java分页实现（一）
分页实现
1.工具类 MyPagination.java
package com.wgh.tools;
import java.util.ArrayList;
import java.util.List;
import com.wgh.model.Diary;
public class MyPagination {
public List list=null;
private int recordCount=0; //记录数
private int pagesize=0; //每页显示的记录数
private int maxPage=0; //最大页数
//初始化分页信息
public List getInitPage(List list,int Page,int pagesize){
List newList=new ArrayList();
this.list=list;
recordCount=list.size(); //获取list集合的元素个数
this.pagesize=pagesize;
this.maxPage=getMaxPage(); //获取最大页数
try{
for(int i=(Page-1)*pagesize;i<=Page*pagesize-1;i++){
try{
if(i>=recordCount){break;}
}catch(Exception e){}
newList.add((Diary)list.get(i));
}
}catch(Exception e){
e.printStackTrace();//输出异常信息
}
return newList;
}
//获取指定页的数据
public List getAppointPage(int Page){
List newList=new ArrayList();
try{
for(int i=(Page-1)*pagesize;i<=Page*pagesize-1;i++){
try{
if(i>=recordCount){break;}
}catch(Exception e){}
newList.add((Diary)list.get(i));
}
}catch(Exception e){
e.printStackTrace();//输出异常信息
}
return newList;
}
//获取最大记录数
public int getMaxPage(){
int maxPage=(recordCount%pagesize==0)?(recordCount/pagesize):(recordCount/pagesize+1);
return maxPage;
}
//获取总记录数
public int getRecordSize(){
return recordCount;
}
//获取当前页数
public int getPage(String str){
if(str==null){//当页数等于null时，让其等于0
str="0";
}
int Page=Integer.parseInt(str);
if(Page<1){//当页数小于1时，让其等于1
Page=1;
}else{
if(((Page-1)*pagesize+1)>recordCount){//当页数大于最大页数时，让其等于最大页数
Page=maxPage;
}
}
return Page;
}
/**
* 在页面中输出分页导航
* @param Page
* @param url
* @param para
* @return
*/
public String printCtrl(int Page,String url,String para){
String strHtml=" 当前页数：【"+Page+"/"+maxPage+"】 ";
try{
if(Page>1){
strHtml=strHtml+"第一页 ";
strHtml=strHtml+"上一页";
}
if(Page下一页 最后一页 ";
}
strHtml=strHtml+"
";
}catch(Exception e){
e.printStackTrace();
}
return strHtml;
}
}
2.控制类（数据的 删减查） DiaryServlet.java
package com.wgh.servlet;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;
import java.util.List;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import com.wgh.dao.DiaryDao;
import com.wgh.model.Diary;
import com.wgh.tools.MyPagination;
import javax.servlet.annotation.WebServlet;
/**
* Servlet implementation class DiaryServlet
*/
@WebServlet("/DiaryServlet")
public class DiaryServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
MyPagination pagination = null;// 数据分页类的对象
DiaryDao dao = null;// 日记相关的数据库操作类的对象
/**
* @see HttpServlet#HttpServlet()
*/
public DiaryServlet() {
super();
// TODO Auto-generated constructor stub
dao = new DiaryDao();// 实例化日记相关的数据库操作类的对象
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType("text/heml;charset=UTF-8");
request.setCharacterEncoding("UTF-8");
String action = request.getParameter("action");
if ("preview".equals(action)) {
preview(request, response); // 预览九宫格日记
} else if ("save".equals(action)) {
save(request, response); // 保存九宫格日记
} else if ("listAllDiary".equals(action)) {
listAllDiary(request, response); // 查询全部九宫格日记
} else if ("listMyDiary".equals(action)) {
listMyDiary(request, response); // 查询我的日记
} else if ("delDiary".equals(action)) {
delDiary(request, response); // 删除我的日记
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
/**
* 功能：删除日记
*
* @param request
* @param response
* @throws ServletException
* @throws IOException
*/
private void delDiary(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
int id = Integer.parseInt(request.getParameter("id")); // 获取要删除的日记的ID
String imgName = request.getParameter("imgName"); // 获取图片名
String url = request.getParameter("url"); // 获取返回的URL地址
int rtn = dao.delDiary(id);// 删除日记
PrintWriter out = response.getWriter();
if (rtn > 0) {// 当删除日记成功时
/************* 删除日记图片及缩略图 ******************/
String path = getServletContext().getRealPath("\\")+ "images\\diary\\";
java.io.File file = new java.io.File(path + imgName + "scale.jpg");// 获取缩略图
file.delete(); //删除指定的文件
file = new java.io.File(path + imgName + ".png");// 获取日记图片
file.delete();
/*******************************/
out
.println("");
} else {// 当删除日记失败时
out
.println("");
}
}
/**
* 功能：查询我的日记
*
* @param request
* @param response
* @throws IOException
* @throws ServletException
*/
private void listMyDiary(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();
// 获取日记内容
String strPage = (String) request.getParameter("Page");// 获取当前页码
int Page = 1;
List list = null;
if (strPage == null) {
int userid = Integer.parseInt(session.getAttribute("uid")
.toString()); // 获取用户ID号
String sql = "select d.*,u.username from tb_diary d inner join tb_user u on u.id=d.userid where d.userid="
+ userid + " order by d.writeTime DESC";// 应用内联接查询日记信息
pagination = new MyPagination();
list = dao.queryDiary(sql); // 获取日记内容
int pagesize = 4; // 指定每页显示的记录数
list = pagination.getInitPage(list, Page, pagesize); // 初始化分页信息
request.getSession().setAttribute("pagination", pagination);// 保存分页信息
