Question

在我的应用程序中，我有一个上传按钮。当用户选择某个文件时，我必须验证其扩展名。（让用户只上传.txt文件）。如果它是txt - 将其保存在服务器上，否则 - 对此类文件不执行任何操作。

我尝试过这样的事情：

//Check file type on start event:
@Override
public void uploadStarted(StartedEvent event) {
    String contentType = event.getFilename();
    if (!contentType.endsWith("txt")) {
        isValid = false;
        upload.interruptUpload();
    }
}

//If it is txt, do some actions:
@Override
public OutputStream receiveUpload(String filename, String mimeType) {
    FileOutputStream fos = null;
    if(isValid) {
        try {
            createUserDir(filename);
            fos = new FileOutputStream(file);
            //some more actions
        } catch (final java.io.FileNotFoundException e) {
            log.error(e);
            return null;
        }
    }
    return fos;
}

//Error msg for a user
@Override
public void uploadFailed(Upload.FailedEvent event) {
    root.getWindow().showNotification("Error Header", "Error Msg",
            Window.Notification.TYPE_ERROR_MESSAGE);
}

它几乎可以工作，除了事实，上传组件捕获错误：

com.vaadin.terminal.gwt.server.UploadException：上传失败 com.vaadin.terminal.gwt.server.AbstractCommunicationManager.streamToReceiver（AbstractCommunicationManager.java:623）在 com.vaadin.terminal.gwt.server.AbstractCommunicationManager.doHandleSimpleMultipartFileUpload（AbstractCommunicationManager.java:476）在 com.vaadin.terminal.gwt.server.CommunicationManager.handleFileUpload（CommunicationManager.java:259）在 com.vaadin.terminal.gwt.server.AbstractApplicationServlet.service（AbstractApplicationServlet.java:495）在javax.servlet.http.HttpServlet.service（HttpServlet.java:723）at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:290）在 org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:206）在 org.apache.catalina.core.StandardWrapperValve.invoke（StandardWrapperValve.java:233）在 org.apache.catalina.core.StandardContextValve.invoke（StandardContextValve.java:191）在 org.apache.catalina.authenticator.AuthenticatorBase.invoke（AuthenticatorBase.java:563）在 org.apache.catalina.core.StandardHostValve.invoke（StandardHostValve.java:127）在 org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:103）在 org.apache.catalina.core.StandardEngineValve.invoke（StandardEngineValve.java:109）在 org.apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:293）在 org.apache.coyote.http11.Http11Processor.process（Http11Processor.java:861）在 org.apache.coyote.http11.Http11Protocol $ Http11ConnectionHandler.process（Http11Protocol.java:620）在 org.apache.tomcat.util.net.JIoEndpoint $ Worker.run（JIoEndpoint.java:489）在java.lang.Thread.run（未知来源）引起： com.vaadin.terminal.gwt.server.NoOutputStreamException at com.vaadin.terminal.gwt.server.AbstractCommunicationManager.streamToReceiver（AbstractCommunicationManager.java:568） ......还有17个

那么，用错误的文件终止上传的正确方法是什么？

Answer 1

返回NullOutputStream（extends OutputStream）而不是null：

//Check file type on start event:
@Override
public void uploadStarted(StartedEvent event) {
    String contentType = event.getFilename();
    if (!contentType.endsWith("txt")) {
        isValid = false;
        upload.interruptUpload();    
    }
}

//If it is txt, do some actions:
@Override
public OutputStream receiveUpload(String filename, String mimeType) {
    FileOutputStream fos = null; // Stream to write to
    if (filename != null && !filename.isEmpty() && isValid) {
        try {
            createUserDir(filename);
            fos = new FileOutputStream(file);
            return fos;
        } catch (final java.io.FileNotFoundException e) {
            log.error(e);
            return new NullOutputStream();
        }
    } else {/*Show error "Please select a file to upload."*/};

    uploadControl.interruptUpload();
    return new NullOutputStream(); 
}

NullOutputStream类通过“package com.vaadin.external.org.apache.commons.io.output”打包，因此您应该可以使用该类。

如果您有任何疑问，请与我们联系！

Vaadin 6上传组件：如何终止文件上传进程而不在服务器上保存错误文件

1 个答案: