檔案上傳步驟

1. 導包

匯入commons-io和commons-fileupload jar包

2. 前端頁面

action:頁面請求,需和web.xml中匹配

method:設定為post,沒有檔案大小限制

enctype:值為multipart/form-data用於識別是否為檔案表單還是普通文字表單

<form action="upload.do" enctype="multipart/form-data" method="post">
    <input type="file" name="file1">
    <br>
    <input type="file" name="file2">
    <br>
    <input type="submit">
    <br>
</form>
 

3. 註冊web.xml

    <servlet>
        <servlet-name>FileUploadServlet</servlet-name>
        <servlet-class>com.juyss.servlet.FileUploadServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>FileUploadServlet</servlet-name>
        <url-pattern>/upload.do</url-pattern>
    </servlet-mapping>
 

4. 編寫Servlet

實現步驟

1. 判斷表單為普通文字表單還是檔案表單

2. 建立上傳檔案的儲存根路徑

3. 建立臨時檔案的儲存根路徑

4. 獲取FileItem物件

   ​ 需要ServletFileUpload物件

   ​ 需要用到DiskFileItemFactory物件,用於處理上傳路徑和限制檔案大小

5. 通過FileItem物件獲取檔名,檔案字尾

6. 使用UUID建立唯一儲存路徑

7. 使用fileItem.getInputStream()獲取檔案輸入流

8. 建立檔案輸出流FileOutputStream fos = new FileOutputStream(savePath + "/" + fileName)

9. 關閉流資源,同時刪除臨時檔案fileItem.delete()

public class FileUploadServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("進入了FileUploadServlet.class");

        //判斷表單是否為帶有檔案的表單
        if (!ServletFileUpload.isMultipartContent(request)) {
            return; //終止方法執行
        }

        //定義檔案上傳後儲存的根路徑
        String rootPath = this.getServletContext().getRealPath("/WEB-INF/upload");
        File rootFile = new File(rootPath);
        if (!rootFile.exists()) {
            rootFile.mkdir();
        }

        //定義檔案快取路徑
        String tempPath = this.getServletContext().getRealPath("/WEB-INF/temp");
        File tempFile = new File(tempPath);
        if (!tempFile.exists()) {
            tempFile.mkdir();
        }

        //建立DiskFileItemFactory物件,處理上傳路徑和限制檔案大小
        DiskFileItemFactory fileItemFactory = new DiskFileItemFactory(1024 * 1024, tempFile);

        //建立ServletFileUpload物件
        ServletFileUpload servletFileUpload = new ServletFileUpload(fileItemFactory);

        //獲取FileItem物件
        List<FileItem> fileItems = null;
        try {
            fileItems = servletFileUpload.parseRequest(request);
        } catch (FileUploadException e) {
            e.printStackTrace();
        }
        if (fileItems==null){
            System.out.println("fileItem空指標");
            return;
        }
        Iterator<FileItem> iterator = fileItems.iterator();

        //遍歷fileItems集合
        while (iterator.hasNext()) {
            FileItem fileItem = iterator.next();
            if (fileItem.isFormField()) {//是普通文字表單
                continue; //跳出迴圈
            } else {//是檔案表單
                //獲取檔案欄位名,標籤中name屬性的值
                String fieldName = fileItem.getFieldName();
                //獲取檔案上傳欄位中的檔名,一般來說為為檔名(不包含路徑資訊),在opera瀏覽器中可能會包含檔案路徑資訊
                String name = fileItem.getName();
                System.out.println("檔案欄位名:"+fieldName);
                System.out.println("檔名:"+name);

                //判斷檔名是否合法
                if (name.trim().equals("") || name == null) {
                    continue;
                }

                //獲取檔名和檔案字尾

                String fileName; //檔名
                if (name.contains("/")){ //判斷name是否包含路徑資訊
                    fileName = name.substring(name.lastIndexOf("/"));
                }else{
                    fileName = name;
                }

                String fileExtension = fileName.substring(fileName.indexOf(".") + 1);//獲取檔案字尾
                System.out.println("檔名:" + fileName);
                System.out.println("檔案型別:" + fileExtension);
                //獲取隨機UUID
                String uuid = UUID.randomUUID().toString();

                //使用uuid建立唯一的資料夾作為檔案存放路徑
                String savePath = rootPath + "/" + uuid; //檔案存放路徑
                File savePathFile = new File(savePath);
                if (!savePathFile.exists()) { //路徑不存在就建立
                    savePathFile.mkdir();
                }

                //獲取輸入流讀取上傳的檔案
                InputStream is = fileItem.getInputStream();

                //用輸出流儲存到本地
                FileOutputStream fos = new FileOutputStream(savePath + "/" + fileName);

                int len;
                byte[] bytes = new byte[1024 * 1024];
                while((len = is.read(bytes))!=-1){
                    fos.write(bytes,0,len);
                }

                fos.close();
                is.close();
                //刪除臨時檔案
                fileItem.delete();
            }
        }


    }

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