文件上傳和下載

2019-11-15 01:12:25

字體：大中小

供稿：網(wǎng)友

文件上傳和下載1. 文件上傳1.1 快速入門1.1.1提供上傳頁面,upload.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>  </head>  <body>  <!--   1. 表單提交方式post  2. 表單的enctype="multipart/form-data"  1. 表單要上傳文件輸入項type="file"   -->  <form method="post" enctype="multipart/form-data" action="/upload/upload">      上傳人: <input type="text" name="name"><br/>      請上傳圖片:<input type="file" name="file"><br>      <input type="submit" value="上傳">  </form>  </body></html>

1.1.2編寫servlet處理提供的數(shù)據(jù)

fileupload組件工作流程

DiskFileItemFactory
工廠得到servletFileupload解析器
servletFileupload關(guān)聯(lián) request
解析器將form映射為FileItem
isFormField判斷Item是普通字段還是文件.true表示是普通字段```import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.util.List;

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.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;

/**

完成文件上傳 */public class UploadServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { / 由于form的enctype屬性原因,以下代碼獲取不了上傳數(shù)據(jù): String * name=request.getParameter("name"); String * file=request.getParameter("file"); ServletInputStream in = * request.getInputStream(); */

// apache提供了開源的commons-fileupload組件,只需要在工程中導(dǎo)入使用// 1.導(dǎo)入commons-fileupload-1.2.1.jar,commons-io-1.4.jar到lib// 2.拿到工廠DiskFileItemFactory factory = new DiskFileItemFactory();// 3.拿到解析器對象ServletFileUpload uploader = new ServletFileUpload(factory);// 4.關(guān)聯(lián)到requestList<FileItem> list;try {    list = uploader.parseRequest(request);    for (FileItem fileItem : list) {        if (fileItem.isFormField()) {            // 普通的輸入項            // 獲得普通輸入項字段的名稱            String fieldName = fileItem.getFieldName();            // 獲得普通輸入項字段的名稱對應(yīng)的值            String fieldValue = fileItem.getString();        } else {            // 文件上傳輸入項            // 獲得上傳文件名字            String name = fileItem.getName();            // 獲得上傳文件輸入流            InputStream in = fileItem.getInputStream();            OutputStream out = new FileOutputStream("D://" + name);            int len = 0;            byte[] buf = new byte[1024];            while ((len = in.read(buf)) != -1) {                out.write(buf, 0, len);            }            in.close();            out.close();        }    }} catch (Exception e) {    // TODO Auto-generated catch block    e.PRintStackTrace();}

}

public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response);}}

##### 1.2 文件上傳若干需要注意的細節(jié) 1. 文件上傳時普通的輸入項中文的亂碼問題java//這里使用UTF-8進行解碼String fieldValue=fileItem.getString("UTF-8");2. 上傳時中文文件名稱亂碼java//設(shè)置解析事,中文文件名解析的碼表uploader.setHeaderEncoding("UTF-8");3. 上傳的時候,表單必須設(shè)置三個值.判斷文件上傳的時候,提交的數(shù)據(jù)是否是文件上傳的表單java//判斷是否文件上傳的表單if(!ServletFileUpload.isMultipartContent(request)){ //說明不是文件上傳的表單,下面的代碼不再執(zhí)行 request.setAttribute("message", "對不起,您的表單不符合規(guī)范,請檢查表單屬性設(shè)置..."); request.getRequestDispatcher("/upload.jsp").forward(request, response); return;}4. 限定上傳文件的大小.java//限定上傳文件的大小uploader.setFileSizeMax(102410242);//以kb為單位,限制單個文件大小uploader.setSizeMax(1024102420);//限制總的文件大小20M當(dāng)超過大小限制時,就會拋出異常.就可以捕獲異常javacatch (FileUploadBase.FileSizeLimitExceededException e) { // 單個文件大小超過限制 request.setAttribute("message", "對不起,上傳單個文件大小超過限制..."); request.getRequestDispatcher("/upload.jsp").forward(request, response); } catch (FileUploadBase.SizeLimitExceededException e) { // 總的文件大小超過限制 request.setAttribute("message", "對不起,總的文件大小超過限制..."); request.getRequestDispatcher("/upload.jsp").forward(request, response); }5. 限制上傳的文件類型java//將允許的文件類型準(zhǔn)備好String[] extensions={".jpg",".bmp",".png"};如果不合法javaboolean flag = false;for (String ex : extensions) { if (name.endsWith(ex)) { flag = true; break; }}if (!flag) { // 文件類型不合法,需要給用戶友好信息 request.setAttribute("message", "對不起,文件類型不合法..."); request.getRequestDispatcher("/upload.jsp").forward( request, response); return;}6. 針對不同瀏覽器解決文件上傳名稱的問題javaString name = fileItem.getName();// 有些瀏覽器獲得的name是E:/1.bmp// 這個索引是最后一個/所在索引位置int lastIndex = name.lastIndexOf("/");if (lastIndex != -1) { name = name.substring(lastIndex + 1);}7. 解決文件上傳時,同名文件被覆蓋問題.為了解決這個問題,生成文件名字要唯一,可以使用java提供的UUID的類.生成一個隨機128值.java//生成不同名文件名,避免覆蓋問題 name=UUID.randomUUID().toString().replace("-", "")+"_"+name;8. 上傳的內(nèi)容是惡意內(nèi)容,網(wǎng)站被攻擊將上傳文件放在一個特定文件夾下,不讓外界直接訪問.上傳文件放在WEB-INF目錄下保護起來.java//獲得WEB-INF目錄下upload文件夾的路徑 String filePath=getServletContext().getRealPath("/WEB-INF/upload"); InputStream in = fileItem.getInputStream(); FileOutputStream out = new FileOutputStream(new File(filePath,UUIDName));

