JSP分页

ゝ一纸荒年。 2024-04-18 18:58 73阅读 0赞

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### 分页类别 ###

分页又分为真分页(物理分页)和假分页(逻辑分页)

#### 真分页 ####

需要多少数据就查询多少数据

Mysql:limit

Oracle:rownum

缺点：不可移植

#### 假分页 ####

先将数据查询出来，通过list的截取获取到分页的数据

缺点：如果数据量太大，性能非常低

#### 思路 ####

这里我们做真分页，先从数据库中进行查询，拿到总记录数，设定每页显示的记录数量，从前端将当前页的下标传过来，然后通过当前页可以得出上一页下一页

总记录数：从数据库中查询得出
    
    总页数：总记录数除以每页需要显示的记录数量
    
    当前页：前端传过来，第一次进入默认第一页
    
    首页：当前页为第一页
    
    尾页：当前为总页数的那页
    
    上一页：如果当前页不是第一页就当前页-1
    
    下一页：如果当前页不是尾页就当前页+1

#### 代码实现Demo ####

首先封装一个工具类，将首页尾页上一页下一页这些计算出来，方便后来使用

package com.ifueen.util;
    
    import java.util.List;
    
    /**
     * @author admin
     *	分页的工具类
     * @param <T>
     */
    public class PageBeanUtil<T> {
        
    		//当前页
    		private Integer localPage;
    		//总页数
    		private Integer totalPage;
    		//每页显示数量
    		private Integer pageSize = 5;
    		//总记录量
    		private Integer totalNum;
    		//首页
    		private Integer firstPage = 1;
    		//上一页
    		private Integer prePage;
    		//下一页
    		private Integer nextPage;
    		//尾页
    		private Integer lastPage;
    		//显示的数据
    		private List<T> list;
    		public PageBeanUtil() {
        
    			// TODO Auto-generated constructor stub
    		}
    		public PageBeanUtil(Integer localPage, Integer totalNum) {
        
    			super();
    			this.localPage = localPage;	//当前页
    			this.totalNum = totalNum;	//总记录数
    			//总页数：如果总记录数对每页记录数能够整除，就取除数，如果不能整除，就取除数加1
    			this.totalPage = this.totalNum % this.pageSize == 0 ? 
    					this.totalNum / this.pageSize : this.totalNum / this.pageSize+1;
    			//上一页：如果当前页为第一页，就返回当前页，否则就返回当前页-1
    			this.prePage = this.localPage == 1 ? this.localPage : this.localPage - 1;
    			//下一页：如果当前页为最后一页，就返回最后一页，否则就返回当前页+1
    			this.nextPage = this.localPage == this.totalPage ? this.totalPage : this.localPage + 1;
    			//最后一页：就等于总页数
    			this.lastPage = this.totalPage;
    		}
    		public Integer getLocalPage() {
        
    			return localPage;
    		}
    		public void setLocalPage(Integer localPage) {
        
    			this.localPage = localPage;
    		}
    		public Integer getTotalPage() {
        
    			return totalPage;
    		}
    		public void setTotalPage(Integer totalPage) {
        
    			this.totalPage = totalPage;
    		}
    		public Integer getPageSize() {
        
    			return pageSize;
    		}
    		public void setPageSize(Integer pageSize) {
        
    			this.pageSize = pageSize;
    		}
    		public Integer getTotalNum() {
        
    			return totalNum;
    		}
    		public void setTotalNum(Integer totalNum) {
        
    			this.totalNum = totalNum;
    		}
    		public Integer getFirstPage() {
        
    			return firstPage;
    		}
    		public void setFirstPage(Integer firstPage) {
        
    			this.firstPage = firstPage;
    		}
    		public Integer getPrePage() {
        
    			return prePage;
    		}
    		public void setPrePage(Integer prePage) {
        
    			this.prePage = prePage;
    		}
    		public Integer getNextPage() {
        
    			return nextPage;
    		}
    		public void setNextPage(Integer nextPage) {
        
    			this.nextPage = nextPage;
    		}
    		public Integer getLastPage() {
        
    			return lastPage;
    		}
    		public void setLastPage(Integer lastPage) {
        
    			this.lastPage = lastPage;
    		}
    		public List<T> getList() {
        
    			return list;
    		}
    		public void setList(List<T> list) {
        
    			this.list = list;
    		}
    }

控制器里

package com.ifueen.controller.system;
    
