I wish to set up a few application wide variables with servletContext.setAttributes on servlet context initialization phase .How can I achieve this.
Implement javax.servlet.SevletContextListener which gets a callback when javax.servlet.ServletContext is initialized.
Here is the example:
public class MyServletContextListener implements ServletContextListener
{
public void contextInitialized(ServletContextEvent sce)
{
ServletContext sc = sce.getServletContext();
//do your initialization here.
sc.setAttribute(.....);
}
public void contextDestroyed(ServletContextEvent sce)
{
ServletContext sc = sce.getServletContext();
//do your cleanup here
}
}
If you would like to tie your logic closer to the servlet (and not use a listener), you can override the servlets init method. Like so:
#Override
public void init() throws ServletException {
ServletContext sc = getServletContext();
// Store our attribute(s)!
// Check first to make sure it hasn't already been set by another Servlet instance.
if (sc.getAttribute("key") == null)
sc.setAttribute("key", "value");
}
And you don't have to call through to super.init(config). See docs.
Related
I am trying to create an UI component that allow the user to customize the timeout of sessions. So I created a servlet as below:
public class SessionTimeoutServlet extends AbstractBaseServlet {
private static final long serialVersionUID = 2567293974465204729L;
public static final String REQUEST_TIMEOUT_PARAMETR_NAME = "timeout";
private static final String TIMEOUT_TYPE_INIT_PARAMETER_NAME = "timeoutType";
private static final String WEB_TYPE_TIMEOUT = "web";
private static final String WEBSERVICE_TYPE_TIMEOUT = "webService";
#EJB(mappedName = SessionSettingsRemote.BEAN_NAME)
private SessionSettingsRemote sessionSettingsBean;
#PostConstruct
public void initTimeout() {
try {
String timeoutType = getServletContext().getInitParameter(TIMEOUT_TYPE_INIT_PARAMETER_NAME);
if (WEBSERVICE_TYPE_TIMEOUT.equals(timeoutType)) {
setCustomTimeout(sessionSettingsBean.getSessionSettingsDTO().getWebServiceSessionTimeoutInterval());
} else if (WEB_TYPE_TIMEOUT.equals(timeoutType)) {
setCustomTimeout(sessionSettingsBean.getSessionSettingsDTO().getWebSessionTimeoutInterval());
} else {
setCustomTimeout(30);
}
} catch (ApplicationException e) {
setCustomTimeout(30);
}
}
#Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int timeout = Integer.parseInt(request.getParameter(REQUEST_TIMEOUT_PARAMETR_NAME));
setCustomTimeout(timeout);
}
public static void setCustomTimeout(int customTimeout) {
SessionManagerListener.setCustomTimeout(customTimeout);
}
}
However, when I deploy this on GlassFish, I get below exception.
Caused by: java.lang.IllegalStateException: ServletConfig has not been initialized
at javax.servlet.GenericServlet.getServletContext(GenericServlet.java:199)
at com.accedian.ems.uiapplication.server.servlets.SessionTimeoutServlet.initTimeout(SessionTimeoutServlet.java:33)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.sun.enterprise.container.common.impl.util.InjectionManagerImpl$3.run(InjectionManagerImpl.java:766)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.enterprise.container.common.impl.util.InjectionManagerImpl.invokeLifecycleMethod(InjectionManagerImpl.java:760)
at com.sun.enterprise.container.common.impl.util.InjectionManagerImpl.inject(InjectionManagerImpl.java:531)
at com.sun.enterprise.container.common.impl.util.InjectionManagerImpl.injectInstance(InjectionManagerImpl.java:141)
at com.sun.enterprise.container.common.impl.util.InjectionManagerImpl.injectInstance(InjectionManagerImpl.java:127)
at com.sun.enterprise.container.common.impl.util.InjectionManagerImpl.createManagedObject(InjectionManagerImpl.java:347)
at com.sun.enterprise.web.WebContainer.createServletInstance(WebContainer.java:991)
at com.sun.enterprise.web.WebModule.createServletInstance(WebModule.java:2130)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1404)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1381)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:5732)
I have used getServletConfig() before getServletContext() but it was null. So why is my config and context are not properly set ?
Servlets predate managed beans and annotations and all the fancy stuff you see since Java EE 6. Previously, you have to explicitly implement a predefined abstract/template method in order to perform a task at a certain moment in the lifecycle.
For servlets, in order to hook on its initialization the same way you'd use #PostConstruct on a "normal" managed bean, you have to override the predefined GenericServlet#init() method.
#Override
public void init() {
// ...
}
The getServletContext() will be available there.
If you pay attention to the GenericServlet javadoc, you'll notice that there's also an init(ServletConfig). It's however strongly recommended to not use that method, but use init() instead. The default implementation of init(ServletConfig) namely takes care that the ServletContext is properly set. You'd have to mind calling super.init(config) to not make the same mistake. As a historical note, see that the canonical name of a #PostConstruct method as you see on managed beans, "init", is inherited from exactly this Servlet API.
