DocumentGenerator Annotation

DocumentGenerator.java

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Service
public @interface DocumentGenerator {
    DocumentGenerationEntityType value();
}

DocumentGeneratorBeanFactory.java

package com.assist.core.factory;

import com.assist.commons.annotations.DocumentGenerator;
import com.assist.commons.documentGeneration.DocumentInfoDto;
import com.assist.commons.documentGeneration.constants.DocumentGenerationEntityType;
import com.assist.commons.documentGeneration.service.EntityDocumentGenerationService;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import org.apache.commons.lang.NotImplementedException;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.ListableBeanFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Service;

@Service
public class DocumentGeneratorBeanFactory implements ApplicationContextAware, InitializingBean {

    private final Map<DocumentGenerationEntityType, EntityDocumentGenerationService> typeBeanMap =
        new HashMap<>();

    @Autowired
    private ListableBeanFactory listableBeanFactory;

    private ApplicationContext applicationContext;

    public <EntityInfoDto extends DocumentInfoDto, EntityDto> EntityDocumentGenerationService<EntityInfoDto, EntityDto> getBean(
        DocumentGenerationEntityType entityType) {
        return typeBeanMap.get(entityType);
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        initializeTypeBeanMap();
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }

    //Method to initialize or create a map to store entityType and corresponding bean of entityType
    private void initializeTypeBeanMap() {
        Map<String, Object> beansWithAnnotation =
            applicationContext.getBeansWithAnnotation(DocumentGenerator.class);

        for (String beanName : beansWithAnnotation.keySet()) {

            EntityDocumentGenerationService documentGenerationService =
                listableBeanFactory.getBean(beanName, EntityDocumentGenerationService.class);
            DocumentGenerator beanHandler =
                listableBeanFactory.findAnnotationOnBean(beanName, DocumentGenerator.class);
            if (Objects.isNull(beanHandler)) {
                throw new NotImplementedException(beanName + " Bean not found!");
            }
            DocumentGenerationEntityType entityType = beanHandler.value();
            typeBeanMap.put(entityType, documentGenerationService);
        }
    }
}

example.java

/// factory usage
private <EntityInfo extends DocumentInfoDto, EntityDto>
EntityDocumentGenerationService<EntityInfo, EntityDto> getEntityDocumentGenerationService(
    DocumentGenerationEntityType entityType) {
    try {
        return documentGeneratorBeanFactory.getBean(entityType);
    } catch (Exception e) {
        throw new IllegalStateException(entityType + " PDF Implementation Not Found");
    }
}

private <EntityInfo extends DocumentInfoDto, EntityDto>
EntityDocumentCreationService<EntityInfo, EntityDto> getEntityDocumentCreationService(
    DocumentGenerationEntityType entityType) {
    EntityDocumentGenerationService<EntityInfo, EntityDto> generationService =
        this.<EntityInfo, EntityDto>getEntityDocumentGenerationService(entityType);

    if (!(generationService instanceof EntityDocumentCreationService)) {
        throw new IllegalStateException(
            "Can not create document for " + entityType.getDisplayName());
    }
    return (EntityDocumentCreationService<EntityInfo, EntityDto>) generationService;
}