页面分页实现、文件上传和下载
分页实现
思路：
-
确定每页显示的数据数量
-
确定分页显示所需的总页数
-
编写SQL查询语句，实现数据查询
-
# oracle select * from (select ROWNUM rn,t.* from (select * from 要查询的表名 [where 条件][...] ) t where ROWNUM <= 结束索引) temp where temp.rn >= 开始索引;
-
-
在面中进行分页显示设置
封装Pageable类
import java.util.List;
public class Pageable<Type> {
private int currPageNo; // 当前页码
private int pageSize; // 页面大小，即每页显示记录数
private int totalCount; // 总记录数
private int totalPageCount; // 总页数
List<Type> list; // 每页Type类型的集合
public Pageable() {
}
public Pageable(int currPageNo, int pageSize) {
this.currPageNo = currPageNo;
this.pageSize = pageSize;
}
public int getCurrPageNo() {
return currPageNo;
}
public void setCurrPageNo(int currPageNo) {
this.currPageNo = currPageNo;
}
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;
}
public int gettotalPageCount() {
return totalPageCount;
}
public void settotalPageCount(int totalPageCount) {
this.totalPageCount = totalPageCount;
}
public List<Type> getList() {
return list;
}
public void setList(List<Type> list) {
this.list = list;
}
}
计算总页数：totalPageCunt = (int)Math.celi(1.0 * totalCount / pageSize)
开始索引:startIndex = (currPageNo - 1 ) * pageSize + 1
结束索引endIndex= currPageNo * pageSize + 1
文件上传
前端代码
<!-- 文件上传一定要有enctype="multipart/form-data" 且必须为post提交 -->
<form action='#' method='post' enctype="multipart/form-data">
账号：<input type="text" name="username" placeholder="请输入账号"><br>
密码：<input type="password" name="password" placeholder="请输入密码"><br>
<input type="file" name="file"><br>
<input type="submit" value="上传">
</form>
后端代码
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadBase;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.Date;
import java.util.List;
@WebServlet("/uploadFile")
public class UploadFileServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
ServletOutputStream out = response.getOutputStream();
try {
// 文件上传
// 1、创建文件工厂
DiskFileItemFactory factory = new DiskFileItemFactory();
factory.setSizeThreshold(1024 * 1024 * 10); // 设置缓存大小
String realPath = getServletContext().getRealPath("/tempfile");
File file = new File(realPath);
if (!file.exists()) {
file.mkdirs();
}
factory.setRepository(file);
// 2、创建upload对象
ServletFileUpload upload = new ServletFileUpload(factory);
request.setCharacterEncoding("utf8");
// 设置单文件大小
upload.setSizeMax(1024 * 500);
// 设置总文件大小
upload.setFileSizeMax(1024 * 1024 * 5);
// 3、解析request
List<FileItem> list = null;
list = upload.parseRequest(request);
// 4、遍历集合
for (FileItem item : list) {
if (item.isFormField()) { // 普通的表单字段
String fieldName = item.getFieldName();
String value = item.getString();
value = new String(value.getBytes(StandardCharsets.ISO_8859_1), StandardCharsets.UTF_8);
System.out.println(fieldName + " - " + value);
} else {
String fieldName = item.getFieldName();
String fileName = item.getName();
long size = item.getSize();
if ("".equals(fileName) && size == 0) {
break;
}
String contentType = item.getContentType();
System.out.println(fieldName + " - " + fileName + " - " + size + " - " + contentType);
if (!contentType.contains("image")) {
out.print("文件只能是图片！");
return;
}
String suffix = fileName.substring(fileName.lastIndexOf('.'));
String simpleName = fileName.substring(0, fileName.lastIndexOf('.'));
String newFileName = simpleName + "_" + new Date().getTime() + suffix;
realPath = getServletContext().getRealPath("/upload");
file = new File(realPath + "/" + newFileName);
if (!file.getParentFile().exists()) {
file.getParentFile().mkdirs();
}
file.createNewFile();
// 保存起来
item.write(file);
}
}
} catch (FileUploadBase.SizeLimitExceededException e) {
out.print("文件太大了！最大500kb哦！");
} catch (Exception ignore) {
}
response.sendRedirect(request.getContextPath() + "/fileList.jsp");
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
用到的JAR包
- commons-fileupload-1.2.1.jar
- commons-io-1.3.2.jar
文件下载
前台jsp代码
<%@ page import="java.io.File" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>文件展示</title>
</head>
<body>
<%
String realPath = application.getRealPath("/upload");
File path = new File(realPath);
if (!path.exists()) {
out.print("文件夹不存在！");
return;
}
File[] files = path.listFiles();
%>
<ul>
<%
for (File file : files) {
%>
<li><%=file.getName()%> <a href="<%=request.getContextPath()%>/downloadFile?fileName=<%=file.getName()%>">下载</a></li>
<%
}
%>
</ul>
</body>
</html>
后台代码
import javax.activation.MimetypesFileTypeMap;
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 java.io.*;
import java.net.URLDecoder;
import java.net.URLEncoder;
@WebServlet("/downloadFile")
public class DownloadFileServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf8");
// 获取请求文件名
String fileName = request.getParameter("fileName");
// 获取文件路径
String filePath = getServletContext().getRealPath("/upload") + "/" + fileName;
// 设置Content-Disposition
response.addHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF8"));
//好了 ，现在通过IO流来传送数据
FileInputStream input = new FileInputStream(filePath);
OutputStream output = response.getOutputStream();
byte[] buff = new byte[1024 * 10];//可以自己 指定缓冲区的大小
int len = 0;
while ((len = input.read(buff)) > -1) {
output.write(buff, 0, len);
}
//关闭输入输出流
input.close();
output.close();
response.sendRedirect(request.getContextPath() + "/fileList.jsp");
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
