前面写了Servlet（一）到（五），主要是在网上搜罗的视频、对分页这块还是不太清楚。于是有找到一些视频，重新学习了一下。主要是对分页的认识和设计思路。也是为了方便我以后回忆一下。。
一、分页常识
pageSize //每页有多少条记录 --用户设定
rowCount //一共有多少条记录 --从数据库中查的
pageIndex //当前查看的是第几页 --用户选择的
beginRow //从第几行开始查询 --计算得到 pageSize*(pageIndex-1)
pageCount //总共有多少页 --计算
//栗子
if(rowCount%pageSize==0){
pageCount=rowCount/pageSize;
}
else{
pageCount=rowCount/pageSize+1
}
二、PageInfo 类
public class PageInfo {
private int pageSize; // 页面大小
private int pageCount; // 页面总数
private int pageIndex; // 当前页
private int beginRow; // 开始页
private int rowCount; // 总条数
private boolean hasNext; // 是否有后一页
private boolean hasPre; // 是否有前一页
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public int getPageCount() {
return pageCount;
}
public void setPageCount(int pageCount) {
this.pageCount = pageCount;
}
public int getPageIndex() {
return pageIndex;
}
public void setPageIndex(int pageIndex) {
this.pageIndex = pageIndex;
}
public int getBeginRow() {
return beginRow;
}
public void setBeginRow(int beginRow) {
this.beginRow = beginRow;
}
public int getRowCount() {
return rowCount;
}
public void setRowCount(int rowCount) {
this.rowCount = rowCount;
}
public boolean isHasNext() {
return hasNext;
}
public void setHasNext(boolean hasNext) {
this.hasNext = hasNext;
}
public boolean isHasPre() {
return hasPre;
}
public void setHasPre(boolean hasPre) {
this.hasPre = hasPre;
}
}
三、分页工具类
public class PageUtil {
public static PageInfo getPageInfo(int pageSize, int rowCount, int pageIndex) {
PageInfo p=new PageInfo();
pageSize=getPageSize(pageSize);
p.setPageSize(pageSize);
p.setRowCount(rowCount);
p.setPageCount(getPageCount(pageSize,rowCount));
p.setBeginRow(getBeginRow(pageSize,pageIndex));
p.setHasNext(isHasNext(pageIndex,getPageCount(pageSize,rowCount)));
p.setHasPre(isHasPre(pageIndex));
p.setPageIndex(pageIndex);
return p;
}
//判断当是否有前一页
private static boolean isHasPre(int pageIndex) {
if(pageIndex==1){
return false;
}
else {
return true;
}
}
//判断是不是有下一页
private static boolean isHasNext(int pageIndex, int pageCount) {
if(pageIndex==pageCount||pageCount==0){
return false;
}
else{
return true;
}
}
//计算从第几行开始查询
private static int getBeginRow(int pageSize, int pageIndex) {
return pageSize*(pageIndex-1);
}
//计算页的总数
private static int getPageCount(int pageSize, int rowCount) {
if(rowCount%pageSize==0){
return rowCount/pageSize;
}
else{
return rowCount/pageSize+1;
}
}
//返回pageSize
private static int getPageSize(int pageSize) {
return pageSize==0?10:pageSize;
}
}
四、页面
<script type="text/javascript">
function subForm(){
//form1.action="AdminServlet?flag=manage";
form1.submit();
}
</script> <body> <form action ="AdminServlet" method="post" name="form1">
<input type="hidden" name=flag value="manage" />
<table width=80% border=1 cellspacing=0s>
<c:forEach var="u" items="${adminList}">
<tr>
<td>${u.id }</td>
<td>${u.userName }</td>
<td>${u.password }</td>
<td>${u.note }</td>
<td><a href="admin/admin_edit.jsp?id=${u.id }" >修改</a> | <a onclick="return confirm('确定要删除吗?')"
href="AdminServlet?flag=del&id=${u.id }" >删除</a></td>
</tr>
</c:forEach>
</table> 共有 ${ pageInfo.rowCount} 条记录，当前第 ${ pageInfo.pageIndex} 页， 共 ${ pageInfo.pageCount}页
<c:choose>
<c:when test="${pageInfo.hasPre }">
<a href="AdminServlet?flag=manage&pageIndex=1" >首页</a>
<a href="AdminServlet?flag=manage&pageIndex=${pageInfo.pageIndex-1 }" >前一页 </a>
</c:when>
<c:otherwise>
首页 前一页
</c:otherwise>
</c:choose> <c:choose>
<c:when test="${pageInfo.hasNext }">
<a href="AdminServlet?flag=manage&pageIndex=${pageInfo.pageIndex+1 }" >下一页</a>
<a href="AdminServlet?flag=manage&pageIndex=${pageInfo.pageCount }" >尾页 </a>
</c:when>
<c:otherwise>
下一页 尾页
</c:otherwise>
</c:choose> <a href="javascript:subForm()" >转到</a> 第 <input type="text" name="pageIndex" value=${pageInfo.pageIndex }> 页 </form>
五、控制层
private void manage(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int pageSize=4;
int rowCount=_dao.getUserCount();
String pageIndexStr=request.getParameter("pageIndex");
int pageIndex=1;
if(!StrUtil.isNullOrEmpty(pageIndexStr)){
pageIndex=Integer.parseInt(pageIndexStr);
}
PageInfo pageInfo=PageUtil.getPageInfo(pageSize,rowCount,pageIndex);
List<UserInfo> adminList=_dao.getUserList(pageInfo);
request.setAttribute("adminList", adminList);
request.setAttribute("pageInfo", pageInfo);
request.getRequestDispatcher("/admin/admin_manage.jsp").forward(request, response);
}