Spring中 ApplicationContextAware 接口使用理解

古城微笑少年丶 2022-05-24 09:11 221阅读 0赞

一、这个接口有什么用？

当一个类实现了这个接口（ApplicationContextAware）之后，这个类就可以方便获得ApplicationContext中的所有bean。换句话说，就是这个类可以直接获取spring配置文件中，所有有引用到的bean对象。

二、怎么使用这个接口？

例如我有一个方法类AppUtil，这个方法类中需要使用到的ApplicationContext中的某个bean（companyService）。

一、因为spring要建立属于自己的容器，就必须要加载自己的配置文件。

这个时候，需要注册ContextLoaderListener或者这个类的子类。

在web.xml加上以下的信息：

<table style="border-spacing:0px;width:1263px;font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;color:rgb(51,51,51);margin:.3em 0px;padding:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;font-size:13px;background:rgb(245,245,245) none;"> 
 <tbody style="float:none;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;background:none;"> 
  <tr style="border-top:0px;background:none;float:none;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;"> 
   <td style="margin:0px;"> 
    <div style="padding:0px .5em 0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;text-align:right;vertical-align:baseline;min-height:auto;white-space:pre;background:none;">
      1 
    </div> 
    <div style="padding:0px .5em 0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;text-align:right;vertical-align:baseline;min-height:auto;white-space:pre;background:none;">
      2 
    </div> 
    <div style="padding:0px .5em 0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;text-align:right;vertical-align:baseline;min-height:auto;white-space:pre;background:none;">
      3 
    </div></td> 
   <td style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;padding:0px;margin:0px;border-width:0px;font-size:13px;line-height:1.1em;float:none;vertical-align:baseline;min-height:auto;background:none;"> 
    <div style="width:1216px;padding:0px;margin:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;background:none;"> 
     <div style="padding:0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;background:none;"> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&lt;</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(255,120,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;font-weight:bold;min-height:auto;">listener</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&gt;</code> 
     </div> 
     <div style="padding:0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;background:none;"> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&lt;</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(255,120,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;font-weight:bold;min-height:auto;">listener-class</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&gt;org.springframework.web.context.ContextLoaderListener&lt;/</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(255,120,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;font-weight:bold;min-height:auto;">listener-class</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&gt;</code> 
     </div> 
     <div style="padding:0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;background:none;"> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&lt;/</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(255,120,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;font-weight:bold;min-height:auto;">listener</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&gt;</code> 
     </div> 
    </div></td> 
  </tr> 
 </tbody> 
</table>

当然，这样子的话只会读取默认路径下的application.xml配置文件的。如果需要读取特定路径下的配置文件。需要在web.xml中添加如下信息。可以参考我的示例，指定配置文件，如下：

<table style="border-spacing:0px;width:1263px;font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;color:rgb(51,51,51);margin:.3em 0px;padding:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;font-size:13px;background:rgb(245,245,245) none;"> 
 <tbody style="float:none;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;background:none;"> 
  <tr style="border-top:0px;background:none;float:none;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;"> 
   <td style="margin:0px;"> 
    <div style="padding:0px .5em 0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;text-align:right;vertical-align:baseline;min-height:auto;white-space:pre;background:none;">
      1 
    </div> 
    <div style="padding:0px .5em 0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;text-align:right;vertical-align:baseline;min-height:auto;white-space:pre;background:none;">
      2 
    </div> 
    <div style="padding:0px .5em 0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;text-align:right;vertical-align:baseline;min-height:auto;white-space:pre;background:none;">
      3 
    </div> 
    <div style="padding:0px .5em 0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;text-align:right;vertical-align:baseline;min-height:auto;white-space:pre;background:none;">
      4 
    </div></td> 
   <td style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;padding:0px;margin:0px;border-width:0px;font-size:13px;line-height:1.1em;float:none;vertical-align:baseline;min-height:auto;background:none;"> 
    <div style="width:1216px;padding:0px;margin:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;background:none;"> 
     <div style="padding:0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;background:none;"> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&lt;</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(255,120,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;font-weight:bold;min-height:auto;">context-param</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&gt;</code> 
     </div> 
     <div style="padding:0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;background:none;"> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&lt;</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(255,120,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;font-weight:bold;min-height:auto;">param-name</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&gt;contextConfigLocation&lt;/</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(255,120,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;font-weight:bold;min-height:auto;">param-name</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&gt;</code> 
     </div> 
     <div style="padding:0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;background:none;"> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&lt;</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(255,120,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;font-weight:bold;min-height:auto;">param-value</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&gt;classpath:conf/app-context.xml&lt;/</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(255,120,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;font-weight:bold;min-height:auto;">param-value</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&gt;</code> 
     </div> 
     <div style="padding:0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;background:none;"> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&lt;/</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(255,120,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;font-weight:bold;min-height:auto;">context-param</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&gt;</code> 
     </div> 
    </div></td> 
  </tr> 
 </tbody> 
</table>

