复用代码系列：Spring的ContextHolder

超、凢脫俗 2022-05-26 13:15 272阅读 0赞

[复用代码系列目录][Link 1]

从Spring的ApplicationContext上下文中获取指定的Bean，复用代码如下：

代码一：

package com.spring.context_holder;
    
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.beans.BeansException;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.ApplicationContextAware;
    
    /**
     * 以静态变量保存Spring Application， 可以在任何代码任何地方任何时候取出ApplicationContext
     * 
     *
     */
    public class SpringContextHolder implements ApplicationContextAware {
     
        private static ApplicationContext applicationContext;
        
        private static Logger logger = LoggerFactory.getLogger(SpringContextHolder.class);
        /**
         * 实现ApplicationContextAware接口的context注入函数，将其存入静态变量
         */
        public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
            SpringContextHolder.applicationContext = applicationContext;
            logger.debug("SpringContextHolder注入ApplicationContext");
        }
    
        /**
         * 获取存储在静态变量中的ApplicationContext
         * 
         * @return
         */
        public static ApplicationContext getApplicationContext() {
            checkApplicationContext();
            return applicationContext;
        }
    
        /**
         * 从静态变量ApplicationContext中获取Bean，自动转型为所赋值对象的类型
         * @param <T>
         * @param name
         * @return
         */
        @SuppressWarnings("unchecked")
        public static <T> T getBean(String name){
            checkApplicationContext();
            return (T) applicationContext.getBean(name);
        }
        
        @SuppressWarnings("unchecked")
        public static <T> T getBean(Class<T> clazz){
            checkApplicationContext();
            return (T) applicationContext.getBeansOfType(clazz);
        }
        /**
         * 清除ApplicationContext静态变量.
         */
        public static void cleanApplicationContext(){
            applicationContext=null;
        }
        /**
         * 检查是否获取到了ApplicationContext
         */
        private static void checkApplicationContext() {
            if (applicationContext == null) {
                throw new IllegalStateException(
                        "applicationContext未注入,请在applicationContext.xml中定义SpringContextHolder");
            }
        }
    }

代码二：

package com.spring.context_holder;
    import org.springframework.beans.BeansException;
    import org.springframework.beans.factory.DisposableBean;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.ApplicationContextAware;
    import org.springframework.context.annotation.Lazy;
    import org.springframework.stereotype.Service;
    
    
    @Service
    @Lazy(false)
    /**
     * 获取bean的工具类（通过注入applicationCotnext）
     *
     */
    public class SpringUtils implements ApplicationContextAware,DisposableBean
    {
        public static  ApplicationContext applicationContext = null;
    
        @SuppressWarnings("unchecked")
        public static <T> T getBean(String beanName){
            isInjected();
            return (T) applicationContext.getBean(beanName);
        }
    
        public static <T> T getBean(Class<T> requiredType){
            isInjected();
            return applicationContext.getBean(requiredType);
        }
    
    
        @Override
        public void destroy() throws Exception {    
            System.out.println("springUtils工具类清除注入的applicationContext");
            SpringUtils.applicationContext = null;
        }
    
        @Override
        public void setApplicationContext(ApplicationContext applicationContext)
                throws BeansException {
            System.out.println("springUtils工具类注入的applicationContext");
            SpringUtils.applicationContext = applicationContext;
        }
    
        /**
         * 判断是否注入
         * @return
         */
        public static void isInjected(){
            if(SpringUtils.applicationContext == null){
                throw new RuntimeException("springUtils applicationContext is not injected!");
            }
        }
    
        public static void main(String[] args) {
            System.out.println(applicationContext);
        }
    
    
    }

代码三：

package com.spring.context_holder;
    
    import org.springframework.beans.BeansException;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.ApplicationContextAware;
    
    public class SpringBeanFactoryUtils  implements ApplicationContextAware {
        private static ApplicationContext appCtx;    
        /**  
         * 此方法可以把ApplicationContext对象inject到当前类中作为一个静态成员变量。  
         * @param applicationContext ApplicationContext 对象.  
         * @throws BeansException  
         * @author wangdf 
         */    
         
        public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {    
            appCtx = applicationContext;    
        }  
           
        /** 
         * 获取ApplicationContext 
         * @return 
         * @author wangdf 
         */  
        public static ApplicationContext getApplicationContext(){  
            return appCtx;  
        }  
           
        /**  
         * 这是一个便利的方法，帮助我们快速得到一个BEAN  
         * @param beanName bean的名字  
         * @return 返回一个bean对象  
         * @author wangdf 
         */    
        public static Object getBean(String beanName) {    
            return appCtx.getBean(beanName);    
        }    
    }

[Link 1]: https://blog.csdn.net/sunct/article/details/80175458