idea新建一個Mybatis項目（使用Maven）

新建一個mybatis項目需要首先配置好maven環境
具體的mavne問題在我的其他博客中有提到
思路：搭建環境–>導入Mybatis–>編寫代碼–>測試
新建項目：
1.新建一個普通的maven項目
2.刪除src目錄
3.導入maven依賴

<!--導入依賴-->
    <dependencies>
        <!--導入mysql依賴-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.45</version>
        </dependency>
        <!--導入mybatis依賴-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <!--導入junit-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

1.創建一個模塊

• 編寫mybatis的核心配置文件

<?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">
<!--核心配置文件-->
<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/essy?useSSL=false&amp;useUnicode=true&amp;characterEncoding=UTF-8;"/>
                <property name="username" value="1234"/>
                <property name="password" value="1234"/>
            </dataSource>
        </environment>
    </environments>

</configuration>`

• 編寫mybatis的工具類

package com.superman.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;

//sqlSessionFactory工廠模式 sqlSession
public class MybatisUtil {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            //使用mybatis的第一步：獲取sqlSessionFactory對象，mybatis官網
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //有了sqlSessionFactory，我們就可以從中獲得sessionSql的實例
    //sqlSession包含了面向數據庫執行SQL命令所需的所有方法

    public static SqlSession getSqlSession() {
        SqlSession sqlSession=sqlSessionFactory.openSession();
        return sqlSession;
    }

}

2.編寫代碼

• 實體類

package com.superman.pojo;

//實體類
public class User {
    private int id;
    private String username;
    private String birthday;
    private String sex;
    private  String address;

    public User() {
    }

    public User(int id, String username, String birthday, String sex, String address) {
        this.id = id;
        this.username = username;
        this.birthday = birthday;
        this.sex = sex;
        this.address = address;
    }

    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 getBirthday() {
        return birthday;
    }

    public void setBirthday(String birthday) {
        this.birthday = birthday;
    }

    public String getSex() {
        return sex;
    }

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

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

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

• dao接口

package com.superman.dao;

import com.superman.pojo.User;

import java.util.List;

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

• 同時配置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=綁定一個對應的Dao/Mapper接口-->

<mapper namespace="com.superman.dao.UserDao">
    <select id="getUserList" resultType="com.superman.pojo.User">
        select * from eesy.user
    </select>
</mapper>

3.測試代碼
注意點：
org.apache.ibatis.binding.BindingException: Type interface com.superman.dao.UserDao is not known to the MapperRegistry.
MapperRegistry是什麼？
核心配置文件中註冊mappers

package com.superman.dao;

import com.superman.pojo.User;
import com.superman.utils.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {

    @Test
    public void test() {
        //第一步：獲得sqlsession對象
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        //方式一：執行SQL
        UserDao mapper=sqlSession.getMapper(UserDao.class);
        List<User> userList=mapper.getUserList();

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

    //關閉SqlSession
        sqlSession.close();
    }

}

可能遇到的問題有java不支持發行版本5，在我的另一篇博客中有提到。
同時還涉及到一個過濾的問題：
需要在所有的pom.xml文件中增加下面的代碼

<!--在build中配置resources，來防止我們資源導出失敗的問題-->
    <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>

總結：
1.mybatis的工具類
2.因爲工具類需要resources配置文件，所以在resources中寫一個配置文件
3.環境準備完成以後寫實體類
4.寫完實體類以後寫接口
5.爲接口寫一個mapper.xml
6.寫一個test進行測試