Google app engine ClassNotFoundException使用Google App Engine for Java

我和一位朋友正在使用JavaSDK涉足应用程序引擎。我们已经 把一个“你好，世界”的例子放在一起，没有问题；但是,什么时候? 我们尝试添加代码，使用 在com.google.api.client.http中，我们的代码编译得很好，但是 导致运行时错误：

HTTP ERROR 500

Problem accessing /surreality. Reason:

   com/google/api/client/http/HttpTransport

Caused by:

HTTP ERROR 500

Problem accessing /surreality. Reason:

   com/google/api/client/http/javanet/NetHttpTransport

Caused by:

java.lang.NoClassDefFoundError: com/google/api/client/http/javanet/
NetHttpTransport
       at
com.surreality.scratch.SurrealityServlet.performSearch(SurrealityServlet.java:
31)
       at
com.surreality.scratch.SurrealityServlet.doGet(SurrealityServlet.java:
18)
       at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
       at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
       at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:
511)

（……切）

有关守则是：

package com.surreality.scratch;

import java.io.IOException;
import javax.servlet.http.*;
import java.util.List;
import com.google.api.client.googleapis.*;
import com.google.api.client.http.*;
import com.google.api.client.http.javanet.*;
import com.google.api.client.util.Key;

@SuppressWarnings("serial")
public class SurrealityServlet extends HttpServlet {

       public void doGet(HttpServletRequest req, HttpServletResponse resp)
                       throws IOException {
               resp.setContentType("text/plain");
               try {
                       this.performSearch(resp);
                       resp.getWriter().println("Here...");
               } catch (Exception e) {
                       resp.getWriter().println("Onoes!");
               }
       }

       public void performSearch(HttpServletResponse resp) throws Exception
{

               try {
                       resp.getWriter().println("Perform Search ....");
                       resp.getWriter().println("-------------------");

                       HttpTransport transport = new NetHttpTransport(); // This line
causes our servlet to implode on every request
               } catch (Exception e) {
                       resp.getWriter().println("failed");
                       throw e;
               }
       }
}

我们最好的猜测是构建类路径和 运行时类路径，但我们的运行时类路径似乎还可以。这个 HttpTransport类位于google-api-client-1.4.1-beta.jar中 库，并且包含在Eclipse生成的命令行中 要运行项目，请执行以下操作：

