引入依赖
<!-- 通用Mapper插件
文档地址：https://gitee.com/free/Mapper/wikis/Home -->
<dependency>
<groupId>tk.mybatis</groupId>
<artifactId>mapper-spring-boot-starter</artifactId>
<version>2.0.2</version>
</dependency>
<!-- 分页插件
文档地址：https://github.com/pagehelper/Mybatis-PageHelper/blob/master/wikis/zh/HowToUse.md -->
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper-spring-boot-starter</artifactId>
<version>1.2.5</version>
</dependency>
数据源配置
spring.datasource.url=jdbc:mysql://localhost:3306/chapter7?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull&allowMultiQueries=true&useSSL=false
spring.datasource.password=root
spring.datasource.username=root
# 如果想看到mybatis日志需要做如下配置
logging.level.com.battcn=DEBUG
########## Mybatis 自身配置 ##########
mybatis.mapper-locations=classpath:com/battcn/mapper/*.xml
mybatis.type-aliases-package=com.battcn.entity
# 驼峰命名规范 如：数据库字段是 order_id 那么 实体字段就要写成 orderId
mybatis.configuration.map-underscore-to-camel-case=true
########## 通用Mapper ##########
# 主键自增回写方法,默认值MYSQL,详细说明请看文档
mapper.identity=MYSQL
mapper.mappers=tk.mybatis.mapper.common.BaseMapper
# 设置 insert 和 update 中，是否判断字符串类型!=''
mapper.not-empty=true
# 枚举按简单类型处理
mapper.enum-as-simple-type=true
########## 分页插件 ##########
pagehelper.helper-dialect=mysql
pagehelper.params=count=countSql
pagehelper.reasonable=false
pagehelper.support-methods-arguments=true
通用Mapper配置：
mapper.enum-as-simple-type： 枚举按简单类型处理，如果有枚举字段则需要加上该配置才会做映射
mapper.not-empty： 设置以后，会去判断 insert 和 update 中符串类型!=’’
分页插件配置：
pagehelper.reasonable： 分页合理化参数，默认值为false。当该参数设置为 true 时，pageNum<=0 时会查询第一页， pageNum>pages（超过总数时），会查询最后一页。默认false 时，直接根据参数进行查询。
support-methods-arguments： 支持通过 Mapper 接口参数来传递分页参数，默认值false，分页插件会从查询方法的参数值中，自动根据上面 params 配置的字段中取值，查找到合适的值时就会自动分页。
实体Model
@Getter
@Setter
@Table(name = "t_user") ---此处与JPA使用的注解不一样
public class User3 implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String username;
private String password;
public User3() {}
public User3(String username, String password) {
this.username = username;
this.password = password;
}
}
UserMapper
UserMapper.java
@Mapper
public interface UserMapper2 extends BaseMapper<User>{
/**
* 根据用户名统计（TODO 假设它是一个很复杂的SQL）
*
* @param username 用户名
* @return 统计结果
*/
int countByUsername(String username);
}
UserMapper.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" >
<mapper namespace="xin.rtime.mapper.UserMapper2">
<select id="countByUsername" resultType="java.lang.Integer">
SELECT count(1) FROM t_user WHERE username = #{username}
</select>
</mapper>
示例验证
@EnableAutoConfiguration
@RunWith(SpringRunner.class)
@SpringBootTest(classes = Chapter7Application.class, webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class Chapter7ApplicationTests {
private static final Logger log = LoggerFactory.getLogger(Chapter7Application.class);
@Autowired
private UserMapper2 userMapper;
@Test
public void test1() throws Exception {
final User3 user1 = new User3("u1", "p1");
final User3 user2 = new User3("u1", "p2");
final User3 user3 = new User3("u3", "p3");
userMapper.insertSelective(user1);
log.info("[user1回写主键] - [{}]", user1.getId());
userMapper.insertSelective(user2);
log.info("[user2回写主键] - [{}]", user2.getId());
userMapper.insertSelective(user3);
log.info("[user3回写主键] - [{}]", user3.getId());
final int count = userMapper.countByUsername("u1");
log.info("[调用自己写的SQL] - [{}]", count);
// TODO 模拟分页
userMapper.insertSelective(new User3("u1", "p1"));
userMapper.insertSelective(new User3("u1", "p1"));
userMapper.insertSelective(new User3("u1", "p1"));
userMapper.insertSelective(new User3("u1", "p1"));
userMapper.insertSelective(new User3("u1", "p1"));
userMapper.insertSelective(new User3("u1", "p1"));
userMapper.insertSelective(new User3("u1", "p1"));
userMapper.insertSelective(new User3("u1", "p1"));
userMapper.insertSelective(new User3("u1", "p1"));
userMapper.insertSelective(new User3("u1", "p1"));
// TODO 分页 + 排序 this.userMapper.selectAll() 这一句就是我们需要写的查询，有了这两款插件无缝切换各种数据库
final PageInfo<Object> pageInfo = PageHelper.startPage(1, 10).setOrderBy("id desc").doSelectPageInfo(() -> this.userMapper.selectAll());
log.info("[lambda写法] - [分页信息] - [{}]", pageInfo.toString());
PageHelper.startPage(1, 10).setOrderBy("id desc");
final PageInfo<User3> userPageInfo = new PageInfo<>(this.userMapper.selectAll());
log.info("[普通写法] - [{}]", userPageInfo);
}
}