cdmlib-remote-webapp configuration and bootstrapping¶

• Table of contents
• cdmlib-remote-webapp configuration and bootstrapping
  • Bootstrap
    • DispatcherServlet context
    • main application context
  • Participating classes and configuration files
    • web.xml
    • applicationContext.xml
    • cdmlib-remote-servlet.xml
    • CdmSpringMVCConfig
    • CdmSwaggerConfig

This page describes how spring mvc in cdmlib-remote-webapp is configured and whow the application is being bootstrapped based on this configuration.

Bootstrap¶

The bootstraping startst with the web.xml file in which the main application context and the DispatcherServlet context configured to be picked up by the application container.

Spring has support for hierarchical bean factories, so in the case of the spring mvc, the dispatcher servlet context is a child of the main application context:

• Main application context (beans such as data sources, jpa configuration, business services) --> /WEB-INF/applicationContext.xml

  • -child context-> dispatcher servlet context (MVC specific configuration, components, beans) --> /WEB-INF/cdmlib-remote-servlet.xml

If the servlet context was asked for a bean called "abc" it will look in the servlet context first, if it does not find it there it will look in the parent context, which is the application context.

For very detailed explanation on this topic, see http://stackoverflow.com/questions/15818047/spring-namespace-vs-contextconfiglocation-init-parameters-in-web-xml#answer-15825207

DispatcherServlet context¶

The DispatcherServlet builds the MVC context, handles all HTTP requests and delegates them to other components of the MVC architecture.

The configuration file for this context is the /WEB-INF/cdmlib-remote-servlet.xml

main application context¶

The main application context the the context in which the core cdm application with model, persistence and services is initialized.

The configuration file for this context is the /WEB-INF/applicationContext.xml

Participating classes and configuration files¶

web.xml¶

The file /cdmlib-remote-webapp/src/main/webapp/WEB-INF/web.xml contains an listener entry and the configuration of the Spring dispatcher servlet:

ContextLoaderListener:

<!-- Creates the Spring Container shared by all Servlets and Filters -->
<context-param>
  <param-name>contextConfigLocation</param-name>
  <param-value>/WEB-INF/applicationContext.xml</param-value>
</context-param>
<listener>
    <!-- loads by default /WEB-INF/applicationContext.xml but this can be overridden above -->
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

Which creates the Spring Container shared by all Servlets and Filters. The ContextLoaderListener will load the main applicationContext configuration file /WEB-INF/applicationContext.xml

DispatcherServlet:

<servlet>
    <description>CDM Remote API</description>
    <servlet-name>cdmlib-remote</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
    <!-- loads by default policy /WEB-INF/cdmlib-remote-servlet.xml  -->
</servlet>

applicationContext.xml¶

The cdmlib-remote-webapp is configured using the MVC Java Config therefore the applicationContext.xml does not contain a @ mvc:annotation-driven/ @ but an <context:annotation-config /> entry:

• @@ activates the annotations only on beans which have already been discovered and registered, see http://howtodoinjava.com/2014/07/19/spring-mvc-difference-between-contextannotation-config-vs-contextcomponent-scan/ for detailed explanations.

/WEB-INF/applicationContext.xml

<context:annotation-config />

cdmlib-remote-servlet.xml¶

This is the configuration of the MVC context of the cdmlib-remote servlet. It contains two parts, of which the first one lets spring find the CdmSpringMVCConfig class which is the main configuration bean for the MVC context. This class defines a couple of component scans to expose further beans to the context:

<!-- 
  Initialize SpringMVCConfig and its dependency SpringSwaggerConfig.
  All further component scans are defined in this mvc configuration class 
-->
<context:component-scan base-package="eu/etaxonomy/cdm/remote/config" />

In addition to the CdmSpringMVCConfig class this component scan also covers the

The second part in this file is a conditional entry is an import directive which is only evaluated when the JVM option -Dspring.profiles.active=remoting is supplied. This import causes the initialization of the HTTP Invoker based remoting services needed by the Taxonomic Editor to be able to connect to the CDM Server:

<!-- FIXME:Remoting Expose remoting services currently only for testing -->
<!-- Using Spring Beans Profile (>3.1) http://spring.io/blog/2011/02/11/spring-framework-3-1-m1-released/ 
  only valid if it is at the end of the xml file activated by the vmarg -Dspring.profiles.active=remoting -->
<beans profile="remoting">
  <import resource="classpath:/eu/etaxonomy/cdm/remoting-services.xml" />
</beans>

CdmSpringMVCConfig¶

The Java configuration bean for the spring MVC context, that is it is annotated with @Configuration but it has not the @EnableWebMvc annotation, since it directly subclasses @WebMvcConfigurationSupport@. "... An alternative more advanced option is to extend directly from this class and override methods as necessary remembering to add @Configuration to the subclass and @Bean to overridden @Bean methods. For more details see the Javadoc of @EnableWebMvc. ..."

The reason for this is that the method WebMvcConfigurationSupport.requestMappingHandlerMapping() needs to be overridden in the @CdmSpringMVCConfig@. We may be able go without this method override once we no longer need CdmAntPathMatcher. which is only needed since the controllers need absolute method level RequestMapping values in some few cases. TODO

It enables swagger by the type annotation:

@EnableSwagger

and defines a couple of component scans:

@ComponentScan(basePackages = {
        "eu.etaxonomy.cdm.remote.l10n",
        "eu.etaxonomy.cdm.remote.controller",
        "eu.etaxonomy.cdm.remote.service",
        "eu.etaxonomy.cdm.remote.config"
        }
)

CdmSwaggerConfig¶

This is also a spring java configuration class and thus annotated with @@Configuration@.

It provides the cdmlib-remote-webapp specific configuration for swagger.