通用Mapper

1.引入坐标

<dependency>
    <groupId>tk.mybatis</groupId>
    <artifactId>mapper</artifactId>
    <version>3.1.2</version>
</dependency> 

2.sqlMapConfig.xml中配置插件类

<plugins>
    <plugin interceptor="tk.mybatis.mapper.mapperhelper.MapperInterceptor">
        <!--通用Mapper接口,多个通用接口用逗号隔开-->
        <property name="mappers" value="tk.mybatis.mapper.common.Mapper"/>
    </plugin>
</plugins> 

3.使用注解配置实体类

@Table(name = "t_user")//表名
    public class User {
    @Id//主键
    @GeneratedValue(strategy = GenerationType.IDENTITY)//主键生成策略
    private Integer id;
    private String username;
} 

4.定义通用mapper接口

public interface UserMapper extends Mapper<User> {
} 

5.使用

//select

User user = userMapper.selectOne(user);  //只返回一条

List<User> users = userMapper.select(null); //查询全部

//insert

int insert = userMapper.insert(user); //null值会保存

int i = userMapper.insertSelective(user); //null值不会保存