Mybatis后台物理分页查询

　　分页查询在日常开发中是非常常见的，往往分为逻辑分页、物理分页。如果数据量较大，对内存、网络传输的消耗非常大的时候选择物理分页。
本章节我们主要讲物理分页查询，以一个例子展开，把B库的user表每次查询100条循环查询并批量插入A库的user表中。
　　我们的项目框架是jeesite，首先我们为项目配置A库，B库数据源，见配置多数据源文章。下面我们将列举此功能的代码：

1.Controller代码：

@Controller
@RequestMapping(value = "${adminPath}/acm/syncuser")
public class SyncuserController extends BaseController {
    @Autowired
    private LocalUserService localUserService;
    @Autowired
    private RemoteUserService remoteUserService;
    @Autowired
    private UserDao userDao;
    
    @ModelAttribute
    public User get(@RequestParam(required = false) String id) {
        if (StringUtils.isNotBlank(id)) {
            return userService.get(id);
        } else {
            return new User();
        }
    }
     /**
     *根据数据条数与每页多少条数据计算页数 
     * totalNum 数据条数
     * pageSize 每页多少条
     * 
     */
   public int pageCount (int totalNum,int pageSize){
       return totalNum > 0 ? ((totalNum < pageSize) ? 1 : ((totalNum % pageSize)==0 ? ((totalNum / pageSize) + 1) : (totalNum / pageSize))) : 0;
    }  
    

    /**
         * 同步
         * 
         * @param user
         * @param model
         * @return
         * @throws Exception
         */
    @RequiresPermissions("acm:syncuser:edit")
    @RequestMapping(value = "sync")
    public String syncUserData(User user, Model model) {
        //本地用户表保存获取的远程用户表数据的前要清空本地用户表
                localUserService.truncateTable();
        //远程用户表行数
        int count = remoteUserService.rowsCount();
        int totalPage = pageCount(count,Integer.parseInt(Global.getConfig("pagesize")));//每页pagesize条数据时得总共页数,pagesize在配置文件中配置
        Map map = new HashMap();
        for(int i = 1;i<=totalPage;i++ ) {
            map.put("page", (i-1)*Integer.parseInt(Global.getConfig("pagesize")));
            map.put("rows", Integer.parseInt(Global.getConfig("pagesize")));
            List<User> remoteUserList = remoteUserService.findList(map);
            if(remoteUserList.size()>0) {
                userDao.insertBath(remoteUserList);
            }
         }
    }

}

2.Entity代码：

public class User extends DataEntity<User>{
    private String code ;//可读标识
    private String name  ;//名称
    private String appType ;
    private String ownerDomainId ;
    private Integer sort;//排序号
    private String memo ;//描述
    private String iconId ;//图标id
    private String url1;//扩展url字段1
    private String url2  ;//扩展url字段2
    private String url3 ;//扩展url字段3
    private String url4;//扩展url字段4
    private String secretkey ;//秘钥
    private String scope;
//省略get，set方法
    }

3.Service代码:

@Service
@Transactional(readOnly = true)
public class LocalUserService extends CrudService<UserDao, User>{
    public User get(String id) {
        return dao.get(id);
    }
    public Page<User> findPage(Page<User> page, User user) {
        user.setPage(page);
        page.setList(dao.findList(user));
        return page;
      }
    public List<User> findList(User user) {
        return super.findList(user);
    }
    
    @Transactional(readOnly = false)
    public void update(User user) {
        dao.update(user);
    }
    
    @Transactional(readOnly = false)
    public void save(User user) {
        dao.insert(user);
    }
    
    @Transactional(readOnly = false)
    public void truncateTable() {
        dao.truncateTable();
    }
}