9. 避免上傳文件夾文件過多,導(dǎo)致打開文件夾出現(xiàn)性能上問題,比如文件過多,打開較慢需要設(shè)計一套算法,保障上傳文件分散放在多級目錄

1.每隔一段時間創(chuàng)建一個文件夾,然后放上傳的文件2.哈希算法,根據(jù)hash值二進制每隔4位的值創(chuàng)建一層目錄.javaprivate String generatedRandomDir(String filePath, String uUIDName) { int hashCode = uUIDName.hashCode(); int dir1 = hashCode & 0xf;// 一級目錄 int dir2 = (hashCode >> 4) & 0xf;// 二級目錄 String path = filePath + File.separator + dir1 + File.separator + dir2; File file = new File(path); if (!file.exists()) { file.mkdirs(); } return path; }10. 上傳時設(shè)置監(jiān)聽器監(jiān)聽上傳進度javaProgressListener progressListener = new ProgressListener() { private long megaBytes = -1;

            public void update(long pBytesRead, long pContentLength,                    int pItems) {                long mBytes = pBytesRead / 1000000;                if (megaBytes == mBytes) {                    return;                }                megaBytes = mBytes;                System.out.println("We are currently reading item "                        + pItems);                if (pContentLength == -1) {                    System.out.println("So far, " + pBytesRead                            + " bytes have been read.");                } else {                    System.out.println("So far, " + pBytesRead + " of "                            + pContentLength + " bytes have been read.");                }            }        };        // 設(shè)置監(jiān)聽器一定在解析之前設(shè)置        uploader.setProgressListener(progressListener);

11. 為了加快上傳速度,可以設(shè)置臨時緩沖區(qū)大小以及上傳時臨時文件存放位置.上傳完成后,臨時文件給刪掉.java//設(shè)置臨時緩存區(qū)大小factory.setSizeThreshold(102412042);//2M//設(shè)置上傳時,臨時文件的位置factory.setRepository(new File(getServletContext().getRealPath("/tmp")));java//刪除臨時文件,該方法放在流關(guān)閉之后fileItem.delete();

 實現(xiàn)代碼

import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;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 org.apache.commons.fileupload.FileItem;import org.apache.commons.fileupload.FileUploadBase;import org.apache.commons.fileupload.ProgressListener;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class Upload2Servlet extends HttpServlet { /** * 文件上傳,需要注意的問題 */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 將允許的文件類型準(zhǔn)備好 String[] extensions = { ".jpg", ".bmp", ".png" };

