ApplicationContextAware 理解

我們常用的IOC 容器是 ApplicationContext, 她的頂層接口是 BeanFactory,  ApplicationContext 對BeanFactory 進行了擴展。

package org.springframework.context;

import org.springframework.beans.factory.HierarchicalBeanFactory;
import org.springframework.beans.factory.ListableBeanFactory;
import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
import org.springframework.core.env.EnvironmentCapable;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.lang.Nullable;

public interface ApplicationContext extends EnvironmentCapable, ListableBeanFactory, HierarchicalBeanFactory, MessageSource, ApplicationEventPublisher, ResourcePatternResolver {
    @Nullable
    String getId();

    String getApplicationName();

    String getDisplayName();

    long getStartupDate();

    @Nullable
    ApplicationContext getParent();

    AutowireCapableBeanFactory getAutowireCapableBeanFactory() throws IllegalStateException;
}

其中 ListableBeanFactory、HierarchicalBeanFactory 分別繼承自 BeanFactory, BeanFactory 內容如下，記錄下來，方便多看，多熟悉

package org.springframework.beans.factory;

import org.springframework.beans.BeansException;
import org.springframework.core.ResolvableType;
import org.springframework.lang.Nullable;

public interface BeanFactory {
    String FACTORY_BEAN_PREFIX = "&";

    Object getBean(String var1) throws BeansException;

    <T> T getBean(String var1, Class<T> var2) throws BeansException;

    Object getBean(String var1, Object... var2) throws BeansException;

    <T> T getBean(Class<T> var1) throws BeansException;

    <T> T getBean(Class<T> var1, Object... var2) throws BeansException;

    <T> ObjectProvider<T> getBeanProvider(Class<T> var1);

    <T> ObjectProvider<T> getBeanProvider(ResolvableType var1);

    boolean containsBean(String var1);

    boolean isSingleton(String var1) throws NoSuchBeanDefinitionException;

    boolean isPrototype(String var1) throws NoSuchBeanDefinitionException;

    boolean isTypeMatch(String var1, ResolvableType var2) throws NoSuchBeanDefinitionException;

    boolean isTypeMatch(String var1, Class<?> var2) throws NoSuchBeanDefinitionException;

    @Nullable
    Class<?> getType(String var1) throws NoSuchBeanDefinitionException;

    String[] getAliases(String var1);
}

我們拿到 IOC 容器的方式有3種，使用ApplicationContext接口下的三個實現類：ClassPathXmlApplicationContext、FileSystemXmlApplicationContext、AnnotationConfigApplicationContext, 但是 SpringBoot 中，IOC 配置文件都被簡化了，無法通過上述3種方式拿到 IOC 容器，但是有時候需求又必須是用 Spring 容器才能實現，所以：

ApplicationContextAware 就是用來獲取框架自動初始化到IOC 容器對象的。

例：

import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;


@Component
public class SpringContextUtil implements ApplicationContextAware {

    private static ApplicationContext applicationContext;


    /**
     * Spring容器會在創建該Bean之后，自動調用該Bean的setApplicationContext方法
     * @param applicationContext
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) {
        if(SpringContextUtil.applicationContext == null) {
            SpringContextUtil.applicationContext = applicationContext;
        }
    }

    //獲取applicationContext
    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    //通過name獲取 Bean.
    public static Object getBean(String name){
        return getApplicationContext().getBean(name);
    }

    //通過class獲取Bean.
    public static <T> T getBean(Class<T> clazz){
        return getApplicationContext().getBean(clazz);
    }

    //通過name,以及Clazz返回指定的Bean
    public static <T> T getBean(String name,Class<T> clazz){
        return getApplicationContext().getBean(name, clazz);
    }

}

使用IOC 容器對象

    static RiskBlo riskBlo ;
    @PostConstruct
    public void init() {        
        riskBlo = SpringContextUtil.getBean(RiskBlo.class);        
    }

 

 

些許混亂，邊看邊記錄， 后面整理在吸收