spring cloud系列-05.获取spring容器中的bean工具类

1.ApplicationContextAware介绍
下面是这个接口的源代码，里面有具体介绍

/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.context;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.Aware;

/**
 * Interface to be implemented by any object that wishes to be notified
 * of the {@link ApplicationContext} that it runs in.
 *
 * <p>Implementing this interface makes sense for example when an object
 * requires access to a set of collaborating beans. Note that configuration
 * via bean references is preferable to implementing this interface just
 * for bean lookup purposes.
 *
 * <p>This interface can also be implemented if an object needs access to file
 * resources, i.e. wants to call {@code getResource}, wants to publish
 * an application event, or requires access to the MessageSource. However,
 * it is preferable to implement the more specific {@link ResourceLoaderAware},
 * {@link ApplicationEventPublisherAware} or {@link MessageSourceAware} interface
 * in such a specific scenario.
 *
 * <p>Note that file resource dependencies can also be exposed as bean properties
 * of type {@link org.springframework.core.io.Resource}, populated via Strings
 * with automatic type conversion by the bean factory. This removes the need
 * for implementing any callback interface just for the purpose of accessing
 * a specific file resource.
 *
 * <p>{@link org.springframework.context.support.ApplicationObjectSupport} is a
 * convenience base class for application objects, implementing this interface.
 *
 * <p>For a list of all bean lifecycle methods, see the
 * {@link org.springframework.beans.factory.BeanFactory BeanFactory javadocs}.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Chris Beams
 * @see ResourceLoaderAware
 * @see ApplicationEventPublisherAware
 * @see MessageSourceAware
 * @see org.springframework.context.support.ApplicationObjectSupport
 * @see org.springframework.beans.factory.BeanFactoryAware
 */
public interface ApplicationContextAware extends Aware {

    /**
     * Set the ApplicationContext that this object runs in.
     * Normally this call will be used to initialize the object.
     * <p>Invoked after population of normal bean properties but before an init callback such
     * as {@link org.springframework.beans.factory.InitializingBean#afterPropertiesSet()}
     * or a custom init-method. Invoked after {@link ResourceLoaderAware#setResourceLoader},
     * {@link ApplicationEventPublisherAware#setApplicationEventPublisher} and
     * {@link MessageSourceAware}, if applicable.
     * @param applicationContext the ApplicationContext object to be used by this object
     * @throws ApplicationContextException in case of context initialization errors
     * @throws BeansException if thrown by application context methods
     * @see org.springframework.beans.factory.BeanInitializationException
     */
    void setApplicationContext(ApplicationContext applicationContext) throws BeansException;

}

大概意思就是当一个类实现了ApplicationContextAware 接口之后就能获取到ApplicationContext中的所有bean，换句话说就是这个类可以获取到spring配置文件中的所有加载的bean。

2.获取spring容器中的bean工具类

import java.util.Objects;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

/**
 * 操作springbean共通类
 * @author Administrator add on 2017/12/12
 *
 */
@Component
public class SpringBeanUtils implements ApplicationContextAware{

    private static ApplicationContext applicationContext;

    /**
     * 设置applicationContext
     * 覆盖ApplicationContextAware方法
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException{
        if(Objects.isNull(SpringBeanUtils.applicationContext)){
            SpringBeanUtils.applicationContext = applicationContext;
        }
    }

    /**
     * 获取applicationContext
     * @return applicationContext
     */
    public static ApplicationContext getApplicationContext(){
        return applicationContext;
    }

    /**
     * 根据bean名称获取bean
     * @param name
     * @return
     */
    public static Object getBean(String name){
        return getApplicationContext().getBean(name);
    }

    /**
     * 根据bean class获取bean
     * @param clazz
     * @return
     */
    public static <T> T getBean(Class<T> clazz){
        return getApplicationContext().getBean(clazz);
    }

    /**
     * 根据bean名称和bean class获取bean
     * @param name
     * @param clazz
     * @return
     */
    public static <T> T getBean(String name, Class<T> clazz){
        return getApplicationContext().getBean(name, clazz);
    }

}