Is there a possibility to get the actual reference to the current ApplicationContext ? :
package myPackage;
public class AFactory {
public static A createA() {
// I need to access to the current instance of ApplicationContext here, passing it to another object's method for example
}
}
In my applicationContext.xml:
<bean id="myBeanA" class="myPackage.AFactory" factory-method="createA">
</bean>
UPDATE --------------------------------------------------------
I thought an example with Java would be more popular and would work in Scala but it's trickier in Scala due to the fact that "static" method are defined outside the class:
object ActorSystemFactory {
var applicationContext: ApplicationContext = _
def createActorSystem = {
val system = ActorSystem("AkkaScalaSpring")
SpringExtensionImpl(system)(applicationContext)
system
}
}
class ActorSystemFactory extends ApplicationContextAware {
def setApplicationContext(context: ApplicationContext) {
ActorSystemFactory.applicationContext = context
}
}
For those who know Scala, here Spring warns logically about the fact that there isn't createActorSystem static method in the class.
Has someone ever handled this case?
Make your bean implements ApplicationContextAware
public class AFactory implements ApplicationContextAware {
private static ApplicationContext applicationContext = null;
public static ApplicationContext getApplicationContext() {
return applicationContext;
}
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
}
Related
I am developing a SpringBoot project and I want to get the bean by its name using applicationContext. I have tried many solution from web but could not succeed. My Requirement is that I have a controller
ControllerA
and inside the controller I have a method getBean(String className). I want to get instance of registered bean. I have hibernate entities and I want to get an instance of the bean by passing the name of class only in getBean method.
Please help if someone know the solution.
You can Autowire the ApplicationContext, either as a field
#Autowired
private ApplicationContext context;
or a method
#Autowired
public void context(ApplicationContext context) { this.context = context; }
Finally use
context.getBean(SomeClass.class)
You can use ApplicationContextAware.
ApplicationContextAware:
Interface to be implemented by any object that wishes to be notified
of the ApplicationContext that it runs in. Implementing this interface
makes sense for example when an object requires access to a set of
collaborating beans.
There are a few methods for obtaining a reference to the application context. You can implement ApplicationContextAware as in the following example:
package hello;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
#Component
public class ApplicationContextProvider implements ApplicationContextAware {
private ApplicationContext applicationContext;
#Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
public ApplicationContext getContext() {
return applicationContext;
}
}
Update:
When Spring instantiates beans, it looks for ApplicationContextAware implementations, If they are found, the setApplicationContext() methods will be invoked.
In this way, Spring is setting current applicationcontext.
Code snippet from Spring's source code:
private void invokeAwareInterfaces(Object bean) {
.....
.....
if (bean instanceof ApplicationContextAware) {
((ApplicationContextAware)bean).setApplicationContext(this.applicationContext);
}
}
Once you get the reference to Application context, you get fetch the bean whichever you want by using getBean().
actually you want to get the object from the Spring engine, where the engine already maintaining the object of your required class at that starting of the spring application(Initialization of the Spring engine).Now the thing is you just have to get that object to a reference.
in a service class
#Autowired
private ApplicationContext context;
SomeClass sc = (SomeClass)context.getBean(SomeClass.class);
now in the reference of the sc you are having the object.
Hope explained well. If any doubt please let me know.
Even after adding #Autowire if your class is not a RestController or Configuration Class, the applicationContext object was coming as null. Tried Creating new class with below and it is working fine:
#Component
public class SpringContext implements ApplicationContextAware{
private static ApplicationContext applicationContext;
#Override
public void setApplicationContext(ApplicationContext applicationContext) throws
BeansException {
this.applicationContext=applicationContext;
}
}
you can then implement a getter method in the same class as per your need to get the bean. Like:
applicationContext.getBean(String serviceName,Interface.Class)
Using SpringApplication.run(Class<?> primarySource, String... arg) worked for me. E.g.:
#SpringBootApplication
public class YourApplication {
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(YourApplication.class, args);
}
}
As an alternative approach you can use ConfigurableApplicationContext to get bean of any class which is annotated with #Component, #Repository or #Service.
