【Java编码】Java原生实现上传下载文件

Java实现上传下载文件

一、上传源码

	/*** 1. 上传*/private void upload(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {try {// 1. 创建工厂对象FileItemFactory factory = new DiskFileItemFactory();// 2. 文件上传核心工具类ServletFileUpload upload = new ServletFileUpload(factory);// 设置大小限制参数upload.setFileSizeMax(10*1024*1024);	// 单个文件大小限制upload.setSizeMax(50*1024*1024);		// 总文件大小限制upload.setHeaderEncoding("UTF-8");		// 对中文文件编码处理// 判断if (upload.isMultipartContent(request)) {// 3. 把请求数据转换为list集合List<FileItem> list = upload.parseRequest(request);// 遍历for (FileItem item : list){// 判断：普通文本数据if (item.isFormField()){// 获取名称String name = item.getFieldName();// 获取值String value = item.getString();System.out.println(value);} // 文件表单项else {/******** 文件上传 ***********/// a. 获取文件名称String name = item.getName();// ----处理上传文件名重名问题----// a1. 先得到唯一标记String id = UUID.randomUUID().toString();// a2. 拼接文件名name = id + "#" + name;						// b. 得到上传目录String basePath = getServletContext().getRealPath("/upload");// c. 创建要上传的文件对象File file = new File(basePath,name);// d. 上传item.write(file);item.delete();  // 删除组件运行时产生的临时文件}}}} catch (Exception e) {e.printStackTrace();}}

二、下载源码

	/***  2.下载*/private void down(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// 获取用户下载的文件名称(url地址后追加数据,get)String fileName = request.getParameter("fileName");fileName = new String(fileName.getBytes("ISO8859-1"),"UTF-8");// 先获取上传目录路径String basePath = getServletContext().getRealPath("/upload");// 获取一个文件流InputStream in = new FileInputStream(new File(basePath,fileName));// 如果文件名是中文，需要进行url编码fileName = URLEncoder.encode(fileName, "UTF-8");// 设置下载的响应头response.setHeader("content-disposition", "attachment;fileName=" + fileName);// 获取response字节流OutputStream out = response.getOutputStream();byte[] b = new byte[1024];int len = -1;while ((len = in.read(b)) != -1){out.write(b, 0, len);}// 关闭out.close();in.close();
}

三、测试案例

package cn.demo.servlet;import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.UUID;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;/*** 处理文件上传与下载* @author Douglas*/
public class FileServlet extends HttpServlet {/*** 请求入口*/public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// 获取请求参数： 区分不同的操作类型String method = request.getParameter("method");if ("upload".equals(method)) {// 上传upload(request,response);}else if ("downList".equals(method)) {// 进入下载列表downList(request,response);}else if ("down".equals(method)) {// 下载down(request,response);}}/*** 1. 上传*/private void upload(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {try {// 1. 创建工厂对象FileItemFactory factory = new DiskFileItemFactory();// 2. 文件上传核心工具类ServletFileUpload upload = new ServletFileUpload(factory);// 设置大小限制参数upload.setFileSizeMax(10*1024*1024);	// 单个文件大小限制upload.setSizeMax(50*1024*1024);		// 总文件大小限制upload.setHeaderEncoding("UTF-8");		// 对中文文件编码处理// 判断if (upload.isMultipartContent(request)) {// 3. 把请求数据转换为list集合List<FileItem> list = upload.parseRequest(request);// 遍历for (FileItem item : list){// 判断：普通文本数据if (item.isFormField()){// 获取名称String name = item.getFieldName();// 获取值String value = item.getString();System.out.println(value);} // 文件表单项else {/******** 文件上传 ***********/// a. 获取文件名称String name = item.getName();// ----处理上传文件名重名问题----// a1. 先得到唯一标记String id = UUID.randomUUID().toString();// a2. 拼接文件名name = id + "#" + name;						// b. 得到上传目录String basePath = getServletContext().getRealPath("/upload");// c. 创建要上传的文件对象File file = new File(basePath,name);// d. 上传item.write(file);item.delete();  // 删除组件运行时产生的临时文件}}}} catch (Exception e) {e.printStackTrace();}	}/*** 2. 进入下载列表*/private void downList(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// 实现思路：先获取upload目录下所有文件的文件名，再保存；跳转到down.jsp列表展示//1. 初始化map集合Map<包含唯一标记的文件名, 简短文件名>  ;Map<String,String> fileNames = new HashMap<String,String>();//2. 获取上传目录，及其下所有的文件的文件名String bathPath = getServletContext().getRealPath("/upload");// 目录File file = new File(bathPath);// 目录下，所有文件名String list[] = file.list();// 遍历，封装if (list != null && list.length > 0){for (int i=0; i<list.length; i++){// 全名String fileName = list[i];// 短名String shortName = fileName.substring(fileName.lastIndexOf("#")+1);// 封装fileNames.put(fileName, shortName);}}// 3. 保存到request域request.setAttribute("fileNames", fileNames);// 4. 转发request.getRequestDispatcher("/downlist.jsp").forward(request, response);}/***  3. 处理下载*/private void down(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// 获取用户下载的文件名称(url地址后追加数据,get)String fileName = request.getParameter("fileName");fileName = new String(fileName.getBytes("ISO8859-1"),"UTF-8");// 先获取上传目录路径String basePath = getServletContext().getRealPath("/upload");// 获取一个文件流InputStream in = new FileInputStream(new File(basePath,fileName));// 如果文件名是中文，需要进行url编码fileName = URLEncoder.encode(fileName, "UTF-8");// 设置下载的响应头response.setHeader("content-disposition", "attachment;fileName=" + fileName);// 获取response字节流OutputStream out = response.getOutputStream();byte[] b = new byte[1024];int len = -1;while ((len = in.read(b)) != -1){out.write(b, 0, len);}// 关闭out.close();in.close();}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doGet(request, response);}}