jsp+servlet分页查询

分页查询

1. 减少服务器内存开销

2. 提高用户体验

效果图

思绪图

分页显示Bean文件代码

package cn.ytmj.findlist.domain;

import java.util.List;

/**
 * @author rui
 * @create 2019-08-17 23:34
 * 分页对象
 * 使用泛型为多种页面提供服务
 */
public class PageBean<T> {
    private int totalCount;  //总记录数
    private int  totalPage; // 总页数
    private List<T> list;   //每页的数据list集合
    private int currentPage; //当前页码
    private int rows; //每页显示的条数
    public PageBean(){}

    public int getTotalCount() {
        return totalCount;
    }

    public void setTotalCount(int totalCount) {
        this.totalCount = totalCount;
    }

    public int getTotalPage() {
        return totalPage;
    }

    public void setTotalPage(int totalPage) {
        this.totalPage = totalPage;
    }

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

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

    public int getCurrentPage() {
        return currentPage;
    }

    public void setCurrentPage(int currentPage) {
        this.currentPage = currentPage;
    }

    public int getRows() {
        return rows;
    }

    public void setRows(int rows) {
        this.rows = rows;
    }

    @Override
    public String toString() {
        return "PageBean{" +
                "totalCount=" + totalCount +
                ", totalPage=" + totalPage +
                ", list=" + list +
                ", currentPage=" + currentPage +
                ", rows=" + rows +
                '}';
    }
}

FindUserByPageServlet代码

@WebServlet("/findUserByPageServlet")
public class FindUserByPageServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取数据
        String currentPage = request.getParameter("currentPage");
        String rows = request.getParameter("rows");
        if(null==currentPage||"".equals(currentPage)){
            currentPage="1";
        }
        if(null==rows||"".equals(rows)){
            rows="5";
        }
        //调用service
        UserService userService = new UserServiceImpl();
        PageBean<User> pageBean = userService.findUserByPage(Integer.parseInt(currentPage), Integer.parseInt(rows));
        request.setAttribute("pageBean", pageBean);
        //转发
        request.getRequestDispatcher("/list.jsp").forward(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}
}

service

PageBean<User> findUserByPage(int currentPage, int rows);

serviceimpl

   public class UserServiceImpl implements UserService {
    UserDao userDao = new UserDaoImpl();
   @Override
    public PageBean<User> findUserByPage(int currentPage, int rows) {
        PageBean<User> pageBean = new PageBean<>();
        if (currentPage <= 0) {
            currentPage = 1;
        }
        int totalCount = userDao.findTotalCount();
        //计算总页数
        int totalPage = totalCount % ows == 0 ? totalCount / rows : totalCount / rows + 1;
        pageBean.setTotalPage(totalPage);
        if (currentPage > totalPage) {
            currentPage = totalPage;
        }
        List<User> list = userDao.findUserByPage(currentPage, rows);

        pageBean.setTotalCount(totalCount);
        pageBean.setCurrentPage(currentPage);
        pageBean.setRows(rows);
        pageBean.setList(list);

        return pageBean;
    }
}

dao

	//查询当前页面的所有数据
    List<User> findUserByPage(int currentPage, int rows);
	//总条数
    int findTotalCount();

daoimpl

• 通过JDBCUtils获取DataSource

  package cn.ytmj.findlist.util;
  
  import com.alibaba.druid.pool.DruidDataSourceFactory;
  
  import javax.sql.DataSource;
  import java.io.IOException;
  import java.io.InputStream;
  import java.sql.Connection;
  import java.sql.SQLException;
  import java.util.Properties;
  
  /**
   * JDBC工具类 使用Durid连接池
   */
  public class JDBCUtils {
  
      private static DataSource ds ;
  
      static {
  
          try {
              //1.加载配置文件
              Properties pro = new Properties();
              //使用ClassLoader加载配置文件，获取字节输入流
              InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
              pro.load(is);
  
              //2.初始化连接池对象
              ds = DruidDataSourceFactory.createDataSource(pro);
  