    import java.util.List;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Controller;
    import org.springframework.ui.Model;
    import org.springframework.web.bind.annotation.RequestMapping;
    
    import com.ifueen.domain.City;
    import com.ifueen.domain.Jobs;
    import com.ifueen.service.ICityService;
    import com.ifueen.service.IJobsService;
    import com.ifueen.util.PageBeanUtil;
    
    @Controller
    @RequestMapping("/system/jobs")
    public class SystemJobsController {
        
    	
    	@Autowired
    	private IJobsService js;
    	
    	/**
    	 *分页
    	 */
    	@RequestMapping("/page")
    	public String jobspage(Integer localPage,Model model) {
        
    		PageBeanUtil<Jobs> pageBean = js.querypage(localPage);
    		model.addAttribute("pageBean",pageBean);
    		return "WEB-INF/system/jobs";
    	}
    }

service层接口

package com.ifueen.service;
    
    import java.util.List;
    
    import com.ifueen.domain.Jobs;
    import com.ifueen.util.JobsConditionUtil;
    import com.ifueen.util.PageBeanUtil;
    
    public interface IJobsService {
        
    
    	PageBeanUtil<Jobs> querypage(Integer localPage);
    }

service接口的实现类

package com.ifueen.service.impl;
    
    import java.util.List;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    import com.ifueen.dao.IjobsDao;
    import com.ifueen.domain.Jobs;
    import com.ifueen.service.IJobsService;
    import com.ifueen.util.JobsConditionUtil;
    import com.ifueen.util.PageBeanUtil;
    
    @Service
    public class JobsServiceimpl implements IJobsService {
        
    
    	@Autowired
    	private IjobsDao jsd;
    	/**
    	 * 分页
    	 */
    	@Override
    	public PageBeanUtil<Jobs> querypage(Integer localPage) {
        
    		// TODO Auto-generated method stub
    		if (localPage == null) {
         // 解决空指针异常问题
    			localPage = 1;
    		}
    		Integer totalNum = jsd.queryNum();
    		PageBeanUtil<Jobs> pageBeanUtil = new PageBeanUtil<>(localPage, totalNum);
    		Integer one = (localPage - 1) * pageBeanUtil.getPageSize();// 分页两个参数中的第一个
    		List<Jobs> list = jsd.Page(one, pageBeanUtil.getPageSize());
    		pageBeanUtil.setList(list);
    		return pageBeanUtil;
    	}
    }

dao层接口

package com.ifueen.dao;
    
    import java.util.List;
    
    import com.ifueen.domain.Jobs;
    
    public interface IjobsDao {
        
    	Integer queryNum();
    
    	List<Jobs> Page(Integer one, Integer pageSize);
    
    }

dao层接口的实现类，这里面进行对数据库的操作，这里引用了springJDBC来进行操作的，要先导入springJDBC包和去xml里面配置，不懂的话可以去搜一下怎么用springJDBC

package com.ifueen.dao.impl;
    
    import java.util.List;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.jdbc.core.BeanPropertyRowMapper;
    import org.springframework.jdbc.core.JdbcTemplate;
    import org.springframework.stereotype.Repository;
    
    import com.ifueen.dao.IjobsDao;
    import com.ifueen.domain.Jobs;
    
    /**
     * @author admin
     *
     */
    /**
     * @author admin
     *
     */
    @Repository
    public class JobsDaoimpl implements IjobsDao{
    