    // 判斷是否文件上傳的表單    if (!ServletFileUpload.isMultipartContent(request)) {        // 說明不是文件上傳的表單,下面的代碼不再執(zhí)行        request.setAttribute("message", "對不起,您的表單不符合規(guī)范,請檢查表單屬性設(shè)置...");        request.getRequestDispatcher("/upload.jsp").forward(request,                response);        return;    }    try {        DiskFileItemFactory factory = new DiskFileItemFactory();        //設(shè)置臨時緩存區(qū)大小        factory.setSizeThreshold(1024*1204*2);//2M        //設(shè)置上傳時,臨時文件的位置        factory.setRepository(new File(getServletContext().getRealPath("/tmp")));        ServletFileUpload uploader = new ServletFileUpload(factory);        // 限定上傳文件的大小        uploader.setFileSizeMax(1024 * 1024 * 2);// 以kb為單位,限制單個文件大小        uploader.setSizeMax(1024 * 1024 * 20);// 限制總的文件大小20M        // 設(shè)置解析事,中文文件名解析的碼表        uploader.setHeaderEncoding("UTF-8");        // 設(shè)置監(jiān)聽器,監(jiān)聽上傳進度        // 這里的update方法不定時被解析器調(diào)用到,        // pBytesRead:上傳文件已經(jīng)解析多少        // pContentLength:上傳單個文件總的大小        // pItems:當(dāng)前上傳的是第幾個Item        ProgressListener progressListener = new ProgressListener() {            private long megaBytes = -1;            public void update(long pBytesRead, long pContentLength,                    int pItems) {                long mBytes = pBytesRead / 1000000;                if (megaBytes == mBytes) {                    return;                }                megaBytes = mBytes;                System.out.println("We are currently reading item "                        + pItems);                if (pContentLength == -1) {                    System.out.println("So far, " + pBytesRead                            + " bytes have been read.");                } else {                    System.out.println("So far, " + pBytesRead + " of "                            + pContentLength + " bytes have been read.");                }            }        };        // 設(shè)置監(jiān)聽器一定在解析之前設(shè)置        uploader.setProgressListener(progressListener);        List<FileItem> list = uploader.parseRequest(request);        for (FileItem fileItem : list) {            if (fileItem.isFormField()) {                String fieldName = fileItem.getFieldName();                // 這里使用UTF-8進行解碼                String fieldValue = fileItem.getString("UTF-8");            } else {                String name = fileItem.getName();                // 有些瀏覽器獲得的name是E:/1.bmp.針對不同瀏覽器解決上傳時文件名稱問題                // 這個索引是最后一個/所在索引位置                int lastIndex = name.lastIndexOf("//");                if (lastIndex != -1) {                    name = name.substring(lastIndex + 1);                }                boolean flag = false;                for (String ex : extensions) {                    if (name.endsWith(ex)) {                        flag = true;                        break;                    }                }                if (!flag) {                    // 文件類型不合法,需要給用戶友好信息                    request.setAttribute("message", "對不起,文件類型不合法...");                    request.getRequestDispatcher("/upload.jsp").forward(                            request, response);                    return;                }                // 獲得WEB-INF目錄下upload文件夾的路徑                String filePath = getServletContext().getRealPath(                        "/WEB-INF/upload");                // 生成不同名文件名,避免覆蓋問題                String UUIDName = UUID.randomUUID().toString()                        .replace("-", "")                        + "_" + name;                // 生成隨機文件夾,保存上傳文件                filePath = generatedRandomDir(filePath, UUIDName);                InputStream in = fileItem.getInputStream();                FileOutputStream out = new FileOutputStream(new File(                        filePath, UUIDName));                int len = 0;                byte[] buf = new byte[1024];                while ((len = in.read(buf)) != -1) {                    out.write(buf, 0, len);                }                in.close();                out.close();                //刪除臨時文件,該方法放在流關(guān)閉之后                fileItem.delete();            }        }    } catch (FileUploadBase.FileSizeLimitExceededException e) {        // 單個文件大小超過限制        request.setAttribute("message", "對不起,上傳單個文件大小超過限制...");        request.getRequestDispatcher("/upload.jsp").forward(request,                response);    } catch (FileUploadBase.SizeLimitExceededException e) {        // 總的文件大小超過限制        request.setAttribute("message", "對不起,總的文件大小超過限制...");        request.getRequestDispatcher("/upload.jsp").forward(request,                response);    } catch (Exception e) {        e.printStackTrace();    }}private String generatedRandomDir(String filePath, String uUIDName) {    int hashCode = uUIDName.hashCode();    int dir1 = hashCode & 0xf;// 一級目錄    int dir2 = (hashCode >> 4) & 0xf;// 二級目錄    String path = filePath + File.separator + dir1 + File.separator + dir2;    File file = new File(path);    if (!file.exists()) {        file.mkdirs();    }    return path;}public void doPost(HttpServletRequest request, HttpServletResponse response)        throws ServletException, IOException {    doGet(request, response);}public static void main(String[] args) {    System.out.println(UUID.randomUUID().toString().replace("-", ""));}

