I'm trying to get Spring Boot dependency injection to allow me to do the following:
interface MyBean
#Component
class MyBeanA : MyBean
#Component
class MyBeanB : MyBean
#Component
class MyBeanConsumer(myBean: MyBean)
Here, Spring complains that there are multiple beans of type MyBean. I would like it to create two instances of MyBeanConsumer. One with MyBeanA and one with MyBeanB. I need to do this for a number of beans, so I'm trying to avoid boilerplate configuration classes like this:
#Configuration
class MyBeanConfiguration {
#Bean
fun consumers(myBeans: List<MyBean>) = myBeans.map { MyBeanConsumer(it) }
}
Is this possible in Spring?
you can use the Qualifier annotation and specify the name of the bean requested.
you can visit this
Spring #Autowired and #Qualifier
If everywhere in your program you want to inject them as List of beans you can go with this approach.
#Configuration public MyConfigurationClass {
#Bean
#Qualifier("mylist")
public List<MyType> configure() {
//create your dynamical list here
}
}
But if you want to use them as individual bean somewhere in your program and also you want to inject all of them as a List somewhere else you can do that this way:
#Configuration
public class AppConfig implements BeanFactoryPostProcessor {
#Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
for (int i = 0; i < 3; i++) {
System.out.println("register my bean: " + i);
beanFactory.registerSingleton("bean-" + i, new MyBean("MyBean-" + i));
}
}
Read the following answer for further detail:
How to create multiple beans of same type according to configuration in Spring?
Related
I am using Spring boot. I have some question regarding the spring boot beans.
But I have doubt
I use bean which are default scope that is singleton. So they will have only one instance per application.
#Configuration
public class ...{
#Bean
public void method() {}
}
And
Now i use bean which scope is prototype. So they will have each instance per request.
#Configuration
public class ...{
#Bean
#Scope("prototype")
public void method() {}
}
But
I want single instance per user..? all request use single instance per user.
#Configuration
class Abc {
#Bean
#Scope("session")
public YourBean getYourBean() {
return new YourBean();
}
}
You will need to define one singleton bean with a property using prototype bean:(xml example)
With #bean definition:
#Component
#Scope("singleton")
public class SingletonBean {
// ..
#Autowired
private PrototypeBean prototypeBean;
//..
}
#Component
#Scope("prototype")
public class PrototypeBean {
//.......
}
Example: https://www.baeldung.com/spring-inject-prototype-bean-into-singleton
I'm a Spring rookie and trying to benefit from the advantages of the easy 'profile' handling of Spring. I already worked through this tutorial: https://spring.io/blog/2011/02/14/spring-3-1-m1-introducing-profile and now I'd like to adapt that concept to an easy example.
I've got two profiles: dev and prod. I imagine a #Configuration class for each profile where I can instantiate different beans (implementing a common interface respectively) depending on the set profile.
My currently used classes look like this:
StatusController.java
#RestController
#RequestMapping("/status")
public class StatusController {
private final EnvironmentAwareBean environmentBean;
#Autowired
public StatusController(EnvironmentAwareBean environmentBean) {
this.environmentBean = environmentBean;
}
#RequestMapping(method = RequestMethod.GET)
Status getStatus() {
Status status = new Status();
status.setExtra("environmentBean=" + environmentBean.getString());
return status;
}
}
EnvironmentAwareBean.java
public interface EnvironmentAwareBean {
String getString();
}
EnvironmentAwareBean.java
#Service
public class DevBean implements EnvironmentAwareBean {
#Override
public String getString() {
return "development";
}
}
EnvironmentAwareBean.java
#Service
public class ProdBean implements EnvironmentAwareBean {
#Override
public String getString() {
return "production";
}
}
DevConfig.java
#Configuration
#Profile("dev")
public class DevConfig {
#Bean
public EnvironmentAwareBean getDevBean() {
return new DevBean();
}
}
ProdConfig.java
#Configuration
#Profile("prod")
public class ProdConfig {
#Bean
public EnvironmentAwareBean getProdBean() {
return new ProdBean();
}
}
Running the example throws this exception during startup (SPRING_PROFILES_DEFAULT is set to dev):
(...) UnsatisfiedDependencyException: (...) nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [EnvironmentAwareBean] is defined: expected single matching bean but found 3: prodBean,devBean,getDevBean
Is my approach far from a recommended configuration? In my opinion it would make more sense to annotate each Configuration with the #Profile annotation instead of doing it for each and every bean and possibly forgetting some variants when new classes are added later on.
Your implementations of EnvironmentAwareBean are all annotated with #Service.
This means they will all be picked up by component scanning and hence you get more than one matching bean. Do they need to be annotated with #Service?
Annotating each #Configuration with the #Profile annotation is fine. Another way as an educational exercise would be to not use #Profile and instead annotate the #Bean or Config classes with your own implementation of #Conditional.
