Initial commit for "Spring Custom Annotation with Dynamic Qualifier"
article.
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xsalefter
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package org.baeldung.customannotation;
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import org.springframework.context.annotation.ComponentScan;
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import org.springframework.context.annotation.Configuration;
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@Configuration
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@ComponentScan("org.baeldung.customannotation")
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public class CustomAnnotationConfiguration {
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}
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package org.baeldung.customannotation;
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import java.lang.annotation.Documented;
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import java.lang.annotation.ElementType;
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import java.lang.annotation.Retention;
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import java.lang.annotation.RetentionPolicy;
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import java.lang.annotation.Target;
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@Retention(RetentionPolicy.RUNTIME)
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@Target({ ElementType.FIELD, ElementType.PARAMETER, ElementType.METHOD })
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@Documented
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public @interface DataAccess {
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Class<?>entity();
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}
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package org.baeldung.customannotation;
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import org.springframework.beans.BeansException;
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import org.springframework.beans.factory.annotation.Autowired;
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import org.springframework.beans.factory.config.BeanPostProcessor;
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import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
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import org.springframework.stereotype.Component;
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import org.springframework.util.ReflectionUtils;
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import org.springframework.util.ReflectionUtils.FieldCallback;
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@Component
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public class DataAccessAnnotationProcessor implements BeanPostProcessor {
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private ConfigurableListableBeanFactory configurableListableBeanFactory;
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@Autowired
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public DataAccessAnnotationProcessor(ConfigurableListableBeanFactory bf) {
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configurableListableBeanFactory = bf;
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}
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@Override
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public Object postProcessBeforeInitialization(Object bean, String beanName)
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throws BeansException {
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scanDataAccessAnnotation(bean, beanName);
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return bean;
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}
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@Override
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public Object postProcessAfterInitialization(Object bean, String beanName)
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throws BeansException {
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return bean;
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}
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protected void scanDataAccessAnnotation(Object bean, String beanName) {
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Class<?> managedBeanClass = bean.getClass();
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FieldCallback fcb = new DataAccessFieldCallback(configurableListableBeanFactory, bean);
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ReflectionUtils.doWithFields(managedBeanClass, fcb);
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}
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}
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package org.baeldung.customannotation;
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import java.lang.reflect.Constructor;
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import java.lang.reflect.Field;
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import java.lang.reflect.ParameterizedType;
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import java.lang.reflect.Type;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
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import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
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import org.springframework.util.ReflectionUtils;
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import org.springframework.util.ReflectionUtils.FieldCallback;
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public final class DataAccessFieldCallback implements FieldCallback {
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private static Logger logger = LoggerFactory.getLogger(DataAccessFieldCallback.class);
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private static int AUTOWIRE_MODE = AutowireCapableBeanFactory.AUTOWIRE_BY_NAME;
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private static String ERROR_ENTITY_VALUE_NOT_SAME = "@DataAccess(entity) "
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+ "value should have same type with injected generic type.";
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private static String WARN_NON_GENERIC_VALUE = "@DataAccess annotation assigned "
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+ "to raw (non-generic) declaration. This will make your code less type-safe.";
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private static String ERROR_CREATE_INSTANCE = "Cannot create instance of "
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+ "type '{}' or instance creation is failed because: {}";
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private ConfigurableListableBeanFactory configurableListableBeanFactory;
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private Object bean;
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public DataAccessFieldCallback(final ConfigurableListableBeanFactory bf, final Object bean) {
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configurableListableBeanFactory = bf;
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this.bean = bean;
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}
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@Override
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public void doWith(final Field field)
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throws IllegalArgumentException, IllegalAccessException {
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if (!field.isAnnotationPresent(DataAccess.class)) {
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return;
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}
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ReflectionUtils.makeAccessible(field);
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final Type fieldGenericType = field.getGenericType();
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// In this example, get actual "GenericDAO' type.