Let's say you want to get a bean of the class BaseComponent :
#Service
public class BaseComponent {
public String getMessage() {
return "hello world";
}
}
Now you can use ConfigurableApplicationContext to get the bean:
#Component
public class DemoComponent {
#Autowired
ConfigurableApplicationContext applicationContext;
public BaseComponent getBeanOfBaseComponent() {
return applicationContext.getBean(BaseComponent.class);
}
}
You can use the ApplicationContextAware class that can provide the application context.
public class ApplicationContextProvider implements ApplicationContextAware {
private static ApplicationContext ctx = null;
public static ApplicationContext getApplicationContext() {
return ctx;
}
#Override
public void setApplicationContext(final ApplicationContext ctx) throws BeansException {
ApplicationContextProvider.ctx = ctx;
}
/**
* Tries to autowire the specified instance of the class if one of the specified
* beans which need to be autowired are null.
*
* #param classToAutowire the instance of the class which holds #Autowire
* annotations
* #param beansToAutowireInClass the beans which have the #Autowire annotation
* in the specified {#classToAutowire}
*/
public static void autowire(Object classToAutowire, Object... beansToAutowireInClass) {
for (Object bean : beansToAutowireInClass) {
if (bean == null) {
ctx.getAutowireCapableBeanFactory().autowireBean(classToAutowire);
}
}
}
}
If you are inside of Spring bean (in this case #Controller bean) you shouldn't use Spring context instance at all. Just autowire className bean directly.
BTW, avoid using field injection as it's considered as bad practice.
One API method I use when I'm not sure what the bean name is org.springframework.beans.factory.ListableBeanFactory#getBeanNamesForType(java.lang.Class<?>). I simple pass it the class type and it retrieves a list of beans for me. You can be as specific or general as you'd like to retrieve all the beans associated with that type and its subtypes, example
#Autowired
ApplicationContext ctx
...
SomeController controller = ctx.getBeanNamesForType(SomeController)
Easy way in configration class call the BEAN annoted method . Yes u heard it right---- :P calling SpringBoot #Bean annoted method return the same bean from config .I was trying to call a logout in #predestroy method in config class from a bean and direcltly called the method to get the same bean .
P.S. : I added debug in the #bean annotated method but it didn't entered the method even when i called it.Sure to blame -----> Spring Magic <----
You can use ServiceLocatorFactoryBean. First you need to create an interface for your class
public interface YourClassFactory {
YourClass getClassByName(String name);
}
Then you have to create a config file for ServiceLocatorBean
#Configuration
#Component
public class ServiceLocatorFactoryBeanConfig {
#Bean
public ServiceLocatorFactoryBean serviceLocatorBean(){
ServiceLocatorFactoryBean bean = new ServiceLocatorFactoryBean();
bean.setServiceLocatorInterface(YourClassFactory.class);
return bean;
}
}
Now you can find your class by name like that
#Autowired
private YourClassfactory factory;
YourClass getYourClass(String name){
return factory.getClassByName(name);
}
Just use:
org.springframework.beans.factory.BeanFactory#getBean(java.lang.Class)
Example:
#Component
public class Example {
#Autowired
private ApplicationContext context;
public MyService getMyServiceBean() {
return context.getBean(MyService.class);
}
// your code uses getMyServiceBean()
}
I would like to register spring bean in runtime, so i built that class:
public class SpringBeanRegister implements BeanRegister, ApplicationContextAware {
private ConfigurableApplicationContext context;
public void registerBean(Object object) {
ConfigurableListableBeanFactory factory = context.getBeanFactory();
factory.registerSingleton("beanName", object);
}
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.context = (ConfigurableApplicationContext) applicationContext; // -- safe?
}
}
is this cast always safe ?
At the moment (Spring 4.1) there is only implementation of ApplicationContext that does not implement the ConfigurableApplicationContext interface: that is org.springframework.test.web.servlet.setup.StubWebApplicationContext from spring-test
So I think you are relative save and need to pay some attention to the tests.
But just because there is no meaningful implementation at the moment, it does not mean that there is no change in future version, or somebody/some Framework has implemented it already!
In spring, if a bean implements ApplicationContextAware, then it is able to access the applicationContext. Therefore it is able to get other beans.
e.g.
public class SpringContextUtil implements ApplicationContextAware {
private static ApplicationContext applicationContext;
public void setApplicationContext(ApplicationContext context) throws BeansException {
applicationContext = context;
}
public static ApplicationContext getApplicationContext() {
return applicationContext;
}
}
Then SpringContextUtil.getApplicationContext.getBean("name") can get the bean "name".
