JAVA解决在@autowired,@Resource注入为null的问题

亦凉 2022-06-16 14:25 475阅读 0赞

使用SpringMVC或者SSH过程中，有时可能会遇到这么一个问题。就是在一个普通的JAVA类（不是controller也不是action类）中无法注入在spring配置文件中配置的bean。比如你在一个普通java类想调用某个在spring中配置的service，你会发现不管你用@Resource还是@Autowired注解都无法注入，对象始终是null。那是因为一般普通的Java类没有被spring代理，自然无法通过spring注入相关的对象。难道这样就不能调用了吗？这里提供下面一个类来解决这个问题：

SpringContextUtil

package com.im.utils;
    
    import org.springframework.beans.BeansException;
    import org.springframework.beans.factory.NoSuchBeanDefinitionException;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.ApplicationContextAware;
    
    /**
     * 这个类是为了解决在普通类调用service的问题
     * 
     * @ClassName SpringContextUtil
     * @Description
     * @author kokjuis 189155278@qq.com
     * @date 2016-6-12
     * @content
     *      
     */
    public class SpringContextUtil implements ApplicationContextAware {
    	private static ApplicationContext applicationContext; // Spring应用上下文
    
    	// 下面的这个方法上加了@Override注解，原因是继承ApplicationContextAware接口是必须实现的方法
    	@Override
    	public void setApplicationContext(ApplicationContext applicationContext)
    			throws BeansException {
    		SpringContextUtil.applicationContext = applicationContext;
    	}
    
    	public static ApplicationContext getApplicationContext() {
    		return applicationContext;
    	}
    
    	public static Object getBean(String name) throws BeansException {
    		return applicationContext.getBean(name);
    	}
    
    	public static Object getBean(String name, Class requiredType)
    			throws BeansException {
    
    		return applicationContext.getBean(name, requiredType);
    	}
    
    	public static boolean containsBean(String name) {
    		return applicationContext.containsBean(name);
    	}
    
    	public static boolean isSingleton(String name)
    			throws NoSuchBeanDefinitionException {
    		return applicationContext.isSingleton(name);
    	}
    
    	public static Class getType(String name)
    			throws NoSuchBeanDefinitionException {
    		return applicationContext.getType(name);
    	}
    
    	public static String[] getAliases(String name)
    			throws NoSuchBeanDefinitionException {
    		return applicationContext.getAliases(name);
    	}
    }

然后在spring配置文件中配置一下这个类：

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans"
    	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx"
    	xmlns:aop="http://www.springframework.org/schema/aop" xmlns:task="http://www.springframework.org/schema/task"
    	xmlns:cache="http://www.springframework.org/schema/cache"
    	xsi:schemaLocation="http://www.springframework.org/schema/beans
    	 http://www.springframework.org/schema/beans/spring-beans-4.3.xsd
    	 http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.3.xsd  
         http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.3.xsd 
         http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-4.3.xsd 
         http://www.springframework.org/schema/cache http://www.springframework.org/schema/cache/spring-cache.xsd">
    
     
    	<bean id="SpringContextUtil" class="com.im.utils.SpringContextUtil"
    		scope="singleton"></bean>
    
    
    </beans>

然后通过这个类提供的方法就能正常的获取在spring中托管的bean了，使用很简单：

/**
         * 获取spring托管的redis连接池
         */
        private JedisPool jedisPool = (JedisPool) SpringContextUtil.getBean("jedisPool");