mybatis-分页显示数据

分页用到的两个实体类

package com.yangwei.shop.entity;

/**
 * 注意  get，set，remove 方法与一般的实体类的不同
*/

public class SystemContext {

    private static ThreadLocal<Integer> pageSize = new ThreadLocal<Integer>();
    private static ThreadLocal<Integer> pageIndex = new ThreadLocal<Integer>();
    private static ThreadLocal<Integer> pageOffset = new ThreadLocal<Integer>();
    /**
     * 升序还是降序
     */
    private static ThreadLocal<String> order = new ThreadLocal<String>();
    /**
     * 根据那个字段排序
     */
    private static ThreadLocal<String> sort = new ThreadLocal<String>();
    
    
    public static String getOrder() {
        return order.get();
    }

    public static void setOrder(String _order) {
        order.set(_order);
    }
    
    public static void removeOrder() {
        order.remove();
    }

    public static String getSort() {
        return sort.get();
    }

    public static void setSort(String _sort) {
        sort.set(_sort);
    }
    
    public static void removeSort() {
        sort.remove();
    }

    public static int getPageOffset() {
        return pageOffset.get();
    }

    public static void setPageOffset(int _pageOffset) {
        pageOffset.set(_pageOffset);
    }
    
    public static void removePageOffset() {
        pageOffset.remove();
    }

    public static void setPageSize(int _pageSize) {
        pageSize.set(_pageSize);
    }
    
    public static int getPageSize() {
        return pageSize.get();
    }
    
    public static void removePageSize() {
        pageSize.remove();
    }
    
    public static void setPageIndex(int _pageIndex) {
        pageIndex.set(_pageIndex);
    }
    
    public static int getPageIndex() {
        return pageIndex.get();
    }
    
    public static void removePageIndex() {
        pageIndex.remove();
    }
}

package com.yangwei.shop.entity;

import java.util.List;

public class Pager<E> {
    /**
     * 第几页
     */
    private int pageIndex;
    /**
     * 每页显示多少条
     */
    private int pageSize;
    /**
     * 分页的开始值
     */
    private int pageOffset;
    /**
     * 总共多少条记录
     */
    private int totalRecord;
    /**
     * 总共多少页
     */
    private int totalPage;
    /**
     * 放置具体数据的列表
     */
    private List<E> datas;
    
    public int getPageIndex() {
        return pageIndex;
    }
    public void setPageIndex(int pageIndex) {
        this.pageIndex = pageIndex;
    }
    public int getPageSize() {
        return pageSize;
    }
    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }
    public int getTotalRecord() {
        return totalRecord;
    }
    public void setTotalRecord(int totalRecord) {
        this.totalRecord = totalRecord;
    }
    public int getTotalPage() {
        return totalPage;
    }
    public void setTotalPage(int totalPage) {
        this.totalPage = totalPage;
    }
    public List<E> getDatas() {
        return datas;
    }
    public void setDatas(List<E> datas) {
        this.datas = datas;
    }
    public int getPageOffset() {
        return pageOffset;
    }
    public void setPageOffset(int pageOffset) {
        this.pageOffset = pageOffset;
    }
    
}

接下来就是真正的分页了，  mybatis中mapper.xml配置文件中的两条查询语句如下

    <!-- 多个参数的形式，需要使用map来存储-->
    <select id="find" parameterType="map" resultType="User">
        <!-- 只要是#{}这种形式的，都会以？形式替代，对应字符串形式，都会加上引号-->
        <!-- 只要是${}这种形式的，不会用？形式替代，传过来什么，就什么替代-->
        select * from t_user where 
            ( username like #{name} or nickname like #{name} )
            order by ${sort} ${order}
        limit #{pageOffset},#{pageSize}
        
        <!--
        对应的sql便是
        select * from t_user where (username like ? or nickname like ?)
            order by id desc limit ? ?
        -->
    </select>
    <select id="count" parameterType="map" resultType="int">
        select count(*) from t_user where 
            ( username like #{name} or nickname like #{name} )
        
    </select>

java代码实现分页

/**
     * 分页显示
     */
    public static Pager<User> testFind(String name){
        int pageOffset=SystemContext.getPageOffset();
        int pageSize=SystemContext.getPageSize();
        String order=SystemContext.getOrder();
        String sort=SystemContext.getSort(); 
        Pager<User> pages=new Pager<User>();
        SqlSession session=null;
        
        try {
            session = MyBatisUtil.createSession();
            Map<String,Object> map=new HashMap<String,Object>();
            //使用like模糊查询的时候，注意百分号加在这里
            map.put("name", "%"+name+"%");
            map.put("pageOffset", pageOffset);
            map.put("pageSize", pageSize);
            map.put("order", order);
            map.put("sort", sort);
            List<User> users=session.selectList(User.class.getName()+".find", map);
        
            pages.setDatas(users);
            pages.setPageOffset(pageOffset);
            pages.setPageSize(pageSize);
            
            int count=session.selectOne(User.class.getName()+".count", map);
            pages.setTotalRecord(count);
            
            //所有的数据都存到了Pager对象中
        } finally{
            MyBatisUtil.closeSession(session);
        }
        return pages;
        
    }

测试上面分页代码

　　　　　　　SystemContext.setPageOffset(0);
            SystemContext.setPageSize(15);
            SystemContext.setOrder("desc");
            SystemContext.setSort("id");
            
            Pager<User> ps = testFind("zhang");
            System.out.println(ps.getTotalRecord());
            for(User u: ps.getDatas()){
                System.out.println(u.getNickname());
            }