}

#### 2. 文件下載1. 告訴瀏覽器以下載方式打開要訪問的數(shù)據(jù)

//設(shè)置content-diposition:attachement:filename=1.txt2. 將下載的文件當(dāng)作一個流與response.getOutputStream關(guān)聯(lián)起來.javaInputStream in=new FileInputStream("d:/aa/bb/1.txt");OutputStream out=response.getOutStream();----IO流拷貝```

3.綜合練習(xí),完成文件上傳和下載

要求:

數(shù)據(jù)庫保存上傳文件信息
使用上傳組件

步驟:

搭建環(huán)境,組合工程(包結(jié)構(gòu),數(shù)據(jù)庫,必要的jar包,封裝數(shù)據(jù)的java類)

準(zhǔn)備好數(shù)據(jù)庫 sql create database upload_download; use upload_download; create table upfiles ( id varchar(100) primary key, uuidname varchar(80), filename varchar(80), savepath varchar(150), uploadtime timestamp,//數(shù)據(jù)庫自動將當(dāng)前時間插入 description varchar(255), username varchar(10) );
導(dǎo)入jar包
準(zhǔn)備封裝數(shù)據(jù)的javaBean java package com.domain; import java.sql.Timestamp; /** create table upfiles ( id varchar(100) primary key, uuidname varchar(80), filename varchar(80), savepath varchar(150), uploadtime timestamp, description varchar(255), username varchar(10) ); */ public class UpFile { private String id; private String uuidname;//上傳文件的名稱,文件的uuid名 private String filename;//上傳文件的真實名稱 private String savepath;//上傳文件的路徑 private Timestamp uploadtime;//上傳時間 private String description;//文件描述 private String username;//上傳人 public String getId() { return id; } public void setId(String id) { this.id = id; } public String getUuidname() { return uuidname; } public void setUuidname(String uuidname) { this.uuidname = uuidname; } public String getFilename() { return filename; } public void setFilename(String filename) { this.filename = filename; } public String getSavepath() { return savepath; } public void setSavepath(String savepath) { this.savepath = savepath; } public Timestamp getUploadtime() { return uploadtime; } public void setUploadtime(Timestamp uploadtime) { this.uploadtime = uploadtime; } public String getDescription() { return description; } public void setDescription(String description) { this.description = description; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } }

3.1 文件下載

package com.web; import java.io.IOException; import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse; import org.apache.commons.fileupload.FileUploadBase.FileSizeLimitExceededException;import org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException;import org.apache.commons.fileupload.servlet.ServletFileUpload; import service.UpfileService; import com.domain.UpFile;import com.utils.WebUtils; public class UploadServlet extends HttpServlet {     public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        // 判斷是否是文件上傳的request        if (!ServletFileUpload.isMultipartContent(request)) {            // 說明不是文件上傳的表單,下面的代碼不再執(zhí)行            request.setAttribute("message", "對不起,您的表單不符合規(guī)范,請檢查表單屬性設(shè)置...");            request.getRequestDispatcher("/upload.jsp").forward(request,                    response);            return;        }         // 封裝一個方法,完成文件上傳        UpFile upFile;        try {            upFile = WebUtils.doFileUpload(request);        } catch (FileSizeLimitExceededException e) {            request.setAttribute("message", "對不起,上傳單個文件大小超過限制...");            request.getRequestDispatcher("/upload.jsp").forward(request,                    response);            return;        } catch (SizeLimitExceededException e) {            request.setAttribute("message", "對不起,總的文件大小超過限制.....20M.");            request.getRequestDispatcher("/upload.jsp").forward(request,                    response);            return;        }        // 判斷upFile是否為空,為空不執(zhí)行后面語句        if (upFile == null) {            return;        }        System.out.println(upFile);         UpfileService ups = new UpfileService();         ups.upload(upFile);        // 上傳成功,給用戶友好提示        response.setContentType("text/html;charset=utf-8");        response.getWriter().print(                "上傳成功<a href='" + request.getContextPath()                        + "/upload.jsp'>再次上傳</a>");    }     public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    } }