In case you wonders, the #PreDestroy equivalent is the GenericServlet#destroy() method.
#Override
public void destroy() {
// ...
}
How does a web container know that a particular servlet hasn't been initialized. Is there any particular flag which shows the status of the servlet or anything else managed by the servlet
Container initial servlet during start up ( or restart ) one by one as mentioned in web.xml. You can also find if a servelt is initiated or destroyed by override init and destroy methods.
public class PrecompressedResourceServlet extends HttpServlet {
private static final Logger LOG = LoggerFactory
.getLogger(PrecompressedResourceServlet.class);
#Override
public void init() throws ServletException {
LOG.info("The PrecompressedResourceServlet initialized...");
super.init();
}
}
In the classic web.xml type configuration you could configure context parameters like so
web.xml
...
<context-param>
<param-name>p-name</param-name>
<param-value>-value</param-value>
</context-param>
...
How is this achieved in spring-boot. I have a filter that requires parameters.
I'm using #EnableAutoConfiguration and have included <artifactId>spring-boot-starter-jetty</artifactId> in my pom.
You can set parameters using the server.servlet.context-parameters application property. For example:
server.servlet.context-parameters.p-name=p-value
In Spring Boot 1.x, which is no longer supported, this property was named server.context-parameters:
servlet.context-parameters=p-name=p-value
Alternatively, you can configure parameters programmatically by declaring a ServletContextInitializer bean:
#Bean
public ServletContextInitializer initializer() {
return new ServletContextInitializer() {
#Override
public void onStartup(ServletContext servletContext) throws ServletException {
servletContext.setInitParameter("p-name", "-value");
}
};
}
You can actually achieve this using Java config. If you have filter that requires some parameters, just put them in your application.yml (or .properties), inject them using #Value in your config class and register them in FilterRegistrationBean.
For example:
#Value("${myFilterParam}")
private String myFilterParam;
#Bean(name="myFilter")
public FilterRegistrationBean myFilter() {
FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(new MyFilter());
filterRegistrationBean.setInitParameters(Collections.singletonMap("p-name", "p-value"));
return filterRegistrationBean;
}
Also JavaDoc for FilterRegistrationBean:
http://docs.spring.io/spring-boot/docs/current/api/org/springframework/boot/context/embedded/FilterRegistrationBean.html
Update
You can register parameters for servlet context in SpringBootServletInitializer#onStartup() method. Your Application class can extend the SpringBootServletInitializer and you can override the onStartup method and set the parameters there. Example:
#Configuration
#EnableAutoConfiguration
#ComponentScan
public class Application extends SpringBootServletInitializer {
#Override
protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
return application.sources(Application.class);
}
#Override
public void onStartup(ServletContext servletContext) throws ServletException {
servletContext.setInitParameter("p-name", "p-value");
super.onStartup(servletContext);
}
public static void main(String[] args) {
SpringApplication.run(Application.class);
}
}
Other alternative is to define ServletContextInitializer bean as suggested by Andy Wilkinson.
Since Spring Boot 2.0.0 they updated the way to add context param:
server.servlet.context-parameters.yourProperty.
You can see more updates on this link
Also you can define InitParameterConfiguringServletContextInitializer in your configuration. Example:
#Bean
public InitParameterConfiguringServletContextInitializer initParamsInitializer() {
Map<String, String> contextParams = new HashMap<>();
contextParams.put("p-name", "-value");
return new InitParameterConfiguringServletContextInitializer(contextParams);
}
I have a POJO that was instantiated from a servlet. I need to make a lookup of an EJB within this POJO, either CDI or JNDI. My JEE container is TomEE 1.6.0.
My question is this: need the EJB have remote interface? Because if I instantiate it directly from the servlet by #EJB the remote interface does not need...
Just see this simple example which always throws NameNotFoundException.
#Stateless
public class MyEJB
{
public String sayHello()
{
return "Hello";
}
}
The next servlet try yo lookup MyEJB:
#WebServlet("/myServlet")
public class MyServlet extends HttpServlet
{
private static final long serialVersionUID=1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException,IOException
{
try
{
Context ctx = new InitialContext();
MyEJB ejb = (MyEJB) ctx.lookup("MyEJB");
System.out.println(ejb.sayHello());
}
catch(Exception ex)
{
ex.printStackTrace();
throw new RuntimeException(ex);
}
}
}
The line: MyEJB ejb = (MyEJB) ctx.lookup("MyEJB"); always throws NameNotFoundException. But if I use #EJB it work fine. But I need do the lookup in JNDI mode because finally I will instantiate this EJB within a POJO.
