我需要将图片上传到数据存储区。使用servlet接收图像。
UploadServlet.java 位于以下位置发生异常：
String pid =
ImageDAO.getInstance().insertImage(image);
UploadServlet.java：
import com.google.appengine.api.datastore.Blob;
import dao.ImageDAO;
import model.Image;
import org.apache.commons.fileupload.FileItemIterator;
import org.apache.commons.fileupload.FileItemStream;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.*;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
public class UploadServlet extends HttpServlet{
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletFileUpload upload = new ServletFileUpload();
FileItemIterator iterator = null;
try {
iterator = upload.getItemIterator(req);
while (iterator.hasNext()) {
FileItemStream item = iterator.next();
InputStream stream = item.openStream();
if (item.isFormField()) {
// Handle form field
Blob bImg = new
Blob(IOUtils.toByteArray(stream));
Image image = new Image(bImg);
String fileName = item.getName();
if (fileName != null) {
fileName = FilenameUtils.getName(fileName);
}
image.setName(fileName);
image.setDate(new Date());
String pid =
ImageDAO.getInstance().insertImage(image);
} else {
// Handle the uploaded file
}
}
resp.sendRedirect("image");
} catch (FileUploadException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
ImageDAO.java 中的代码为：
public String insertImage(Image image) {
PersistenceManager pm = PMF.get().getPersistenceManager();
try {
pm.makePersistent(image);
} finally {
pm.close();
}
return image.getId().toString();
}
错误：
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:859)
at java.util.ArrayList$Itr.next(ArrayList.java:831)
at com.google.appengine.datanucleus.DatastoreConnectionFactoryImpl$DatastoreManagedConnection.close(DatastoreConnectionFactoryImpl.java:146)
at org.datanucleus.store.connection.ConnectionManagerImpl.closeAllConnections(ConnectionManagerImpl.java:181)
at org.datanucleus.store.AbstractStoreManager$1.preClose(AbstractStoreManager.java:260)
at org.datanucleus.ObjectManagerImpl.close(ObjectManagerImpl.java:1112)
at org.datanucleus.api.jdo.JDOPersistenceManager.internalClose(JDOPersistenceManager.java:359)
at org.datanucleus.api.jdo.JDOPersistenceManagerFactory.releasePersistenceManager(JDOPersistenceManagerFactory.java:1106)
at org.datanucleus.api.jdo.JDOPersistenceManager.close(JDOPersistenceManager.java:343)
at dao.ImageDAO.insertImage(ImageDAO.java:25)
at UploadServlet.doPost(UploadServlet.java:60)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:127)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:63)
at org.mortbay.jetty.servlet.ServletHandler$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.DevAppServerModulesFilter.doDirectRequest(DevAppServerModulesFilter.java:366)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectModuleRequest(DevAppServerModulesFilter.java:349)
at com.google.appengine.tools.development.DevAppServerModulesFilter.doFilter(DevAppServerModulesFilter.java:116)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:98)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:490)
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)
更新 当项目部署在Google App Engine服务器上时，问题就消失了。我需要修复此问题才能在本地计算机上调试应用程序。