Java File upload download function implementation Code _java

This example for you to share the file upload download Java implementation code for your reference, the specific contents are as follows

Front desk:

1. Submission Method:Post
2. The form has the file to upload the form item: <input type= "file"/>
3. Specify the form type:
Default type: enctype= "application/x-www-form-urlencoded"
File Upload type: multipart/form-data

FileUpload

File upload function is more commonly used in the development, Apache also provides file upload components!
FileUpload components:
1. Download source
2. Introduction of JAR file in project
Commons-fileupload-1.2.1.jar "File Upload component Core jar package"
Commons-io-1.4.jar "encapsulates the relevant tool classes for file processing"

Use:

public class Uploadservlet extends HttpServlet {//upload directory, save uploaded resources public void doget (HttpServletRequest request, HTT
   Pservletresponse response) throws Servletexception, IOException {/********* file Upload component: Processing file upload ************/try { 1.
   File Upload Factory Fileitemfactory factory = new Diskfileitemfactory (); 2.

   Create File upload core tool class Servletfileupload upload = new Servletfileupload (factory);
   First, set the maximum size allowed for a single file: 30M Upload.setfilesizemax (30*1024*1024);
   Second, set the File upload form to allow the total size: 80M Upload.setsizemax (80*1024*1024);
   Third, set the upload form file name code//equivalent: Request.setcharacterencoding ("UTF-8");


   Upload.setheaderencoding ("UTF-8"); 3. Determine if the current form is a file upload form if (upload.ismultipartcontent) {//4. Convert the request data to a Fileitem object, and then use a collection package list<fileitem& Gt
    List = Upload.parserequest (request); Traversal: Get each uploaded data for (Fileitem item:list) {//Judge: Normal text data if (Item.isformfield ()) {//Normal text data Str ing fieldName = item.getfieldname (); Form element name String COntent = Item.getstring (); The form element name, corresponding data//item.getstring ("UTF-8");
     Specifies the encoding System.out.println (FieldName + "" + content); //Upload file (file stream)----> upload to upload directory else {//plain text data String fieldName = Item.getfieldname ();//table cell   element name String name = Item.getname ();  FileName String content = item.getstring (); The form element name, the corresponding data String type = Item.getcontenttype (); File type InputStream in = Item.getinputstream ();
       Upload file Stream * * Four, file name duplicate * for different user readme.txt files, do not want to overwrite!
       * Background processing: To add a unique tag to the user!
      *//A. Randomly generate a unique tag String id = uuid.randomuuid (). toString ();

      B. stitching name with filename = id + "#" + name;
      Get upload Base path String path = Getservletcontext (). Getrealpath ("/upload");

      Creates the target file, filename = new file (path,name);
      Tool class, File upload item.write (files); Item.delete ();
     Delete system-generated temporary files System.out.println (); }} else {System.out.println ("current tableSingle not file upload form, processing failed!
   ");
  } catch (Exception e) {e.printstacktrace (); 
  }//manual implementation process private void upload (HttpServletRequest request) throws IOException, Unsupportedencodingexception { /* Request.getparameter (""); Get/post request.getquerystring (); Gets the data submitted by get Request.getinputstream (); Get post submitted data * */*********** manually get file Upload form data ************///1.
  Gets the form data stream InputStream in = Request.getinputstream (); 2.
  Convert stream InputStreamReader instream = new InputStreamReader (in, "UTF-8"); 3.
  Buffered stream BufferedReader reader = new BufferedReader (instream);
  Output data String str = NULL;
  while (str = Reader.readline ())!= null) {System.out.println (str);
  }//Close Reader.close ();
  Instream.close ();
 In.close (); 
  public void DoPost (HttpServletRequest request, httpservletresponse response) throws Servletexception, IOException {
 This.doget (request, response);
 }

}

Case:

index.jsp

<body> 
  <a href= "${pagecontext.request.contextpath}/upload.jsp" > File upload </a>
  <a href= "${ PageContext.request.contextPath}/fileservlet?method=downlist "> File download </a> 

</body>

upload.jsp

<body> 
  <form name= "frm_test" action= "${pagecontext.request.contextpath}/fileservlet?method=upload" Method= "POST" enctype= "Multipart/form-data" >
   <%--<input type= "hidden" name= "method" value= "Upload" >--%>

   user name: <input type= "text" name= "UserName" > <br/>
  File: <input type= "file" Name= "File_ IMG "> <br/>