} else {
pagination = (MyPagination) request.getSession().getAttribute(
"pagination");// 获取分页信息
Page = pagination.getPage(strPage);
list = pagination.getAppointPage(Page); // 获取指定页数据
}
request.setAttribute("diaryList", list); // 保存当前页的日记信息
request.setAttribute("Page", Page); // 保存的当前页码
request.setAttribute("url", "listMyDiary");// 保存当前页的URL地址
request.getRequestDispatcher("listAllDiary.jsp").forward(request,
response);// 重定向页面到listAllDiary.jsp
}
/**
* 功能：预览九宫格日记
*
* @param request
* @param response
* @throws ServletException
* @throws IOException
*/
public void preview(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String title = request.getParameter("title");// 获取日记标题
String template = request.getParameter("template");// 获取日记模板
String weather = request.getParameter("weather");// 获取天气
// 获取日记内容
String[] content = request.getParameterValues("content");
for (int i = 0; i < content.length; i++) {
if (content[i].equals(null) || content[i].equals("")
|| content[i].equals("请在此输入文字")) {
content[i] = "没啥可说的"; //为没有设置内容的项目设置默认值
}
}
HttpSession session = request.getSession(true); //获取HttpSession
session.setAttribute("template", template);// 保存选择的模板
session.setAttribute("weather", weather); // 保存天气
session.setAttribute("title", title); // 保存日记标题
session.setAttribute("diary", content); // 保存日记内容
request.getRequestDispatcher("preview.jsp").forward(request, response);// 重定向页面
}
/**
* 功能：保存九宫格日记
*
* @param request
* @param response
* @throws ServletException
* @throws IOException
*/
@SuppressWarnings("deprecation")
public void save(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
HttpSession session = request.getSession(true);
BufferedImage image = (BufferedImage) session.getAttribute("diaryImg");
String url = request.getRequestURL().toString();// 获取请求的URL地址
url = request.getRealPath("/");// 获取请求的实际地址
long date = new Date().getTime();// 获取当前时间
Random r = new Random(date);
long value = r.nextLong();// 生成一个长整型的随机数
url = url + "images/diary/" + value;// 生成图片的URL地址
String scaleImgUrl = url + "scale.jpg";// 生成缩略图的URL地址
url = url + ".png";
ImageIO.write(image, "PNG", new File(url));
/***************** 生成图片缩略图 ******************************************/
File file = new File(url); // 获取原文件
Image src = ImageIO.read(file);
int old_w = src.getWidth(null);// 获取原图片的宽
int old_h = src.getHeight(null);// 获取原图片的高
int new_w = 0;// 新图片的宽
int new_h = 0;// 新图片的高
double temp = 0;// 缩放比例
/********* 计算缩放比例 ***************/
double tagSize = 60;
if (old_w > old_h) {
temp = old_w / tagSize;
} else {
temp = old_h / tagSize;
}
/*************************************/
new_w = (int) Math.round(old_w / temp);// 计算新图片的宽
new_h = (int) Math.round(old_h / temp);// 计算新图片的高
image = new BufferedImage(new_w, new_h, BufferedImage.TYPE_INT_RGB);
src = src.getScaledInstance(new_w, new_h, Image.SCALE_SMOOTH);
image.getGraphics().drawImage(src, 0, 0, new_w, new_h, null);
ImageIO.write(image, "JPG", new File(scaleImgUrl)); // 保存缩略图文件
/***********************************************************************/
/**** 将填写的日记保存到数据库中 *****/
Diary diary = new Diary();
diary.setAddress(String.valueOf(value));// 设置图片地址
diary.setTitle(session.getAttribute("title").toString());// 设置日记标题
diary.setUserid(Integer
.parseInt(session.getAttribute("uid").toString()));// 设置用户ID
int rtn = dao.saveDiary(diary); // 保存日记
PrintWriter out = response.getWriter();
if (rtn > 0) {// 当保存成功时
out
.println("");
} else {// 当保存失败时
out
.println("");
}
/*********************************/
}
/**
* 功能：查询全部九宫格日记
*
* @param request
* @param response
* @throws ServletException
* @throws IOException
*/
public void listAllDiary(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
String strPage = (String) request.getParameter("Page");// 获取当前页码
int Page = 1;
List list = null;
if (strPage == null) {// 当页面初次运行
String sql = "select d.*,u.username from tb_diary d inner join tb_user u on u.id=d.userid order by d.writeTime DESC limit 50";
pagination = new MyPagination();
list = dao.queryDiary(sql); // 获取日记内容
int pagesize = 5; // 指定每页显示的记录数
list = pagination.getInitPage(list, Page, pagesize); // 初始化分页信息
request.getSession().setAttribute("pagination", pagination);
} else {
pagination = (MyPagination) request.getSession().getAttribute(
"pagination");
Page = pagination.getPage(strPage);// 获取当前页码
list = pagination.getAppointPage(Page); // 获取指定页数据
}
request.setAttribute("diaryList", list); // 保存当前页的日记信息
request.setAttribute("Page", Page); // 保存的当前页码
request.setAttribute("url", "listAllDiary");// 保存当前页面的URL
request.getRequestDispatcher("listAllDiary.jsp").forward(request,
response);// 重定向页面
}
}
3.分页的显示
<%response.sendRedirect(“DiaryServlet?action=listAllDiary”); %>
<%=pagination.printCtrl(Integer.parseInt(request.getAttribute("Page").toString()),"DiaryServlet?action="+request.getAttribute("url"),"")%>