          } catch (IOException e) {
              e.printStackTrace();
          } catch (Exception e) {
              e.printStackTrace();
          }
      }
  
      /**
       * 获取连接池对象
       */
      public static DataSource getDataSource(){
          return ds;
      }
  
      /**
       * 获取连接Connection对象
       */
      public static Connection getConnection() throws SQLException {
          return  ds.getConnection();
      }
  }
  
  

 public class UserDaoImpl implements UserDao {
    private JdbcTemplate jdbcTemplate = new JdbcTemplate(JDBCUtils.getDataSource());
    @Override
    public List<User> findUserByPage(int currentPage, int rows) {
        String sql = "select * from user limit ? , ? ";
        List<User> list = jdbcTemplate.query(sql, new BeanPropertyRowMapper<User>(User.class), (currentPage - 1) * rows, rows);
        return list;
    }

    @Override
    public int findTotalCount() {
        String sql = "select count(*) from user";
        int count = jdbcTemplate.queryForObject(sql,Integer.class);
        return count;
    }
 }

jsp页面分页显示相关代码

Bootstrap分页按钮模板(轻微修改)，以备后用

            <div style="float: left">
                <nav>
                    <ul class="pagination">
                        <li>
                            <a href="#" aria-label="Previous">
                                <span aria-hidden="true">&laquo;</span>
                            </a>
                        </li>
                        <li class="active"><a href="#">1 <span class="sr-only"></span></a></li>
                        <li><a href="#">2</a></li>
                        <li><a href="#">3</a></li>
                        <li><a href="#">4</a></li>
                        <li><a href="#">5</a></li>
                        <li>
                            <a href="#" aria-label="Next">
                                <span aria-hidden="true">&raquo;</span>
                            </a>
                        </li>
                        <span style="font-size: 25px ;margin-left: 5px">共16条数据，共4页</span>
                    </ul>
                </nav>
            </div>

修改后jsp代码

 <div style="float: left">
                <nav>
                    <ul class="pagination">
                        <%-- 判断是否是第一页--%>
                        <c:if test="${pageBean.currentPage==1}">
                        <li class="disabled">
                            </c:if>
                            <c:if test="${pageBean.currentPage!=1}">
                        <li>
                            </c:if>
                            <a href="${pageContext.request.contextPath}/findUserByPageServlet?currentPage=${pageBean.currentPage-1}&rows=5"
                               aria-label="Previous">
                                <span aria-hidden="true">&laquo;</span>
                            </a>
                        </li>
                        <c:forEach var="i" varStatus="s" step="1" begin="1" end="${pageBean.totalPage}">
                            <c:if test="${pageBean.currentPage == i}">
                                <li class="active">

                                    <a href="${pageContext.request.contextPath}/findUserByPageServlet?currentPage=${i}&rows=5"

                                       name="li">${i}</a></li>
                            </c:if>
                            <c:if test="${pageBean.currentPage != i}">
                                <li>
                                    <a href="${pageContext.request.contextPath}/findUserByPageServlet?currentPage=${i}&rows=5"
                                       name="li">${i}</a></li>
                            </c:if>
                        </c:forEach>
                        <%-- 判断是否是最后页--%>
                        <c:if test="${pageBean.currentPage >= pageBean.totalPage}">
                        <li class="disabled">
                            </c:if>
                            <c:if test="${pageBean.currentPage!=pageBean.totalPage}">
                        <li>
                            </c:if>
                            <a href="${pageContext.request.contextPath}/findUserByPageServlet?currentPage=${pageBean.currentPage+1}&rows=5"
                               aria-label="Next">
                                <span aria-hidden="true">&raquo;</span>
                            </a>
                        </li>
                        <span style="font-size: 25px ;margin-left: 5px">共${pageBean.totalCount}条数据，共${pageBean.totalPage}页</span>
                    </ul>
                </nav>
            </div>
        </div>

jsp+servlet实现登录，数据操作（分页查询,模糊查询等）githubhttps://github.com/PoetryAndYou/List-Operation