一个用servlet写的上传下载

深碍√TFBOYSˉ_ 2022-09-23 08:19 144阅读 0赞

本人闲来无事，写了个servlet，实现上传下载功能。启动服务后，可以在一个局域网内当一个小小的文件服务器。

一、准备工作

下载两个jar包：

commons-fileupload-1.3.1.jar  
commons-io-2.2.jar

二、创建一个web工程

我的工程名叫：z-upload

三、配置web.xml

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xmlns="http://java.sun.com/xml/ns/javaee"
    	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    	id="WebApp_ID" version="3.0">
    	<display-name>z-upload</display-name>
    	<servlet>
    		<servlet-name>UploadService</servlet-name>
    		<servlet-class>com.syz.servlet.UploadService</servlet-class>
    	</servlet>
    	<servlet-mapping>
    		<servlet-name>UploadService</servlet-name>
    		<url-pattern>/*</url-pattern>
    	</servlet-mapping>
    </web-app>

从以上配置可以看出，我的servlet类是UploadService，匹配的url是/\*，意思是匹配所有访问url。

四、写servlet类

package com.syz.servlet;
    
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.OutputStream;
    import java.io.PrintWriter;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    import java.util.Iterator;
    import java.util.List;
    
    import javax.servlet.ServletContext;
    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.FileUploadException;
    import org.apache.commons.fileupload.ProgressListener;
    import org.apache.commons.fileupload.disk.DiskFileItemFactory;
    import org.apache.commons.fileupload.servlet.ServletFileUpload;
    
    
    public class UploadService extends HttpServlet {
    
        public static final String LIST = "/list";
    
        public static final String FORM = "/form";
    
        public static final String HANDLE = "/handle";
    
        public static final String DOWNLOAD = "/download";
    
        public static final String DELETE = "/delete";
    
        public static final String UPLOAD_DIR = "/upload";
    
        private static final long serialVersionUID = 2170797039752860765L;
    
        public void execute(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
            System.out.println("execute...");
            System.out.println("------------begin---------------");
            req.setCharacterEncoding("UTF-8");
            String host = req.getRemoteHost();
            System.out.println("host:" + host);
            String uri = req.getRequestURI();
            System.out.println("uri:" + uri);
            ServletContext servletContext = this.getServletConfig()
                    .getServletContext();
            // 上传文件的基本路径
            String basePath = servletContext.getRealPath(UPLOAD_DIR);
            // 上下文路径
            String contextPath = servletContext.getContextPath();
            System.out.println("contextPath:" + contextPath);
            // 截取上下文之后的路径
            String action = uri.substring(contextPath.length());
            System.out.println("action:" + action);
            // 依据action不同进行不同的处理
            if (action.equals(FORM)) {
                form(contextPath, resp);
            }
            else if (action.equals(HANDLE)) {
                boolean isMultipart = ServletFileUpload.isMultipartContent(req);
                System.out.println("isMultipart:" + isMultipart);
                if (!isMultipart) {
                    return;
                }
                DiskFileItemFactory factory = new DiskFileItemFactory();
                File repository = (File) servletContext
                        .getAttribute(ServletContext.TEMPDIR);
                System.out.println("repository:" + repository.getAbsolutePath());
                System.out.println("basePath:" + basePath);
                factory.setSizeThreshold(1024 * 100);
                factory.setRepository(repository);
                ServletFileUpload upload = new ServletFileUpload(factory);
                // 创建监听
                ProgressListener progressListener = new ProgressListener() {
                    public void update(long pBytesRead, long pContentLength,
                            int pItems) {
                        System.out.println("当前文件大小:" + pContentLength + "\t已经处理:"
                                + pBytesRead);
                    }
                };
                upload.setProgressListener(progressListener);
                List<FileItem> items = null;
                try {
                    items = upload.parseRequest(req);
                    System.out.println("items size:" + items.size());
                    Iterator<FileItem> ite = items.iterator();
                    while(ite.hasNext()){
                        FileItem item = ite.next();
                        if(item.isFormField()){
                            // handle FormField
                        }else{
                            // handle file
                            String fieldName = item.getFieldName();
                            String fileName = item.getName();
                            fileName = fileName.substring(
                                    fileName.lastIndexOf(File.separator) + 1);
                            String contentType = item.getContentType();
                            boolean isInMemory = item.isInMemory();
                            long sizeInBytes = item.getSize();
                            System.out.println(fieldName + "\t" + fileName + "\t"
                                    + contentType + "\t" + isInMemory + "\t"
                                    + sizeInBytes);
                            File file = new File(
                                    basePath + "/" + fileName + "_" + getSuffix());
                            // item.write(file);
                            InputStream in = item.getInputStream();
                            OutputStream out = new FileOutputStream(file);
                            byte[] b = new byte[1024];
                            int n = 0;
                            while ((n = in.read(b)) != -1) {
                                out.write(b, 0, n);
                            }
                            out.flush();
                            in.close();
                            out.close();
                        }
                    }
                    // 处理完后重定向到文件列表页面
                    String href1 = contextPath + LIST;
                    resp.sendRedirect(href1);
                }
                catch (FileUploadException e) {
                    e.printStackTrace();
                }
                catch (Exception e) {
                    e.printStackTrace();
                }
            }
            else if (action.equals(LIST)) {
                list(contextPath, basePath, resp);
            }
            else if (action.equals(DOWNLOAD)) {
                String id = req.getParameter("id");
                System.out.println("id:" + id);
                if (id == null) {
                    return;
                }
                File file = new File(basePath);
                File[] list = file.listFiles();
                int len = list.length;
                boolean flag = false;
                for (int i = 0; i < len; i++) {
                    File f = list[i];
                    String fn = f.getName();
                    if (f.isFile() && fn.lastIndexOf("_") > -1) {
                        String fid = fn.substring(fn.lastIndexOf("_"));
                        if (id.equals(fid)) {
                            download(f, resp);
                            flag = true;
                            break;
                        }
                    }
                }
                if (!flag) {
                    notfound(contextPath, resp);
                }
            }
            else if (action.equals(DELETE)) {
                String id = req.getParameter("id");
                System.out.println("id:" + id);
                if (id == null) {
                    return;
                }
                File file = new File(basePath);
                File[] list = file.listFiles();
                int len = list.length;
                boolean flag = false;
                for (int i = 0; i < len; i++) {
                    File f = list[i];
                    String fn = f.getName();
                    if (f.isFile() && fn.lastIndexOf("_") > -1) {
                        String fid = fn.substring(fn.lastIndexOf("_"));
                        if (id.equals(fid)) {
                            f.delete();
                            flag = true;
                            break;
                        }
                    }
                }
                if (flag) {
                    // 处理完后重定向到文件列表页面
                    String href1 = contextPath + LIST;
                    resp.sendRedirect(href1);
                }
                else {
                    notfound(contextPath, resp);
                }
            }
            else {
                show404(contextPath, resp);
            }
            System.out.println("------------end---------------");
        }
    
