How to add a hook to the application context initialization event

Question

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

User · Answer

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

User · Answer

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 lt String  Object gt  myDataMap   MyDataProviderBean getDataMap             sc setAttribute  myMap   myDataMap            2- Added below entry in web xml   lt listener gt       lt listener-class gt org springframework web context ContextLoaderListener lt  listener-class gt   lt  listener gt    lt listener gt       lt listener-class gt com context listener MyAppContextListener lt  listener-class gt   lt  listener gt    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 lt String  Object gt  myDataMap   new HashMap lt String  Object gt                 if  context    null  amp  amp  context getAttribute  myMap    null                                 myDataMap  Map lt String  Object gt  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

User · Answer

Spring has some standard events which you can handle    To do that  you must create and register a bean that implements the ApplicationListener interface  something like this   package test pack age   import org springframework context ApplicationContext  import org springframework context ApplicationEvent  import org springframework context ApplicationListener  import org springframework context event ContextRefreshedEvent   public class ApplicationListenerBean implements ApplicationListener         Override     public void onApplicationEvent ApplicationEvent event            if  event instanceof ContextRefreshedEvent                ApplicationContext applicationContext     ContextRefreshedEvent  event  getApplicationContext                   now you can do applicationContext getBean                                             You then register this bean within your servlet xml or applicationContext xml file    lt bean id  eventListenerBean  class  test pack age ApplicationListenerBean    gt    and Spring will notify it when the application context is initialized   In Spring 3  if you are using this version   the ApplicationListener class is generic and you can declare the event type that you are interested in  and the event will be filtered accordingly  You can simplify a bit your bean code like this   public class ApplicationListenerBean implements ApplicationListener lt ContextRefreshedEvent gt          Override     public void onApplicationEvent ContextRefreshedEvent event            ApplicationContext applicationContext   event getApplicationContext               now you can do applicationContext getBean

User · Answer

Create your annotation     Retention RetentionPolicy RUNTIME      public  interface AfterSpringLoadComplete           Create class       public class PostProxyInvokerContextListener implements ApplicationListener lt ContextRefreshedEvent gt          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 lt   gt  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   lt bean class  ua adeptius PostProxyInvokerContextListener   gt    and use annotation where you wan on any method that you want to run after context initialized  like       AfterSpringLoadComplete     public void init

User · Answer

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 lt ApplicationReadyEvent gt         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 lt   gt  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

[spring] How to add a hook to the application context initialization event?

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