SSM实现分页查询Demo

最终效果：

1、数据访问层

1、数据库建表：

DROP TABLE IF EXISTS tb_user;
CREATE TABLE tb_user (
	id INT NOT NULL AUTO_INCREMENT,
	userName VARCHAR(40),
	password VARCHAR(100),
	email VARCHAR(40),
	phone VARCHAR(40),
	roleName VARCHAR(40),
	PRIMARY KEY(id)
)ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

2、封装实体类：

/**
 * 用户实体类----对应数据表tb_user
 */
@Data
public class User {

    private Integer id;
    private String username;
    private String password;
    private String email;
    private String phone;
    private String rolename;

    public User() {
    }

   public User(String username, String password, String email, String phone, String rolename) {
      super();
      this.username = username;
      this.password = password;
      this.email = email;
      this.phone = phone;
      this.rolename = rolename;
   }
}

3、操作数据库的接口：

public interface UserDao {

    /**
     * 查询所有用户数据
     */
    List<User> selectUserList();
    /**
     * 查询用户记录总数
     */
    int selectCount();

    /**
     * 分页查询
     */
    List<User> findByPage(HashMap<String, Object> map);
}

Mapper配置文件：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.hh.dao.UserDao">

   <resultMap id="BaseResultMap" type="com.hh.entity.User">
      <id column="id" property="id" jdbcType="INTEGER" />
      <result column="userName" property="username" jdbcType="VARCHAR" />
      <result column="password" property="password" jdbcType="VARCHAR" />
      <result column="email" property="email" jdbcType="VARCHAR" />
      <result column="phone" property="phone" jdbcType="VARCHAR" />
      <result column="roleName" property="rolename" jdbcType="VARCHAR" />
   </resultMap>

   <sql id="Base_Column_List">
      id, userName, password, email, phone, roleName
   </sql>
   
   <!-- 根据分页数据start 和size查询数据 -->
   <select id="findByPage" parameterType="Map" resultMap="BaseResultMap">
      select <include refid="Base_Column_List"/> from tb_user
      <if test="start!=null and size!=null">
         limit #{start},#{size}
      </if>
   </select>

   <!--查询所有用户数据 -->
   <select id="selectUserList" resultType="com.hh.entity.User">
      select <include refid="Base_Column_List" /> from tb_user
   </select>

   <!-- 查询用户记录总数 -->
   <select id="selectCount" resultType="int">
      select count(*) from tb_user
   </select>

</mapper>

4、封装与分页相关的数据：

/**
 * 分页实体类:存储当前页所有分页相关的数据
 *
 * 分页的三个基本属性：
 *  1、每页几条记录pageSize，可以有默认值
 *  2、当前第几页currPage，可以有默认值
 *  3、总记录数totalCount，不可以有默认值，必须从数据库中查到
 */

@Data
@NoArgsConstructor
public class PageBean<User> {
    /**
     * 当前页面显示的数据
     */
    private List<User> lists;

    /**
     * 1、当前第几页
     */
    private int currPage;

    /**
     * 2、每页显示几条记录
     */
    private int pageSize;

    /**
     * 3、总共有多少条记录
     */
    private int totalCount;

    /**
     * 总页数：这个不是基本属性，可以通过计算得出：totalCount/pageSize
     */
    private int totalPage;
}

2、业务层

/**
 * User类业务层实现类
 */
@Service
public class UserService {

	@Resource
	private UserDao userDao;

	public List<User> selectUserList() {
		return userDao.selectUserList();
	}

	public int selectCount() {
		return userDao.selectCount();
	}

	public PageBean<User> findByPage(int currentPage) {

		HashMap<String,Object> map = new HashMap<>();
		PageBean<User> pageBean = new PageBean<>();

		//在业务层要做的就是给PageBean的所有属性赋值

		//1、当前页数
        pageBean.setCurrPage(currentPage);

		//2、每页显示的数据
		int pageSize=5;
		pageBean.setPageSize(pageSize);

		//3、总记录数
		int totalCount = userDao.selectCount();
		pageBean.setTotalCount(totalCount);

		//4、根据总记录数和每页显示的记录数计算总页数
		double tc = totalCount;
        Double num =Math.ceil(tc/pageSize);//向上取整
        pageBean.setTotalPage(num.intValue());


        //每页的起始编号为(id编号)：(currentPage-1)*pageSize
		map.put("start",(currentPage-1)*pageSize);
		//每页查询的记录数
		map.put("size", pageBean.getPageSize());

		//5、从数据库中查询出每页显示的数据
		List<User> lists = userDao.findByPage(map);
		pageBean.setLists(lists);

		return pageBean;
	}
}

3、表现层

@Controller
public class UserController {
	@Resource
	private UserService userService;

	@RequestMapping("/main")
	public String main(@RequestParam(value="currentPage", defaultValue="1", required=false)int currentPage,Model model){

		PageBean<User> pagemsg = userService.findByPage(currentPage);
		model.addAttribute("pagemsg", pagemsg);

		List<User> lists = userService.selectUserList();
		model.addAttribute("userLists", lists);

		return "main";
	}
}

登录页面：

<h2>欢迎登陆</h2>

<form action="main" method="post">
   <input type="submit" value="分页查询"/>
</form>

前台页面JSP：

<body>
   欢迎你
   <c:if test="${empty requestScope.pagemsg}">
      没有任何用户信息！
   </c:if>
   <c:if test="${!empty requestScope.pagemsg}">
      <table border="1" cellpadding="10" cellspacing="0" class="table1">
      <thead>
         <tr>
            <td>编号</td>
            <td>用户名</td>
            <td>密码</td>
            <td>邮件</td>
            <td>联系电话</td>
            <td>职位</td>
         </tr>
         </thead>
         <c:forEach items="${requestScope.pagemsg.lists}" var="u">
            <tr>
               <th>${u.id }</th>
               <th>${u.username }</th>
               <th>${u.password }</th>
               <th>${u.email }</th>
               <th>${u.phone }</th>
               <th>${u.rolename }</th>
            </tr>
         </c:forEach>      
      </table>   
   </c:if>

<table  border="0" cellspacing="0" cellpadding="0"  width="900px">
<tr>

<td class="td2">
   <span>第${requestScope.pagemsg.currPage }/ ${requestScope.pagemsg.totalPage}页</span>&nbsp;&nbsp;
   <span>总记录数：${requestScope.pagemsg.totalCount }&nbsp;&nbsp;每页显示:${requestScope.pagemsg.pageSize}</span>&nbsp;&nbsp;
   <span>
       <c:if test="${requestScope.pagemsg.currPage != 1}">
           <a href="${pageContext.request.contextPath }/main?currentPage=1">[首页]</a>&nbsp;&nbsp;
           <a href="${pageContext.request.contextPath }/main?currentPage=${requestScope.pagemsg.currPage-1}">[上一页]</a>&nbsp;&nbsp;
       </c:if>
       
       <c:if test="${requestScope.pagemsg.currPage != requestScope.pagemsg.totalPage}">
           <a href="${pageContext.request.contextPath }/main?currentPage=${requestScope.pagemsg.currPage+1}">[下一页]</a>&nbsp;&nbsp;
           <a href="${pageContext.request.contextPath }/main?currentPage=${requestScope.pagemsg.totalPage}">[尾页]</a>&nbsp;&nbsp;
       </c:if>
   </span>
</td>
</tr>
</table>
</body>

页面效果展示：