复用代码系列：Spring的ContextHolder

复用代码系列目录

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);    
    }    
}