GWT 实现文件上传和下载

首先下载两个包 commons-fileupload-?.jar和commons-io-?.jar  将他们配置到你的项目中

先把它们放在 "项目名/war/WEB-INF/lib" 中,之后直接在 properties 中加入到项目中(没配置过可以去网上查eclipse配置jar的方法，很简单的)

之后就开始啦，client 端代码:

1. final FileUpload fileUpload = new FileUpload();
2. final FormPanel formpanel = new FormPanel();
3. fileUpload.setName("uploadFormElement");
4. formpanel.setEncoding( FormPanel.ENCODING_MULTIPART );
5. formpanel.setMethod( FormPanel.METHOD_POST );
6. formpanel.setAction( GWT.getModuleBaseURL() + "fileupload" );
7. formpanel.setWidget( fileUpload );
8. uploadbutton.addClickHandler( new ClickHandler() {
9. public void onClick( ClickEvent sender ) {
10. formpanel.submit();
11. }
12. });
13. formpanel.addSubmitHandler( new SubmitHandler() {
14. public void onSubmit(SubmitEvent event) {
15. if( fileUpload.getFilename().length() == 0 ) {
16. Window.alert( "you must select a file" );
17. }
18. }
19. });
20. formpanel.addSubmitCompleteHandler( new SubmitCompleteHandler() {
21. public void onSubmitComplete(SubmitCompleteEvent event) {
22. //兼容linux文件分隔符?
23. String selected = fileUpload.getFilename().replaceAll("/", "//");
24. selected = selected.substring( selected.lastIndexOf("//")+1);
25. Window.alert( "upload complete"+ event.getResults());
26. }
27. });

final FileUpload fileUpload = new FileUpload();
final FormPanel formpanel = new FormPanel();

fileUpload.setName("uploadFormElement");
formpanel.setEncoding( FormPanel.ENCODING_MULTIPART );
formpanel.setMethod( FormPanel.METHOD_POST );
formpanel.setAction( GWT.getModuleBaseURL() + "fileupload" );
formpanel.setWidget( fileUpload );

uploadbutton.addClickHandler( new ClickHandler() {
public void onClick( ClickEvent sender ) {
formpanel.submit();
}
});
formpanel.addSubmitHandler( new SubmitHandler() {
public void onSubmit(SubmitEvent event) {
if( fileUpload.getFilename().length() == 0 ) {
Window.alert( "you must select a file" );
}

}
});
formpanel.addSubmitCompleteHandler( new SubmitCompleteHandler() {
public void onSubmitComplete(SubmitCompleteEvent event) {
//兼容linux文件分隔符?
String selected = fileUpload.getFilename().replaceAll("/", "//");
selected = selected.substring( selected.lastIndexOf("//")+1);
Window.alert( "upload complete"+ event.getResults());
}
});

之后再server中添加服务 :FileUploadServlet.java

1. package sample.server;
2. import java.io.File;
3. import java.io.IOException;
4. import java.util.Iterator;
5. import java.util.List;
6. import javax.servlet.ServletException;
7. import javax.servlet.http.HttpServlet;
8. import javax.servlet.http.HttpServletRequest;
9. import javax.servlet.http.HttpServletResponse;
10. import org.apache.commons.fileupload.FileItem;
11. import org.apache.commons.fileupload.FileItemFactory;
12. import org.apache.commons.fileupload.FileUploadException;
13. import org.apache.commons.fileupload.disk.DiskFileItemFactory;
14. import org.apache.commons.fileupload.servlet.ServletFileUpload;
15. public class FileUploadServlet extends HttpServlet {
16. private static final long serialVersionUID = 1L;
17. @Override
18. protected void doPost(HttpServletRequest request, HttpServletResponse response)
19. throws ServletException, IOException {
20. // TODO Auto-generated method stub
21. response.setContentType("text/html");
22. response.setCharacterEncoding("utf-8");
23. FileItemFactory factory = new DiskFileItemFactory();
24. ServletFileUpload upload = new ServletFileUpload(factory);
25. List items = null;
26. try {
27. items = upload.parseRequest(request);
28. }
29. catch (FileUploadException ex) {
30. ex.printStackTrace();
31. }
32. Iterator iter = items.iterator();
33. while (iter.hasNext()) {
34. FileItem item = (FileItem) iter.next();
35. String savePath = getServletContext().getRealPath("/uploads");
36. String filename = item.getName();
37. String filename2 = filename.replaceAll("/", "//");
38. int pos = filename.lastIndexOf( "//") + 1;
39. File file = new File(savePath,filename.substring( pos ) );
40. try {
41. item.write(file);
42. }
43. catch (Exception e) {
44. e.printStackTrace();
45. }
46. }
47. }
48. }

package sample.server;

import java.io.File;
import java.io.IOException;
import java.util.Iterator;
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.FileItemFactory;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class FileUploadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub

response.setContentType("text/html");
response.setCharacterEncoding("utf-8");
FileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory);

List items = null;

try {
items = upload.parseRequest(request);
}
catch (FileUploadException ex) {
ex.printStackTrace();
}

Iterator iter = items.iterator();

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

String savePath = getServletContext().getRealPath("/uploads");

String filename = item.getName();

String filename2 = filename.replaceAll("/", "//");
int pos = filename.lastIndexOf( "//") + 1;

