mybatis —— 普通分页和分页插件

1、普通分页

实体类

package com.etc.entity;

import java.util.List;

public class Page<T> {
	/**
	 * 每页条数
	 */
	private int pageSize = 10;
	
	/**
	 * 第几页 
	 */
	private int pageIndex = 1;
	
	/**
	 * 总的记录数 
	 */
	private long totalRowCount;
	
	/**
	 * 数据 
	 */
	private List<T> data;
	
	/**
	 * 是否有上一页 
	 */
	private boolean hasPrevPage;
	
	
	/**
	 * 是否有下一页 
	 */
	private boolean hasNextPage;


	/**
	 * @return the pageSize
	 */
	public int getPageSize() {
		return pageSize;
	}


	/**
	 * @param pageSize the pageSize to set
	 */
	public void setPageSize(int pageSize) {
		this.pageSize = pageSize;
	}


	/**
	 * @return the pageIndex
	 */
	public int getPageIndex() {
		return pageIndex;
	}


	/**
	 * @param pageIndex the pageIndex to set
	 */
	public void setPageIndex(int pageIndex) {
		this.pageIndex = pageIndex;
	}


	/**
	 * @return the totalRowCount
	 */
	public long getTotalRowCount() {
		return totalRowCount;
	}


	/**
	 * @param totalRowCount the totalRowCount to set
	 */
	public void setTotalRowCount(long totalRowCount) {
		this.totalRowCount = totalRowCount;
	}


	/**
	 * @return the data
	 */
	public List<T> getData() {
		return data;
	}


	/**
	 * @param data the data to set
	 */
	public void setData(List<T> data) {
		this.data = data;
	}


	/**
	 * @return the totalPageCount
	 */
	public long getTotalPageCount() {
		if(this.totalRowCount % this.pageSize == 0){
			return this.totalRowCount / this.pageSize;
		}else{
			return this.totalRowCount / this.pageSize + 1;
		}
	}


	/**
	 * @return the hasPrevPage
	 */
	public boolean getHasPrevPage() {
		//什么情况下有上一页，如果当前页>1
		return this.pageIndex > 1;
	}


	/**
	 * @return the hasNextPage
	 */
	public boolean getHasNextPage() {
		//如果当前页和总的页数一样，则没有下一页，其它情况都有下一页
		return this.pageIndex == this.getTotalPageCount() ? false : true;
	}
	
	public Page(){
		
	}

	/**
	 * 有参构造方法
	 * @param pageSize 每页的条数
	 * @param pageIndex 当前页码
	 * @param totalRowCount 总的记录数
	 * @param data 数据
	 */
	public Page(int pageSize, int pageIndex, long totalRowCount, List<T> data) {
		super();
		this.pageSize = pageSize;
		this.pageIndex = pageIndex;
		this.totalRowCount = totalRowCount;
		this.data = data;
	}	
}

service

    /**
     * 根据关键词进行查询
     * @return 用户列表
     */
    public Page<User> viewUserByKeywords(int pageIndex,int pageSize,String keywords){
        if(keywords == null){
            keywords = "";
        }
        String condition = "%" + keywords + "%";
        Page<User> result;
        int start = (pageIndex - 1) * pageSize;
        long totalRowCount = this.getTotalRowCount(keywords);
        UserExample example = new UserExample();
        UserExample.Criteria criteria = example.createCriteria();
        criteria.andUsernameLike(condition);

        UserExample.Criteria criteria2 = example.createCriteria();
        criteria2.andGenderLike(condition);

