在片段中生成错误以将文件上传到Google appengine

Question

以下代码段在IDE中生成错误，当我单击以部署应用程序时。

        <form  action="<%= blobstoreService.createUploadUrl("/upload") %>" method="post" enctype="multipart/form-data">
          <input type="file" name="myFile"/>
          <input type="submit" value="submit"/>

错误：

error: cannot find symbol
[javac]       out.print( blobstoreService.createUploadUrl("/upload") );
[javac]                  ^
[javac]   symbol:   variable blobstoreService
[javac]   location: class UploadTester_jsp
[javac] 1 error

我需要添加什么？为什么我会收到此错误？

Answer 1

您必须声明然后初始化变量blobstoreService。

<%@ page import="com.google.appengine.api.blobstore.BlobstoreServiceFactory" %>
<%@ page import="com.google.appengine.api.blobstore.BlobstoreService" %>
....

<%
    BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService();
%>

以上是直接来自documentation。