net.sf.jstuff.integration.spring.SpringBeanInjector Maven / Gradle / Ivy

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/*
 * Copyright 2010-2022 by Sebastian Thomschke and contributors.
 * SPDX-License-Identifier: EPL-2.0
 */
package net.sf.jstuff.integration.spring;

import java.util.List;
import java.util.Map.Entry;

import javax.annotation.PreDestroy;

import org.eclipse.jdt.annotation.Nullable;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.stereotype.Component;

import net.sf.jstuff.core.collection.ObjectCache;
import net.sf.jstuff.core.logging.Logger;
import net.sf.jstuff.core.validation.Assert;

/**
 * Injects spring beans into unmanaged Java objects having {@link org.springframework.beans.factory.annotation.Autowired},
 * {@link org.springframework.beans.factory.annotation.Value} and {@link javax.inject.Inject} annotations.
 *
 *  * <context:annotation-config />
 *
 * <bean class="net.sf.jstuff.integration.spring.SpringBeanInjector" />
 * 
 *
 * or
 *
 *  * <context:annotation-config />
 *
 * <context:component-scan base-package="net.sf.jstuff.integration.spring" />
 * 
 *
 * @author Sebastian Thomschke
 */
@Component
public final class SpringBeanInjector {
   private static final Logger LOG = Logger.create();

   private static @Nullable SpringBeanInjector instance;

   /**
    * @return the default instance (the last instantiated one by any spring context)
    */
   public static SpringBeanInjector get() {
      return Assert.notNull(instance, //
         "No SpringBeanInjector instance created yet. Add  to your spring configuration!");
   }

   private final ObjectCache registeredSingletons = new ObjectCache<>(true);

   @Autowired
   private DefaultListableBeanFactory beanFactory;

   @Autowired
   private List destructors;

   private SpringBeanInjector() {
      Assert.isNull(instance, "A instance of " + getClass().getName() + " already exists.");

      LOG.infoNew(this);

      instance = this;
   }

   /**
    * Executes @PreDestroy and {@link DisposableBean#destroy} life-cycle methods.
    */
   private void destroy(final Object unmanagedBean) throws Exception {
      LOG.entry(unmanagedBean);

      // process @PreDestroy
      for (final DestructionAwareBeanPostProcessor destructor : destructors) {
         destructor.postProcessBeforeDestruction(unmanagedBean, "bean");
      }

      if (unmanagedBean instanceof DisposableBean) {
         ((DisposableBean) unmanagedBean).destroy();
      }

      LOG.exit();
   }

   /**
    * Injects declared dependencies but does not execute any life-cycle methods.
    */
   public void inject(final Object unmanagedBean) {
      LOG.entry(unmanagedBean);

      // process @Autowired, @Inject
      beanFactory.autowireBean(unmanagedBean);

      LOG.exit();
   }

   @PreDestroy
   private void onDestroy() {
      for (final Entry s : registeredSingletons.getAll().entrySet()) {
         try {
            // removes the bean from the context, but does not it's call destroy life-cycle methods
            beanFactory.destroySingleton(s.getKey());

            // call life-cycle methods
            destroy(s.getValue());
         } catch (final Exception ex) {
            LOG.error(ex);
         }
      }
      instance = null;
   }

   /**
    * Fully initializes the unmanaged bean, registers it with the spring context and enables
    * life-cycle callback methods.
    */
   public void registerSingleton(final String beanName, final Object uninitializedBean) {
      LOG.entry(uninitializedBean);

      // process @Autowired, @Inject
      beanFactory.autowireBean(uninitializedBean);

      // process @PostConstruct, InitializingBean#afterPropertiesSet
      beanFactory.initializeBean(uninitializedBean, beanName);

      // add to spring context
      beanFactory.registerSingleton(beanName, uninitializedBean);

      // register for @Destroy processing
      registeredSingletons.put(beanName, uninitializedBean);

      LOG.exit();
   }

}