        UserExample.Criteria criteria3 = example.createCriteria();
        criteria3.andAddressLike(condition);

        example.or(criteria2);
        example.or(criteria3);

        example.setStartRow(start);
        example.setPageSize(pageSize);
        List<User> users = userDao.selectByExample(example);
        result = new Page<>(pageSize, pageIndex, totalRowCount, users);
        return result;
    }

servlet

	private void doSearch(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException{
		int pageIndex = 1;
		String pageIndexStr = request.getParameter("pageIndex");
		if (pageIndexStr != null && !"".equals(pageIndex)) {
			pageIndex = Integer.parseInt(pageIndexStr);
		}
		int pageSize = 20;
		String keywords = request.getParameter("keywords");
		Page<User> page = service.viewUserByKeywords(pageIndex, pageSize, keywords);
		request.setAttribute("page", page);
		request.getRequestDispatcher("/admin/user/usersbypage.jsp").forward(
				request, response);
	}

jsp页面

    <form action="UserServlet?op=search" method="post">
    	搜索关键词：<input type="text" name="keywords" />
    	<input type="submit" value="搜索"/>
    </form>
    <hr />
    <table width="500px" border="1px" cellspacing="0">
        <tr>
          <th>序号</th>
          <th>用户名</th>
          <th>年龄</th>
          <th>学历</th>
          <th>地址</th>
          <th>操作</th>
        </tr>
        <c:if test="${fn:length(page.data) == 0}">
          <tr>
			<td colspan="6">暂无数据</td>
          </tr>
        </c:if>

        <c:if test="${fn:length(page.data) > 0}">
         <c:forEach items="${page.data }" var="user" varStatus="vs">
	        <tr align="center">
	          <td>${(page.pageIndex - 1)*page.pageSize + vs.count }</td>
	          <td>${user.username }</td>
	          <td>${user.age }</td>
	          <td>${user.degreeName }</td>
	          <td>${user.address }</td>
	        </tr> 
	        </c:forEach>
        </c:if>
      </table>
              当前是第${page.pageIndex}页,共${page.totalPageCount }页，总记录数为${page.totalRowCount }条。
      <hr>
      <form action="UserServlet?op=getusersbypage" method="post" id="pageForm">
      	<input type="hidden" name="pageIndex" id="pageIndex" />
      	<button onclick="javascript:findPage(1)">首页</button>
      	<c:if test="${page.hasPrevPage }">
      		<button onclick="javascript:findPage(${page.pageIndex-1})">上一页</button>
      	</c:if>
      	<c:forEach begin="1" end="${page.totalPageCount }" step="1" var="index">
      	    <button onclick="javascript:findPage(${index})">${index }</button>
        </c:forEach>
      	<c:if test="${page.hasNextPage }">
      		<button onclick="javascript:findPage(${page.pageIndex+1})">下一页</button>
      	</c:if>    
      	<button onclick="javascript:findPage(${page.totalPageCount})">尾页</button> 
      	<input type="text" id="toPage" /> <button onclick="jump(${page.totalPageCount})">跳转</button>   
      </form>
      <script>
      	function findPage(pageIndex){
      		var form = document.getElementById('pageForm');
      		var page = document.getElementById('pageIndex') ;
      		page.value = pageIndex;
      		form.submit();
      	}
      	
      	function jump(totalPageCount){
      		var pageIndex = document.getElementById('toPage').value;
      		if(pageIndex < 1){
      			findPage(1);
      		}else if(pageIndex > totalPageCount){
      			findPage(totalPageCount);
      		}else{
      			findPage(pageIndex);
      		}
      	}
  
      </script>

2、分页插件

使用说明地址：https://github.com/pagehelper/Mybatis-PageHelper/blob/master/wikis/en/HowToUse.md

导入依赖

<dependency>
	    <groupId>com.github.pagehelper</groupId>
	    <artifactId>pagehelper</artifactId>
	    <version>5.1.4</version>
</dependency>

mybatis配置文件中配置

plugins在配置文件中的位置必须符合要求，否则会报错，顺序如下:

properties?, settings?, typeAliases?, typeHandlers?, objectFactory?,objectWrapperFactory?, plugins?, environments?, databaseIdProvider?, mappers?

<plugins>
	    <plugin interceptor="com.github.pagehelper.PageInterceptor" />
</plugins>