该篇博客记录采用pagehelper分页插件实现Mybatis分页功能

一、依赖

• pom.xml

<!-- pagehelper -->
<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper-spring-boot-starter</artifactId>
    <version>1.2.5</version>
</dependency>

二、配置

• application.yml

# pagehelper
pagehelper:
   helperDialect: mysql
   reasonable: true
   supportMethodsArguments: true
params: count=countSql

• CURD通用接口封装

public interface CurdService<T> {
    /**
     * 分页查询
     * 这里统一封装了分页请求和结果，避免直接引入具体框架的分页对象, 如MyBatis或JPA的分页对象
     * 从而避免因为替换ORM框架而导致服务层、控制层的分页接口也需要变动的情况，替换ORM框架也不会
     * 影响服务层以上的分页接口，起到了解耦的作用
     * @param pageRequest 自定义，统一分页查询请求
     * @return PageResult 自定义，统一分页查询结果
     */
    PageResult findPage(PageRequest pageRequest);
}

• 分页请求封装

public class PageRequest {
    /**
     * 当前页码
     */
    private int pageNum = 1;
    /**
     * 每页数量
     */
    private int pageSize = 10;
    /**
     * 查询参数
     */
    private Map<String, Object> params = new HashMap<>();
    
    public int getPageNum() {
        return pageNum;
    }
    public void setPageNum(int pageNum) {
        this.pageNum = pageNum;
    }
    public int getPageSize() {
        return pageSize;
    }
    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }
    public Map<String, Object> getParams() {
        return params;
    }
    public void setParams(Map<String, Object> params) {
        this.params = params;
    }
    public Object getParam(String key) {
        return getParams().get(key);
    }
}

• 分页结果封装

public class PageResult {
    /**
     * 当前页码
     */
    private int pageNum;
    /**
     * 每页数量
     */
    private int pageSize;
    /**
     * 记录总数
     */
    private long totalSize;
    /**
     * 页码总数
     */
    private int totalPages;
    /**
     * 分页数据
     */
    private List<?> content;
    public int getPageNum() {
        return pageNum;
    }
    public void setPageNum(int pageNum) {
        this.pageNum = pageNum;
    }
    public int getPageSize() {
        return pageSize;
    }
    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }
    public long getTotalSize() {
        return totalSize;
    }
    public void setTotalSize(long totalSize) {
        this.totalSize = totalSize;
    }
    public int getTotalPages() {
        return totalPages;
    }
    public void setTotalPages(int totalPages) {
        this.totalPages = totalPages;
    }
    public List<?> getContent() {
        return content;
    }
    public void setContent(List<?> content) {
        this.content = content;
    }
}

• 分页助手封装

public class MybatisPageHelper {

    public static final String findPage = "findPage";
    
    /**
     * 分页查询, 约定查询方法名为 “findPage” 
     * @param pageRequest 分页请求
     * @param mapper Dao对象，MyBatis的 Mapper  
     * @param args 方法参数
     * @return
     */
    public static PageResult findPage(PageRequest pageRequest, Object mapper) {
        return findPage(pageRequest, mapper, findPage);
    }
    
    /**
     * 调用分页插件进行分页查询
     * @param pageRequest 分页请求
     * @param mapper Dao对象，MyBatis的 Mapper  
     * @param queryMethodName 要分页的查询方法名
     * @param args 方法参数
     * @return
     */
    @SuppressWarnings({ "unchecked", "rawtypes" })
    public static PageResult findPage(PageRequest pageRequest, Object mapper, String queryMethodName, Object... args) {
        // 设置分页参数
        int pageNum = pageRequest.getPageNum();
        int pageSize = pageRequest.getPageSize();
        PageHelper.startPage(pageNum, pageSize);
        // 利用反射调用查询方法
        Object result = ReflectionUtils.invoke(mapper, queryMethodName, args);
        return getPageResult(pageRequest, new PageInfo((List) result));
    }

    /**
     * 将分页信息封装到统一的接口
     * @param pageRequest 
     * @param page
     * @return
     */
    private static PageResult getPageResult(PageRequest pageRequest, PageInfo<?> pageInfo) {
        PageResult pageResult = new PageResult();
        pageResult.setPageNum(pageInfo.getPageNum());
        pageResult.setPageSize(pageInfo.getPageSize());
        pageResult.setTotalSize(pageInfo.getTotal());
        pageResult.setTotalPages(pageInfo.getPages());
        pageResult.setContent(pageInfo.getList());
        return pageResult;
    }
}

