java - SparkJava 与 Gradle 上的 AppEngine

Question

我基于 Google Tutorial 创建新项目并切换到Java 1.8， 添加 SparkJava 依赖项:

dependencies {
    compile 'com.google.appengine:appengine:+'
    compile 'com.sparkjava:spark-core:2.5.5'
    compile 'com.google.cloud:google-cloud-datastore:0.13.0-beta'
}

并根据SparkJava文档创建web.xml配置:

<web-app xmlns="http://java.sun.com/xml/ns/javaee" version="2.5">
    <filter>
        <filter-name>SparkFilter</filter-name>
        <filter-class>spark.servlet.SparkFilter</filter-class>
        <init-param>
            <param-name>applicationClass</param-name>
            <param-value>me.drozdzynski.test.App</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>SparkFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

编译并启动本地 Google 开发服务器后，出现错误:

WARNING: failed JettyContainerService$ApiProxyHandler@14028087: java.lang.NoClassDefFoundError: java.util.Optional is a restricted class. Please see the Google  App Engine developer's guide for more details.
Apr 19, 2017 7:22:01 AM com.google.apphosting.utils.jetty.JettyLogger warn
WARNING: Error starting handlers
java.lang.NoClassDefFoundError: java.util.Optional is a restricted class. Please see the Google  App Engine developer's guide for more details.
    at com.google.appengine.tools.development.agent.runtime.Runtime.reject(Runtime.java:50)
    at spark.Service.<init>(Service.java:74)
    at spark.Service.ignite(Service.java:99)
    at spark.Spark$SingletonHolder.<clinit>(Spark.java:49)
    at spark.Spark.getInstance(Spark.java:53)
    at spark.Spark.<clinit>(Spark.java:59)
    at me.drozdzynski.test.App.init(App.java:11)
    at spark.servlet.SparkFilter.init(SparkFilter.java:69)
    at org.mortbay.jetty.servlet.FilterHolder.doStart(FilterHolder.java:97)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:662)
    at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
    at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1250)
    at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
    at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:467)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
    at org.mortbay.jetty.Server.doStart(Server.java:224)
    at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
    at com.google.appengine.tools.development.JettyContainerService.startContainer(JettyContainerService.java:268)
    at com.google.appengine.tools.development.AbstractContainerService.startup(AbstractContainerService.java:284)
    at com.google.appengine.tools.development.AutomaticInstanceHolder.startUp(AutomaticInstanceHolder.java:26)
    at com.google.appengine.tools.development.AbstractModule.startup(AbstractModule.java:87)
    at com.google.appengine.tools.development.Modules.startup(Modules.java:105)
    at com.google.appengine.tools.development.DevAppServerImpl.doStart(DevAppServerImpl.java:262)
    at com.google.appengine.tools.development.DevAppServerImpl.access$000(DevAppServerImpl.java:45)
    at com.google.appengine.tools.development.DevAppServerImpl$1.run(DevAppServerImpl.java:217)
    at com.google.appengine.tools.development.DevAppServerImpl$1.run(DevAppServerImpl.java:215)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.google.appengine.tools.development.DevAppServerImpl.start(DevAppServerImpl.java:215)
    at com.google.appengine.tools.development.DevAppServerMain$StartAction.apply(DevAppServerMain.java:349)
    at com.google.appengine.tools.util.Parser$ParseResult.applyArgs(Parser.java:47)
    at com.google.appengine.tools.development.DevAppServerMain.run(DevAppServerMain.java:222)
    at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:213)

Answer 1

Google App Engine 只有一组有限的可用 Java 类。实际列表can be found here 。 java.util.Optional 不在该列表中，因此无法使用。因此，您无法在 Google App Engine 上使用 Spark-java。