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final Class<?> generic = field.getType();
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final Class<?> classValue = field.getDeclaredAnnotation(DataAccess.class).entity();
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if (genericTypeIsValid(classValue, fieldGenericType)) {
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final String beanName = classValue.getSimpleName() + generic.getSimpleName();
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final Object beanInstance = getBeanInstance(beanName, generic, classValue);
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field.set(bean, beanInstance);
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} else {
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throw new IllegalArgumentException(ERROR_ENTITY_VALUE_NOT_SAME);
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}
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}
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/**
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* For example, if user write:
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* <pre>
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* @DataAccess(entity=Person.class)
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* private GenericDAO<Account> personGenericDAO;
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* </pre>
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* then this is should be failed.
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*/
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public boolean genericTypeIsValid(final Class<?> clazz, final Type field) {
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if (field instanceof ParameterizedType) {
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final ParameterizedType parameterizedType = (ParameterizedType) field;
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final Type type = parameterizedType.getActualTypeArguments()[0];
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return type.equals(clazz);
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} else {
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logger.warn(WARN_NON_GENERIC_VALUE);
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return true;
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}
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}
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public final Object getBeanInstance(final String beanName, final Class<?> genericClass, final Class<?> paramClass) {
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Object daoInstance = null;
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if (!configurableListableBeanFactory.containsBean(beanName)) {
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logger.info("Creating new DataAccess bean named '{}'.", beanName);
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Object toRegister = null;
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try {
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final Constructor<?> ctr = genericClass.getConstructor(Class.class);
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toRegister = ctr.newInstance(paramClass);
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} catch (final Exception e) {
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logger.error(ERROR_CREATE_INSTANCE, genericClass.getTypeName(), e);
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throw new RuntimeException(e);
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}
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daoInstance = configurableListableBeanFactory.initializeBean(toRegister, beanName);
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configurableListableBeanFactory.autowireBeanProperties(daoInstance, AUTOWIRE_MODE, true);
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configurableListableBeanFactory.registerSingleton(beanName, daoInstance);
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logger.info("Bean named '{}' created successfully.", beanName);
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} else {
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daoInstance = configurableListableBeanFactory.getBean(beanName);
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logger.info("Bean named '{}' already exist used as current bean reference.", beanName);
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}
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return daoInstance;
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}
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}
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package org.baeldung.customannotation;
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import java.util.Collections;
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import java.util.List;
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import java.util.Optional;
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public class GenericDAO<E> {
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private Class<E> entityClass;
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private String message;
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public GenericDAO(Class<E> entityClass) {
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this.entityClass = entityClass;
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}
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public List<E> findAll() {
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message = "Would create findAll query from " + entityClass.getSimpleName();
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return Collections.emptyList();
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}
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public Optional<E> persist(E toPersist) {
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message = "Would create persist query from " + toPersist.getClass().getSimpleName();
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return Optional.empty();
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}
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/** Only used for unit-testing. */
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public final String getMessage() {
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return message;
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}
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}
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package org.baeldung.customannotation;
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import java.io.Serializable;
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public class Account implements Serializable {
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private static final long serialVersionUID = 7857541629844398625L;
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private Long id;
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private String email;
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private Person person;
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public Account() {
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}
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public Long getId() {
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return id;
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}
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public void setId(Long id) {
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this.id = id;
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}
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public String getEmail() {
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return email;
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}
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public void setEmail(String email) {
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this.email = email;
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}
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public Person getPerson() {
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return person;
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}
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public void setPerson(Person person) {
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this.person = person;
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}
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}
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package org.baeldung.customannotation;
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import org.springframework.stereotype.Repository;
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@Repository
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public class BeanWithGenericDAO {
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@DataAccess(entity=Person.class)
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private GenericDAO<Person> personGenericDAO;
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public BeanWithGenericDAO() {}
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public GenericDAO<Person> getPersonGenericDAO() {
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return personGenericDAO;
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}
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}
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package org.baeldung.customannotation;
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import static org.hamcrest.CoreMatchers.equalTo;
