第一个Mybatis程序（查询）

第一个Mybatis程序

思路：搭建环境------>导入Mybatis------>编写代码------>测试
可参考Mybatis入门官方文档：https://mybatis.org/mybatis-3/zh/getting-started.html

搭建环境

1.搭建数据库（一个简单的User表，包含:id,name,pwd）
2. 新建一个普通的Maven项目
3.导入maven依赖（mysql驱动，mybatis，junit）

在resources目录下，新建mybatis-config.xml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">
<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&amp;characterEncoding=utf-8&amp;useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="com/feng/dao/UserMapper.xml"/>
    </mappers>
</configuration>

<mappers>
    <mapper resource="com/feng/dao/UserMapper.xml"/>
</mappers>为对于后面的xml文件进行注册

编写Mybatis工具类

package com.feng.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;

public class MybatisUtil {
    
    
    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 getSession(){
    
    
        return sqlSessionFactory.openSession();
    }
}

编写实体类

package com.feng.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 getName1() {
    
    
        return name;
    }

    public void setName1(String name1) {
    
    
        this.name = name1;
    }

    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 + '\'' +
                '}';
    }
}

Dao接口

package com.feng.dao;

import com.feng.pojo.User;

import java.util.List;

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

实现接口

<?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.feng.dao.UserDao">
    <select id="getAllUser" resultType="com.feng.pojo.User">
    select * from mybatis.user
  </select>
</mapper>

Junit测试

1.获得SqlSession对象
2.getMapper
3.关闭SqlSession

import com.feng.dao.UserDao;
import com.feng.pojo.User;
import com.feng.utils.MybatisUtil;
import org.apache.ibatis.session.SqlSession;

import java.util.List;

public class Test {
    
    
    public static void main(String[] args) {
    
    
        SqlSession session = MybatisUtil.getSession();
        UserDao mapper = session.getMapper(UserDao.class);
        List<User> allUser = mapper.getAllUser();
        for (User user : allUser) {
    
    
            System.out.println(user);
        }
        SqlSession .close();
    }
}

运行结果如下

总结遇到的问题

问题1

Could not find resource mybatis-config.xml

解决办法

新建文件的时候未加.xml后缀

问题2

Exception in thread “main” org.apache.ibatis.binding.BindingException:
Invalid bound statement (not found): com.feng.dao.UserDao.getAllUse
r

解决办法

问题3

解决办法

就比如说上面的就说由于代码中的是name1，数据库字段中的为name，导致无法读取