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In web development, it often involves uploading and downloading files, for example, when registering an account, we need to upload our own avatar and so on.
We can make it easy to upload files using struts.
Now, let's say we're going to upload our avatar at the time of registration. The new project name is Strutsfileupanddown and introduces Struts1.3
(1) First, write the registered JSP page register.jsp
Its body content is as follows:
<Body><H1> Registered Users</H1><%--If the form has a file control, you need to re-specify how the form is encoded--%><FormEnctype="Multipart/form-data"action="/strutsfileupanddown/register.do"Method="POST" > Name:<input type= "text" name=" name "/>< Br> head: <input type= "file" name= "photo"/> <br> < Input type= "submit" value=< Span class= "Hljs-value" > "register"/> </form> </BODY> (2) Add the corresponding actionform, the name is UserForm
PublicClassuserform extends ActionForm {private String name = null; private formfile photo = null; public String getname () {return Name } public void setName (String name) { this.name = name;} public formfile getphoto () {return Photo } public void setPhoto (FormFile Photo) {this.photo = Photo;}} (2) Add the corresponding action, name registeraction, and configure path /register to
The most important thing is how the action is written, and when we click Register, it is the action that handles the logic, and the file is passed through this action.
UserForm userForm = (UserForm) form;String username = userForm.getName();FormFile formFile = userForm.getPhoto();
File name String fileName = Formfile.getfilename ();Gets the input stream InputStream is = Formfile.getinputstream ();//get an output stream //first get the absolute path after uploading the file folder to the tomcat server string path = Request.getservletcontext (). Getrealpath ( "file"); OutputStream OS = new fileoutputstream (path + "\ \" + fileName); //read the file and write it out to the server file folder int len = 0;//do a cache byte[" bytes = new byte[1024]; Loop processing while (len = is.read (bytes)) > 0) {//read a little, write a little Os.write (bytes, 0, Len);} Of course, this whole process has to deal with exceptions. If it doesn't go wrong, we can pass the file on to the server.
"Note that some simple configuration steps are omitted here."
1.2 Improvements(1) Problem 1: Chinese garbled processing, if the user upload the file is Chinese name will appear garbled
At this point, the filter can be a good solution to this problem. Just add a filter and set the request's encoding to Utf-8.
Publicclass encodingfilter implements Span class= "Hljs-title" >filter { @Override public void destroy () {} @Override public void dofilter (ServletRequest arg0, Servletresponse arg1, Filterchain arg2) throws IOException, Servletexception { Arg0.setcharacterencoding ( @Override public void init (filterconfig arg0) throws servletexception {}} The configuration is as follows:
<Filter><filter-name>encodingfilter</< Span class= "Hljs-title" >filter-name> <filter-class> Com.gavin.filter.encodingfilter</filter-class></filter>< filter-mapping> <filter-name>encodingfilter</filter-name> < Url-pattern>/*</url-pattern> </FILTER-MAPPING> (2) Question 2: Here we save the file name of the server is the user upload name, then if there are two users upload the same file name will be overwritten, so we will be on the server side of the file name processing
Here, we no longer use the name of the user-uploaded file. So what can you do to ensure that the file name is unique?
String uuid = UUID.randomUUID().toString();
public Span class= "Hljs-class" >class mytools {/** * get file suffix * @param fileName * @return */ Span class= "Hljs-keyword" >public static String getFileSuffix ( String fileName) {return filename.substring (Filename.lastindexof ( /** * get uuid * @return */ Public static string getuuid () {String uuid = Uuid.randomuuid (). ToString (); return uuid;}
(3) Question 3: What if the user uploads not the picture? What if a user uploads a picture that is too large?
So here we have to file restrictions, to the type and size of the file limit, if not meet the requirements, then jump to an error page and give a hint:
Here I limit the file size limit to 10MB, as follows:
if (fileSize > 10 * 1024 * 1024) { request.setAttribute("error", "文件大小不能超过10MB!"); return mapping.findForward("error");}if(!formFile.getContentType().startsWith("image/")){ request.setAttribute("error", "文件格式有错，请检查!"); return mapping.findForward("error");}
"Note" The type of file is not a picture, not by the suffix name to determine, to invoke the Formfile method, the specific file type you can view the Tomcat installation directory under the Conf folder in the Web. xml file configuration.
So, finally, a complete registeraction is this:
PublicClassRegisteractionExtendsAction {Public ActionforwardExecute (actionmapping mapping, actionform form, httpservletrequest request, httpservletresponse response) {UserForm UserForm = (userForm) Form; String username = userform.getname (); Formfile formfile = Userform.getphoto ();Through Formfile we can obtain various information about the user uploading files, such as size, name, etc. String fileName = Formfile.getfilename ();int fileSize = Formfile.getfilesize ();if (FileSize >10 *1024 *1024x768) {Request.setattribute ("Error","File size cannot exceed 10mb!");Return Mapping.findforward ("Error"); }if (!formfile.getcontenttype (). StartsWith ("image/")) {Request.setattribute ("Error","File format is wrong, please check!");Return Mapping.findforward ("Error"); } InputStream is =Null OutputStream OS =Null String uuid = Mytools.getuuid (); String suffix = mytools.getfilesuffix (fileName); String newfilename = uuid + suffix;try {is = Formfile.getinputstream (); String path = Request.getservletcontext (). Getrealpath ("File"); SYSTEM.OUT.PRINTLN (path); OS =New FileOutputStream (Path +"\ \" + NewFileName);int len =0;byte[] bytes =Newbyte[1024]; while (len = is.read (bytes)) > 0) {os.write (bytes, 0, Len); } //here omitted to save the operation of the database //logical normal Jump, also omitted} catch (Exception e) {e.printstacktrace ();} finally {try {if (OS = null) {os.close ();} if (is! = null) {is.close ();}} catch (Exception E2) {e2.printstacktrace ();}} Request.setattribute ( "error", "Registration Error! "); return mapping.findforward ( "error");}} File download, we have introduced the native Servlet, we can refer to the "servlet--use HTTP response header content-disposition download file example."
Of course, when we wrote the downloaded business logic in a servlet, there was nothing different here, except that we were going to write the business logic in a struts action, and that action did not need to be configured with the appropriate form.
When we click on the downloaded hyperlink, let it request this action. And finally let the action jump to the original page:
return mapping.findForward("goback");
struts1.3--File Upload and download
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