javaweb paging principle explained in detail
- 2020-06-19 10:27:11
- OfStack
This article examples for you to share javaweb pagination principle specific implementation code, for your reference, the specific content is as follows
public class Page {
private int currentPage;
private int totalPage;
private int count;
private int PageSize;
private List<Product> list;
private String category;
}
servlet:
package com.learning.web.servlet;
import java.io.IOException;
import java.util.List;
import javax.enterprise.inject.New;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.learning.domain.Page;
import com.learning.domain.Product;
import com.learning.service.ProductService;
@WebServlet("/showProductByPage")
public class ShowProductByPage extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int currentPage=1;
int pageSize=4;
// The first 1 Time is empty
String currentPageString=request.getParameter("currentPage");
if (currentPageString!=null) {
currentPage=Integer.parseInt(currentPageString);
}
String category = request.getParameter("category");
if ("".equals(category)) {
category=null;
}
ProductService productService=new ProductService();
Page page=productService.showProductByPage(currentPage,pageSize,category);
request.setAttribute("page", page);
request.getRequestDispatcher("/product_list.jsp").forward(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
service:
public Page showProductByPage(int currentPage, int pageSize, String category) {
try {
Page page=new Page();
int count=productDao.count(category);
page.setCount(count);
page.setList(productDao.findProductsByPage(currentPage,pageSize,category));
int totalPage=(int) Math.ceil(1.0*count/pageSize);
page.setPageSize(pageSize);
page.setCurrentPage(currentPage);
page.setTotalPage(totalPage);
page.setCategory(category);
return page;
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
Dao:
public int count(String category) throws SQLException {
QueryRunner queryRunner=new QueryRunner(C3P0Util.getDataSource());
String sql=" select count(*) from products ";
if (category!=null) {
sql+=" where category='"+category+"'";
}
long l= (Long)queryRunner.query(sql, new ScalarHandler(1));
return (int) l;
}
public List<Product> findProductsByPage(int currentPage, int pageSize, String category) throws SQLException {
QueryRunner queryRunner=new QueryRunner(C3P0Util.getDataSource());
String sql=" select * from products ";
if (category!=null) {
sql+=" where category='"+category+"'";
}
sql+=" limit ?,?";
return queryRunner.query(sql, new BeanListHandler<Product>(Product.class),(currentPage-1)*pageSize,pageSize);
}