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:

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());
            }
        });

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;

    @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();
            }
        }
    }
}

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

<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>

<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 );

    }

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();
    }
}

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！！！！