我正在尝试通过在他们的网站上运行示例来学习使用 Java 的 Google App Engine 的用法。我在 Linux 中使用 Eclipse Juno 作为我的 IDE。它成功地托管在我的本地计算机上，但是在尝试将其部署到 App Engine 时，它无法编译 JSP 文件。
SignGuestbookServlet.java
package com.guest.book;
import java.io.IOException;
import java.util.Date;
import java.util.logging.Logger;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.google.appengine.api.datastore.DatastoreService;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
import com.google.appengine.api.datastore.Entity;
import com.google.appengine.api.datastore.Key;
import com.google.appengine.api.datastore.KeyFactory;
import com.google.appengine.api.users.User;
import com.google.appengine.api.users.UserService;
import com.google.appengine.api.users.UserServiceFactory;
public class SignGuestbookServlet extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = 1L;
private static final Logger log = Logger.getLogger(SignGuestbookServlet.class.getName());
public void doPost(HttpServletRequest req, HttpServletResponse resp)
throws IOException {
UserService userService = UserServiceFactory.getUserService();
User user = userService.getCurrentUser();
String guestbookName=req.getParameter("guestbookName")==null?"default":req.getParameter("guestbookName");
Key guestbookKey=KeyFactory.createKey("Guestbook", guestbookName);
String content = req.getParameter("content");
Date date=new Date();
Entity greeting = new Entity("Greeting",guestbookKey);
greeting.setProperty("user", user);
greeting.setProperty("content", content);
greeting.setProperty("date", date);
DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
datastore.put(greeting);
resp.sendRedirect("/guestbook.jsp?guestbookName="+guestbookName);
}
}
留言簿.jsp
<%@ page import="com.google.appengine.api.users.User" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="java.util.List" %>
<%@ page import="com.google.appengine.api.users.User" %>
<%@ page import="com.google.appengine.api.users.UserService" %>
<%@ page import="com.google.appengine.api.users.UserServiceFactory" %>
<%@ page import="com.google.appengine.api.datastore.DatastoreServiceFactory" %>
<%@ page import="com.google.appengine.api.datastore.DatastoreService" %>
<%@ page import="com.google.appengine.api.datastore.Query" %>
<%@ page import="com.google.appengine.api.datastore.Entity" %>
<%@ page import="com.google.appengine.api.datastore.FetchOptions" %>
<%@ page import="com.google.appengine.api.datastore.Key" %>
<%@ page import="com.google.appengine.api.datastore.KeyFactory" %><html>
<head>
<title>Guestbook</title>
</head>
<body>
<%
String guestbookName= request.getParameter("guestbookName");
if(guestbookName==null)
{
guestbookName="default";
}
pageContext.setAttribute("guestbookName", guestbookName);
UserService userService = UserServiceFactory.getUserService();
User user = userService.getCurrentUser();
if (user != null) {
pageContext.setAttribute("user", user);
%>
<p>Hello, <%= user.getNickname() %>! (You can
<a href="<%= userService.createLogoutURL(request.getRequestURI()) %>">sign out</a>.)</p>
<%
} else {
%>
<p>Hello!
<a href="<%= userService.createLoginURL(request.getRequestURI()) %>">Sign in</a>
to include your name with greetings you post.</p><br>
<%
}
%>
<%
DatastoreService datastore=DatastoreServiceFactory.getDatastoreService();
Key guestbookKey = KeyFactory.createKey("Guestbook",guestbookName);
Query query= new Query("Greeting",guestbookKey).addSort("date",Query.SortDirection.DESCENDING);
List<Entity> greetings = datastore.prepare(query).asList(FetchOptions.Builder.withLimit(5));
if(greetings.isEmpty())
{%>
<p> Guestbook <%= guestbookName %> has no messages.</p>
<%
}
else
{
%>
<p>Messages in Guestbook <%= guestbookName %>.</p><br>
<%
for(Entity greeting : greetings)
{
if(greeting.getProperty("user")==null){
%>
<p>An anonymous person wrote:</p>
<%
}
else
{
%>
<p><b><%= greeting.getProperty("user") %></b> wrote: </p>
<%
}
%>
<blockquote><%= greeting.getProperty("content") %></blockquote>
<%
}
}
%>
<form action="/sign" title="Dash" method="post">
<div><textarea name="content" rows="3" cols="60"></textarea></div>
<div><input type="submit" value="Post Greeting" /></div>
<input type="hidden" name="guestbookName" value="<%= guestbookName %>"/>
</form>
</body>
</html>
错误日志
com.google.appengine.tools.admin.JspCompilationException: Failed to compile jsp files.
Exception in thread "main" java.lang.ExceptionInInitializerError
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:188)
at org.apache.jasper.JspCompilationContext.createCompiler(JspCompilationContext.java:238)
at org.apache.jasper.JspCompilationContext.createCompiler(JspCompilationContext.java:214)
at org.apache.jasper.JspC.processFile(JspC.java:1181)
at org.apache.jasper.JspC.execute(JspC.java:1341)
at com.google.appengine.tools.development.LocalJspC.main(LocalJspC.java:40)
Caused by: java.lang.NullPointerException
at com.google.appengine.tools.development.LocalJspC$LocalCompiler.<clinit>(LocalJspC.java:53)
... 7 more
Error while executing: /usr/lib/jvm/java-7-openjdk-amd64/bin/java -classpath /home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/impl/appengine-api-labs.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/impl/google_sql.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/impl/appengine-local-runtime.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/impl/appengine-api.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/impl/appengine-api-stubs.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/shared/jsp/repackaged-appengine-ant-1.7.1.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/shared/jsp/repackaged-appengine-tomcat-juli-6.0.29.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/shared/jsp/repackaged-appengine-jasper-6.0.29.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/shared/jsp/repackaged-appengine-jasper-el-6.0.29.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/shared/jsp/repackaged-appengine-ant-launcher-1.7.1.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/shared/jsp-api.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/shared/appengine-local-runtime-shared.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/shared/servlet-api.jar:/home/abdul/eclipse/plugins/com.google.appengine.eclipse.sdkbundle_1.7.7.1/appengine-java-sdk-1.7.7.1/lib/shared/el-api.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/classes:/tmp/1366711497850-0:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/jdo-api-3.0.1.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/repackaged-appengine-jasper-jdt-6.0.29.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/appengine-api-labs.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/repackaged-appengine-jakarta-standard-1.1.2.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/jta-1.1.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/datanucleus-appengine-2.1.2.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/datanucleus-core-3.1.3.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/appengine-endpoints.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/appengine-jsr107cache-1.7.7.1.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/repackaged-appengine-ant-1.7.1.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/repackaged-appengine-tomcat-juli-6.0.29.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/repackaged-appengine-jakarta-jstl-1.1.2.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/datanucleus-api-jdo-3.1.3.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/repackaged-appengine-jasper-6.0.29.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/geronimo-jpa_2.0_spec-1.0.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/repackaged-appengine-jasper-el-6.0.29.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/repackaged-appengine-ant-launcher-1.7.1.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/asm-4.0.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/datanucleus-api-jpa-3.1.3.jar:/tmp/appcfg7995795059214651808.tmp/WEB-INF/lib/jsr107cache-1.1.jar: -Dcom.google.apphosting.runtime.use_java6=false com.google.appengine.tools.development.LocalJspC -uriroot /tmp/appcfg7995795059214651808.tmp -p org.apache.jsp -l -v -webinc /tmp/appcfg7995795059214651808.tmp/WEB-INF/generated_web.xml -d /tmp/1366711497850-0 -javaEncoding UTF-8