基于 Spring 代码的配置 - IllegalArgumentException: A ServletContext is required

Question

我在这里找到了一个 100% 基于代码的 spring 配置示例：

http://docs.spring.io/spring/docs/3.1.x/javadoc-api/org/springframework/web/WebApplicationInitializer.html

内容：

public class MyWebAppInitializer implements WebApplicationInitializer {

@Override
public void onStartup(ServletContext container) {
  // Create the 'root' Spring application context
  AnnotationConfigWebApplicationContext rootContext =
    new AnnotationConfigWebApplicationContext();
  rootContext.register(AppConfig.class);

  // Manage the lifecycle of the root application context
  container.addListener(new ContextLoaderListener(rootContext));

  // Create the dispatcher servlet's Spring application context
  AnnotationConfigWebApplicationContext dispatcherContext =
    new AnnotationConfigWebApplicationContext();
  dispatcherContext.register(DispatcherConfig.class);

  // Register and map the dispatcher servlet
  ServletRegistration.Dynamic dispatcher =
    container.addServlet("dispatcher", new DispatcherServlet(dispatcherContext));
  dispatcher.setLoadOnStartup(1);
  dispatcher.addMapping("/");
}

}

在上面的示例中，他们在注册配置类后从未调用 refresh()。 但是 API 说 - 必须调用 refresh() 才能使上下文完全处理新类。 所以我在每个注册语句之后添加了 refresh()

rootContext.register(AppConfig.class);
rootContext.refresh();

dispatcherContext.register(DispatcherConfig.class);
dispatcherContext.refresh();

结果：

SEVERE: ContainerBase.addChild: start: 
org.apache.catalina.LifecycleException: Failed to start component    [StandardEngine[Catalina].StandardHost[localhost].StandardContext[]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:726)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:702)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:699)
at org.apache.catalina.startup.HostConfig.manageApp(HostConfig.java:1647)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:300)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:465)
at org.apache.catalina.mbeans.MBeanFactory.createStandardContext(MBeanFactory.java:415)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:300)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.invoke(DefaultMBeanServerInterceptor.java:819)
at com.sun.jmx.mbeanserver.JmxMBeanServer.invoke(JmxMBeanServer.java:801)
at javax.management.remote.rmi.RMIConnectionImpl.doOperation(RMIConnectionImpl.java:1487)
at javax.management.remote.rmi.RMIConnectionImpl.access$300(RMIConnectionImpl.java:97)
at javax.management.remote.rmi.RMIConnectionImpl$PrivilegedOperation.run(RMIConnectionImpl.java:1328)
at javax.management.remote.rmi.RMIConnectionImpl.doPrivilegedOperation(RMIConnectionImpl.java:1420)
at javax.management.remote.rmi.RMIConnectionImpl.invoke(RMIConnectionImpl.java:848)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:322)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at sun.rmi.transport.Transport$1.run(Transport.java:174)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:556)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:811)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:670)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:724)
    Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'defaultServletHandlerMapping' defined in class path resource [org/springframework/web/servlet/config/annotation/DelegatingWebMvcConfiguration.class]: Instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanDefinitionStoreException: Factory method [public org.springframework.web.servlet.HandlerMapping org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport.defaultServletHandlerMapping()] threw exception; nested exception is java.lang.IllegalArgumentException: A ServletContext is required to configure default servlet handling
at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:592)

但如果我删除 refresh()（显然）它工作正常（我使用 Tomcat 8.0） 最后，我不完全理解是否必须在这样的代码中使用 refresh()。如果没有 - 我应该什么时候使用它？

Answer 1

在您的情况下，这仅对传递给 DispatcherServlet 的 ApplicationContext 重要。 DispatcherServlet 构造函数状态

给定的 Web 应用程序上下文可能会也可能不会被刷新。如果 它还没有被刷新（推荐的方法），那么 将发生以下情况：

• 如果给定上下文还没有父级，则根应用程序上下文将设置为父级。
• 如果给定的上下文尚未分配一个 id，则会为其分配一个
• ServletContext 和 ServletConfig 对象将被委托给应用程序上下文
• postProcessWebApplicationContext 将被调用
• 通过指定的任何ApplicationContextInitializers “contextInitializerClasses” init-param 或通过 将应用 setContextInitializers 属性。
• 如果上下文实现ConfigurableApplicationContext，则将调用refresh()

如果上下文已经被刷新，以上都不会 发生，假设用户已经执行了这些操作 （或不）根据他们的具体需求。

所以对于DispatcherServlet，您必须执行以下操作

AnnotationConfigWebApplicationContext dispatcherContext = new AnnotationConfigWebApplicationContext();
dispatcherContext.register(DispatcherConfig.class);

// will take care of calling refresh() on the ApplicationContext
ServletRegistration.Dynamic dispatcher = container.addServlet("dispatcher", new DispatcherServlet(dispatcherContext));

这对于DispatcherServlet 配置是必需的，因为由于@EnableWebMvc（或等效的<mvc:annotation-driven>）而生成的一些bean 需要由Servlet 容器提供的ServletContext 和/或ServletConfig 对象.

根上下文不应该有这样的依赖，所以这样做是安全的

AnnotationConfigWebApplicationContext rootContext = new AnnotationConfigWebApplicationContext();
rootContext.register(AppConfig.class);
rootContext.refresh();

请注意，您可以通过将 @Configuration 类作为参数传递给其构造函数来创建 AnnotationConfigWebApplicationContext 对象。