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import static org.hamcrest.CoreMatchers.is;
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import static org.hamcrest.CoreMatchers.not;
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import static org.hamcrest.CoreMatchers.notNullValue;
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import static org.hamcrest.CoreMatchers.sameInstance;
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import static org.junit.Assert.assertThat;
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import org.junit.Test;
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import org.junit.runner.RunWith;
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import org.springframework.test.context.ContextConfiguration;
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import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
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@RunWith(SpringJUnit4ClassRunner.class)
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@ContextConfiguration(classes = { CustomAnnotationConfiguration.class })
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public class DataAccessAnnotationTest {
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@DataAccess(entity = Person.class)
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private GenericDAO<Person> personGenericDAO;
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@DataAccess(entity = Account.class)
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private GenericDAO<Account> accountGenericDAO;
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@DataAccess(entity = Person.class)
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private GenericDAO<Person> anotherPersonGenericDAO;
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@Test
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public void whenGenericDAOInitialized_thenNotNull() {
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assertThat(personGenericDAO, is(notNullValue()));
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assertThat(accountGenericDAO, is(notNullValue()));
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}
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@Test
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public void whenGenericDAOInjected_thenItIsSingleton() {
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assertThat(personGenericDAO, not(sameInstance(accountGenericDAO)));
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assertThat(personGenericDAO, not(equalTo(accountGenericDAO)));
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assertThat(personGenericDAO, sameInstance(anotherPersonGenericDAO));
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}
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@Test
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public void whenFindAll_thenMessagesIsCorrect() {
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personGenericDAO.findAll();
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assertThat(personGenericDAO.getMessage(), is("Would create findAll query from Person"));
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accountGenericDAO.findAll();
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assertThat(accountGenericDAO.getMessage(), is("Would create findAll query from Account"));
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}
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@Test
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public void whenPersist_thenMakeSureThatMessagesIsCorrect() {
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personGenericDAO.persist(new Person());
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assertThat(personGenericDAO.getMessage(), is("Would create persist query from Person"));
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accountGenericDAO.persist(new Account());
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assertThat(accountGenericDAO.getMessage(), is("Would create persist query from Account"));
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}
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}
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package org.baeldung.customannotation;
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import static org.hamcrest.CoreMatchers.is;
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import static org.hamcrest.CoreMatchers.notNullValue;
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import static org.junit.Assert.assertThat;
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import java.lang.reflect.Type;
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import org.junit.Rule;
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import org.junit.Test;
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import org.junit.rules.ExpectedException;
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import org.junit.runner.RunWith;
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import org.springframework.beans.factory.annotation.Autowired;
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import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
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import org.springframework.test.context.ContextConfiguration;
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import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
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@RunWith(SpringJUnit4ClassRunner.class)
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@ContextConfiguration(classes = { CustomAnnotationConfiguration.class })
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public class DataAccessFieldCallbackTest {
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@Autowired
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private ConfigurableListableBeanFactory configurableListableBeanFactory;
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@Autowired
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private BeanWithGenericDAO beanWithGenericDAO;
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@Rule
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public ExpectedException ex = ExpectedException.none();
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@Test
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public void whenObjectCreated_thenObjectCreationIsSuccessful() {
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final DataAccessFieldCallback dataAccessFieldCallback = new DataAccessFieldCallback(configurableListableBeanFactory, beanWithGenericDAO);
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assertThat(dataAccessFieldCallback, is(notNullValue()));
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}
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@Test
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public void whenMethodGenericTypeIsValidCalled_thenReturnCorrectValue()
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throws NoSuchFieldException, SecurityException {
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final DataAccessFieldCallback callback = new DataAccessFieldCallback(configurableListableBeanFactory, beanWithGenericDAO);
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final Type fieldType = BeanWithGenericDAO.class.getDeclaredField("personGenericDAO").getGenericType();
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final boolean result = callback.genericTypeIsValid(Person.class, fieldType);
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assertThat(result, is(true));
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}
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@Test
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public void whenMethodGetBeanInstanceCalled_thenReturnCorrectInstance() {
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final DataAccessFieldCallback callback = new DataAccessFieldCallback(configurableListableBeanFactory, beanWithGenericDAO);
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final Object result = callback.getBeanInstance("personGenericDAO", GenericDAO.class, Person.class);
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assertThat((result instanceof GenericDAO), is(true));
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}
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}
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@ -0,0 +1,31 @@
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package org.baeldung.customannotation;
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import java.io.Serializable;
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public class Person implements Serializable {
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private static final long serialVersionUID = 9005331414216374586L;
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private Long id;
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private String name;
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public Person() {
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}
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public Long getId() {
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return id;
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}
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public void setId(Long id) {
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this.id = id;
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}
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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}
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