我的意图是将现有的WAR部署到嵌入式Jetty 9.4.5。

不幸的是，尝试打开页面（JSP）时出现以下错误：

An error occurred at line: [52] in the generated java file: [/tmp/embedded-jetty-jsp/jsp/org/apache/jsp/WEB_002dINF/jsp/MainLayout_jsp.java]
Type mismatch: cannot convert from HashSet<?> to Set<String>

An error occurred at line: [52] in the generated java file: [/tmp/embedded-jetty-jsp/jsp/org/apache/jsp/WEB_002dINF/jsp/MainLayout_jsp.java]
Cannot instantiate the type HashSet<?>

An error occurred at line: [52] in the generated java file: [/tmp/embedded-jetty-jsp/jsp/org/apache/jsp/WEB_002dINF/jsp/MainLayout_jsp.java]
Syntax error on token "<", ? expected after this token

Java中有问题的行如下：

private static final java.util.Set<java.lang.String> _jspx_imports_packages = new java.util.HashSet<>();

似乎Jasper尝试将代码编译为Java 1.6或更低版本，因此无法解释菱形运算符（我使用的是Java 1.8.0_141）。

我试图设置版本，但没有成功：

ServletHolder holderJsp = new ServletHolder("jsp",JspServlet.class);
holderJsp.setInitOrder(0);
holderJsp.setInitParameter("logVerbosityLevel","DEBUG");
holderJsp.setInitParameter("compilerTargetVM","1.7");
holderJsp.setInitParameter("compilerSourceVM","1.7");
holderJsp.setInitParameter("keepgenerated","true");
webAppContext.addServlet(holderJsp,"*.jsp");

启动Jetty的代码是

public class JettyRunner {

  private static File getScratchDir() throws IOException {
     File tempDir = new File(System.getProperty("java.io.tmpdir"));
     File scratchDir = new File(tempDir.toString(), "embedded-jetty-jsp");

     if (!scratchDir.exists()) {
        if (!scratchDir.mkdirs()) {
           throw new IOException("Unable to create scratch directory: " + scratchDir);
        }
     }
     return scratchDir;
  }

  private static List<ContainerInitializer> jspInitializers() {
     JettyJasperInitializer sci = new JettyJasperInitializer();
     ContainerInitializer initializer = new ContainerInitializer(sci, null);
     List<ContainerInitializer> initializers = new ArrayList<ContainerInitializer>();
     initializers.add(initializer);
     return initializers;
  }


  public static void main(String[] args) {
     Server server = new Server(8080);

     WebAppContext webAppContext = new WebAppContext();
     File warFile = new File("existing.war");
     webAppContext.setWar(warFile.getAbsolutePath());
     webAppContext.setContextPath("/acme");

     webAppContext.setConfigurations(new Configuration[] {
              new AnnotationConfiguration(),
              new WebInfConfiguration(),
              new WebXmlConfiguration(),
              new MetaInfConfiguration(),
              new FragmentConfiguration(),
              new EnvConfiguration(),
              new PlusConfiguration(),
              new JettyWebXmlConfiguration()
     });

     webAppContext.setAttribute("javax.servlet.context.tempdir", getScratchDir());
     webAppContext.setAttribute("org.eclipse.jetty.containerInitializers", jspInitializers());
     webAppContext.setAttribute(InstanceManager.class.getName(), new SimpleInstanceManager());
     webAppContext.addBean(new ServletContainerInitializersStarter(webAppContext), true);

     ServletHolder holderJsp = new ServletHolder("jsp",JspServlet.class);
     holderJsp.setInitOrder(0);
     holderJsp.setInitParameter("logVerbosityLevel","DEBUG");
     holderJsp.setInitParameter("compilerTargetVM","1.7");
     holderJsp.setInitParameter("compilerSourceVM","1.7");
     holderJsp.setInitParameter("keepgenerated","true");
     webAppContext.addServlet(holderJsp,"*.jsp");

     webAppContext.setAttribute("org.eclipse.jetty.server.webapp.ContainerIncludeJarPattern",".*/[^/]*jstl.*\\.jar$");
     org.eclipse.jetty.webapp.Configuration.ClassList classlist = org.eclipse.jetty.webapp.Configuration.ClassList.setServerDefault(server);
     classlist.addAfter("org.eclipse.jetty.webapp.FragmentConfiguration", "org.eclipse.jetty.plus.webapp.EnvConfiguration", "org.eclipse.jetty.plus.webapp.PlusConfiguration");
     classlist.addBefore("org.eclipse.jetty.webapp.JettyWebXmlConfiguration", "org.eclipse.jetty.annotations.AnnotationConfiguration");

     HashLoginService hashLoginService = new HashLoginService();
     hashLoginService.setName("Test Realm");
     hashLoginService.setConfig("jetty-realm.properties");

     webAppContext.getSecurityHandler().setLoginService(hashLoginService);

     server.setHandler(webAppContext);

     // Start Jetty
     server.start();
     server.join();
  }

}

任何提示将不胜感激！
谢谢，V。

---------------------------更新1 --------------------- ------
我设置了server.setDumpAfterStart(true);（感谢@JoakimErdfelt的提示！），并注释掉了我设置compilerTargetVM等的代码（因此我没有将JspServlet添加到webAppContext！），我可以看到

|   += org.eclipse.jetty.server.session.SessionHandler483422889==dftMaxIdleSec=1800 - STARTED
|   |   += org.eclipse.jetty.security.ConstraintSecurityHandler@7c75222b - STARTED
|   |   |   +- org.eclipse.jetty.security.DefaultAuthenticatorFactory@4c203ea1
|   |   |   += org.eclipse.jetty.servlet.ServletHandler@27f674d - STARTED
|   |   |   |   += jsp@19c47==org.eclipse.jetty.jsp.JettyJspServlet,jsp=null,order=0,inst=true - STARTED
|   |   |   |   |   +- fork=false
|   |   |   |   |   +- compilerSourceVM=1.7
|   |   |   |   |   +- logVerbosityLevel=DEBUG
|   |   |   |   |   +- compilerTargetVM=1.7
|   |   |   |   |   +- scratchdir=/tmp/embedded-jetty-jsp/jsp
|   |   |   |   |   +- xpoweredBy=false

因此，Java源设置为1.7，但JVM仍无法解释菱形运算符！
兄弟…有什么主意吗？
非常感谢你！