mybatis基本环境配置

1. 创建maven并导入坐标

在pom.xml文件中添加如下代码

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.4</version>
        </dependency>

        <!-- 数据库连接 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.49</version>
        </dependency>

        <!-- 日志 -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>

        <!-- 单元测试 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.1</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>

2. 创建实体类和dao的接口

User类

import java.io.Serializable;
import java.util.Date;

public class User implements Serializable {
     
    private Integer id;
    private String username;
    private String password;
    private String gender;
    private Date birthday;

    public Integer getId() {
     
        return id;
    }

    public void setId(Integer id) {
     
        this.id = id;
    }

    public String getUsername() {
     
        return username;
    }

    public void setUsername(String username) {
     
        this.username = username;
    }

    public String getPassword() {
     
        return password;
    }

    public void setPassword(String password) {
     
        this.password = password;
    }

    public String getGender() {
     
        return gender;
    }

    public void setGender(String gender) {
     
        this.gender = gender;
    }

    public Date getBirthday() {
     
        return birthday;
    }

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

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

创建UserDao接口

import java.util.List;

/**
 * 用户持久层接口
 */
public interface UserDao {
     

    List<User> findAll();
}

3.创建Mybatis的主配置文件

在resources下创建Mybatis的主配置文件

<?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">

<!--  mybatis的主配置文件  -->
<configuration>
    <!--  配置环境  -->
    <environments default="mysql">
        <!-- 配置mysql的环境  -->
        <environment id="mysql">
            <!-- 配置事务类型  -->
            <transactionManager type="JDBC"></transactionManager>
            <!-- 配置事务源（连接池） -->
            <dataSource type="POOLED">
                <!-- 配置连接数据库的4个基本信息  -->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/stu"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 指定映射配置文件的位置，映射配置文件指的是每个dao独立的配置文件  -->
    <mappers>
        <mapper resource="com/tech/dao/UserDao.xml"></mapper>
    </mappers>
</configuration>

4.创建映射配置文件

根据主配置文件上mapper的resource设置，在resources包下创建映射配置文件UserDao.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映射到UserDao接口， resultType表示将查询结果封装到哪里 -->
<mapper namespace="com.tech.dao.UerDao" resultType="com.tech.domain.User">	
    <select id="findAll" resultType="com.tech.domain.User">
        select * from user
    </select>
</mapper>

注意事项：

1.mybatis的映射文件位置必须和dao接口的包结构相同
2.映射配置文件的mapper标签中namespace属性的取值必须是dao接口的全限定类型名
3.映射配置文件的，id属性的取值必须是dao接口的方法名

当我们遵从了这三点，开发中就无须写dao的实现类