lookup method - Injecting a prototype bean into a singleton bean issue - spring

Question

I am developing code for the Injecting a prototype bean into a singleton bean code, so far I developed code like below and when I run the main method, I see the below error is coming.
Jan 04, 2017 2:59:41 PM org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext#6ed322: startup date [Wed Jan 04 14:59:41 IST 2017]; root of context hierarchy
Jan 04, 2017 2:59:41 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [spring.xml]
Constructor:: RequestProcessor instance created!
Constructor:: RequestProcessor instance created!
Request ID : 1212
Exception in thread "main" java.lang.AbstractMethodError: com.injection.testing.RequestProcessor.createValidator()Lcom/injection/testing/RequestValidator;
at com.injection.testing.RequestProcessor.handleRequest(RequestProcessor.java:12)
at com.injection.testing.MainDemo.main(MainDemo.java:13)
spring.xml
<!-- Lookup way -->
<bean id="requestProcessor" class="com.injection.testing.RequestProcessor" >
<lookup-method name="getValidator" bean="validator" />
</bean>
<bean id="validator" class="com.injection.testing.RequestValidator" scope="prototype" />
RequestProcessor.java
public abstract class RequestProcessor {
private RequestValidator validator;
public RequestProcessor(){
System.out.println("Constructor:: RequestProcessor instance created!");
}
public void handleRequest(String requestId){
System.out.println("Request ID : "+ requestId);
RequestValidator validator = createValidator(); //here Spring will create new instance of prototype bean
validator.validate(requestId);
}
public RequestValidator getValidator() {
return validator;
}
public void setValidator(RequestValidator validator) {
this.validator= validator;
}
protected abstract RequestValidator createValidator();
}
RequestValidator.java
public class RequestValidator {
private List<String> errorMessages = new ArrayList<String>();
public RequestValidator() {
System.out.println("Constructor:: RequestValidator instance created!");
}
// Validates the request and populates error messages
public void validate(String requestId){
System.out.println("RequestValidator :"+requestId);
}
public List<String> getErrorMessages() {
return errorMessages;
}
}
MainDemo.java
public class MainDemo {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
//RequestValidator requestValidator = (RequestValidator) context.getBean("validator");
RequestProcessor processor = (RequestProcessor) context.getBean("requestProcessor");
processor.handleRequest("1212");
System.out.println("------------------------");
processor.handleRequest("1213");
}
}
pom.xml
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>4.3.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>4.3.5.RELEASE</version>
</dependency>
<dependency>
<groupId>cglib</groupId>
<artifactId>cglib-nodep</artifactId>
<version>3.2.4</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
</dependencies>

Answer 1

Update your spring.xml to shown below
<bean id="requestProcessor" class="com.injection.testing.RequestProcessor">
<lookup-method name="createValidator" bean="validator" />
</bean>
Basically you need to specify the name of the abstract method name in lookup-method xml attribute.
I got below output after the corrected configuration
Jan 04, 2017 4:11:20 PM org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext#13c675d: startup date [Wed Jan 04 16:11:20 IST 2017]; root of context hierarchy
Jan 04, 2017 4:11:20 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [spring.xml]
Constructor:: RequestProcessor instance created!
Request ID : 1212
Constructor:: RequestValidator instance created!
RequestValidator :1212
Request ID : 1213
Constructor:: RequestValidator instance created!
RequestValidator :1213