spring - ServletContext

public interface ServletContext

Defines a set of methods that a servlet uses to communicate with its servlet container, for example, to get the MIME type of a file, dispatch requests, or write to a log file.

There is one context per "web application" per Java Virtual Machine. (A "web application" is a collection of servlets and content installed under a specific subset of the server's URL namespace such as /catalog and possibly installed via a .war file.)

In the case of a web application marked "distributed" in its deployment descriptor, there will be one context instance for each virtual machine. In this situation, the context cannot be used as a location to share global information (because the information won't be truly global). Use an external resource like a database instead.

The ServletContext object is contained within the ServletConfig object, which the Web server provides the servlet when the servlet is initialized.

source - http://docs.oracle.com/javaee/7/api/javax/servlet/ServletContext.html

* tomcat 구현 

org.apache.catalina.core

Class ApplicationContextFacade

• java.lang.Object
• org.apache.catalina.core.ApplicationContextFacade

• All Implemented Interfaces:

  ServletContext

  ---

  
  

  public class ApplicationContextFacade
  extends Object
  implements ServletContext

  Facade object which masks the internal ApplicationContext object from the web application.

  
  

org.apache.catalina.core

Class ApplicationContext

• java.lang.Object
• org.apache.catalina.core.ApplicationContext

• All Implemented Interfaces:

  ServletContext

  Direct Known Subclasses:

  ReplicatedContext.ReplApplContext

  ---

  
  

  public class ApplicationContext
  extends Object
  implements ServletContext

  Standard implementation of ServletContext that represents a web application's execution environment. An instance of this class is associated with each instance of StandardContext.

- HttpSession.getServletContext() 호출 시 ApplicationContextFacade를 얻을 수 있음. ApplicationContextFacade 생성자 호출 시 ApplicationContext를 인자로 넘김

- ApplicationContext.attributes(protected Map<String,Object> attributes = new ConcurrentHashMap<>())에서 web.xml 정보 확인할 수 있음

source - https://tomcat.apache.org/tomcat-8.0-doc/api/org/apache/catalina/core/ApplicationContextFacade.html

https://tomcat.apache.org/tomcat-8.0-doc/api/org/apache/catalina/core/ApplicationContext.html

* spring에서 WebApplicationContext를 얻기(Find a custom WebApplicationContext for this web app.)

org.springframework.web.context

Interface WebApplicationContext

• All Superinterfaces:

  ApplicationContext, ApplicationEventPublisher, BeanFactory, EnvironmentCapable, HierarchicalBeanFactory, ListableBeanFactory, MessageSource, ResourceLoader, ResourcePatternResolver

  All Known Subinterfaces:

  ConfigurablePortletApplicationContext, ConfigurableWebApplicationContext

  All Known Implementing Classes:

  AbstractRefreshablePortletApplicationContext, AbstractRefreshableWebApplicationContext, AnnotationConfigWebApplicationContext, GenericWebApplicationContext, GroovyWebApplicationContext,StaticPortletApplicationContext, StaticWebApplicationContext, XmlPortletApplicationContext, XmlWebApplicationContext

  ---

  
  

  public interface WebApplicationContext
  extends ApplicationContext

  Interface to provide configuration for a web application. This is read-only while the application is running, but may be reloaded if the implementation supports this.

  This interface adds a getServletContext() method to the generic ApplicationContext interface, and defines a well-known application attribute name that the root context must be bound to in the bootstrap process.

  Like generic application contexts, web application contexts are hierarchical. There is a single root context per application, while each servlet in the application (including a dispatcher servlet in the MVC framework) has its own child context.

  In addition to standard application context lifecycle capabilities, WebApplicationContext implementations need to detect ServletContextAware beans and invoke the setServletContext method accordingly.

  Since:

  January 19, 2001

  Author:

  Rod Johnson, Juergen Hoeller

  See Also:

  ServletContextAware.setServletContext(javax.servlet.ServletContext)

source - http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/context/WebApplicationContext.html

- org.springframework.web.context.support.WebApplicationContextUtils.getWebApplicationContext(ServletContext sc, String attrName) 호출

- sc는 ApplicationContextFacade에 해당하고 attrName은 web.xml에서 설정한 DispatcherServlet 서블릿 이름

- web.xml 설정을 javaConfig(WebApplicationInitializer)로 대체한 경우 ContextLoaderListener으로 등록되어 WebApplicationContextUtils.getWebApplicationContext(ServletContext sc)을 호출해야하며 이 메서드는 attrName을 org.springframework.web.context.WebApplicationContext.ROOT으로 하여 WebApplicationContextUtils.getWebApplicationContext(ServletContext sc, String attrName)를 호출함

- 소스코드 

Object attr = sc.getAttribute(attrName);

return (WebApplicationContext) attr;

- 이후 WebApplicationContext를 통해서 bean을 얻을 수 있음 

UserService userService = (UserService) webApplicationContext.getBean("userService");