PageHelper实现了通用的分页查询，其支持的数据有，mysql、Oracle、DB2、PostgreSQL等主流的数据库。

使用说明：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-config.xml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>

接口

    Long getTotalRowCount(String keywords);
    
    Page<User> getUsersByPage(int pageIndex, int pageSize);

    Page<User> getUsersByPage(String keywords, int pageIndex, int pageSize);

    PageInfo<User> getUsersByPage2(int pageIndex, int pageSize);

    PageInfo<User> getUsersByPage2(String keywords, int pageIndex, int pageSize);

xml

 <select id="getTotalRowCount" resultType="java.lang.Long">
      select count(*) count
      from t_user
      where 1 = 1
      <if test="keywords != null and keywords != ''">
          and UserName like concat('%',#{keywords},'%')
      </if>
  </select>

<select id="getUsersByPage" resultType="User">
  select Id,
  UserName,
  Password
  from t_user
  where 1 = 1
  <if test="keywords != null and keywords != ''">
    and UserName like concat('%',#{keywords},'%')
  </if>
  limit #{startIndex},#{pageSize}
</select>

<select id="getUsersByPage2" resultType="User">
      select Id,
      UserName,
      Password
      from t_user
      where 1 = 1
      <if test="keywords != null and keywords != ''">
          and UserName like concat('%',#{keywords},'%')
      </if>
</select>

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;
	}	
}

 servie实现类

  @Override
    public Long getTotalRowCount(String keywords){
        return userDao.getTotalRowCount(keywords);
    }

    @Override
    public Page<User> getUsersByPage(int pageIndex, int pageSize){
        int startIndex = (pageIndex - 1) * pageSize;
        List<User> users = userDao.getUsersByPage(null,startIndex,pageSize);
        Long totalRowCount = userDao.getTotalRowCount(null);
        com.etc.entity.Page<User> page = new com.etc.entity.Page<User>(pageIndex,pageSize,totalRowCount,users);
        return page;
    }

    @Override
    public  Page<User> getUsersByPage(String keywords, int pageIndex, int pageSize){
        int startIndex = (pageIndex - 1) * pageSize;
        List<User> users = userDao.getUsersByPage(keywords,startIndex,pageSize);
        Long totalRowCount = userDao.getTotalRowCount(keywords);
        com.etc.entity.Page<User> page = new com.etc.entity.Page<User>(pageIndex,pageSize,totalRowCount,users);
        return page;
    }

    @Override
    public  PageInfo<User> getUsersByPage2(int pageIndex, int pageSize){
        PageHelper.startPage(pageIndex,pageSize,true);
        List<User> users = userDao.getUsersByPage2(null);
        PageInfo<User> pageInfo = new PageInfo<>(users);
        return pageInfo;
    }

    @Override
    public  PageInfo<User> getUsersByPage2(String keywords, int pageIndex, int pageSize){
        PageHelper.startPage(pageIndex,pageSize,true);
        List<User> users = userDao.getUsersByPage2(keywords);
        PageInfo<User> pageInfo = new PageInfo<>(users);
        return pageInfo;
    }

 测试类

 @Test
    /**
     * 自定义分页类，没有传递关键词参数
     */
    public void testGetUsersByPageWithoutKeywords(){
         com.etc.entity.Page<User> page = userService.getUsersByPage(3,2);
         System.out.println(page);
    }

    @Test
    /**
     * 自定义分页类，有传递关键词参数
     */
    public void testGetUsersByPageWithKeywords(){
        com.etc.entity.Page<User> page = userService.getUsersByPage("e",2,1);
        System.out.println(page);
    }


    @Test
    /**
     * 使用分页插件，没有传递关键词参数
     */
    public void testGetUsersByPage2WithoutKeywords(){
        com.github.pagehelper.PageInfo<User> page = userService.getUsersByPage2(3,2);
        System.out.println(page);
    }

    @Test
    /**
     * 使用分页插件，传递关键词参数
     */
    public void testGetUsersByPage2WithKeywords(){
        com.github.pagehelper.PageInfo<User> page = userService.getUsersByPage2("e",2,1);
        System.out.println(page);
    }
}

自定义分页查询jsp页面

        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);
      		}
      	}

分页插件页面

         当前是第${page.pageNum}页,共${page.pages }页，总记录数为${page.total }条。
      <hr>
      <form action="UserServlet?op=getusersbypage" method="post" id="pageForm">
      	<input type="hidden" name="pageIndex" id="pageIndex" />
      	<button onclick="javascript:findPage(1)">首页</button>
      	<c:if test="${page.hasPreviousPage }">
      		<button onclick="javascript:findPage(${page.pageNum-1})">上一页</button>
      	</c:if>
      	<c:forEach begin="1" end="${page.pages }" step="1" var="index">
      	    <button onclick="javascript:findPage(${index})">${index }</button>
        </c:forEach>
      	<c:if test="${page.hasNextPage }">
      		<button onclick="javascript:findPage(${page.pageNum+1})">下一页</button>
      	</c:if>    
      	<button onclick="javascript:findPage(${page.pages})">尾页</button>
      	<input type="text" id="toPage" /> <button onclick="jump(${page.pages})">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);
      		}
      	}