97 lines
4.2 KiB
Java
97 lines
4.2 KiB
Java
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) " + "value should have same type with injected generic type.";
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private static String WARN_NON_GENERIC_VALUE = "@DataAccess annotation assigned " + "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 " + "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) 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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