SpringBoot+MyBatis 简单分页功能

迷南。 2022-05-11 15:03 157阅读 0赞

### 项目结构： ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9sdWNpZmVyLmJsb2cuY3Nkbi5uZXQ_size_16_color_FFFFFF_t_70][]

**说明：**我这里创建了controller包（存放controller层类）、mapper包（存放mapper接口）、pojo包（存放实体类）、service包（存放service接口及实现类）、dto包（存放从前端传过来的数据）。通常pojo中的数据，不可能全部用到，也许只用到了部分，这时候可以用dto层。

### **pom.xml:（并不是pom.xml完整内容，但是是所用到的所有包）** ###

<parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.1.1.RELEASE</version>
            <relativePath/> 
        </parent>
    
     <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <optional>true</optional>
            </dependency>
            <dependency>
                <groupId>com.github.pagehelper</groupId>
                <artifactId>pagehelper</artifactId>
                <version>5.1.2</version>
            </dependency>
            <dependency>
                <groupId>tk.mybatis</groupId>
                <artifactId>mapper-spring-boot-starter</artifactId>
                <version>2.0.4</version>
            </dependency>
            <dependency>
                <groupId>org.mybatis.spring.boot</groupId>
                <artifactId>mybatis-spring-boot-starter</artifactId>
                <version>1.3.2</version>
            </dependency>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>

### pojo:实体类  ###

package com.lucifer.test.pojo;
    
    import lombok.Data;
    
    /**
     * 实体类
     */
    @Data
    public class User {
    
        private int id;
        private String name;
        private int age;
        private String sex;
    }

使用lombok包的@Data注解，避免写繁琐的get、set、toString方法。并且可以使实体类更加简洁。

### dto:从前端传过来的数据 ###

package com.lucifer.test.vo;
    
    import lombok.Data;
    
    @Data
    public class UserDto {
        private String name;
        /**
         * 每页大小
         */
        private int pageSize;
        /**
         * 页码
         */
        private int pageNum;
    }

### mapper接口： （这里继承了通用mapper接口，但是目前这个demo没有用到，只用到了自定义mapper） ###

package com.lucifer.test.mapper;
    
    import com.lucifer.test.pojo.User;
    import org.apache.ibatis.annotations.Select;
    import tk.mybatis.mapper.common.BaseMapper;
    import tk.mybatis.mapper.common.MySqlMapper;
    
    import java.util.List;
    
    /**
     * mapper接口
     */
    public interface UserMapper extends BaseMapper<User>, MySqlMapper<User> {
    
        @Select("select * from user where name=#{name}")
        public List<User> findByName(String name);
    }

### userService接口：  ###

package com.lucifer.test.service;
    
    
    import com.github.pagehelper.PageInfo;
    import com.lucifer.test.dto.UserDto;
    
    
    public interface UserService {
    
        /**
         * 分页
         *
         * @param userDto
         * @return
         */
        PageInfo findByNamePage(UserDto userDto);
    }

### UserServiceImpl ：实现类 ###

package com.lucifer.test.service;
    
    import com.github.pagehelper.PageHelper;
    import com.github.pagehelper.PageInfo;
    import com.lucifer.test.mapper.UserMapper;
    import com.lucifer.test.pojo.User;
    import com.lucifer.test.dto.UserDto;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    import java.util.List;
    
    @Service
    public class UserServiceImpl implements UserService {
    
        @Autowired
        private UserMapper userMapper;
    
        @Override
        public PageInfo findByNamePage(UserDto userDto) {
            PageHelper.startPage(userDto.getPageNum(), userDto.getPageSize());
            
            List<User> userList = userMapper.findByName(userDto.getName());
            
            PageInfo<User> pageInfo = new PageInfo<>(userList);
            return pageInfo;
        }
    }

### 注：参考：[MyBatis 分页插件 PageHelper（官网）][MyBatis _ PageHelper] ###

**官方示例中：可以看出PageHelper调用api,需要在sql之前执行。**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3NDk1Nzg2_size_16_color_FFFFFF_t_70][]

**注：官方给的提示，PageHelper分页后多次查询，只会对第一条分页，后面的需要再次调用分页API。 **

### ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3NDk1Nzg2_size_16_color_FFFFFF_t_70 1][] ###

### controller： 控制层 ###

package com.lucifer.test.controller;
    
    import com.github.pagehelper.PageInfo;
    import com.lucifer.test.service.UserService;
    import com.lucifer.test.dto.UserDto;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.PostMapping;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RestController;
    
    /**
     * 控制层
     */
    @RestController
    @RequestMapping("lucifer")
    public class UserController {
    
        @Autowired
        private UserService userService;
    
        /**
         * 根据name分页
         *
         * @param userDto
         * @return
         */
        @PostMapping(value = "page")
        public PageInfo selectByUserNamePage(@RequestBody UserDto userDto) {
            return userService.findByNamePage(userDto);
        }
    }

### **spring boot的启动类**： ###

package com.lucifer.test;
    
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    import tk.mybatis.spring.annotation.MapperScan;
    
    @SpringBootApplication
    @MapperScan(value = "com.lucifer.test.mapper")
    public class TestApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(TestApplication.class, args);
        }
    
    }

**加上@MapperScan注解，避免繁琐的在每个mapper接口中加上@Mapper注解。**

### application.yml：  ###

#数据库连接配置#
    spring:
      datasource:
        username: root
        password: 123456
        url: jdbc:mysql://192.168.160.129:3306/test?autoReconnect=true&useUnicode=true&createDatabaseIfNotExist=true&characterEncoding=utf8&serverTimezone=UTC
      #  driverClassName: com.mysql.jdbc.Driver
    #开启驼峰命名、指定mapper文件位置#
    #mybatis:
    #  configuration:
    #    map-underscore-to-camel-case: true
    #  mapper-locations: classpath:mybatis/*.xml
    #控制台打印sql语句，指定自己的mapper接口路径#
    logging:
      level:
        com.lucifer.test.mapper: debug

### 注： ###

application.yml中的配置很重要，数据库的配置最好和我类似，如果你的url不是跟我的类似：

url: jdbc:mysql://ip地址:3306/数据库名?autoReconnect=true&useUnicode=true&createDatabaseIfNotExist=true&characterEncoding=utf8&serverTimezone=UTC

而是这种：

url: jdbc:mysql://ip地址:3306/数据库名

那么你很大可能存在着数据库有值，却在项目中查询不到任何数据，显示是0条。

### 测试结果： ###

我这里是用postman测试：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3NDk1Nzg2_size_16_color_FFFFFF_t_70 2][]

返回结果：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3NDk1Nzg2_size_16_color_FFFFFF_t_70 3][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9sdWNpZmVyLmJsb2cuY3Nkbi5uZXQ_size_16_color_FFFFFF_t_70]: /images/20220505/0ed9149057314f52888bf98ae41becff.png
[MyBatis _ PageHelper]: https://pagehelper.github.io/docs/howtouse/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3NDk1Nzg2_size_16_color_FFFFFF_t_70]: /images/20220505/7bd17b13b9ad48029bc11fe1c4af347e.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3NDk1Nzg2_size_16_color_FFFFFF_t_70 1]: /images/20220505/3048985e01134951ae67be7063989fa7.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3NDk1Nzg2_size_16_color_FFFFFF_t_70 2]: /images/20220505/139b37c348b74813bc9a07d84a64e375.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3NDk1Nzg2_size_16_color_FFFFFF_t_70 3]: /images/20220505/f054e2dba0804dc0b858ec24b3cb1af5.png