java分页查询接口的实现

谁践踏了优雅 2022-07-12 02:30 384阅读 0赞

## java分页查询接口的实现 ##

分页要传入当前所在页数和每页显示记录数，再分页查询数据库，部分代码如下所示。

传入参数实体类：

public class MessageReq {
    
        private String memberId;//会员id
        private int currentPage;//当前页
        private int pageSize;//一页多少条记录
        private int startIndex;//从哪一行开始
        private int endIndex;//从哪一行结束
    
    
        public String getMemberId() {
            return memberId;
        }
        public void setMemberId(String memberId) {
            this.memberId = memberId;
        }
        public int getCurrentPage() {
            return currentPage;
        }   
        public int getStartIndex() {
            return startIndex;
        }
        public int getEndIndex() {
            return endIndex;
        }
        public void setCurrentPage(int currentPage) {
            this.currentPage = currentPage;
        }
        public void setStartIndex(int startIndex) {
            this.startIndex = startIndex;
        }
        public void setEndIndex(int endIndex) {
            this.endIndex = endIndex;
        }
        public int getPageSize() {
            return pageSize;
        }
        public void setPageSize(int pageSize) {
            this.pageSize = pageSize;
        }
        //根据当前所在页数和每页显示记录数计算出startIndex和endIndex
        public void setStartIndexEndIndex(){
             this.startIndex=(this.getCurrentPage()-1)*this.getPageSize();
             this.endIndex= (this.getCurrentPage()-1)*this.getPageSize()+this.getPageSize();
        }
    
    }

分页工具类：

public class Page<T>{
        private int currentPage = 1; // 当前页
        private int pageSize = 20; //每页显示记录数
        private int startRecord = 1; //起始查询记录
        private int totalPage = 0; //总页数
        private int totalRecord = 0; //总记录数
    
        private List<T> datas;
    
        public Page(){}
    
        public Page(int currentPage, int pageSize) {
            this.currentPage = currentPage;
            this.pageSize = pageSize;
            if(this.currentPage <= 0) {
                this.currentPage = 1;
            }
            if(this.pageSize <=0) {
                this.pageSize = 1;
            }
        }
    
        public Page(int currentPage, int pageSize, int totalRecord) {
            this(currentPage, pageSize);
            this.totalRecord = totalRecord;
            if(this.totalRecord <=0) {
                this.totalRecord = 1;
            }
        }
    
        public int getCurrentPage() {
            if(currentPage <= 0) {
                return 1;
            }
            return currentPage;
        }
    
        public void setCurrentPage(int currentPage) {
            this.currentPage = currentPage;
        }
    
        public int getPageSize() {
            return pageSize;
        }
        public void setPageSize(int pageSize) {
            this.pageSize = pageSize;
        }
        public int getTotalRecord() {
            if(totalRecord < 0) {
                return 0;
            }
            return totalRecord;
        }
        public void setTotalRecord(int totalRecord) {
            this.totalRecord = totalRecord;
        }
        public List<T> getDatas() {
            return datas;
        }
        public void setDatas(List<T> datas) {
            this.datas = datas;
        }
    
        public int getTotalPage() {
            if(totalRecord <= 0) {
                return 0;
            }
            int size = totalRecord / pageSize;//总条数/每页显示的条数=总页数
            int mod = totalRecord % pageSize;//最后一页的条数
            if(mod != 0) {
                size++;
            }
            totalPage = size;
            return totalPage;
        }
    
        public int getStartRecord() {
            startRecord = (getCurrentPage() - 1) * pageSize;
            return startRecord;
        }
    
    }

Manager层

public interface MessageManager {
    
        //分页查询消息
        public Page<Message> queryMessage(MessageReq req);
    }

@Component
    public class MessageManagerImpl implements MessageManager{ 
    
        @Autowired
        private MessageMapper messageMapper;
    
        @Override
        public Page<Message> queryMessage(MessageReq req) {
            Page<Message> page = new Page<Message>();
            int pageCount = messageMapper.getMessageNum(req.getMemberId());//得到总条数
            page = initPage(page, pageCount, req);
            List<Message> message= messageMapper.queryMessage(req);
            if (!message.isEmpty()) {
                page.setDatas(message);
            }
            return page;
        }
    
        private Page<Message> initPage(Page<Message> page, int pageCount,
                MessageReq messageReq) {
            page.setTotalRecord(pageCount);
            page.setCurrentPage(messageReq.getCurrentPage());
            page.setPageSize(messageReq.getPageSize());
            messageReq.setStartIndexEndIndex();
            return page;    
        }   
    
    }

Dao层

public interface MessageMapper {
    
        //分页查询
        public List<Message> queryMessage(Messagereq);
    
        //查询总条数
        public int getMessageNum(String memberId);
    }

mybatis的.xml文件

<?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.sf.ccsp.member.dao.mapper.MessageMapper">
       <resultMap id="MessageResultMap" type="com.sf.ccsp.member.dao.domain.message.Message" >
          <result column="ID" property="id" jdbcType="VARCHAR" />
          <result column="MEMBERID" property="memberId" jdbcType="VARCHAR" />
          <result column="MESSAGE_CLASSIFY" property="messageClassify" jdbcType="VARCHAR" />
          <result column="MESSAGE_CODE" property="messageCode" jdbcType="VARCHAR" />
          <result column="MESSAGE_CONTENT" property="messageContent" jdbcType="VARCHAR" />
          <result column="MESSAGE_STATUS" property="messageStatus" jdbcType="VARCHAR" />
       </resultMap>
    
       <select id="queryMessage" resultMap="MessageResultMap" parameterType="com.sf.ccsp.member.client.request.MessageReq">
         select *
         from cx_customer_message
         where MEMBERID = #{memberId, jdbcType=VARCHAR}
         and ISVALID = '1'
         LIMIT #{startIndex,jdbcType=INTEGER},#{pageSize,jdbcType=INTEGER}  
       </select>
    
        <select id="getMessageNum" resultType="INTEGER" parameterType="String">
          select count(*)
          from cx_customer_message
          where MEMBERID = #{memberId, jdbcType=VARCHAR}
        </select>
    
    </mapper>