1、配置开发环境
- jdk：1.8
- mysql：8.0
- maven：3.6.1
- idea：2021.3
2、导入依赖和配置文件
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在pom.xml中导入mybatis需要的依赖
<!--mysql--> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.27</version> </dependency> <!--mybatis--> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.9</version> </dependency> <!--junit--> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.13.2</version> <scope>test</scope> </dependency> -
配置mybatis的核心文件
<!--在resources目录下建一个名为mybatis-config的xml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> <!--配置mysql--> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <dataSource type="POOLED"> <property name="driver" value="com.mysql.cj.jdbc.Driver"/> <property name="url" value="jdbc:mysql://127.0.0.1:3306/langsin?characterEncoding=UTF-8&useSSL=false&useUnicode=true&serverTimezone=Asia/Shanghai&allowPublicKeyRetrieval=true&rewriteBatchedStatements=true"/> <property name="username" value="root"/> <property name="password" value="123456"/> </dataSource> </environment> </environments> <!--注册接口的实现文件--> <mappers> <mapper resource="dao/UserMapper.xml"/> </mappers> </configuration>
注释：配置文件中，关于mysql连接的driver、url、username、password写自己的
3、编写程序
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创建生成sqlSession对象的工具类，sqlSession对象 ≈ Connection对象
public class MybatisTools { //定义sqlSessionFactory实例 private static SqlSessionFactory sqlSessionFactory; //加载配置文件，初始化sqlSessionFactory实例（建造者模式） static { try { String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); } catch (IOException e) { e.printStackTrace(); } } //生成执行SQL的sqlSession对象 public static SqlSession getSqlSession(){ return sqlSessionFactory.openSession(); } } -
创建实体类
1. Plugins中下载lombok插件 2. 导入lombok依赖，能够使用注解自动生成构造器和一些object的方法<!--lombok--> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.18.22</version> <scope>provided</scope> </dependency>@Data //object全方法 @NoArgsConstructor //无参构造器 @AllArgsConstructor //全参构造器 public class User { private Long userId; private String username; private String password; private String cname; private String gender; private Integer age; private String telephone; private String email; private String address; private Integer roleId; private String isLogin; } -
创建UserMapper接口，= UserDao
public interface UserMapper { List<User> queryUserList(); } -
创建UserMapper.xml文件，≈ UserDaoImpl
<?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跟接口关联--> <mapper namespace="dao.UserMapper"> <!--id跟接口中的方法关联--> <!--resultMap是返回值，这里可以用resultType，用map是为了跟表中各列的关联，能正确输出数据--> <select id="queryUserList" resultMap="userMap"> select * from user </select> <resultMap id="userMap" type="pojo.User"> <id column="user_id" property="userId"/> <result column="role_id" property="roleId"/> <result column="is_login" property="isLogin"/> </resultMap> </mapper>
4、测试
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测试代码
public class UserMapperTest { @Test public void test01(){ //通过工具类获取sqlSession对象 SqlSession sqlSession = MybatisTools.getSqlSession(); //通过映射接口实现文件就能确定dao层有哪些方法 //param：UserMapper的类对象 //原因：在UserMapper.xml文件中已经绑定了接口，因此找类对象间接就找到了xml文件 UserMapper mapper = sqlSession.getMapper(UserMapper.class); //调用方法，没什么说的 List<User> list = mapper.queryUserList(); for (User user : list) { System.out.println(user); } //关闭资源 sqlSession.close(); } } -
测试结果
User(userId=6, username=gousheng, password=123456, cname=张狗蛋, gender=男, age=33, telephone=15555555555, email=999, address=北京东城, roleId=1, isLogin=0) User(userId=10, username=jiadao, password=123456, cname=贾岛, gender=, age=35, telephone=, email=jiadao@baomidou.com, address=大唐长安街, roleId=3, isLogin=0) User(userId=11, username=wangwei, password=123213, cname=王维, gender=男, age=35, telephone=13647854785, email=wangwei@baomidou.com, address=大唐长安街44号, roleId=3, isLogin=0) User(userId=12, username=libai, password=123213, cname=李白, gender=男, age=35, telephone=138455625621, email=libai@baomidou.com, address=null, roleId=2, isLogin=0) User(userId=14, username=dufu, password=123213, cname=杜甫, gender=null, age=35, telephone=null, email=dufu@baomidou.com, address=null, roleId=2, isLogin=0) User(userId=15, username=zhangfei, password=123456, cname=杜牧, gender=男, age=24, telephone=13645674567, email=zhangfei@163.com, address=济南市趵突泉, roleId=2, isLogin=0) User(userId=1329378113234169858, username=menghaoran, password=123213, cname=孟浩然, gender=null, age=35, telephone=null, email=menghaoran@baomidou.com, address=null, roleId=2, isLogin=0) User(userId=1407985458301927426, username=hezhizhang, password=123456, cname=孟浩然, gender=null, age=22, telephone=13645784578, email=haoran@163.com, address=湖北襄阳, roleId=2, isLogin=0) User(userId=1407985458301927427, username=hezhizhang, password=123456, cname=孟浩然, gender=null, age=22, telephone=13645784578, email=haoran@163.com, address=湖北襄阳, roleId=2, isLogin=0)
5、总结
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与jdbc开发的不同
#1.jdbc中是获取Connection对象，mybatis是获取sqlSession对象 #2.mybatis改用xml文件的方式来实现接口，实现了java代码和SQL语句解耦合 -
异常
#1.异常一 org.apache.ibatis.binding.BindingException: Type interface dao.UserMapper is not known to the MapperRegistry. 意思：实现文件未注册 解决：在mybatis核心配置文件中注册实现文件（后续可以通过包扫描解决，pojo也可以包扫描起别名。用了MP这些基本的SQL也不用写了） #2.异常二 Error parsing SQL Mapper Configuration. Cause: java.io.IOException: Could not find resource dao/UserMapper.xml 意思：在target下找不到xml文件（idea就是这样的） 解决：在pom.xml中加入以下配置，然后使用maven命令clean清理target目录重新运行<!--使得idea能够将java目录下的xml文件编译到target目录--> <build> <resources> <resource> <directory>src/main/java</directory> <includes> <include>**/*.xml</include> </includes> </resource> </resources> </build> -
mybatis使用步骤
#1.导入相关依赖 #2.书写mybatis-config.xml核心文件 #3.创建mybatis工具类 #4.创建UserMapper接口 #5.书写UserMapper.xml实现文件 #6.测试代码 上述6步，在日后的使用中，只需改动其中4步即可 2.核心文件中可能需要注册更多的实现文件 4.接口中增加新方法，或者增加新接口 5.实现文件中对于新方法要有对应的SQL语句 6.测试代码也就是业务根据实际需求变化