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Servlet Config
In a Servlet environment, you have the option of configuring the Servlet container
programmatically as an alternative or in combination with a web.xml
file.
The following example registers a DispatcherServlet
:
-
Java
-
Kotlin
import org.springframework.web.WebApplicationInitializer;
public class MyWebApplicationInitializer implements WebApplicationInitializer {
@Override
public void onStartup(ServletContext container) {
XmlWebApplicationContext appContext = new XmlWebApplicationContext();
appContext.setConfigLocation("/WEB-INF/spring/dispatcher-config.xml");
ServletRegistration.Dynamic registration = container.addServlet("dispatcher", new DispatcherServlet(appContext));
registration.setLoadOnStartup(1);
registration.addMapping("/");
}
}
import org.springframework.web.WebApplicationInitializer
class MyWebApplicationInitializer : WebApplicationInitializer {
override fun onStartup(container: ServletContext) {
val appContext = XmlWebApplicationContext()
appContext.setConfigLocation("/WEB-INF/spring/dispatcher-config.xml")
val registration = container.addServlet("dispatcher", DispatcherServlet(appContext))
registration.setLoadOnStartup(1)
registration.addMapping("/")
}
}
WebApplicationInitializer
is an interface provided by Spring MVC that ensures your
implementation is detected and automatically used to initialize any Servlet 3 container.
An abstract base class implementation of WebApplicationInitializer
named
AbstractDispatcherServletInitializer
makes it even easier to register the
DispatcherServlet
by overriding methods to specify the servlet mapping and the
location of the DispatcherServlet
configuration.
This is recommended for applications that use Java-based Spring configuration, as the following example shows:
-
Java
-
Kotlin
public class MyWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
@Override
protected Class<?>[] getRootConfigClasses() {
return null;
}
@Override
protected Class<?>[] getServletConfigClasses() {
return new Class<?>[] { MyWebConfig.class };
}
@Override
protected String[] getServletMappings() {
return new String[] { "/" };
}
}
class MyWebAppInitializer : AbstractAnnotationConfigDispatcherServletInitializer() {
override fun getRootConfigClasses(): Array<Class<*>>? {
return null
}
override fun getServletConfigClasses(): Array<Class<*>>? {
return arrayOf(MyWebConfig::class.java)
}
override fun getServletMappings(): Array<String> {
return arrayOf("/")
}
}
If you use XML-based Spring configuration, you should extend directly from
AbstractDispatcherServletInitializer
, as the following example shows:
-
Java
-
Kotlin
public class MyWebAppInitializer extends AbstractDispatcherServletInitializer {
@Override
protected WebApplicationContext createRootApplicationContext() {
return null;
}
@Override
protected WebApplicationContext createServletApplicationContext() {
XmlWebApplicationContext cxt = new XmlWebApplicationContext();
cxt.setConfigLocation("/WEB-INF/spring/dispatcher-config.xml");
return cxt;
}
@Override
protected String[] getServletMappings() {
return new String[] { "/" };
}
}
class MyWebAppInitializer : AbstractDispatcherServletInitializer() {
override fun createRootApplicationContext(): WebApplicationContext? {
return null
}
override fun createServletApplicationContext(): WebApplicationContext {
return XmlWebApplicationContext().apply {
setConfigLocation("/WEB-INF/spring/dispatcher-config.xml")
}
}
override fun getServletMappings(): Array<String> {
return arrayOf("/")
}
}
AbstractDispatcherServletInitializer
also provides a convenient way to add Filter
instances and have them be automatically mapped to the DispatcherServlet
, as the
following example shows:
-
Java
-
Kotlin
public class MyWebAppInitializer extends AbstractDispatcherServletInitializer {
// ...
@Override
protected Filter[] getServletFilters() {
return new Filter[] {
new HiddenHttpMethodFilter(), new CharacterEncodingFilter() };
}
}
class MyWebAppInitializer : AbstractDispatcherServletInitializer() {
// ...
override fun getServletFilters(): Array<Filter> {
return arrayOf(HiddenHttpMethodFilter(), CharacterEncodingFilter())
}
}
Each filter is added with a default name based on its concrete type and automatically
mapped to the DispatcherServlet
.
The isAsyncSupported
protected method of AbstractDispatcherServletInitializer
provides a single place to enable async support on the DispatcherServlet
and all
filters mapped to it. By default, this flag is set to true
.
Finally, if you need to further customize the DispatcherServlet
itself, you can
override the createDispatcherServlet
method.