web分页实现

1.index.jsp
<h2><a href="${pageContext.request.contextPath }/showProductsByPage?currPage=1">分页展示商品</a></h2>


2.Servlet
public class ShowProductsByPageServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		doPost(request,response);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		//接收第几页
		int currPage=Integer.parseInt(request.getParameter("currPage"));
		
		//设置每页显示的条数
		int pageSize=4;
		
		//调用service
		ProductService productServcie=new ProductServiceImpl();
		PageBean<Product>bean=null;
		try {
			bean=productServcie.showProductByPage(currPage,pageSize);
		} catch (Exception e) {
			e.printStackTrace();
		}
		
		//将当前页的数据放入域中
		request.setAttribute("pb", bean);
		//转发到分页的页面
		request.getRequestDispatcher("/product_page.jsp").forward(request, response);
	}

}



3.Service
public PageBean<Product> showProductByPage(int currPage, int pageSize) throws SQLException {
		//展示当前页的数据    =limit (currPage-1)*pageSize,pageSize
		ProductDao productDao=new ProductDao();
		List<Product>list=productDao.findByCurrPage(currPage,pageSize);
		
		//查询总条数
		int totalCount=productDao.getTotalCount();
		
		return new PageBean<>(list, currPage, pageSize, totalCount);
	}


4.Dao
/**
	 * 获取当前页的数据
	 * @param currPage
	 * @param pageSize
	 * @return
	 * @throws SQLException 
	 */
	public List<Product> findByCurrPage(int currPage, int pageSize) throws SQLException {
		QueryRunner qr=new QueryRunner(DataSourceUtils.getDataSource());
		String sql="select * from product limit ?,?";
		return qr.query(sql, new BeanListHandler<>(Product.class), (currPage-1)*pageSize,pageSize);
	}

	/**
	 * 获取总页数
	 * @return
	 * @throws SQLException 
	 */
	public int getTotalCount() throws SQLException {
		QueryRunner qr=new QueryRunner(DataSourceUtils.getDataSource());
		String sql="select count(*) from product";
		return ((Long)qr.query(sql, new ScalarHandler())).intValue();
	}


5.page.jsp
<body>
	<table border="1" align="center" width="88%">
		<tr>
			<th>pid</th>
			<th>商品名称</th>
			<th>商品价格</th>
			<th>商品描述</th>

		</tr>
		<c:forEach items="${pb.list }" var="p">
			<tr>
				<td width='8%'>${p.id }</td>
				<td width='8%'>${p.pname }</td>
				<td width='8%'>${p.price }</td>
				<td>${p.pdesc }</td>

			</tr>
		</c:forEach>
	</table>
	<center>
		<!-- 若是第一页 首页和上一页不展示 -->
		<c:if test="${pb.currPage!=1 }">
			<a href='${pageContext.request.contextPath}/showProductsByPage?currPage=1'>[首页]  </a>
			<a href='${pageContext.request.contextPath}/showProductsByPage?currPage=${pb.currPage-1}'>[上一页]</a>
		</c:if>
		
		<!-- 将所有的页码展示出来 -->
		<c:forEach begin="1" end="${pb.totalPage }" var="n">
			<!-- 若是当前页 不可点 -->
			<c:if test="${pb.currPage == n }">
				${n }
			</c:if>
			
			<!-- 若不是当前页 可点 -->
			<c:if test="${pb.currPage != n }">
				<a href="${pageContext.request.contextPath}/showProductsByPage?currPage=${n}">${n }</a>
			</c:if>
		</c:forEach>
		
		<!-- 若是最后一页 尾页和下一页不展示 -->
		<c:if test="${pb.currPage!=pb.totalPage }">
			<a href='${pageContext.request.contextPath}/showProductsByPage?currPage=${pb.currPage+1}'>[下一页]</a>
			<a href='${pageContext.request.contextPath}/showProductsByPage?currPage=${pb.totalPage}'>[尾页]  </a>
		</c:if>
		第${pb.currPage }页/共${pb.totalPage }页
	</center>
</body>


6、PageBean
package cn.itcast.domain;

import java.util.List;

public class PageBean <T>{

	private List<T>list; //当前页内容
	
	private int currPage; //当前页 ~~~~~传递
	
	private int pageSize; //每页显示的条数~~~~~固定制

	private int totalCount; //总记录数 ~~~~~~~~查询
	
	private int totalPage;  //总页数~~~~~~~~~~计算

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

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

	public int getCurrPage() {
		return currPage;
	}

	public void setCurrPage(int currPage) {
		this.currPage = currPage;
	}

	

	public int getPageSize() {
		return pageSize;
	}

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

	public int getTotalCount() {
		return totalCount;
	}

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

	
/**
	**
	 * 获取总页数
	 * @return 总页数
	 */
	public int getTotalPage() {
		return (int) Math.ceil(totalCount*1.0/pageSize);
	}

	public PageBean() { }


	public PageBean(List<T> list, int currPage, int pageSize, int totalCount) {
		super();
		this.list = list;
		this.currPage = currPage;
		this.pageSize = pageSize;
		this.totalCount = totalCount;
	}
}
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