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我正在迁移一个旧的网络应用程序。它是用旧式编写的web.xml，现在我们要以编程方式构建 servlet。

这是一个 Spring MVC 应用程序，作为 WAR 模块部署在 Wildfly 10.0.0.Final 下的 EAR 中。

我编写了 Spring 的实现WebApplicationInitializer（目前仍在使用 Spring XML 配置，逐步进行 - 下一步将迁移到 JavaConfig）。虽然我被困在这里，因为 servlet 被初始化了两次，而第二次初始化由于过滤器的名称冲突而失败 -NullPointerException在过滤器创建之后。

这是我的初始化器：

public class MyWebApplicationInitializer implements WebApplicationInitializer {
    private static final Logger log = LoggerFactory.getLogger(MyWebApplicationInitializer.class);

    /**
     * @see org.springframework.web.WebApplicationInitializer#onStartup(javax.servlet.ServletContext)
     */
    @Override
    public void onStartup(ServletContext container) throws ServletException {
        log.debug("******* Initializing Web App *******");
        XmlWebApplicationContext rootContext = new XmlWebApplicationContext();
        rootContext.setConfigLocation("classpath:META-INF/spring/application-context.xml");

        XmlWebApplicationContext webContext = new XmlWebApplicationContext();
        webContext.setConfigLocation("classpath:META-INF/spring/mvc-context.xml");

        container.addListener(new ContextLoaderListener(rootContext));

        ServletRegistration.Dynamic dispatcher = container.addServlet("dispatcher", new DispatcherServlet(webContext));
        dispatcher.setLoadOnStartup(1);
        dispatcher.addMapping("/");

        container.addFilter("log4jEnhancementFilter", Log4jEnhancementFilter.class);

        log.info("******* Web App correctly initialized *******");
    }

}

下面的一些日志：

[ServerService Thread Pool -- 74]:[INFO] @ 2016-04-19 07:19:27,725: io.undertow.servlet.spec.ServletContextImpl.log:313: Spring WebApplicationInitializers detected on classpath: [com.xyz.web.servlet.MyWebApplicationInitializer@6356dd91]
[ServerService Thread Pool -- 74]:[DEBUG] @ 2016-04-19 07:19:27,725: com.xyz.web.servlet.MyWebApplicationInitializer.onStartup:44: ******* Initializing Web App *******
...
[ServerService Thread Pool -- 74]:[INFO] @ 2016-04-19 07:19:27,796: com.xyz.web.servlet.MyWebApplicationInitializer.onStartup:59: ******* Web App correctly initialized *******
...
[ServerService Thread Pool -- 74]:[INFO] @ 2016-04-19 07:19:27,797: io.undertow.servlet.spec.ServletContextImpl.log:313: Spring WebApplicationInitializers detected on classpath: [com.xyz.web.servlet.MyWebApplicationInitializer@427d3c64]
[ServerService Thread Pool -- 74]:[DEBUG] @ 2016-04-19 07:19:27,797: com.xyz.web.servlet.MyWebApplicationInitializer.onStartup:44: ******* Initializing Web App *******
07:19:27,800 ERROR [org.jboss.msc.service.fail] (ServerService Thread Pool -- 74) MSC000001: Failed to start service jboss.undertow.deployment.default-server.default-host./www: org.jboss.msc.service.StartException in service jboss.undertow.deployment.default-server.default-host./www: java.lang.RuntimeException: java.lang.NullPointerException
    at org.wildfly.extension.undertow.deployment.UndertowDeploymentService$1.run(UndertowDeploymentService.java:85)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
    at org.jboss.threads.JBossThread.run(JBossThread.java:320)
Caused by: java.lang.RuntimeException: java.lang.NullPointerException
    at io.undertow.servlet.core.DeploymentManagerImpl.deploy(DeploymentManagerImpl.java:231)
    at org.wildfly.extension.undertow.deployment.UndertowDeploymentService.startContext(UndertowDeploymentService.java:100)
    at org.wildfly.extension.undertow.deployment.UndertowDeploymentService$1.run(UndertowDeploymentService.java:82)
    ... 6 more
Caused by: java.lang.NullPointerException
    at com.xyz.web.servlet.MyWebApplicationInitializer.onStartup(MyWebApplicationInitializer.java:54)
    at org.springframework.web.SpringServletContainerInitializer.onStartup(SpringServletContainerInitializer.java:175)
    at io.undertow.servlet.core.DeploymentManagerImpl.deploy(DeploymentManagerImpl.java:184)
    ... 8 more

如您所见，有一个双重servlet的初始化；第一个成功，第二个由于NPE.

我做错了什么，我该如何解决？

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