google-app-engine - 从 Kotlin 代码中找不到类 def

Question

我有 Kotlin 代码:

         cluster.removeIf { t: SolutionElement -> t.timeStart < minimumDate } //Clusters.kt:66

其中集群对象是 kotlin 可变列表。当我尝试在 Google App Engine 标准环境中运行此代码时，出现错误:

java.lang.NoClassDefFoundError: java/util/function/Predicate
    at com.google.appengine.runtime.Request.process-4a2a3dcd2b375db7(Request.java)
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:820)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
    at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:375)
    at net.toolla.teamly.services.matcher.Clusters.removeExpired(Clusters.kt:66)
    at net.toolla.teamly.services.matcher.Clusters.pickMore(Clusters.kt:31)
    at net.toolla.teamly.services.matcher.BestMatchWorker.getSolutionElements(BestMatchWorker.java:232)
    at net.toolla.teamly.services.matcher.BestMatchWorker.match(BestMatchWorker.java:116)
    at net.toolla.teamly.services.matcher.MatcherService.doPost(MatcherService.java:37)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:326)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
    at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
    at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:454)
    at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:461)
    at com.google.tracing.CurrentContext.runInContext(CurrentContext.java:297)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:320)
    at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:312)
    at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:458)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassNotFoundException: java.util.function.Predicate
    at com.google.appengine.runtime.Request.process-4a2a3dcd2b375db7(Request.java)

在这个模块的 build.gradle 中，我有:

compileKotlin{
    kotlinOptions{
        jvmTarget = 1.6
    }
}

没有那个参数错误是:

Uncaught exception from servlet
java.lang.NoClassDefFoundError: net/toolla/teamly/services/matcher/Clusters$removeExpired$1

其中“removeExpired”是包含上述行的函数的名称。

我将上面的代码更改为一些不太方便且较旧的语法，但如果知道如何使用一些更新的技术，那就太好了。

Answer 1

类(class)java.util.function.Predicate在Java 8中引入。所以用8运行它。关于th

...
 * @since 1.8
 */
@FunctionalInterface
public interface Predicate<T> {

关于那个错误:

java.lang.NoClassDefFoundError: net/toolla/teamly/services/matcher/Clusters$removeExpired$1

确保您的 classpath 上有该类(class)