GWT中的基本文件上传 [英] Basic File upload in GWT

问题描述

我试图找出如何使用GWT的FileUpload小部件上传一个文件。我正在使用GWT和谷歌AppEngine与Java，但我想上传文件到我自己的Linux服务器。
我已经有了下面的代码，但现在我不知道如何提交我的文件到Google AppServer服务器并将其保存到另一台服务器：

 public class FileUploader {
 
 private ControlPanel cp; 
 private FormPanel form = new FormPanel（）; 
 private FileUpload fu = new FileUpload（）; 
 
 public FileUploader（ControlPanel cp）{
 this.cp = cp; 
 this.cp.setPrimaryArea（getFileUploaderWidget（））; 
 
 $ b $ @SuppressWarnings（deprecation）
 public Widget getFileUploaderWidget（）{
 form.setEncoding（FormPanel.ENCODING_MULTIPART）; 
 form.setMethod（FormPanel.METHOD_POST）; 
 // form.setAction（/ *我应该放哪里* /） 
 
 VerticalPanel holder = new VerticalPanel（）; 
 
 fu.setName（upload）; 
 holder.add（fu）; 
 holder.add（new Button（Submit，new ClickHandler（）{
 public void onClick（ClickEvent event）{
 GWT.log（You selected：+ fu.getFilename ），null）; 
 form.submit（）; 
} 
}））; 
 $ b form.addSubmitHandler（new FormPanel.SubmitHandler（）{
 public void onSubmit（SubmitEvent event）{
 if（！。equalsIgnoreCase（fu.getFilename（））） {
 GWT.log（UPLOADING FILE ????，null）; 
 //现在什么???? 
} 
 else {
事件。取消（）; //取消事件
} 
 
} 
}）; 
 $ b $ form.addSubmitCompleteHandler（new FormPanel.SubmitCompleteHandler（）{
 public void onSubmitComplete（SubmitCompleteEvent event）{
 Window.alert（event.getResults（））; 
 } 
}）; 
 
 form.add（持有者）; 
 
退货表单; 
 
 
 
 
 $ b现在，接下来我需要做什么？我需要在web.xml中放置什么，以及如何编写我的servlet，这样我就可以存储文件并返回该对象的url（如果可能的话） 
 
解决方案
这里是我的应用程序的代码：
 $ b $ 1创建了一个接受http请求的类：
 
 
  import java.io.ByteArrayOutputStream; 
 import java.io.IOException; 
 import java.io.InputStream; 
 
 import javax.servlet.ServletException; 
 import javax.servlet.http.HttpServlet; 
 import javax.servlet.http.HttpServletRequest; 
导入javax.servlet.http.HttpServletResponse; 
 import org.apache.commons.fileupload.FileItemIterator; 
 import org.apache.commons.fileupload.FileItemStream; 
 import org.apache.commons.fileupload.servlet.ServletFileUpload; 
 $ b $ public class FileUpload extends HttpServlet {$ b $ public void doPost（HttpServletRequest request，HttpServletResponse response）throws ServletException，IOException {
 ServletFileUpload upload = new ServletFileUpload（）; 
 
尝试{
 FileItemIterator iter = upload.getItemIterator（request）; （iter.hasNext（））{
 FileItemStream item = iter.next（）; 
 
 
 
 String name = item.getFieldName（）; 
 InputStream stream = item.openStream（）; 
 
 
 //处理输入流
 ByteArrayOutputStream out = new ByteArrayOutputStream（）; 
 int len; 
 byte [] buffer = new byte [8192]; （（len = stream.read（buffer，0，buffer.length））！= -1）{
 out.write（buffer，0，len）; 
} 
 
 int maxFileSize = 10 *（1024 * 1024）;如果（out.size（）> maxFileSize）{
 throw new RuntimeException（File is> than+ maxFileSize）; 
 
 
 $ b catch（Exception e）{
 throw new RuntimeException（e）; 
 
 
 
