Spring Framework 4.3 introduced ObjectProvider<T> which extends the existing ObjectFactory<T> interface. This new interface provides improved programmatic resolution of dependencies.
Obtaining an instance of ObjectProvider
Instance of ObjectProvider can be injected in any Spring managed bean.
For example
@Autowired
private ObjectProvide<ExampleBean> objectProvider;
Also Spring 5.1 added following methods in BeanFactory to get an instance of ObjectProvider
ObjectProvider<T> getBeanProvider(Class<T> requiredType);
Example:
ObjectProvider<ExampleBean> beanProvider = context.getBeanProvider(ExampleBean.class);
ObjectProvider<T> getBeanProvider(ResolvableType requiredType);
Example:
ResolvableType resolvableType = ResolvableType.forClass(ExampleBean.class);
ObjectProvider<ExampleBean> beanProvider = context.getBeanProvider(resolvableType);
ObjectProvider methods
Spring 4.3 introduced following methods:
T getIfAvailable() throws BeansException
Returns bean's instance if registered with Spring Context, otherwise returns null.
T getIfUnique() throws BeansException
Returns bean's instance if only one bean (of type T) is registered with the container. If there are more than one beans registered then this method returns null instead of throwing NoUniqueBeanDefinitionException. If there are no beans registered then this method returns null.
T getObject() throws BeansException
Returns bean's instance. If no bean of type T registered then this method will throw NoSuchBeanDefinitionException. If more than one beans of type T are registered, then this method will throw NoUniqueBeanDefinitionException. This method is inherited from ObjectFactory.
T getObject(java.lang.Object... args) throws BeansException
This method is same as the last method but allows to specify explicit construction arguments.
More methods have been added to ObjectProvider in Spring 5.0 and Spring 5.1 which we will discuss in coming tutorials.
Examples
Example bean
public class ExampleBean {
public void doSomething() {
System.out.println("in example bean");
}
}
getIfAvailable() example
@Configuration
public class GetIfAvailableExample {
//remove @Bean then getIfAvailable will return null
@Bean
ExampleBean exampleBean() {
return new ExampleBean();
}
public static void main(String[] args) {
AnnotationConfigApplicationContext context =
new AnnotationConfigApplicationContext(GetIfAvailableExample.class);
ObjectProvider<ExampleBean> beanProvider = context.getBeanProvider(ExampleBean.class);
ExampleBean exampleBean = beanProvider.getIfAvailable();
System.out.println("example bean: " + exampleBean);
if (exampleBean != null) {
exampleBean.doSomething();
}
}
}Outputexample bean: com.logicbig.example.ExampleBean@3911b7d7
in example bean
getIfUnique() example
@Configuration
public class GetIfUnique {
@Bean
ExampleBean exampleBean() {
return new ExampleBean();
}
//uncomment following then getIfUnique will return null
/*@Bean
ExampleBean exampleBean2() {
return new ExampleBean();
}*/
public static void main(String[] args) {
AnnotationConfigApplicationContext context =
new AnnotationConfigApplicationContext(GetIfUnique.class);
ObjectProvider<ExampleBean> beanProvider = context.getBeanProvider(ExampleBean.class);
ExampleBean exampleBean = beanProvider.getIfUnique();
System.out.println("example bean: " + exampleBean);
if (exampleBean != null) {
exampleBean.doSomething();
}
}
}Outputexample bean: com.logicbig.example.ExampleBean@4132c9ac
in example bean
getObject() example
@Configuration
public class GetObjectExample {
@Bean
ExampleBean exampleBean() {
return new ExampleBean();
}
public static void main(String[] args) {
AnnotationConfigApplicationContext context =
new AnnotationConfigApplicationContext(GetObjectExample.class);
ObjectProvider<ExampleBean> beanProvider = context.getBeanProvider(ExampleBean.class);
ExampleBean exampleBean = beanProvider.getObject();
exampleBean.doSomething();
}
}Outputin example bean
getObject(args) example
public class ExampleBean2 {
private String arg;
public ExampleBean2(String arg) {
this.arg = arg;
}
public void doSomething() {
System.out.println("in example bean2, arg: " + arg);
}
}
@Configuration
public class GetObjectWithArgs {
@Bean
@Lazy
ExampleBean2 exampleBean(String arg) {
return new ExampleBean2(arg);
}
public static void main(String[] args) {
AnnotationConfigApplicationContext context =
new AnnotationConfigApplicationContext(GetObjectWithArgs.class);
ObjectProvider<ExampleBean2> beanProvider = context.getBeanProvider(ExampleBean2.class);
ExampleBean2 exampleBean = beanProvider.getObject("test arg");
exampleBean.doSomething();
}
}Outputin example bean2, arg: test arg
Injecting ObjectProvider
@Configuration
public class InjectingObjectProviderExample {
@Bean
ClientBean clientBean() {
return new ClientBean();
}
@Bean
ExampleBean exampleBean() {
return new ExampleBean();
}
public static void main(String[] args) {
new AnnotationConfigApplicationContext(InjectingObjectProviderExample.class);
}
private static class ClientBean {
@Autowired
ObjectProvider<ExampleBean> objectProvider;
@PostConstruct
void postConstruct() {
if (objectProvider != null) {
ExampleBean exampleBean = objectProvider.getObject();
if (exampleBean != null) {
exampleBean.doSomething();
}
}
}
}
}
Outputin example bean
Example ProjectDependencies and Technologies Used: - spring-context 6.1.2 (Spring Context)
Version Compatibility: 5.1.0.RELEASE - 6.1.2 Version compatibilities of spring-context with this example: Versions in green have been tested.
- jakarta.annotation-api 2.1.1 (Jakarta Annotations API)
- JDK 17
- Maven 3.8.1
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