So, why fails this lookup ?
This has nothing to do with remote interfaces.
When you declare MyEJB in servlet using #EJB it works, because servlet is container-managed - your TomEE server instantiates servlet object. However declaration of MyEJB in MyPojo (also using #EJB) won't work, because MyPojo is not container-managed - it is created using new MyPojo(), not by TomEE server.
You could for example make MyPojo another EJB (using #Stateless) and inject it using #EJB to the servlet - not by creating new MyPojo().
I can solve this problem by myself by instrospecting the JNDI tree with this simple class:
import javax.naming.Binding;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NameClassPair;
import javax.naming.NamingEnumeration;
public class JndiInstrospector
{
public static void print()
{
try
{
Context ctx = new InitialContext();
String n = ctx.getNameInNamespace();
_print(n);
}
catch(Exception ex)
{
ex.printStackTrace();
throw new RuntimeException();
}
}
private static void _print(String name) throws Exception
{
try
{
System.out.println("Name in manespace: "+name);
Context ctx = new InitialContext();
NamingEnumeration<Binding> list = ctx.listBindings(name);
while( list.hasMoreElements() )
{
Binding b = list.nextElement();
String s = b.getName();
_print(name+"/"+s);
}
}
catch(Exception ex)
{
// ignore
}
}
}
Finally, the EJB That I was espected to lookup was found at:
"java:/openejb/local/FacadeBeanLocalBean", where FacadadeBean is the name of my EJB (stateless session bean).
I have the Global.asax like the code below:
public class MvcApplication : System.Web.HttpApplication
{
public static void RegisterRoutes(RouteCollection routes)
{
// ....
}
protected void Application_Start()
{
AreaRegistration.RegisterAllAreas();
RegisterRoutes(RouteTable.Routes);
ControllerBuilder.Current.SetControllerFactory(typeof(IOCControllerFactory));
}
}
public class IOCControllerFactory : DefaultControllerFactory
{
private readonly IKernel kernel;
public IOCControllerFactory()
{
kernel = new StandardKernel(new NanocrmContainer());
}
protected override IController GetControllerInstance(RequestContext requestContext, Type controllerType)
{
if (controllerType == null)
return base.GetControllerInstance(requestContext, controllerType);
var controller = kernel.TryGet(controllerType) as IController;
if (controller == null)
return base.GetControllerInstance(requestContext, controllerType);
var standartController = controller as Controller;
if (standartController is IIoCController)
((IIoCController)standartController).SetIoc(kernel);
return standartController;
}
class NanocrmContainer : Ninject.Modules.NinjectModule
{
public override void Load()
{
// ...
Bind<DomainModel.Entities.db>().ToSelf().InRequestScope().WithConstructorArgument("connection", "Data Source=lims;Initial Catalog=nanocrm;Persist Security Info=True;User ID=***;Password=***");
}
}
}
In this case if somewhere it is the class, defined like:
public class UserRepository : IUserRepository
{
private db dataContext;
private IUserGroupRepository userGroupRepository;
public UserRepository(db dataContext, IUserGroupRepository userGroupRepository)
{
this.dataContext = dataContext;
this.userGroupRepository = userGroupRepository;
}
}
then the dataContext instance is created (if no one was created in this request scope) by Ninject.
So the trouble now is - where to invoke dataContext method .Dispose()?
UPD:
so i followed the advice from KeeperOfTheSoul and solved the issue in such way:
public override void ReleaseController(IController controller)
{
base.ReleaseController(controller);
var db = kernel.Get<DomainModel.Entities.db>();
db.Dispose();
}
A good place to handle this is in IControllerFactory.ReleaseController, eg
public override void ReleaseController() {
base.ReleaseController();
//Do whatever you need to clean up the IoC container here
}
In NInject this could be handled by scoping using an activation block, at the start of the request when creating the controller you can store the activation block in the HttpContext's current items, during ReleaseController you can retrieve the previously created activation block and dispose it.
You could also consider using InScope and having the custom scope implement INotifyWhenDisposed. After that the usage is the same as with an activation block, except now you store the scope in the HttpContext's current items.
A pattern that is sometimes used to dispose db connections is to call Dispose from the finaliser.
public class db : IDisposable {
//called by the garbage collector
~db() {
//Call dispose to make sure the resources are cleaned up
Dispose(false);
}
//IDisposable implementation
public void Dispose() {
Dispose(true);
}
//subclasses of db can override Dispose(bool) and clean up their own fields
protected virtual void Dispose (bool disposing) {
if (disposing) {
//Supress finalization as all resources are released by this method
//Calling Dispose on IDisposable members should be done here
GC.SupressFinalize();
}
//Clean up unmanaged resources
//Do not call other objects as they might be already collected if called from the finalizer
}
}
You could hook it into Application_EndRequest.