 $ b code 
 $ b 2）然后在我的web.xml中添加了这些行： 
 
 
 < servlet> 
< servlet-name> fileUploaderServlet< / servlet-name> 
< servlet-class> com.testapp.server.FileUpload< / servlet-class> 
< / servlet> 
< servlet-mapping> 
< servlet-name> fileUploaderServlet< / servlet-name> 
< url-pattern> / testapp / fileupload< / url-pattern> 
< / servlet-mapping> 
  
 3）而form.action做到了这一点：$ b​​ 
 $ b 
  form.setAction（GWT.getModuleBaseURL（）+fileupload）; 
  
 
I'm trying to figure out how to upload one file using GWTs FileUpload widget. I'm using GWT and Google AppEngine with Java but I would like to upload file to my own Linux server. 
I have the following code already but now I can't figure out how to submit my file to the Google AppServer server and save it to another server:
public class FileUploader{

    private ControlPanel cp;
    private FormPanel form = new FormPanel();
    private FileUpload fu =  new FileUpload();

    public FileUploader(ControlPanel cp) {
        this.cp = cp;
        this.cp.setPrimaryArea(getFileUploaderWidget());
    }

    @SuppressWarnings("deprecation")
    public Widget getFileUploaderWidget() {
        form.setEncoding(FormPanel.ENCODING_MULTIPART);
        form.setMethod(FormPanel.METHOD_POST);
        // form.setAction(/* WHAT SHOULD I PUT HERE */);

        VerticalPanel holder = new VerticalPanel();

        fu.setName("upload");
        holder.add(fu);
        holder.add(new Button("Submit", new ClickHandler() {
            public void onClick(ClickEvent event) {
                GWT.log("You selected: " + fu.getFilename(), null);
                form.submit();
            }
        }));

        form.addSubmitHandler(new FormPanel.SubmitHandler() {
            public void onSubmit(SubmitEvent event) {
                if (!"".equalsIgnoreCase(fu.getFilename())) {
                    GWT.log("UPLOADING FILE????", null);
                                        // NOW WHAT????
                }
                else{
                    event.cancel(); // cancel the event
                }

            }
        });

        form.addSubmitCompleteHandler(new FormPanel.SubmitCompleteHandler() {
            public void onSubmitComplete(SubmitCompleteEvent event) {
                Window.alert(event.getResults());
            }
        });

        form.add(holder);

        return form;
    }
}
Now, what do I need to do next? What do i need to put in web.xml and how do I write my servlet so i can store file and return url of that object (if possible)
解决方案
Here's the code from my app:

1) I created a class to accept http request:
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import org.apache.commons.fileupload.FileItemIterator; 
import org.apache.commons.fileupload.FileItemStream; 
import org.apache.commons.fileupload.servlet.ServletFileUpload; 

public class FileUpload extends HttpServlet{
    public void doPost(HttpServletRequest request, HttpServletResponse response)  throws ServletException, IOException {
        ServletFileUpload upload = new ServletFileUpload();

        try{
            FileItemIterator iter = upload.getItemIterator(request);

            while (iter.hasNext()) {
                FileItemStream item = iter.next();

                String name = item.getFieldName();
                InputStream stream = item.openStream();


                // Process the input stream
                ByteArrayOutputStream out = new ByteArrayOutputStream();
                int len;
                byte[] buffer = new byte[8192];
                while ((len = stream.read(buffer, 0, buffer.length)) != -1) {
                    out.write(buffer, 0, len);
                }

                int maxFileSize = 10*(1024*1024); //10 megs max 
                if (out.size() > maxFileSize) { 
                    throw new RuntimeException("File is > than " + maxFileSize);
                }
            }
        }
        catch(Exception e){
            throw new RuntimeException(e);
        }

    }
}
2) Then in my web.xml I've added these lines:
<servlet>
    <servlet-name>fileUploaderServlet</servlet-name>
    <servlet-class>com.testapp.server.FileUpload</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>fileUploaderServlet</servlet-name>
  <url-pattern>/testapp/fileupload</url-pattern>
</servlet-mapping>
3) And for form.action did this:
form.setAction(GWT.getModuleBaseURL()+"fileupload");


                        
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