笔记如下
- 思路:
1.每一页里有十条记录,每页就是一个PageBean,封装了总记录数,当前是第几页,每页条数,当前是第几页的数据
2018-03-01_214242.png
2.两个公式
2018-03-01_214242.png
- *jsp
<body>
<c:if test="${empty pageBean.customers}">
当前页没有数据
</c:if>
<c:if test="${not empty pageBean.customers}">
<h3 style="text-align: center; ">当前是${pageBean.pageNum}页数据</h3>
<table border="1" width="100%">
<tr>
<th>客户姓名</th>
<th>客户性别</th>
<th>客户生日</th>
<th>客户邮箱</th>
<th>客户手机</th>
<th>客户爱好</th>
<th>客户类型</th>
<th>客户描述</th>
</tr>
<c:forEach items="${pageBean.customers}" var="customer">
<tr>
<td>${customer.name}</td>
<td>${customer.gender}</td>
<td>${customer.birthday}</td>
<td>${customer.email}</td>
<td>${customer.cellphone}</td>
<td>${customer.preference}</td>
<td>${customer.type}</td>
<td>${customer.description}</td>
</tr>
</c:forEach>
</table>
<br/>
<div style="text-align: center; ">
<c:if test="${pageBean.pageNum != 1 }">
<a href="${pageContext.request.contextPath}/pagequery?pagenum=1">首页</a>
<a href="${pageContext.request.contextPath}/pagequery?pagenum=${pageBean.pageNum-1}">上一页</a>
</c:if>
<!-- 参考百度左五右四 -->
<c:forEach begin="${pageBean.pageNum-5>0?pageBean.pageNum-5:1}" end="${pageBean.pageNum+4<pageBean.totalPageNum?pageBean.pageNum+4:pageBean.totalPageNum}" var="i">
<c:if test="${pageBean.pageNum == i}">
<font color="red">${i}</font>
</c:if><c:if test="${pageBean.pageNum != i}">
<a href="${pageContext.request.contextPath}/pagequery?pagenum=${i}">${i}</a>
</c:if>
</c:forEach>
<c:if test="${pageBean.pageNum != pageBean.totalPageNum }">
<a href="${pageContext.request.contextPath}/pagequery?pagenum=${pageBean.pageNum+1}">下一页</a>
<a href="${pageContext.request.contextPath}/pagequery?pagenum=${pageBean.totalPageNum}">尾页</a>
</c:if>
</div>
</c:if>
</body>
- web层(PageQueryServlet.java)
//拿到需要看到页是那一页
String pagenum = request.getParameter("pagenum");
//调用业务层去查询目标页的数据
CustomerService cs = new CustomerService();
//返回当前页的目标数据是不够的,还要做导航条
//为了做分页,需要引入一个新的javaBean
PageBean pageBean = cs.pageQuery(pagenum);
//将pagebean存到request域中
request.setAttribute("pageBean", pageBean);
request.getRequestDispatcher("/bean.jsp").forward(request, response);
- 业务层(CustomerService.java)
//完成分页查询的业务方法:
public PageBean pageQuery(String num) {
int numberPerPage = 10;//默认每页十条
int pageNum = Integer.parseInt(num);//当前页是那一页
//从数据库里查找总记录数
int totalRecordsCount = cdao.getToltalCount();
//运用公式
int totalPageNum = (totalRecordsCount + numberPerPage-1)/numberPerPage;//总页数
//select * from customers limit ?,?
int startIndex = (pageNum-1)*numberPerPage;
//从数据库里查找10条记录
List<Customer> customers = cdao.getCurrectPageData(startIndex,numberPerPage);
//封装数据
PageBean pageBean = new PageBean();
pageBean.setNumberPerPage(numberPerPage);
pageBean.setCustomers(customers);
pageBean.setPageNum(pageNum);
pageBean.setTotalPageNum(totalPageNum);
pageBean.setTotalRecordsCount(totalRecordsCount);
return pageBean;
}
dao层(CustomerDaoImpl.java)
//获得总记录条数
@Override
public int getToltalCount() {
QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());
try {
long count = (long) runner.query("select count(*) from customers", new ScalarHandler());
return (int)count;
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
//查询目标页的数据返回
@Override
public List<Customer> getCurrectPageData(int startIndex, int numberPerPage) {
QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());
String sql = "select * from customers limit ?,?";
try {
return runner.query(sql, new BeanListHandler<Customer>(Customer.class),startIndex,numberPerPage);
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
实现效果:
4.png
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