springboot整合mybatis+通用mapper+分页插件

1.引入依赖

<!-- mybatis -->
<dependency>
	<groupId>org.mybatis.spring.boot</groupId>
	<artifactId>mybatis-spring-boot-starter</artifactId>
	<version>2.0.0</version>
</dependency>
<!-- 通用mapper -->
<dependency>
	<groupId>tk.mybatis</groupId>
	<artifactId>mapper-spring-boot-starter</artifactId>
	<version>2.0.0</version>
</dependency>
<!-- mysql -->
<dependency>
	<groupId>mysql</groupId>
	<artifactId>mysql-connector-java</artifactId>
	<scope>runtime</scope>
</dependency>
<!-- druid连接池 -->
<dependency>
	<groupId>com.alibaba</groupId>
	<artifactId>druid-spring-boot-starter</artifactId>
	<version>1.1.14</version>
</dependency>
<!-- 分页插件 -->
<dependency>
	<groupId>com.github.pagehelper</groupId>
	<artifactId>pagehelper-spring-boot-starter</artifactId>
	<version>1.2.10</version>
</dependency>

2.修改配置文件

server:
  port: 8080

spring:
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/admin?useUnicode=true&characterEncoding=UTF-8&useSSL=false
    username: root
    password: root

mybatis:
  #加载mapper文件
  mapper-locations: classpath:mapper/*.xml
  #设置实体类别名
  #type-aliases-package: demo.springboot.mybatismapperpagehelper.domain
  #加载mybatis全局配置文件
  #config-location: classpath:mybatis/SqlMapConfig.xml

mapper:
  #通用mapper的类，可以多个，不要和业务dao放到一起
  mappers: demo.springboot.mybatismapperpagehelper.basedao.BaseMapper

3.BaseMapper

//继承tkmapper中的接口，更多可查看官方文档
//Mapper是基础的增删改查，根据Example查询等
//MySqlMapper是对mysql的一些操作
public interface BaseMapper<T> extends Mapper<T>, MySqlMapper<T> {
}

4.实体类

@Data
public class SysUser {
    //根据主键查询时必须要有@Id注解，否则会报错
    @Id
    private Long id;

    private String username;

    private String password;

    private String nickname;

    private Integer age;
}

5.DAO

//继承第三步中的BaseMapper，泛型是实体类
public interface SysUserDAO extends BaseMapper<SysUser> {
}

6.扫描dao

@SpringBootApplication
//这里使用的扫描注解不是mybatis的，是通用mapper的注解
@MapperScan("demo.springboot.mybatismapperpagehelper.dao")
public class MybatisMapperPagehelperApplication {

    public static void main(String[] args) {
        SpringApplication.run(MybatisMapperPagehelperApplication.class, args);
    }

}

7.测试

@RunWith(SpringRunner.class)
@SpringBootTest
public class MybatisMapperPagehelperApplicationTests {

    @Autowired
    private SysUserDAO userDAO;

    @Test
    public void testSelectByPrimaryKey() {
        //根据主键查询
        SysUser sysUser = userDAO.selectByPrimaryKey(1L);
        System.out.println(sysUser);
    }

    @Test
    public void testSelectAll() {
        //查询所有数据
        List<SysUser> sysUsers = userDAO.selectAll();
        System.out.println(sysUsers);
    }

    @Test
    public void testPageHelper(){
        //第一个参数为页数，第二个为条数。对这个方法后的第一个sql生效，
        //单表分页，一对一分页正确。一对多，多对多分页会出现错误
        //PageHelper.startPage(1, 10);
        //根据id倒序排序
        PageHelper.startPage(1, 2, "id desc");
        List<SysUser> sysUsers = userDAO.selectAll();
        
        //获取分页数据
        PageInfo<SysUser> pageInfo = new PageInfo<>(sysUsers);
        //获取总条数
        System.out.println(pageInfo.getTotal());
        //获取分页页数
        System.out.println(pageInfo.getPageNum());
        //获取分页条数
        System.out.println(pageInfo.getPageSize());
        //获取分页数据，即上面查询到的sysUsers
        System.out.println(pageInfo.getList());
    }
}

• 测试根据主键查询
  控制台日志：
  ==> Preparing: SELECT id,username,password,nickname,age FROM sys_user WHERE id = ?
==> Parameters: 1(Long)
<== Total: 1

• 测试查询所有数据
  控制台日志：
  ==> Preparing: SELECT id,username,password,nickname,age FROM sys_user
==> Parameters:
<== Total: 3

• 测试分页插件
  控制台日志：
  ==> Preparing: SELECT id, username, password, nickname, age FROM sys_user order by id desc LIMIT ?
==> Parameters: 2(Integer)
<== Total: 2

注：通用mapper只能做一些简单的操作，业务复杂的还需要自己手动实现。
分页插件不需要格式化页数（(pageNum-1)*pageSize）,自己写sql时需要格式化页数

项目路径

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