/System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home/bin/
java -Ddatastore.default_high_rep_job_policy_unapplied_job_pct=50 -
Xmx512m -javaagent:/Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/agent/appengine-agent.jar -
XstartOnFirstThread -Xbootclasspath/p:/Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/override/appengine-dev-jdk-overrides.jar -
Dfile.encoding=MacRoman -classpath /Users/Arkaaito/Documents/AppEngine/
scratch/surreality/war/WEB-INF/classes:/Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/shared/appengine-local-runtime-
shared.jar:/Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/shared/el-api.jar:/Applications/eclipse/
plugins/com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/shared/jsp/repackaged-appengine-
ant-1.7.1.jar:/Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/shared/jsp/repackaged-appengine-ant-
launcher-1.7.1.jar:/Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/shared/jsp/repackaged-appengine-
jasper-6.0.29.jar:/Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/shared/jsp/repackaged-appengine-jasper-
el-6.0.29.jar:/Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/shared/jsp/repackaged-appengine-tomcat-
juli-6.0.29.jar:/Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/shared/jsp-api.jar:/Applications/eclipse/
plugins/com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/shared/servlet-api.jar:/Applications/
eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/user/appengine-api-1.0-sdk-1.5.3.jar:/
Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/user/appengine-api-labs-1.5.3.jar:/
Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/user/appengine-jsr107cache-1.5.3.jar:/
Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/user/jsr107cache-1.1.jar:/Applications/
eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/user/orm/datanucleus-
appengine-1.0.9.final.jar:/Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/user/orm/datanucleus-core-1.1.5.jar:/
Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/user/orm/datanucleus-jpa-1.1.5.jar:/
Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/user/orm/geronimo-jpa_3.0_spec-1.1.1.jar:/
Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/user/orm/geronimo-jta_1.1_spec-1.1.1.jar:/
Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/user/orm/jdo2-api-2.3-eb.jar:/
Applications/eclipse/plugins/
com.google.appengine.eclipse.sdkbundle_1.5.3.r37v201108301710/
appengine-java-sdk-1.5.3/lib/appengine-tools-api.jar:/Users/Arkaaito/
Documents/AppEngine/scratch/surreality/war/WEB-INF/lib/google-api-java-
client-1.4.1-beta/dependencies/httpclient-4.0.3.jar:/Users/Arkaaito/
Documents/AppEngine/scratch/surreality/war/WEB-INF/lib/google-api-java-
client-1.4.1-beta/dependencies/httpcore-4.0.1.jar:/Users/Arkaaito/
Documents/AppEngine/scratch/surreality/war/WEB-INF/lib/google-api-java-
client-1.4.1-beta/google-api-client-1.4.1-beta.jar:/Users/Arkaaito/
Documents/AppEngine/scratch/surreality/war/WEB-INF/lib/google-api-java-
client-1.4.1-beta/google-api-client-googleapis-1.4.1-beta.jar:/Users/
Arkaaito/Documents/AppEngine/scratch/surreality/war/WEB-INF/lib/google-
api-java-client-1.4.1-beta/google-api-client-extensions-1.4.1-
beta.jar:/Users/Arkaaito/Documents/AppEngine/scratch/surreality/war/
WEB-INF/lib/google-api-java-client-1.4.1-beta/google-api-client-
googleapis-extensions-1.4.1-beta.jar:/Users/Arkaaito/Documents/
AppEngine/scratch/surreality/war/WEB-INF/lib/geronimo-
jpa_3.0_spec-1.1.1.jar:/Users/Arkaaito/Documents/AppEngine/scratch/
surreality/war/WEB-INF/lib/geronimo-jta_1.1_spec-1.1.1.jar
com.google.appengine.tools.development.DevAppServerMain --port=3333 /
Users/Arkaaito/Documents/AppEngine/scratch/surreality/war

以前有没有人遇到过这个问题，或者有没有人遇到过

---

关于调试应该做什么的建议？我相信这很简单，可能是一个配置问题，但作为新手，除了类路径之外，我们不确定该看什么

您的

WEB-INF/lib

目录中有WEB-INF/lib吗，如果您使用谷歌云引擎和Eclipse，您有一些子目录

google-api-java-client-1.4.1-beta

和

google-api-java-client-1.4.1-beta/dependencies

，这些子目录中的JAR应该直接位于

WEB-INF/lib

：

将jar文件添加到Appengine项目

• 它必须位于目录/{Base Directory}/src/main/webapp/WEB-INF/lib
• 将jar文件复制到此目录
• 在Eclipse->Project->Build Path->Configure Build Path->Libraries->Add External JAR中：转到/{Base Directory}/src/main/webapp/WEB-INF/lib并获取文件

---

是否需要在web应用程序中打包一些API JAR？JAR位于类路径上-是否需要对它们进行其他处理，以便在必要时打包？JAR可能需要复制到您的web-INF/lib文件夹中。您是在使用Maven，还是只是手动下载JAR？手动下载。目前它们位于~/Documents/AppEngine/scratch/surreality/war/WEB-INF/lib/-我已经确认，对于我认为相关的JAR（google-api-client-1.4.1-beta.JAR），生成的命令行中的位置与文件的实际位置匹配。哎哟！嗯，我确实认为问题很简单。我只是没意识到它有那么简单。谢谢@Arkaaito您似乎混淆了运行应用程序引擎所需的配置和运行应用程序的应用程序引擎。类路径是让应用程序引擎运行，不需要特定于应用程序的任何内容。设置应用程序对其所有依赖项的访问与设置标准servlet相同。