        private void show404(String contextPath, HttpServletResponse resp)
                throws IOException {
            resp.setContentType("text/html;charset=utf-8");
            PrintWriter out = resp.getWriter();
            String href1 = contextPath + LIST;
            out.write("<html>");
            out.write("<head><title>404</title></thead>");
            out.write("<body>");
            out.write("<b>您所访问的页面不存在！<a href='" + href1 + "'>点击</a>返回文件列表</b>");
            out.write("</body>");
            out.write("</html>");
            out.close();
        }
    
        private void form(String contextPath, HttpServletResponse resp)
                throws IOException {
            resp.setContentType("text/html;charset=utf-8");
            PrintWriter out = resp.getWriter();
            String href1 = contextPath + LIST;
            out.write("<html>");
            out.write("<head><title>form</title></thead>");
            out.write("<body>");
            out.write("<b><a href='" + href1 + "'>点击</a>返回文件列表</b>");
            out.write(
                    "<form action='handle' method='post' enctype='multipart/form-data' style='margin-top:20px;'>");
            out.write("<input name='file' type='file'/><br>");
            out.write("<input type='submit' value='上传'/><br>");
            out.write("</form>");
            out.write("</body>");
            out.write("</html>");
            out.close();
        }
    
        private void notfound(String contextPath, HttpServletResponse resp)
                throws IOException {
            resp.setContentType("text/html;charset=utf-8");
            PrintWriter out = resp.getWriter();
            String href1 = contextPath + LIST;
            out.write("<html><body><b>操作失败！文件不存在或文件已经被删除！<a href='" + href1
                    + "'>点击</a>返回文件列表</b></body></html>");
            out.close();
        }
    
        private void download(File f, HttpServletResponse resp)
                throws IOException {
            String fn = f.getName();
            String fileName = fn.substring(0, fn.lastIndexOf("_"));
            System.out.println("fileName:" + fileName);
            resp.reset();
            resp.setContentType("application/octet-stream");
            String encodingFilename = new String(fileName.getBytes("GBK"),
                    "ISO8859-1");
            System.out.println("encodingFilename:" + encodingFilename);
            resp.setHeader("content-disposition",
                    "attachment;filename=" + encodingFilename);
            InputStream in = new FileInputStream(f);
            OutputStream out = resp.getOutputStream();
            byte[] b = new byte[1024];
            int n = 0;
            while ((n = in.read(b)) != -1) {
                out.write(b, 0, n);
            }
            out.flush();
            in.close();
            out.close();
        }
    
