImpl转变为一个Mapper配置文件 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">

<!--namespace绑定一个对应的Dao/Mapper接口-->

<mapper namespace="com.spong.dao.UserDao">

    <select id="getUserList" resultType="com.spong.pojo.User">

        select * from mybatis.user

    </select>

</mapper>

MybatisUtils工具类

将sqlSessionFactory的创建以及获取SqlSession的方法封装为工具类，实际请求中使用MybatisUtils工具类的静态方法直接获得SQLSession实例。

package com.spong.util;

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 {

            //获取SqlSessionFactory对象

            String resource = "mybatis-config.xml";

            InputStream inputStream = Resources.getResourceAsStream(resource);

            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

    //获取SQLSession实例，SQLSession中完全包含了面向数据库执行SQL命令所需的所有方法

    public static SqlSession getSqlSession(){

        return sqlSessionFactory.openSession();

    }

}

3、测试

junit测试

@Test

public void test(){

    //第一步，获取SqlSession对象

    SqlSession sqlSession = MybatisUtils.getSqlSession();

    //第二步，执行sql

    UserMapper mapper = sqlSession.getMapper(UserMapper.class);

    List<User> userList = mapper.getUserList();

    for (User user : userList) {

        System.out.println(user);

    }

    //关闭SqlSession

    sqlSession.close();

}

异常：org.apache.ibatis.binding.BindingException: Type interface com.spong.dao.UserDao is not known to the MapperRegistry.

需要在核心配置文件中注册mappers

<!--每一个Mapper.xml文件都要在核心配置文件中注册-->

    <mappers>

        <mapper resource="com/spong/dao/UserMapper.xml"/>

    </mappers>

maven资源导出问题（测试时发现mybatis.xml文件未找到）：

需要在pom.xml中配置

<!--在build中配置resources，防止资源导出失败的问题-->

<build>

    <resources>

        <resource>

            <directory>src/main/resources</directory>

            <includes>

                <include>**/*.properties</include>

                <include>**/*.xml</include>

            </includes>

        </resource>

        <resource>

            <directory>src/main/java</directory>

            <includes>

                <include>**/*.properties</include>

                <include>**/*.xml</include>

            </includes>

        </resource>

    </resources>

</build>

巴特西

第一个Mybatis

第一个Mybatis

1、搭建环境

2、编写代码

3、测试

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