For a regular Servlet, I guess you could declare a context listener, but for Spring MVC would Spring make this any easier?
Furthermore, if I define a context listener and then would need to access the beans defined in my servlet.xml
or applicationContext.xml
, how would I get access to them?
This question is related to
spring
model-view-controller
applicationcontext
Please follow below step to do some processing after Application Context get loaded i.e application is ready to serve.
Create below annotation i.e
@Retention(RetentionPolicy.RUNTIME) @Target(value= {ElementType.METHOD, ElementType.TYPE}) public @interface AfterApplicationReady {}
2.Create Below Class which is a listener which get call on application ready state.
@Component
public class PostApplicationReadyListener implements ApplicationListener<ApplicationReadyEvent> {
public static final Logger LOGGER = LoggerFactory.getLogger(PostApplicationReadyListener.class);
public static final String MODULE = PostApplicationReadyListener.class.getSimpleName();
@Override
public void onApplicationEvent(ApplicationReadyEvent event) {
try {
ApplicationContext context = event.getApplicationContext();
String[] beans = context.getBeanNamesForAnnotation(AfterAppStarted.class);
LOGGER.info("bean found with AfterAppStarted annotation are : {}", Arrays.toString(beans));
for (String beanName : beans) {
Object bean = context.getBean(beanName);
Class<?> targetClass = AopUtils.getTargetClass(bean);
Method[] methods = targetClass.getMethods();
for (Method method : methods) {
if (method.isAnnotationPresent(AfterAppStartedComplete.class)) {
LOGGER.info("Method:[{} of Bean:{}] found with AfterAppStartedComplete Annotation.", method.getName(), beanName);
Method currentMethod = bean.getClass().getMethod(method.getName(), method.getParameterTypes());
LOGGER.info("Going to invoke method:{} of bean:{}", method.getName(), beanName);
currentMethod.invoke(bean);
LOGGER.info("Invocation compeleted method:{} of bean:{}", method.getName(), beanName);
}
}
}
} catch (Exception e) {
LOGGER.warn("Exception occured : ", e);
}
}
}
Finally when you start your Spring application just before log stating application started your listener will be called.
Since Spring 4.2 you can use @EventListener
(documentation)
@Component
class MyClassWithEventListeners {
@EventListener({ContextRefreshedEvent.class})
void contextRefreshedEvent() {
System.out.println("a context refreshed event happened");
}
}
I had a single page application on entering URL it was creating a HashMap (used by my webpage) which contained data from multiple databases. I did following things to load everything during server start time-
1- Created ContextListenerClass
public class MyAppContextListener implements ServletContextListener
@Autowired
private MyDataProviderBean myDataProviderBean;
public MyDataProviderBean getMyDataProviderBean() {
return MyDataProviderBean;
}
public void setMyDataProviderBean(MyDataProviderBean MyDataProviderBean) {
this.myDataProviderBean = MyDataProviderBean;
}
@Override
public void contextDestroyed(ServletContextEvent arg0) {
System.out.println("ServletContextListener destroyed");
}
@Override
public void contextInitialized(ServletContextEvent context) {
System.out.println("ServletContextListener started");
ServletContext sc = context.getServletContext();
WebApplicationContext springContext = WebApplicationContextUtils.getWebApplicationContext(sc);
MyDataProviderBean MyDataProviderBean = (MyDataProviderBean)springContext.getBean("myDataProviderBean");
Map<String, Object> myDataMap = MyDataProviderBean.getDataMap();
sc.setAttribute("myMap", myDataMap);
}
2- Added below entry in web.xml
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<listener>
<listener-class>com.context.listener.MyAppContextListener</listener-class>
</listener>
3- In my Controller Class updated code to first check for Map in servletContext
@RequestMapping(value = "/index", method = RequestMethod.GET)
public String index(@ModelAttribute("model") ModelMap model) {
Map<String, Object> myDataMap = new HashMap<String, Object>();
if (context != null && context.getAttribute("myMap")!=null)
{
myDataMap=(Map<String, Object>)context.getAttribute("myMap");
}
else
{
myDataMap = myDataProviderBean.getDataMap();
}
for (String key : myDataMap.keySet())
{
model.addAttribute(key, myDataMap.get(key));
}
return "myWebPage";
}
With this much change when I start my tomcat it loads dataMap during startTime and puts everything in servletContext which is then used by Controller Class to get results from already populated servletContext .
Create your annotation
@Retention(RetentionPolicy.RUNTIME)
public @interface AfterSpringLoadComplete {
}
Create class
public class PostProxyInvokerContextListener implements ApplicationListener<ContextRefreshedEvent> {
@Autowired
ConfigurableListableBeanFactory factory;
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
ApplicationContext context = event.getApplicationContext();
String[] names = context.getBeanDefinitionNames();
for (String name : names) {
try {
BeanDefinition definition = factory.getBeanDefinition(name);
String originalClassName = definition.getBeanClassName();
Class<?> originalClass = Class.forName(originalClassName);
Method[] methods = originalClass.getMethods();
for (Method method : methods) {
if (method.isAnnotationPresent(AfterSpringLoadComplete.class)){
Object bean = context.getBean(name);
Method currentMethod = bean.getClass().getMethod(method.getName(), method.getParameterTypes());
currentMethod.invoke(bean);
}
}
} catch (Exception ignored) {
}
}
}
}
Register this class by @Component annotation or in xml
<bean class="ua.adeptius.PostProxyInvokerContextListener"/>
and use annotation where you wan on any method that you want to run after context initialized, like:
@AfterSpringLoadComplete
public void init() {}
Source: Stackoverflow.com