第一个Mybatis程序

搭建数据库环境：

CREATE DATABASE mybatis;
USE mybatis;

CREATE TABLE user(
id INT(20) NOT NULL PRIMARY KEY,
name VARCHAR(30) DEFAULT NULL,
pwd VARCHAR(30) DEFAULT NULL
)ENGINE=INNODB DEFAULT CHARSET=utf8;

INSERT INTO user(id,name,pwd) VALUES
(1,'戴','12345'),
(2,'张三','12345'),
(3,'李四','12345')

新建项目
1.新建一个maven项目
2.删除src
3.导入maven的依赖

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.47</version>
</dependency>

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.2</version>
</dependency>

<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.11</version>
    <scope>test</scope>
</dependency>

编写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">

<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=true&amp;useUnicode=true&amp;characterEncoding=utf-8"/>
            <property name="username" value="root"/>
            <property name="password" value="123456"/>
        </dataSource>
    </environment>
</environments>

编写Mybatis工具类

public class MybatisUtils {

public static SqlSessionFactory sqlSessionFactory=null ;
static {
    //使用Mybatis第一步：获取sqlSession对象
    String resource = "mybatis-config.xml";
    InputStream inputStream = null;
    try {
        inputStream = Resources.getResourceAsStream(resource);
         sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

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

}

实体类代码：

public class User {

private int id;
private String name;
private String pwd;

public User(int id, String name, String pwd) {
    this.id = id;
    this.name = name;
    this.pwd = pwd;
}

public User() {
}

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 + '\'' +
            '}';
}

}

Dao接口：

public interface UserDao {

List<User> getUserList();

}

接口实现类由原来的UserDaoImpl转换为一个Mapper.xml配置文件：

<?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">

<select id="getUserList" resultType="com.dai.pojo.User">
    select * from mybatis.user
</select>

测试
junit测试

public class UserDaoTest {

@Test
public void test(){
    //获取sqlSession
    SqlSession sqlSession = MybatisUtils.getSqlSession();

    //执行sql
    UserDao mapper = sqlSession.getMapper(UserDao.class);
    List<User> userList = mapper.getUserList();

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

    //关闭sqlsession
    sqlSession.close();
}

}

注意报错点：

org.apache.ibatis.binding.BindingException: Type interface