package com.utils; import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.util.List;import java.util.UUID; import javax.servlet.ServletException;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse; import org.apache.commons.beanutils.BeanUtils;import org.apache.commons.fileupload.FileItem;import org.apache.commons.fileupload.FileUploadBase;import org.apache.commons.fileupload.FileUploadBase.FileSizeLimitExceededException;import org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException;import org.apache.commons.fileupload.ProgressListener;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload; import com.domain.UpFile; public class WebUtils {     public static UpFile doFileUpload(HttpServletRequest request) throws FileSizeLimitExceededException, SizeLimitExceededException  {        UpFile upFile = new UpFile();         try {            // 拿到工廠            DiskFileItemFactory factory = new DiskFileItemFactory();             // 設(shè)置臨時緩存區(qū)大小            factory.setSizeThreshold(1024 * 1204 * 2);// 2M            // 設(shè)置上傳時,臨時文件的位置            factory.setRepository(new File(request.getsession()                    .getServletContext().getRealPath("/tmp")));             ServletFileUpload uploader = new ServletFileUpload(factory);            // 限定上傳文件的大小            uploader.setFileSizeMax(1024 * 1024 * 2);// 以kb為單位,限制單個文件大小            uploader.setSizeMax(1024 * 1024 * 20);// 限制總的文件大小20M             // 設(shè)置解析事,中文文件名解析的碼表            uploader.setHeaderEncoding("UTF-8");             // 設(shè)置監(jiān)聽器,監(jiān)聽上傳進度             // 這里的update方法不定時被解析器調(diào)用到            // pBytesRead:上傳文件已經(jīng)解析多少            // pContentLength:上傳單個文件總的大小            // pItems:當(dāng)前上傳的是第幾個Item            ProgressListener progressListener = new ProgressListener() {                private long megaBytes = -1;                 public void update(long pBytesRead, long pContentLength,                        int pItems) {                    long mBytes = pBytesRead / 1000000;                    if (megaBytes == mBytes) {                        return;                    }                    megaBytes = mBytes;                    System.out.println("We are currently reading item "                            + pItems);                    if (pContentLength == -1) {                        System.out.println("So far, " + pBytesRead                                + " bytes have been read.");                    } else {                        System.out.println("So far, " + pBytesRead + " of "                                + pContentLength + " bytes have been read.");                    }                }            };            // 設(shè)置監(jiān)聽器一定在解析之前設(shè)置            uploader.setProgressListener(progressListener);            List<FileItem> list = uploader.parseRequest(request);            for (FileItem fileItem : list) {                if (fileItem.isFormField()) {                    String fieldName = fileItem.getFieldName();                    // 這里使用UTF-8進行解碼                    String fieldValue = fileItem.getString("UTF-8");                    // 使用beanUtils封裝java類                    // beanUtils封裝數(shù)據(jù),要求目標(biāo)javaBean字段名稱與表單提交過來的數(shù)據(jù)的名稱一樣,否則封裝不上                    BeanUtils.setProperty(upFile, fieldName, fieldValue);                 } else {                    String filename = fileItem.getName();                    // 有些瀏覽器獲得的name是E:/1.bmp.針對不同瀏覽器解決上傳時文件名稱問題                     // 這個索引是最后一個/所在索引位置                    int lastIndex = filename.lastIndexOf("//");                    if (lastIndex != -1) {                        filename = filename.substring(lastIndex + 1);                    }                     // 獲得WEB-INF目錄下upload文件夾的路徑                    String savepath = request.getSession().getServletContext()                            .getRealPath("/WEB-INF/upload");                     // 生成不同名文件名,避免覆蓋問題                    String uuidname = UUID.randomUUID().toString()                            .replace("-", "")                            + "_" + filename;                    // 生成隨機文件夾,保存上傳文件,避免性能問題                    savepath = generatedRandomDir(savepath, uuidname);                    InputStream in = fileItem.getInputStream();                    FileOutputStream out = new FileOutputStream(new File(                            savepath, uuidname));                    int len = 0;                    byte[] buf = new byte[1024];                    while ((len = in.read(buf)) != -1) {                        out.write(buf, 0, len);                    }                    in.close();                    out.close();                     // 刪除臨時文件                    fileItem.delete();                    upFile.setFilename(filename);                    upFile.setId(UUID.randomUUID().toString());                    upFile.setUuidname(uuidname);                    upFile.setSavepath(savepath);                }            }            return upFile;        } catch (FileUploadBase.FileSizeLimitExceededException e) {            throw e;        } catch (FileUploadBase.SizeLimitExceededException e) {            throw e;         } catch (Exception e) {            e.printStackTrace();            return null;        }    }     private static String generatedRandomDir(String savepath, String uuidname) {        int hashCode = uuidname.hashCode();        int dir1 = hashCode & 0xf;// 一級目錄        int dir2 = (hashCode >> 4) & 0xf;// 二級目錄        String path = savepath + File.separator + dir1 + File.separator + dir2;        File file = new File(path);        if (!file.exists()) {            file.mkdirs();        }         return path;    }}

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