1. Introduce dependencies

<! -- mybatis -->

<dependency>

	<groupId>org.mybatis.spring.boot</groupId>

	<artifactId>mybatis-spring-boot-starter</artifactId>

	<version>2.0.0</version>

</dependency>

<! 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 connection pool -->

<dependency>

	<groupId>com.alibaba</groupId>

	<artifactId>druid-spring-boot-starter</artifactId>

	<version>1.1.14</version>

</dependency>

<! -- Paging plugin -->

<dependency>

	<groupId>com.github.pagehelper</groupId>

	<artifactId>pagehelper-spring-boot-starter</artifactId>

	<version>1.2.10</version>

</dependency>

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2. Modify the configuration file

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:

  Load the mapper file

  mapper-locations: classpath:mapper/*.xml

  Set the entity category name

  #type-aliases-package: demo.springboot.mybatismapperpagehelper.domain

  Load mybatis global configuration file

  #config-location: classpath:mybatis/SqlMapConfig.xml



mapper:

  # Generic mapper class, can be multiple, do not put together with the business DAO

  mappers: demo.springboot.mybatismapperpagehelper.basedao.BaseMapper

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3.BaseMapper

// Inherit the interface from tkmapper

// add, delete, change, query, etc

//MySqlMapper is a set of operations on mysql

public interface BaseMapper<T> extends Mapper<T>, MySqlMapper<T> {

}

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4. The entity class

@Data

public class SysUser {

    // Query by primary key must have @id annotation, otherwise an error will be reported

    @Id

    private Long id;



    private String username;



    private String password;



    private String nickname;



    private Integer age;

}

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5.DAO

// Inheriting BaseMapper from step 3, generics are entity classes

public interface SysUserDAO extends BaseMapper<SysUser> {

}

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6. Scan the dao

@SpringBootApplication

// The scan annotations used here are not mybatis annotations, but general mapper annotations

@MapperScan("demo.springboot.mybatismapperpagehelper.dao")

public class MybatisMapperPagehelperApplication {



    public static void main(String[] args) {

        SpringApplication.run(MybatisMapperPagehelperApplication.class, args);

    }



}

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7. Test

@RunWith(SpringRunner.class)

@SpringBootTest

public class MybatisMapperPagehelperApplicationTests {



    @Autowired

    private SysUserDAO userDAO;



    @Test

    public void testSelectByPrimaryKey(a) {

        // Query by primary key

        SysUser sysUser = userDAO.selectByPrimaryKey(1L);

        System.out.println(sysUser);

    }



    @Test

    public void testSelectAll(a) {

        // Query all data

        List<SysUser> sysUsers = userDAO.selectAll();

        System.out.println(sysUsers);

    }



    @Test

    public void testPageHelper(a){

        // The first argument is the number of pages, and the second argument is the number of pages. For the first SQL after this method,

        // Single table paging, one-to-one paging is correct. One-to-many, many-to-many paging causes an error

        //PageHelper.startPage(1, 10);

        Sort by id in reverse order

        PageHelper.startPage(1.2."id desc");

        List<SysUser> sysUsers = userDAO.selectAll();

        

        // Get paging data

        PageInfo<SysUser> pageInfo = new PageInfo<>(sysUsers);

        // Get the total number of entries

        System.out.println(pageInfo.getTotal());

        // Get the number of paging pages

        System.out.println(pageInfo.getPageNum());

        // Get the number of paging bars

        System.out.println(pageInfo.getPageSize());

        // Get the paging data, which is the sysUsers queried above

        System.out.println(pageInfo.getList());

    }

}

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  • Test according to the primary key query console logs: = = > Preparing: SELECT id, username, password and nickname, age FROM sys_user WHERE id =? ==> Parameters: 1(Long) <== Total: 1

  • Test all console log data query: = = > Preparing: SELECT id, username, password and nickname, age FROM sys_user = = > Parameters: < = = Total: 3

  • Preparing: SELECT ID, username, password, nickname, age FROM sys_user order by ID desc LIMIT? ==> Parameters: 2(Integer) <== Total: 2

Note: General mapper can only do some simple operations, business complex also need to be manually implemented. The paging plug-in does not need to format the number of pages ((pagenum-1)*pageSize) that you need to format when writing your own SQL

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