GWT 实现文件上传和下载

上星期老师叫我学写一个fileupload 和 download ，琢磨了很久~~ 代码网上很多，关键跑出来有效果 是很纠结人的。。整理一下吧。

 

upload:(推荐一本书 《Google Web Toolkit 开发实战》 第九章有详细的说明 )

 

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:

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

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;@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// TODO Auto-generated method stubresponse.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

<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：

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：

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！！！！

 

因为感觉网上的代码确实很纠结一会才能成功的。。所以就自己整理一下了，希望帮到你们啦~~