To do this, we should put this SpringContextUtil inside the applications.xml, e.g.
<bean class="com.util.SpringContextUtil" />
Here the bean SpringContextUtil doesn't include the property applicationContext. I guess when spring bean initialize, this property is set. But how is this done? How does the method setApplicationContext get called?
When spring instantiates beans, it looks for a couple of interfaces like ApplicationContextAware and InitializingBean. If they are found, the methods are invoked. E.g. (very simplified)
Class<?> beanClass = beanDefinition.getClass();
Object bean = beanClass.newInstance();
if (bean instanceof ApplicationContextAware) {
((ApplicationContextAware) bean).setApplicationContext(ctx);
}
Note that in newer version it may be better to use annotations, rather than implementing spring-specific interfaces. Now you can simply use:
#Inject // or #Autowired
private ApplicationContext ctx;
Spring source code to explain how ApplicationContextAware work
when you use ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
In AbstractApplicationContext class,the refresh() method have the following code:
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
enter this method,beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this)); will add ApplicationContextAwareProcessor to AbstractrBeanFactory.
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// Tell the internal bean factory to use the context's class loader etc.
beanFactory.setBeanClassLoader(getClassLoader());
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// Configure the bean factory with context callbacks.
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
...........
When spring initialize bean in AbstractAutowireCapableBeanFactory,
in method initializeBean,call applyBeanPostProcessorsBeforeInitialization to implement the bean post process. the process include inject the applicationContext.
#Override
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
throws BeansException {
Object result = existingBean;
for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
result = beanProcessor.postProcessBeforeInitialization(result, beanName);
if (result == null) {
return result;
}
}
return result;
}
when BeanPostProcessor implement Objectto execute the postProcessBeforeInitialization method,for example ApplicationContextAwareProcessor that added before.
private void invokeAwareInterfaces(Object bean) {
if (bean instanceof Aware) {
if (bean instanceof EnvironmentAware) {
((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
}
if (bean instanceof EmbeddedValueResolverAware) {
((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(
new EmbeddedValueResolver(this.applicationContext.getBeanFactory()));
}
if (bean instanceof ResourceLoaderAware) {
((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);
}
if (bean instanceof ApplicationEventPublisherAware) {
((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);
}
if (bean instanceof MessageSourceAware) {
((MessageSourceAware) bean).setMessageSource(this.applicationContext);
}
if (bean instanceof ApplicationContextAware) {
((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
}
}
}
Interface to be implemented by any object that wishes to be notified of the ApplicationContext that it runs in.
above is excerpted from the Spring doc website https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/context/ApplicationContextAware.html.
So, it seemed to be invoked when Spring container has started, if you want to do something at that time.
It just has one method to set the context, so you will get the context and do something to sth now already in context I think.
ApplicationContextAware Interface ,the current application context, through which you can invoke the spring container services. We can get current applicationContext instance injected by below method in the class
public void setApplicationContext(ApplicationContext context) throws BeansException.
I have all of my DAO's as beans in my applicationContext. Now this works great for autowiring these objects into my controllers to make database calls. However, given that I have embedded objects within some of my POJO's (Example: User class has list of pendingsurvey objects, list of appointment objects, etc) and don't want to grab these embedded objects when I grab the main object (Example: In a page with a list of users I don't need to know their pendingsurveys or appointments), I had set it up so that if the embedded object is null, go to the database to get the data. However, apparently #Autowire doesn't work in this case because the POJO's are not a Spring controlled object or something.
So question now is, how can I get a bean from applicationContext to use in my POJO's? I'm not that good with Spring so specific instructions would be greatly appreciated..
