MyBatis 基本配置和使用
如何使⽤
新建 Maven ⼯程，pom.xml
<dependencies> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.4.5</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.11</version> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.18.6</version> <scope>provided</scope> </dependency> </dependencies> <build> <resources> <resource> <directory>src/main/java</directory> <includes> <include>**/*.xml</include> </includes> </resource> </resources> </build>
新建数据表
use mybatis; create table t_account( id int primary key auto_increment, username varchar(11), password varchar(11), age int )
新建数据表对应的实体类 Account
import lombok.Data; @Data public class Account { private long id; private String username; private String password; private int age; }
第一种：创建 MyBatis 的配置⽂件 config.xml，⽂件名可⾃定义
<?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MyBatis运⾏环境 --> <environments default="development"> <environment id="development"> <!-- 配置JDBC事务管理 --> <transactionManager type="JDBC"></transactionManager> <!-- POOLED配置JDBC数据源连接池 --> <dataSource type="POOLED"> <property name="driver" value="com.mysql.cj.jdbc.Driver"> </property> <property name="url" value="jdbc:mysql://localhost:3306/mybatis? useUnicode=true&characterEncoding=UTF-8"></property> <property name="username" value="root"></property> <property name="password" value="root"></property> </dataSource> </environment> </environments> </configuration>
第二种：创建 MyBatis 的配置⽂件 在application.yml中（简单）
spring: datasource: username: root password: 123456 url: jdbc:mysql://127.0.0.1:3306/jdbc?characterEncoding=UTF-8&useSSL=false&&serverTimezone=Asia/Shanghai driver-class-name: com.mysql.jdbc.Driver mybatis: # 目录地址 config-location: classpath:mybatis/mybatis-config.xml # 目录地址 mapper-locations: classpath:mybatis/mapper/*.xml
创建mapper.xml 写Sql语句
MyBatis 框架需要开发者⾃定义 SQL 语句，写在 Mapper.xml ⽂件中，实际开发中，会为每个实体
类创建对应的 Mapper.xml ，定义管理该对象数据的 SQL。
<?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.southwind.mapper.AccoutMapper"> <insert id="save" parameterType="com.southwind.entity.Account"> insert into t_account(username,password,age) values(#{username},# {password},#{age}) </insert> </mapper> <!-- namespace 通常设置为⽂件所在包+⽂件名的形式。--> <!-- insert 标签表示执⾏添加操作。--> <!-- select 标签表示执⾏查询操作。--> <!-- update 标签表示执⾏更新操作。--> <!-- delete 标签表示执⾏删除操作。--> <!-- id 是实际调⽤ MyBatis ⽅法时需要⽤到的参数。--> <!-- parameterType 是调⽤对应⽅法时参数的数据类型。-->
第一种注册方式在全局配置⽂件 config.xml 中注册 AccountMapper.xml
<?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MyBatis运⾏环境 --> <environments default="development"> <environment id="development"> <!-- 配置JDBC事务管理 --> <transactionManager type="JDBC"></transactionManager> <!-- POOLED配置JDBC数据源连接池 --> <dataSource type="POOLED"> <property name="driver" value="com.mysql.cj.jdbc.Driver"> </property> <property name="url" value="jdbc:mysql://localhost:3306/mybatis? useUnicode=true&characterEncoding=UTF-8"></property> <property name="username" value="root"></property> <property name="password" value="root"></property> </dataSource> </environment> </environments> <!-- 注册AccountMapper.xml --> <mappers> <mapper resource="com/southwind/mapper/AccountMapper.xml"></mapper> </mappers> </configuration>
第二种注册方式在全局配置⽂件 在application.yml 中
# 目录地址 config-location: classpath:mybatis/mybatis-config.xml # 目录地址 mapper-locations: classpath:mybatis/mapper/*.xml
调⽤ MyBatis 的原⽣接⼝执⾏添加操作。
public class Test { public static void main(String[] args) { //加载MyBatis配置⽂件 InputStream inputStream = Test.class.getClassLoader().getResourceAsStream("config.xml"); SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder(); SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream); SqlSession sqlSession = sqlSessionFactory.openSession(); String statement = "com.southwind.mapper.AccoutMapper.save"; Account account = new Account(1L,"张三","123123",22); sqlSession.insert(statement,account); sqlSession.commit(); } }
通过 Mapper 代理实现⾃定义接⼝
1、⾃定义接⼝，定义相关业务⽅法。
2 、编写与⽅法相对应的 Mapper.xml。
import com.southwind.entity.Account; import java.util.List; public interface AccountRepository { public int save(Account account); public int update(Account account); public int deleteById(long id); public List<Account> findAll(); public Account findById(long id); }
创建接⼝对应的 Mapper.xml，定义接⼝⽅法对应的 SQL 语句。
statement 标签可根据 SQL 执⾏的业务选择 insert、delete、update、select。
MyBatis 框架会根据规则⾃动创建接⼝实现类的代理对象。
规则：
Mapper.xml 中 namespace 为接⼝的全类名。 Mapper.xml 中 statement 的 id 为接⼝中对应的⽅法名。 Mapper.xml 中 statement 的 parameterType 和接⼝中对应⽅法的参数类型⼀致。 Mapper.xml 中 statement 的 resultType 和接⼝中对应⽅法的返回值类型⼀致。 <?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.southwind.repository.AccountRepository"> <insert id="save" parameterType="com.southwind.entity.Account"> insert into t_account(username,password,age) values(#{username},# {password},#{age}) </insert> <update id="update" parameterType="com.southwind.entity.Account"> update t_account set username = #{username},password = #{password},age = #{age} where id = #{id} </update> <delete id="deleteById" parameterType="long"> delete from t_account where id = #{id} </delete> <select id="findAll" resultType="com.southwind.entity.Account"> select * from t_account </select> <select id="findById" parameterType="long" resultType="com.southwind.entity.Account"> select * from t_account where id = #{id} </select> </mapper>
调⽤接⼝的代理对象完成相关的业务操作
public class Test { public static void main(String[] args) { InputStream inputStream = Test.class.getClassLoader().getResourceAsStream("config.xml"); SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder(); SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream); SqlSession sqlSession = sqlSessionFactory.openSession(); //获取实现接⼝的代理对象 AccountRepository accountRepository = sqlSession.getMapper(AccountRepository.class); //添加对象 // Account account = new Account(3L,"王五","111111",24); // int result = accountRepository.save(account); // sqlSession.commit(); //查询全部对象 // List<Account> list = accountRepository.findAll(); // for (Account account:list){ // System.out.println(account); // } // sqlSession.close(); //通过id查询对象 // Account account = accountRepository.findById(3L); // System.out.println(account); // sqlSession.close(); //修改对象 // Account account = accountRepository.findById(3L); // account.setUsername("⼩明"); // account.setPassword("000"); // account.setAge(18); // int result = accountRepository.update(account); // sqlSession.commit(); // System.out.println(result); // sqlSession.close(); //通过id删除对象 int result = accountRepository.deleteById(3L); System.out.println(result); sqlSession.commit(); sqlSession.close(); } }