    	@Autowired
    	private JdbcTemplate jdbc;
    	
    	/**
    	 * 查询总记录数
    	 */
    	@Override
    	public Integer queryNum() {
    		// TODO Auto-generated method stub
    		String sql = "select count(id) from jobs";
    		Integer totalNum = jdbc.queryForObject(sql, Integer.class);
    		return totalNum;
    	}
    
    	/**
    	 * 查询分页中的数据
    	 */
    	@Override
    	public List<Jobs> Page(Integer one, Integer pageSize) {
    		// TODO Auto-generated method stub
    		String sql = "select * from view_jobs_city limit ?,?";
    		List<Jobs> page = jdbc.query(sql, new BeanPropertyRowMapper<Jobs>(Jobs.class), one,pageSize);
    		return page;
    	}	
    }

后台就写完了，然后去前端jsp中引用

<div class="container job-table">
    			<table class="table table-hover">
    				<tr>
    					<th class="hidden-sm">编号</th>
    					<th>工作职位</th>
    					<th>地点</th>
    					<th>人数</th>
    					<th>薪资待遇</th>
    					<th>岗位介绍</th>
    					<th>岗位要求</th>
    					<th>是否启用</th>
    					<th>发布时间</th>
    					<th>操作</th>
    				</tr>
    				<c:forEach items="${pageBean.list }" var="j">
    				<tr>
    					<th>#${j.id }</th>
    					<th>${j.title }</th>
    					<th>${j.cname }</th>
    					<th>${j.jobnum }</th>
    					<th>${j.treatment }</th>
    					<th>${j.describes }</th>
    					<th>${j.requires }</th>
    					<c:if test="${j.isenabled }" var="i">
    					<th><span class="glyphicon glyphicon-ok" aria-hidden="true"></span></th>
    					</c:if>
    					<c:if test="${!i}">
    					<th><span class="glyphicon glyphicon-remove" aria-hidden="true"></span></th>
    					</c:if>
    					<th>${j.inputdate }</th>
    					<th>
    						<a href="system/jobs/update?id=${j.id }" class="btn-default tableA"><span class="glyphicon glyphicon-pencil" aria-hidden="true">修改</span></a>
    						<a href="system/jobs/del?id=${j.id }" class="btn-default tableA" οnclick="return del()" id="del"><span class="glyphicon glyphicon-trash" aria-hidden="true">删除</span></a>
    					</th>
    				</tr>
    				</c:forEach>
    			</table>
    			
    			<nav class="navbar-right">
    				<ul class="pagination" id="paging">
    					<li>
    						<span>当前第${pageBean.localPage }页</span>
    					</li>
    					<li>
    						<a href="system/jobs/page?localPage=1">
    							<span aria-hidden="true">首页</span>
    						</a>
    					</li>
    					<li>
    						<a href="system/jobs/page?localPage=${pageBean.prePage }" aria-label="上一页">
    							<span aria-hidden="true">上一页</span>
    						</a>
    					</li>
    					<li>
    
    					</li>
    					<li>
    						<a href="system/jobs/page?localPage=${pageBean.nextPage }" aria-label="下一页">
    							<span aria-hidden="true">下一页</span>
    						</a>
    					</li>
    					<li>
    						<a href="system/jobs/page?localPage=${pageBean.lastPage }" aria-label="尾页">
    							<span aria-hidden="true">尾页</span>
    						</a>
    					</li>
    					<li>
    						<span>总页数：共${pageBean.totalPage }页</span>
    						<span>总记录数：共${pageBean.totalNum }条</span>
    					</li>
    				</ul>
    			</nav>

实现效果如下：

![format_png][]

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[format_png]: https://imgconvert.csdnimg.cn/aHR0cHM6Ly9zMi5heDF4LmNvbS8yMDE5LzA5LzEwL25VNm5SeC5wbmc?x-oss-process=image/format,png