I've tried this but it gives me a bunch of injection dependency errors:
/* applicationContext.xml */
<bean id="userDao" class="UserDao" scope="singleton">
<property name="connectionWrapper" ref="connectionWrapper" />
</bean>
/* User.java - I tried putting in constructor and in the getter for userDao */
ApplicationContext ctx = AppContext.getApplicationContext('applicationContext.xml');
UserDao userDao = (UserDao) ctx.getBean("userDao");
Got it to work, same concept as Ric Jafe's answer but different implementation of it (Source: http://blog.jdevelop.eu/?p=154):
Made this class:
public class ApplicationContextProvider implements ApplicationContextAware {
private static ApplicationContext ctx = null;
public static ApplicationContext getApplicationContext() {
return ctx;
}
public void setApplicationContext(ApplicationContext ctx) throws BeansException {
// Assign the ApplicationContext into a static method
this.ctx = ctx;
}
}
Added this line into applicationContext.xml:
<bean id="applicationContextProvider" class="org.ApplicationContextProvider"></bean>
Called it in my POJO with:
ApplicationContext applicationContext = ApplicationContextProvider.getApplicationContext();
if (applicationContext != null && applicationContext.containsBean("keyName")) {
object = (Object) applicationContext.getBean("keyName");
}
Thanks for all the help guys.
When you load a context like that you are creating a new context, a copy of what was created when the application loaded. To access the same context that your application is using, you have several options, documented here: http://mythinkpond.wordpress.com/2010/03/22/spring-application-context/
For ease of access I'll copy/paste the one that most likely you want to use:
public class MyClass implements ApplicationContextAware {
static final long serialVersionUID = 02L;
ApplicationContext applicationContext = null;
public void doSomething(){
if (applicationContext != null && applicationContext.containsBean("accessKeys")){
MyBean beanA = (MyBean) applicationContext.getBean("mybean");
//Do something with this AccessBean
}
return null;
}
#Override
public void setApplicationContext(final ApplicationContext applicationContext) throws BeansException {
System.out.println("setting context");
this.applicationContext = applicationContext;
}
}
Notice the implements ApplicationContext.
This tells the Spring framework you need the Application Context in this class.. So it autowires it to the applicationContext variable. For this to happen you also need the setter method. Then you can just use it and get your beans. Good coffee :)
P.S. - If you need the context in other classes, you can pass the applicationContext variable to them or use the same method. This way you only have 1 context at all times, containing your beans.
I want to inject an ApplicationContext itself to a bean.
Something like
public void setApplicationContext(ApplicationContect context) {
this.context = context;
}
Is that possible in spring?
Previous comments are ok, but I usually prefer:
#Autowired private ApplicationContext applicationContext;
Easy, using the ApplicationContextAware interface.
public class A implements ApplicationContextAware {
private ApplicationContext context;
public void setApplicationContext(ApplicationContext context) {
this.context = context;
}
}
Then in your actual applicationContext you only need to reference your bean.
<bean id="a" class="com.company.A" />
Yes, just implement the ApplicationContextAware -interface.
I saw some comments above about #Autowired not working still. The following may help.
This will not work:
#Route(value = "content", layout = MainView.class)
public class MyLayout extends VerticalLayout implements RouterLayout {
#Autowired private ApplicationContext context;
public MyLayout() {
comps.add(context.getBean(MyComponentA.class)); // context always null :(
}
You must do this:
#Autowired
public MyLayout(ApplicationContext context) {
comps.add(context.getBean(MyComponentA.class)); //context is set :)
}
or this:
#PostConstruct
private void init() {
comps.add(context.getBean(MyComponentA.class)); // context is set :)
}
Also note that Upload is another component that must be set within the scope of #PostConstruct. This was a nightmare for me to figure out. Hope this helps!
I almost forgot to mention that the #Scope annotation may be necessary for your Bean, as seen below. This was the case when using Upload within a Bean because the UI is not instantiate/attached prior to the Bean being created and will cause a Null Reference Exception to be thrown. It won't do so when using #Route, but will when using #Component - so the latter is not an option and if #Route is not viable, then I would recommend using #Configuration class to create the bean with the prototype scope.
#Configuration
public class MyConfig {
#Bean
#Scope(value = ConfigurableBeanFactory.SCOPE_PROTOTYPE, proxyMode = ScopedProxyMode.TARGET_CLASS)
public MyComponentA getMyBean() {
return new MyComponentA();
}
}
Special solution: get Spring beans from any (non Spring) classes
#Component
public class SpringContext {
private static ApplicationContext applicationContext;
#Autowired
private void setApplicationContext(ApplicationContext ctx) {
applicationContext = ctx;
}
public static <T> T getBean(Class<T> componentClass) {
return applicationContext.getBean(componentClass);
}
}