注意：<param-name>contextConfigLocation</param-name>是不能改变的。

二、方法类AppUtil的处理

1、方法类AppUtil实现ApplicationContextAware接口：

2、为方法类AppUtil增加一个静态的成员ApplicationContext类型的对象。以后方法类AppUtil获取ApplicationContext，就是通过读取这个成员变量的。具体如下所示：

实现ApplicationContextAware接口的默认方法：

3、在spring的配置文件中，注册方法类AppUtil

严格上来说，方法类AppUtil是一个bean,而且从步骤2中我们不难发现，之所以方法类AppUtil能够灵活自如地获取ApplicationContext就是因为spring能够为我们自动地执行了setApplicationContext。但是，spring不会无缘无故地为某个类执行它的方法的，所以，就很有必要通过注册方法类AppUtil的方式告知spring有这样子一个类的存在。其实，方法很简单，就是将方法类AppUtil作为一个普通的bean在spring的配置文件中进行注册：

4、使用静态的成员ApplicationContext类型的对象，appContext，来调用其他bean。

注：配置文件中关于companyService的内容：

<table style="border-spacing:0px;width:1263px;font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;color:rgb(51,51,51);margin:.3em 0px;padding:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;font-size:13px;background:rgb(245,245,245) none;"> 
 <tbody style="float:none;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;background:none;"> 
  <tr style="border-top:0px;background:none;float:none;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;"> 
   <td style="margin:0px;"> 
    <div style="padding:0px .5em 0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;text-align:right;vertical-align:baseline;min-height:auto;white-space:pre;background:none;">
      1 
    </div> 
    <div style="padding:0px .5em 0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;text-align:right;vertical-align:baseline;min-height:auto;white-space:pre;background:none;">
      2 
    </div> 
    <div style="padding:0px .5em 0px 1em;margin:0px;border:0px;float:none;line-height:1.1em;text-align:right;vertical-align:baseline;min-height:auto;white-space:pre;background:none;">
      3 
    </div></td> 
   <td style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;padding:0px;margin:0px;border-width:0px;font-size:13px;line-height:1.1em;float:none;vertical-align:baseline;min-height:auto;background:none;"> 
    <div style="width:1216px;padding:0px;margin:0px;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;background:none;"> 
     <div style="padding:0px 1em;margin:0px;background:none;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&lt;</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(255,120,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;font-weight:bold;min-height:auto;">bean</code>&nbsp; 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(128,128,128);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">id</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">=</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,255);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">"companyService"</code>&nbsp; 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(128,128,128);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">class</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">=</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,255);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">"com.kaiwii.service.system.impl.CompanyServiceImpl"</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&gt;</code> 
     </div> 
     <div style="padding:0px 1em;margin:0px;background:none;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">...</code> 
     </div> 
     <div style="padding:0px 1em;margin:0px;background:none;border:0px;float:none;line-height:1.1em;vertical-align:baseline;min-height:auto;"> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&lt;/</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(255,120,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;font-weight:bold;min-height:auto;">bean</code> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;">&gt;</code> 
     </div> 
     <div> 
      <code style="font-family:Monaco, Menlo, Consolas, 'Courier New', monospace;font-size:14px;line-height:1.1em;color:rgb(0,0,0);background:none;border:0px;float:none;margin:0px;padding:0px;vertical-align:baseline;min-height:auto;"><br></code> 
     </div> 
    </div></td> 
  </tr> 
 </tbody> 
</table>