• HTTP返回结果封装

public class HttpResult {
    private int code = 200;
    private String msg;
    private Object data;
    
    public static HttpResult error() {
        return error(HttpStatus.SC_INTERNAL_SERVER_ERROR, "未知异常，请联系管理员");
    }
    public static HttpResult error(String msg) {
        return error(HttpStatus.SC_INTERNAL_SERVER_ERROR, msg);
    }
    public static HttpResult error(int code, String msg) {
        HttpResult r = new HttpResult();
        r.setCode(code);
        r.setMsg(msg);
        return r;
    }
    public static HttpResult ok(String msg) {
        HttpResult r = new HttpResult();
        r.setMsg(msg);
        return r;
    }
    public static HttpResult ok(Object data) {
        HttpResult r = new HttpResult();
        r.setData(data);
        return r;
    }
    public static HttpResult ok() {
        return new HttpResult();
    }
    public int getCode() {
        return code;
    }
    public void setCode(int code) {
        this.code = code;
    }
    public String getMsg() {
        return msg;
    }
    public void setMsg(String msg) {
        this.msg = msg;
    }
    public Object getData() {
        return data;
    }
    public void setData(Object data) {
        this.data = data;
    }
}

三、实现

• SysUserController.java

@RestController
@RequestMapping("/user")
public class SysUserController {

    @Autowired
    private SysUserService sysUserService;
    
    @PostMapping(value="/findPage")
    public HttpResult findPage(@RequestBody PageRequest pageRequest) {
        return HttpResult.ok(sysUserService.findPage(pageRequest));
    }
}

• SysUserService.java

public interface SysUserService extends CurdService<SysUser> {

}

• SysUserMapper.java

public interface SysUserMapper {
    List<SysUser> findPage();
}

• SysUserServiceImpl.java

//经过对分页查询业务的封装，只需调用MybatisPageHelper.findPage(pageRequest, sysUserMapper)即可实现分页查询功能
@Service
public class SysUserServiceImpl implements SysUserService {

    @Autowired
    private SysUserMapper sysUserMapper;
    
    @Override
    public PageResult findPage(PageRequest pageRequest) {
        return MybatisPageHelper.findPage(pageRequest, sysUserMapper);
    }
}

• SysUserMapper.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="com.coisini.admin.mapper.SysUserMapper">
  <resultMap id="BaseResultMap" type="com.coisini.admin.entity.SysUser">
    <id column="id" jdbcType="BIGINT" property="id" />
    <result column="name" jdbcType="VARCHAR" property="name" />
    <result column="nick_name" jdbcType="VARCHAR" property="nickName" />
    <result column="avatar" jdbcType="VARCHAR" property="avatar" />
    <result column="password" jdbcType="VARCHAR" property="password" />
    <result column="salt" jdbcType="VARCHAR" property="salt" />
    <result column="email" jdbcType="VARCHAR" property="email" />
    <result column="mobile" jdbcType="VARCHAR" property="mobile" />
    <result column="status" jdbcType="TINYINT" property="status" />
    <result column="dept_id" jdbcType="BIGINT" property="deptId" />
    <result column="create_by" jdbcType="VARCHAR" property="createBy" />
    <result column="create_time" jdbcType="TIMESTAMP" property="createTime" />
    <result column="last_update_by" jdbcType="VARCHAR" property="lastUpdateBy" />
    <result column="last_update_time" jdbcType="TIMESTAMP" property="lastUpdateTime" />
    <result column="del_flag" jdbcType="TINYINT" property="delFlag" />
  </resultMap>
  <sql id="Base_Column_List">
    id, name, nick_name, avatar, password, salt, email, mobile, status, dept_id, create_by, 
    create_time, last_update_by, last_update_time, del_flag
  </sql>
  <select id="findPage" resultMap="BaseResultMap">
    select u.*, (select d.name from sys_dept d where d.id = u.dept_id) deptName from sys_user u
  </select>
</mapper>

四、测试

• 关于如何集成Mybatis，参考：mybatis 生成代码配置 mybatis-generator:generate 的使用详解，前半部分有详细的POM代码