@DynamicDataSourceAnnotation
@Service
public class RemoteUserService extends CrudService<RemoteUserDao, User>{
    @DynamicDataSourceAnnotation(dataSource = DataSourceContextHolder.DATA_SOURCE_DRAP)
    public User get(String id) {
        return dao.get(id);
    }
    @DynamicDataSourceAnnotation(dataSource = DataSourceContextHolder.DATA_SOURCE_DRAP)
    public Page<User> findPage(Page<User> page, User user) {
        user.setPage(page);
        page.setList(dao.findList(user));
        return page;
      }
    @DynamicDataSourceAnnotation(dataSource = DataSourceContextHolder.DATA_SOURCE_DRAP)
    public List<user> findList(Map map) {
        return dao.findList(map);
    }
    @DynamicDataSourceAnnotation(dataSource = DataSourceContextHolder.DATA_SOURCE_DRAP)
    public int rowsCount() {
       return dao.rowsCount();
    }
   
}

4.Dao代码:

@MyBatisDao
public interface UserDao  extends CrudDao<User>{
    public void truncateTable();
    public int insertBath(List<User>list);
}

@MyBatisDao
public interface RemoteUserDao  extends CrudDao<User>{
    public List<User> findList(@Param("map")Map<String,Object> map);
    public int rowsCount();
}

5.xml代码:

<?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="dms.microservice.databak.dao.UserDao">
   
    <sql id="userSycnColumns">
        a.id AS "id",
        a.code AS "code",
        a.name AS "name",
        a.app_type AS "appType",
        a.owner_domain_id AS "ownerDomainId",
        a.sort AS "sort",
        a.memo AS "memo",
        a.icon_id AS "iconId",
        a.url1 AS "url1",
        a.url2 AS "url2",
        a.url3 AS "url3",
        a.url4 AS "url4",
        a.secret_key AS "secretkey",
        a.scope AS "scope"
    </sql>
    
    
    <insert id="insertBath" parameterType="java.util.List">
        INSERT INTO PT_USER
        (id ,
            code ,
            name ,
            app_type ,
            owner_domain_id ,
            sort ,
            memo,
            icon_id ,
            url1 ,
            url2 ,
            url3  ,
            url4 ,
            secret_key ,
            scope)
        VALUES
        <foreach collection="list" item="item" index="index"
            separator=",">
            (
                #{item.id},
                #{item.code},
                #{item.name},
                #{item.appType},
                #{item.ownerDomainId},
                #{item.sort},
                #{item.memo},
                #{item.iconId},
                #{item.url1},
                #{item.url2},
                #{item.url3},
                #{item.url4},
                #{item.secretkey},
                #{item.scope}
            )
        </foreach>
    </insert>
    
    <update id="truncateTable">
        truncate table PT_USER
    </update>    
</mapper>

<?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="dms.microservice.databak.dao.RemoteUserDao">
    
    <sql id="userSycnColumns">
        a.id AS "id",
        a.code AS "code",
        a.name AS "name",
        a.app_type AS "appType",
        a.owner_domain_id AS "ownerDomainId",
        a.sort AS "sort",
        a.memo AS "memo",
        a.icon_id AS "iconId",
        a.url1 AS "url1",
        a.url2 AS "url2",
        a.url3 AS "url3",
        a.url4 AS "url4",
        a.secret_key AS "secretkey",
        a.scope AS "scope"
    </sql>
    
    
    <sql id="userSyncJoins">
    </sql>
    
    <select id="get" resultType="PtApp">
        SELECT 
            <include refid="userSycnColumns"/>
        FROM PT_USER a
        <include refid="userSyncJoins"/>
        WHERE a.id = #{id}
    </select>
    
    <select id="findList" resultType="PtApp">
        SELECT 
            <include refid="userSycnColumns"/>
        FROM PT_USER a
        <include refid="userSyncJoins"/>
        WHERE 1=1
        LIMIT #{map.page},#{map.rows}
    </select>
    
    <select id="rowsCount" resultType="int">
        select count(1) from PT_USER;
    </select>
    
    
    
    <update id="truncateTable">
        truncate table PT_USER
    </update>

    
</mapper>