        private void list(String contextPath, String basePath,
                HttpServletResponse resp)
                throws IOException {
            String href_u = contextPath + FORM;
            resp.setContentType("text/html;charset=utf-8");
            PrintWriter out = resp.getWriter();
            out.write("<html>");
            out.write("<head><title>list</title></thead>");
            out.write("<body>");
            out.write("<b>我要<a href='" + href_u + "'>上传</a></b><br>");
            out.write(
                    "<table border='1' style='border-collapse:collapse;width:100%;margin-top:20px;'>");
            out.write("<thead>");
            out.write("<tr>");
            out.write("<th>序号</th><th>文件名</th><th>操作</th>");
            out.write("</tr>");
            out.write("</thead>");
            out.write("<tbody>");
            File file = new File(basePath);
            File[] list = file.listFiles();
            System.out
                    .println("basePath:" + basePath + "\tlist.size:" + list.length);
            int len = list.length;
            int no = 1;
            for (int i = 0; i < len; i++) {
                File f = list[i];
                System.out.println(i + "\t" + f.getName());
                String fn = f.getName();
                if (f.isFile() && fn.lastIndexOf("_") > -1) {
                    String filename = fn.substring(0, fn.lastIndexOf("_"));
                    String id = fn.substring(fn.lastIndexOf("_"));
                    String href1 = contextPath + DOWNLOAD + "?id=" + id;
                    String href2 = contextPath + DELETE + "?id=" + id;
                    StringBuilder sb = new StringBuilder();
                    sb.append("<tr>");
                    sb.append("<td>");
                    sb.append(no++);
                    sb.append("</td>");
                    sb.append("<td>");
                    sb.append(filename);
                    sb.append("</td>");
                    sb.append("<td>");
                    sb.append("<a href='");
                    sb.append(href1);
                    sb.append("'>下载</a> <a href='");
                    sb.append(href2);
                    sb.append("' οnclick='return confirm(\"您确定要删除吗？\");'>删除</a>");
                    sb.append("</td>");
                    sb.append("</tr>");
                    out.write(sb.toString());
                }
            }
            out.write("</tbody>");
            out.write("</table>");
            out.write("</body>");
            out.write("</html>");
            out.close();
        }
    
        public void doGet(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
            System.out.println("doGet...");
            execute(req, resp);
        }
    
        public void doPost(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException {
            System.out.println("doPost...");
            execute(req, resp);
        }
    
        private String getSuffix() {
            Date date = new Date();
            SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmssSSS");
            String suffix = sdf.format(date);
            return suffix;
        }
    }

其实UploadService类可以直接实现service方法，而不用实现doGet、doPost方法。

以上servlet我也不想多解释什么，自己看代码吧。

五、效果图

1.项目结构图

![Center][]

2.404页面

![Center 1][]

/\*会匹配所有包括空字符，所以图片中的路径会匹配，在UploadService中的if判断中出现在else中，因为此时的action是空字符。

3.文件列表页面

![Center 2][]

4.上传表单页面

![Center 3][]

5.下载

![Center 4][]

6.删除

![Center 5][]

7.文件找不到，如果你点删除时，文件在服务器上已经不存在，那么会进入此页面

![Center 6][]

8.打包的源码工程和war包

![Center 7][]

其中z-upload是eclipse源码工程，z-upload.war是打好的war包

全工程就两个jar包，一个web.xml和一个servlet类，可以自己从文章中拷贝过去测试一下，如果是懒人，可以下载

[http://download.csdn.net/detail/yunsyz/9569680][http_download.csdn.net_detail_yunsyz_9569680]

特别提醒，下载要1分哦。

[Center]: /images/20220721/6394d75d0c6444e9832f0b0edd4e2c34.png
[Center 1]: /images/20220721/23b0d244a0a14502beadbdcd434f5f51.png
[Center 2]: /images/20220721/a41aa12f6bf24bfebc511f3eb5633473.png
[Center 3]: /images/20220721/714c5f5f6828438d8b07e14cc2dcf49c.png
[Center 4]: /images/20220721/ece71f6b2ec240e08397bd7384485954.png
[Center 5]: /images/20220721/9cce08a46d9a489c87a446f4bf0e4d95.png
[Center 6]: /images/20220721/c1f8b497d32f4cb59b9887b130c654ca.png
[Center 7]: /images/20220721/3a17a4c516dc4c2a97b6d64b96e8f936.png
[http_download.csdn.net_detail_yunsyz_9569680]: http://download.csdn.net/detail/yunsyz/9569680