  <input type=" Submit "value=" submitted ">
  </form>
 </body>

Fileservlet.java

/** * Process file upload and download * @author Jie.yuan */public class Fileservlet extends HttpServlet {public void doget (Httpservle  Trequest requests, httpservletresponse response) throws Servletexception, IOException {//Get request parameters: differentiate between different operation types String
  method = Request.getparameter ("method");
  if ("Upload". Equals (method)) {//upload upload (request,response);
  else if ("Downlist". Equals (method)) {//Enter the download list downlist (request,response);
  else if (' Down '. Equals (method)) {//Download down (request,response); }/** * 1. Upload/private void upload (HttpServletRequest request, httpservletresponse response) throws Servletexception, Ioexcepti
   On {try {//1. Create Factory object Fileitemfactory factory = new Diskfileitemfactory (); 2.
   File Upload core tool class Servletfileupload upload = new Servletfileupload (factory); Set the size limit parameter Upload.setfilesizemax (10*1024*1024);  Single File size limit Upload.setsizemax (50*1024*1024);  Total file size limit upload.setheaderencoding ("UTF-8");
Code processing for Chinese files
   Judge if (upload.ismultipartcontent) {//3. Convert request data to list collection List<fileitem> list = Upload.par
    Serequest (Request); Traversal for (Fileitem item:list) {//judgment: Normal text data if (Item.isformfield ()) {//get name String name = it
      Em.getfieldname ();
      Gets the value String value = item.getstring ();
     System.out.println (value);
      }//File table single else {/******** file upload ***********///A. Get file name String name = Item.getname (); ----process----//A1 The name of the upload filename.
      First get a unique tag String id = uuid.randomuuid (). toString (); A2.      

      Stitching filename name = id + "#" + name;
      B. Get upload directory String basepath = Getservletcontext (). Getrealpath ("/upload");
      C. Create the file object to upload files = new filename (basepath,name);
      D. Upload item.write (file); Item.delete ();
  Deletes temporary files generated by the component Runtime}} and catch (Exception e) {e.printstacktrace (); }/** * 2. Go to download list * * private void DowNlist (HttpServletRequest request, httpservletresponse response) throws Servletexception, IOException {//Realization idea: Get Uplo first The file name of all files in the ad directory, then save; jump to down.jsp list to show//1.
  Initializes the map collection map< contains a unique tag file name, short file name >;

  map<string,string> fileNames = new hashmap<string,string> (); 2.
  Gets the filename String bathpath = Getservletcontext (). Getrealpath ("/upload") of the uploaded directory and all the files under it.
  Directory File File = new file (Bathpath);
  directory, all filename String list[] = File.list (); Traversal, encapsulating if (list!= null && list.length > 0) {for (int i=0; i<list.length; i++) {//Full name String
    FileName = List[i];
    Short name String shortname = filename.substring (Filename.lastindexof ("#") +1);
   Encapsulation Filenames.put (FileName, shortname); }//3.
  Save to request Domain Request.setattribute ("fileNames", fileNames); 4.

 Forwarding Request.getrequestdispatcher ("/downlist.jsp"). Forward (request, response); }/** * 3. Processing download/private void Down (HttpServletRequest request, HttpServletResponse ResponSE) throws Servletexception, IOException {//Get user-downloaded file name (append data after URL address) String fileName = Request.getparameter ("fi
  Lename ");

  FileName = new String (filename.getbytes ("iso8859-1"), "UTF-8");
  First get the upload directory path String basepath = Getservletcontext (). Getrealpath ("/upload");

  Gets a file stream inputstream in = new FileInputStream (new file (Basepath,filename));
  If the filename is Chinese, url encoding filename = urlencoder.encode (filename, "UTF-8") is required;

  Set Download response header Response.setheader ("Content-disposition", "attachment;filename=" + fileName);
  Gets the response byte stream outputstream out = Response.getoutputstream ();
  Byte[] B = new byte[1024];
  int len =-1;
  while (len = In.read (b))!=-1) {out.write (b, 0, Len);
  }//Close Out.close ();


 In.close (); 
  public void DoPost (HttpServletRequest request, httpservletresponse response) throws Servletexception, IOException {
 This.doget (request, response);
 }

}

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