JavaServlet的文件上传和下载实现方法(2)

import java.io.File; import java.io.IOException; import java.io.PrintWriter; import java.util.ArrayList; import java.util.List; import java.util.UUID; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import net.sf.json.JSONArray; import org.apache.commons.fileupload.FileItem; import org.apache.commons.fileupload.FileUploadException; import org.apache.commons.fileupload.disk.DiskFileItemFactory; import org.apache.commons.fileupload.servlet.ServletFileUpload; import com.stu.util.HttpUtil; /** * 文件名称: com.stu.fileupload.FileUpload.java<br/> * 初始作者: Administrator<br/> * 创建日期: 2018-1-31<br/> * 功能说明: 文件上传 <br/> * =================================================<br/> * 修改记录:<br/> * 修改作者 日期 修改内容<br/> * ================================================<br/> * Copyright (c) 2010-2011 .All rights reserved.<br/> */ public class FileUpload extends HttpServlet { private static final long serialVersionUID = 1L; @Override protected void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { // 获取到当前服务器所在的路径 String serverPath = req.getSession().getServletContext().getRealPath("https://www.jb51.net/"); // 设置保存上传文件的路径 String saveDirPath = serverPath + "img"; File saveDirPathFileObj = new File(saveDirPath); // 如果当用来存放文件的目录不存在时,要创建该目录 if (!saveDirPathFileObj.exists()) { saveDirPathFileObj.mkdirs(); } // 创建一个解析器工厂 DiskFileItemFactory factory = new DiskFileItemFactory(); // 设置工厂的缓存区大小 factory.setSizeThreshold(5 * 1024); // 文件上传的解析器(文件上传对象) ServletFileUpload upload = new ServletFileUpload(factory); // 设置上传文件的最大值 upload.setSizeMax(3 * 1024 * 1024); // 设置编码格式 upload.setHeaderEncoding("UTF-8"); try { // 上传以后的文件名 List<String> uploadFileNames = new ArrayList<String>(); List<FileItem> fileItems = upload.parseRequest(req); System.out.println(fileItems); for (FileItem file : fileItems) { // 新的文件名 String saveFileName = UUID.randomUUID().toString().replace("-", ""); // 文件的后缀 String oldFileName = new String(file.getName().getBytes(), "UTF-8"); System.out.println("oldFileName" + oldFileName); String fileType = oldFileName.substring(oldFileName.lastIndexOf(".")); // 新的文件路径 String saveFilePath = saveDirPath + File.separator + saveFileName + fileType; uploadFileNames.add(saveFileName + fileType); // 保存上传的文件 file.write(new File(saveFilePath)); } System.out.println(uploadFileNames); HttpUtil.setAttribute(req, "urls", uploadFileNames); res.setContentType("application/json;charset=utf-8"); PrintWriter pw = res.getWriter(); pw.print(JSONArray.fromObject(uploadFileNames)); } catch (FileUploadException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } } }

这里面用到了一个HttpUtil类,代码如下:

import javax.servlet.FilterConfig; import javax.servlet.ServletConfig; import javax.servlet.ServletContext; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpSession; /** * 文件名称_com.niit.model2.util.Httputil.java</br> * 初始作逯ܿAdministrator</br> * 创建日期_2018-1-23</br> * 功能说明_这里用一句话描述这个类的作用--此句话需删除 <br/> * =================================================<br/> * 修改记录_br/> * 修改作迠日期 修改内容<br/> * ================================================<br/> * Copyright (c) 2010-2011 .All rights reserved.<br/> */ public class HttpUtil { private HttpUtil() { } /** * 方法描述: [用于向不同的作用域存放属性]</br> * 初始作迺 Administrator<br/> * 创建日期: 2018-1-23-上午11:24:45<br/> * 弿Nj版本: 2.0.0<br/> * =================================================<br/> * 修改记录_br/> * 修改作迠日期 修改内容<br/> * ================================================<br/> * void */ public static void setAttribute(Object scopeObj, String name, Object value) { if (scopeObj instanceof HttpServletRequest) { ((HttpServletRequest) scopeObj).setAttribute(name, value); } if (scopeObj instanceof HttpSession) { ((HttpSession) scopeObj).setAttribute(name, value); } if (scopeObj instanceof ServletContext) { ((ServletContext) scopeObj).setAttribute(name, value); } } /** * 方法描述: [获取作用域中指定名称的属性思</br> * 初始作迺 Administrator<br/> * 创建日期: 2018-1-23-上午11:29:17<br/> * 弿Nj版本: 2.0.0<br/> * =================================================<br/> * 修改记录_br/> * 修改作迠日期 修改内容<br/> * ================================================<br/> * * @param scopeObj * @param name * @return * Object */ public static Object getAttribute(Object scopeObj, String name) { if (scopeObj instanceof HttpServletRequest) { return ((HttpServletRequest) scopeObj).getAttribute(name); } if (scopeObj instanceof HttpSession) { return ((HttpSession) scopeObj).getAttribute(name); } if (scopeObj instanceof ServletContext) { return ((ServletContext) scopeObj).getAttribute(name); } return null; } /** * 方法描述: [获取上下文对象的方法]</br> * 初始作迺 Administrator<br/> * 创建日期: 2018-1-23-上午11:31:26<br/> * 弿Nj版本: 2.0.0<br/> * =================================================<br/> * 修改记录_br/> * 修改作迠日期 修改内容<br/> * ================================================<br/> * * @return * ServletContext */ public static ServletContext getServletContext(Object sourceObj) { if (sourceObj instanceof HttpServletRequest) { return ((HttpServletRequest) sourceObj).getSession().getServletContext(); } if (sourceObj instanceof ServletConfig) { return ((ServletConfig) sourceObj).getServletContext(); } if (sourceObj instanceof FilterConfig) { return ((FilterConfig) sourceObj).getServletContext(); } return null; } /** * 方法描述: [获取项目的实际路径]</br> * 初始作迺 Administrator<br/> * 创建日期: 2018-1-23-上午11:45:47<br/> * 弿Nj版本: 2.0.0<br/> * =================================================<br/> * 修改记录_br/> * 修改作迠日期 修改内容<br/> * ================================================<br/> * * @param req * @return * String */ public static String getContextPath(HttpServletRequest req) { return req.getContextPath(); } }

当然,代码编辑好了也不要忘了在 WebRoot/WEB-INF/web.xml 中添加新建的Servlet,就是刚刚的两个Java文件啦

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