分页查询功能分析
好处：
减轻服务器内存的开销
提升用户体验
分析具体步骤
PageBean实体类：
package com.example.domain;
import java.util.List;
/*
分页对象（分页查询实体类）
*/
public class PageBean<T> {
private int totalCount;// 总记录数
private int totalPage;// 总页码
private List<T> list;// 每页数据 list集合
private int currentPage;// 当前页码
private int rows;// 每页显示的条数
@Override
public String toString() {
return "PageBean{" +
"totalCount=" + totalCount +
", totalPage=" + totalPage +
", list=" + list +
", currentPage=" + currentPage +
", rows=" + rows +
'}';
}
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;
}
}
package com.example.domain;
import java.util.List;
/*
分页对象（分页查询实体类）
*/
public class PageBean<T> {
private int totalCount;// 总记录数
private int totalPage;// 总页码
private List<T> list;// 每页数据 list集合
private int currentPage;// 当前页码
private int rows;// 每页显示的条数
@Override
public String toString() {
return "PageBean{" +
"totalCount=" + totalCount +
", totalPage=" + totalPage +
", list=" + list +
", currentPage=" + currentPage +
", rows=" + rows +
'}';
}
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;
}
}
后台代码实现
UserDao接口：
/**
* 查询总记录数
* @return
*/
int findTotalCount();
/**
* 分页查询每页记录
* @param start
* @param rows
* @return
*/
List<User1> findByPage(int start, int rows);
UserDaoImpl实体类：
@Override
public int findTotalCount() {
//1.定义sql
String sql = "select count(*) from user1";
return template.queryForObject(sql, Integer.class);
}
@Override
public List<User1> findByPage(int start, int rows) {
//1.定义sql语句
String sql = "select * from user1 limit ? , ? ";
return template.query(sql, new BeanPropertyRowMapper<User1>(User1.class),start,rows);
}
UserService接口：
/**
* 批量删除用户
* @param ids
*/
void delSelectedUser(String[] ids);
/**
* 分页查询
* @param currentPage
* @param rows
* @return
*/
PageBean<User1> findUserByPage(String currentPage, String rows);
UserServiceImpl实体类：
@Override
public PageBean<User1> findUserByPage(String _currentPage, String _rows) {
int currentPage = Integer.parseInt(_currentPage);
int rows = Integer.parseInt(_rows);
if (currentPage <= 0){
currentPage = 1;
}else if (currentPage >= 8){
currentPage = 7;
}
//1.创建空的PageBean对象
PageBean<User1> pd = new PageBean<User1>();
//2.设置参数
pd.setCurrentPage(currentPage);
pd.setRows(rows);
//3.调用dao查询totalCount总记录数
int totalCount = dao.findTotalCount();
pd.setTotalCount(totalCount);
//4.调用dao查询List集合
//计算开始的记录索引
int start = (currentPage -1) * rows;
List<User1> list = dao.findByPage(start,rows);
pd.setList(list);
//5.计算总页码
int totalPage = (totalCount % rows) == 0 ? totalCount/rows : (totalCount/rows) + 1;// 三元运算符
pd.setTotalPage(totalPage);
return pd;
}
FindUserByPageServlet类：
package com.example.web.servlet;
import com.example.domain.PageBean;
import com.example.domain.User1;
import com.example.service.UserService;
import com.example.service.impl.UserServiceImpl;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
@WebServlet(name = "FindUserByPageServlet", value = "/findUserByPageServlet")
public class FindUserByPageServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.获取参数
String currentPage = request.getParameter("currentPage");// 获取当前页面参数
String rows = request.getParameter("rows");// 获取每页条数
if (currentPage == null || "".equals(currentPage) ){
currentPage = "1";
}
if (rows == null || "".equals(rows)){
rows = "5";
}
//2.调用service查询
UserService service = new UserServiceImpl();
PageBean<User1> pd = service.findUserByPage(currentPage,rows);
System.out.println(pd);
//3.将PageBean存入request存储
request.setAttribute("pd", pd);
//4.转发到list.jsp页面
request.getRequestDispatcher("/list.jsp").forward(request, response);
}
}
前台代码
list.jsp
<div>
<nav aria-label="Page navigation">
<ul class="pagination">
<c:if test="${pd.currentPage == 1}">
<li class="disabled">
</c:if>
<c:if test="${pd.currentPage != 1}">
<li>
</c:if>
<a href="${pageContext.request.contextPath}/findUserByPageServlet?currentPage=${pd.currentPage-1}&rows=5" aria-label="Previous">
<span aria-hidden="true">«</span>
</a>
</li>
<c:forEach begin="1" end="${pd.totalPage}" var="i">
<!-- 分页选中 -->
<c:if test="${pd.currentPage == i}">
<li class="active"><a href="${pageContext.request.contextPath}/findUserByPageServlet?currentPage=${i}&rows=5">${i}</a></li>
</c:if>
<c:if test="${pd.currentPage != i}">
<li><a href="${pageContext.request.contextPath}/findUserByPageServlet?currentPage=${i}&rows=5">${i}</a></li>
</c:if>
</c:forEach>
<li>
<a href="${pageContext.request.contextPath}/findUserByPageServlet?currentPage=${pd.currentPage+1}&rows=5" aria-label="Next">
<span aria-hidden="true">»</span>
</a>
</li>
<span style="font-size: 25px;margin-left: 5px">
共${pd.totalCount}条记录，共${pd.totalPage}页
</span>
</ul>
</nav>
</div>
index.jsp
<div align="center">
<a
href="${pageContext.request.contextPath}/findUserByPageServlet" style="text-decoration:none;font-size:33px">查询所有用户信息
</a>
</div>
标签：功能,rows,分页,int,list,查询,totalCount,currentPage,public From： https://www.cnblogs.com/xuche/p/17101143.html