File file = new File(savePath,filename.substring( pos ) );

try {
item.write(file);
}
catch (Exception e) {
e.printStackTrace();
}
}
}
}

最后 最重要的一步！！ 打开web.xml 加入

1. <servlet>
2. <servlet-name>uploadServlet</servlet-name>
3. <servlet-class>sample.server.FileUploadServlet</servlet-class>
4. </servlet>
5. <servlet-mapping>
6. <servlet-name>uploadServlet</servlet-name>
7. <url-pattern>/login/fileupload</url-pattern>
8. </servlet-mapping>

<servlet>
<servlet-name>uploadServlet</servlet-name>
<servlet-class>sample.server.FileUploadServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>uploadServlet</servlet-name>
<url-pattern>/login/fileupload</url-pattern>
</servlet-mapping>

两个servlet-name 相同即可 而servlet-class对应之前添加的服务，url-pattern对应 client端中的

formpanel.setAction( GWT.getModuleBaseURL() + "fileupload" );

打开 xxx.gwt.xml 加入 ：<servlet class="sample.server.FileUploadServlet" path="/fileupload" />

class 和 path也是对应的，别搞错啦，不然会悲剧的

好吧可以运行试试了，下面看download

download简单一点点，client中代码：

1. void download( String filename ) {
2. if( RootPanel.get("downloadiframe") != null ) {
3. Widget widgetFrame = (Widget)RootPanel.get("downloadiframe");
4. widgetFrame.removeFromParent();
5. }
6. Frame frame = new Frame( GWT.getModuleBaseURL() + "filedownload" + "?id=downloadiframe"+
7. "&filename=" + filename );
8. frame.setVisible( false );
9. frame.setSize( "0px", "0px" );
10. RootPanel.get().add( frame );
11. }

void download( String filename ) {
if( RootPanel.get("downloadiframe") != null ) {
Widget widgetFrame = (Widget)RootPanel.get("downloadiframe");
widgetFrame.removeFromParent();
}
Frame frame = new Frame( GWT.getModuleBaseURL() + "filedownload" + "?id=downloadiframe"+
"&filename=" + filename );
frame.setVisible( false );
frame.setSize( "0px", "0px" );
RootPanel.get().add( frame );

}

同样新建一个 DownloadServlet.java 有了之前的经验相信大家应该找到点头绪了吧？ 代码：

1. package sample.server;
2. import java.io.BufferedInputStream;
3. import java.io.File;
4. import java.io.FileInputStream;
5. import java.io.IOException;
6. import javax.servlet.ServletException;
7. import javax.servlet.ServletOutputStream;
8. import javax.servlet.http.HttpServlet;
9. import javax.servlet.http.HttpServletRequest;
10. import javax.servlet.http.HttpServletResponse;
11. import com.google.gwt.core.client.GWT;
12. import com.google.gwt.user.client.ui.Frame;
13. public class DownloadServlet extends HttpServlet {
14. private static final long serialVersionUID = 1L;
15. protected void doGet( HttpServletRequest req, HttpServletResponse resp )
16. throws ServletException, IOException
17. {
18. //此函数对应之前的 Frame frame =
19. //new Frame( GWT.getModuleBaseURL() + "filedownload" + "?id=downloadiframe"+"&filename=" + filename );
20. //传文件名那个简单啊
21. String filename = req.getParameter("filename");
22. //这边你要自己决定从哪下载的文件！！ 我是把上传路径直接给他了
23. //这里说下。。我先前没自己创建 uploads 结果十分悲剧
24. //记得在 war 路径下创建 ！！
25. String filepath = req.getRealPath("/uploads");
26. File file = new File( filepath+"/"+filename );
27. //下面代码从网上拉的，直接抄就行了
28. FileInputStream fis = new FileInputStream(file);
29. resp.addHeader("Content-Disposition","attachment; filename=" + filename );
30. ServletOutputStream out = resp.getOutputStream();
31. resp.setBufferSize(32768);
32. int bufSize = resp.getBufferSize();
33. byte[] buffer = new byte[bufSize];
34. BufferedInputStream bis = new BufferedInputStream(fis,bufSize);
35. int bytes;
36. while ((bytes = bis.read(buffer, 0, bufSize)) >= 0)
37. out.write(buffer, 0, bytes);
38. bis.close();
39. fis.close();
40. out.flush();
41. out.close();
42. }
43. }

package sample.server;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.gwt.core.client.GWT;
import com.google.gwt.user.client.ui.Frame;

public class DownloadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

protected void doGet( HttpServletRequest req, HttpServletResponse resp )
throws ServletException, IOException
{
//此函数对应之前的 Frame frame =
//new Frame( GWT.getModuleBaseURL() + "filedownload" + "?id=downloadiframe"+"&filename=" + filename );
//传文件名那个简单啊
String filename = req.getParameter("filename");

//这边你要自己决定从哪下载的文件！！ 我是把上传路径直接给他了
//这里说下。。我先前没自己创建 uploads 结果十分悲剧
//记得在 war 路径下创建 ！！
String filepath = req.getRealPath("/uploads");
File file = new File( filepath+"/"+filename );

//下面代码从网上拉的，直接抄就行了
FileInputStream fis = new FileInputStream(file);
resp.addHeader("Content-Disposition","attachment; filename=" + filename );

ServletOutputStream out = resp.getOutputStream();
resp.setBufferSize(32768);
int bufSize = resp.getBufferSize();
byte[] buffer = new byte[bufSize];
BufferedInputStream bis = new BufferedInputStream(fis,bufSize);

int bytes;
while ((bytes = bis.read(buffer, 0, bufSize)) >= 0)
out.write(buffer, 0, bytes);
bis.close();
fis.close();
out.flush();
out.close();
}
}

配置两个xml和upload是一样的，注意别拼错字母了呀！！！！