Java 使用servlet上传文件GWT_Java_Gwt_Servlets_File Upload

Java 使用servlet上传文件GWT

java gwt servlets file-upload

Java 使用servlet上传文件GWT,java,gwt,servlets,file-upload,Java,Gwt,Servlets,File Upload,我正在用GWT开发一个应用程序，并尝试将文件上载到服务器（或目录）。我正在使用一个表单，通过FileUpload小部件提交所选文件。我在上传文件时使用的servlet有问题： package com.asso.server; import java.io.File; import java.io.IOException; import java.util.List; import javax.servlet.ServletException; import javax.servlet.htt

我正在用GWT开发一个应用程序，并尝试将文件上载到服务器（或目录）。我正在使用一个表单，通过FileUpload小部件提交所选文件。我在上传文件时使用的servlet有问题：

package com.asso.server;

import java.io.File;
import java.io.IOException;
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.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.FilenameUtils;

/**
 * servlet to handle file upload requests
 * 
 * @author hturksoy
 * 
 */
public class FileUploadServlet extends HttpServlet {

        private static final String UPLOAD_DIRECTORY = "c:\\uploaded\\";
        private static final String DEFAULT_TEMP_DIR = ".";

        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp)
                        throws ServletException, IOException {
                // TODO Auto-generated method stub
                super.doGet(req, resp);
        }

        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp)
                        throws ServletException, IOException {

                // process only multipart requests
                if (ServletFileUpload.isMultipartContent(req)) {

                        File tempDir = getTempDir();
                        if (!tempDir.exists()) {
                                tempDir.mkdirs();
                        }

                        // Create a factory for disk-based file items
                        FileItemFactory factory = new DiskFileItemFactory();

                        // Create a new file upload handler
                        ServletFileUpload upload = new ServletFileUpload(factory);

                        // Parse the request
                        try {
                                List<FileItem> items = upload.parseRequest(req);
                                for (FileItem fileItem : items) {
                                        // process only file upload
                                        if (fileItem.isFormField()) continue;

                                        String fileName = fileItem.getName();
                                        // get only the file name not whole path
                                        if (fileName != null) {
                                        fileName = FilenameUtils. getName(fileName);
                                    }

                                        File uploadedFile = new File(UPLOAD_DIRECTORY, fileName);
                                        if (uploadedFile.createNewFile()) {
                                                fileItem.write(uploadedFile);
                                                resp.setStatus(HttpServletResponse.SC_CREATED);
                                                resp.getWriter().print("The file was created successfully.");
                                                resp.flushBuffer();
                                        } else
                                                throw new IOException("The file already exists in repository.");
                                }
                        } catch (Exception e) {
                                resp.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
                                                "An error occurred while creating the file : " + e.getMessage());
                        }

                } else {
                        resp.sendError(HttpServletResponse.SC_UNSUPPORTED_MEDIA_TYPE,
                                                        "Request contents type is not supported by the servlet.");
                }
        }

        private File getTempDir() {
                return new File(DEFAULT_TEMP_DIR);
        }

}

我看到这个主题，它说我应该添加

commons-fileupload-1.3.jar

和

commons-io-2.4.jar

，我已经做了。有解决办法吗？编辑：在将JAR直接添加到WEB-INF/lib之后，我遇到了这个错误

java.lang.NoClassDefFoundError: `java.io.FileOutputStream is a restricted class. Please see the Google  App Engine developer's guide for more details.
    at com.google.appengine.tools.development.agent.runtime.Runtime.reject(Runtime.java:51)
    at org.apache.commons.io.output.DeferredFileOutputStream.thresholdReached(DeferredFileOutputStream.java:178)
    at org.apache.commons.io.output.ThresholdingOutputStream.checkThreshold(ThresholdingOutputStream.java:224)
    at org.apache.commons.io.output.ThresholdingOutputStream.write(ThresholdingOutputStream.java:128)
    at org.apache.commons.fileupload.util.Streams.copy(Streams.java:108)
    at org.apache.commons.fileupload.util.Streams.copy(Streams.java:70)
    at org.apache.commons.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:347)
    at org.apache.commons.fileupload.servlet.ServletFileUpload.parseRequest(ServletFileUpload.java:115)
    at com.asso.server.FileUploadServlet.doPost(FileUploadServlet.java:56)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:123)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:61)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:125)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at com.google.appengine.tools.development.DevAppServerServersFilter.doFilter(DevAppServerServersFilter.java:106)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:94)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:421)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)`

确保没有遗漏将commons-fileupload-1.3.jar和commons-io-2.4.jar文件复制到WEB-INF/lib中的步骤。您还应该检查devmode的启动类路径

示例-我在lib中添加了一个示例jar，可以通过我的启动配置看到相同的示例jar

更新-如果您正在使用GAE，请通读

谷歌应用程序引擎应用程序

您使用的DiskFileItemFactory对象尝试写入文件系统，因此会出现以下异常：

java.lang.NoClassDefFoundError: `java.io.FileOutputStream is a restricted class. Please see the Google  App Engine developer's guide for more details.

以下是来自以下方面的解释：

此实现创建FileItem实例，这些实例保持内存中的内容、较小项目的内容或上的临时文件中的内容磁盘，用于较大的项目。大小阈值，超过该阈值内容将存储在磁盘上，可配置，以及将创建临时文件。如果未进行其他配置，则默认配置值如下：大小阈值为10KB

解决方案：您应该增加文件大小阈值。覆盖默认值。将其设置为要上载到servlet的最大文件大小

DiskFileItemFactory factory= new DiskFileItemFactory(5000000,null);

或

你重启服务器了吗？（关闭开发模式并重新启动而不是重启按钮）是的，我做了很多次！您是使用maven还是将apache JAR复制到WEB-INF/lib中？错误是在开发模式还是生产模式下发生的？我没有将它们复制到WEB-INF/lib，而是将它们添加为外部JAR。但是我在我的构建路径和类路径中有它们，避免将更新发布为答案！！！由于您正在尝试使用google app engine，您的查询可能会回答为“我没有更新”以回答“我更新了”，因为问题尚未解决，还有其他问题。您可以在下面的问题解决的地方查看答案，但是还有一个错误，谢谢您的帮助！

DiskFileItemFactory factory= new DiskFileItemFactory(5000000,null);

DiskFileItemFactory factory= new DiskFileItemFactory();
factory.setSizeThreshold(5000000);