mybatis分页和PageHelper插件的使用

1，加载分页插件 pom.xml

<dependency>
    	<groupId>com.github.pagehelper</groupId>
    	<artifactId>pagehelper</artifactId>
   		<version>5.1.2</version>
	</dependency>

2,在mybatis-config.xml中配置

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

3，创建实体类

package cn.wx.pojo;

import java.util.List;

public class PageInfo {
    //每页显示的个数
    private int pageSize;
    //当前的页数
    private int pageNumber;
    //总页数
    private long total;
    //不确定给哪个对象进行分页
    private List<?> list;

    public int getPageSize() {
        return pageSize;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    public int getPageNumber() {
        return pageNumber;
    }

    public void setPageNumber(int pageNumber) {
        this.pageNumber = pageNumber;
    }

    public long getTotal() {
        return total;
    }

    public void setTotal(long total) {
        this.total = total;
    }

    public List<?> getList() {
        return list;
    }

    public void setList(List<?> list) {
        this.list = list;
    }

    @Override
    public String toString() {
        return "PageInfo [pageSize=" + pageSize + ", pageNumber=" + pageNumber + ", total=" + total + ", list=" + list
                + "]";
    }

}

4，在SUserMapper.java中这样配置‘

’

public List<SUser> selByPage();

public long usersCount();

5，在SUserMapper.xml中配置

<select id="usersCount" resultType="long">
     select count(*) from user
  </select>
  
  <select id="selByPage" parameterType="map" resultType="user">
      select * from user limit #{pageStart},#{pageSize}
  </select>

6，SUserService

public PageInfo showpage(int pageSize, int pageNumber);

7，在SUserServiceImpl中配置

public PageInfo showpage(int pageSize, int pageNumber) {
		
		SqlSession sessionn = MybatisUtil.getSession();
		
		PageInfo pageinfo = new PageInfo();
		
		pageinfo.setPageSize(pageSize);
		pageinfo.setPageNumber(pageNumber);
		
		Map<String,Object> map = new HashMap<String, Object>();
		map.put("pageStart", pageSize*(pageNumber -1));
		map.put("pageSize", pageSize);
		
		List<Object> lists = sessionn.selectList("cn.wx.mapper.UserMapper.selByPage",map);
		
		long count = sessionn.selectOne("cn.wx.mapper.UserMapper.usersCount");
		
		System.out.println(count);
		
		pageinfo.setTotal(count%pageSize == 0 ? count/pageSize:count/pageSize+1);
		
		return pageinfo;
	}

8，测试

UserService userService = new UserServiceImpl();
		
		PageInfo info = userService.showpage(2, 3);
		
		System.out.println(info);

测试结果如下：

以上我们只是把插件配置好了，但是没有使用，现在我们就在用PageHelper插件再测试下

import cn.wx.mapper.SUserMapper;
import cn.wx.pojo.PageInfo;
import cn.wx.pojo.SUser;
import cn.wx.service.UserService;
import cn.wx.service.serviceImpl.UserServiceImpl;
import cn.wx.utils.SqlSessionUtils;
import com.github.pagehelper.PageHelper;
import org.apache.ibatis.session.SqlSession;

import java.util.List;

public class Test12 {
    @org.junit.Test
            public void testDemo02(){
//        UserService userService = new UserServiceImpl();
//
//        PageInfo info = userService.showpage(2, 3);
//
//        System.out.println(info);
        SqlSession session = SqlSessionUtils.getSqlSession();
        SUserMapper mapper = session.getMapper(SUserMapper.class);
        PageHelper.startPage(3, 2);
        List<SUser> list = mapper.selUser();
        System.out.println(list);
        for (int i = 0; i < list.size(); i++) {

            System.out.println(list.get(i));
        }



    }


}

 测试结果如下：

达到了和没有使用插件同样的效果