I am trying to implement factory pattern to get producer from a list of available ones. While doing it i am getting the below exception. Not able to figure out the issue with the code. Can you please let me know what i am missing.
org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.test.interfaces.Producer] is defined: expected single matching bean but found 2: A,B
Please find the code below
public interface Producer<T> {
public void start();
public List<T> produce() throws CEHServiceException;
public void stop();
}
#Component("A")
public class ProducerA extends Producer {
//Autowire Services & Properties
}
#Component("B")
public class ProducerB extends Producer {
//Autowire Services & Properties
}
#Configuration
public class AgentConfiguration {
#Bean
public ServiceLocatorFactoryBean createProducerFactoryBean(){
ServiceLocatorFactoryBean bean = new ServiceLocatorFactoryBean();
bean.setServiceLocatorInterface(ProducerFactory.class);
return bean;
}
}
public interface ProducerFactory {
Producer getProducer(String producerName);
}
#Component
public class AdvancedAgentProcessor {
#Autowired
private ObjectFactory<AdvancedRunnerImpl> runnerFactory;
public void init(){
AdvancedRunnerImpl runner = runnerFactory.getObject();
runner.setProducerName("A");
runner.start();
}
}
#Component
#Scope("prototype")
public class AdvancedRunnerImpl implements Runner {
#Autowired private ProducerFactory producerFactory;
private Producer producer;
private String producerName;
public void start() {
producer = producerFactory.getProducer(this.producerName);
}
}
Full stack tracke
org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.test.etl.interfaces.Producer] is defined: expected single matching bean but found 2: A,B
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:365)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:331)
at org.springframework.beans.factory.config.ServiceLocatorFactoryBean$ServiceLocatorInvocationHandler.invokeServiceLocatorMethod(ServiceLocatorFactoryBean.java:377)
at org.springframework.beans.factory.config.ServiceLocatorFactoryBean$ServiceLocatorInvocationHandler.invoke(ServiceLocatorFactoryBean.java:363)
at com.sun.proxy.$Proxy34.getProducer(Unknown Source)
at com.test.runner.AdvancedRunnerImpl.start(AdvancedRunnerImpl.java:54)
at com.test.app.AdvancedAgentProcessor.init(AdvancedAgentProcessor.java:48)
at com.test.app.DataAgentApplication.main(DataAgentApplication.java:25)
Spring does not know which component to autowire. It seems that the problem is in the ProducerFactoryImplementation but we cannot see it.
There are three possible solutions:
Use Qualifiers so you can tell Spring which specific implementation you want.There is an example in StackOverflow
here
Use the Primary annotation (See more here3). That means that in case of ambiguity Spring will give priority to the #Primary annotated component
Autowire a list of beans. Something like:
#Autowired private List<Producer> myAvalilableProducers;
public Producer getByName(name){
for( Producer producer: myAvalilableProducers){
if(producer.getName().equals(name)){ return producer; }
}
throw new RuntimeException("No producer with name " + name " found");
}
This third option more useful when you do not know the specific instance at compile time or if you really want to inject a list of components.
You have two beans that extend Producer. Somewhere you are trying to autowire a Producer. Spring does not know which Producer to use.
This happens when the dynamic proxy is not able to pick the correct Bean. Please check whether this.producerName is null or empty.
I have Spring bean with annotations:
#Named
#Scope("session")
And this bean property:
#Autowired
ApplicationContext appContext;
The Spring configuration file has entry (that works for other anotations/injections):
<context:component-scan base-package="my.package.name" />
Why appContext is null after such code and configuration?
I am trying to get ApplicationContext (to call getBean(...) on it) and this can be quite involved task (judging from other discussions) in previous Spring versions (e.g. one is required to get ServletContext in Spring web application to create ApplicationContext and getting ServletContext can be quite involved task for beans that don't directly access HTTP Request objects). In Spring 3.x, as I understand, simple #Autwired injection can be used. How AppContext can be accessed?
Here the first problem is you are using #Named which is Java EE annotation and as for as I know Spring yet to support Java EE annotations. Hence instead of using #Named try to use Spring annotation #Service, #Component, #Repository etc.
Here is the example for you I have used JSF Managed bean as well to show how to integrate beans.
#ManagedBean(name="myBacking")
#RequestScoped
public class MyBacking {
private String myText;
#ManagedProperty(value="#{mySpring}")
MySpringBean mySpring;
public String getMyText() {
myText = mySpring.getText();
return myText;
}
public void setMyText(String myText) {
this.myText = myText;
}
public MySpringBean getMySpring() {
return mySpring;
}
public void setMySpring(MySpringBean mySpring) {
this.mySpring = mySpring;
}
}
#Service("mySpring")
#Scope("request")
public class MySpringBean {
#Autowired
MySecond mySecond;
public String getText(){
return "Hello KP" + mySecond.appObj();
}
}
#Service
#Scope("request")
public class MySecond {
#Autowired
ApplicationContext applicationContext;
public String appObj(){
MyThrid mythird =(MyThrid)applicationContext.getBean("myThrid");
return "My Second Bean calld "+ mythird.getTxt();
}
}
#Service
public class MyThrid {
public String getTxt(){
return "from thrid Bean";
}
}
I have a requirement of creating a prototype bean that's stateful, i.e. take parameters in constructor.
I tried to use #Configuration to create that bean, but found it doesn't work if I use a parameterized constructor...
Note that the parameters I want to pass are NOT spring beans...they are simple POJOs...so I can't autowire them.
So this is what I want to do -
#Configuration
public class MyClassFactory {
#Bean
public MyClass getMyClass(Pojo1 pojo1, Pojo2 pojo2) {
return new MyClass (pojo1, pojo2);
}
}
#Scope("PROTOTYPE")
public class MyClass {
public MyClass(Pojo1 pojo1, Pojo2 pojo2) {
...
}
#Autowired SomeService1 service1;
#Autowired SomeService1 service2;
...
}
Of course I can make MyClass applicationContextAware, and pick up services from it, rather than making it a prototype bean...but was wondering why above pattern is not allowed...