> For the complete documentation index, see [llms.txt](https://bohans.gitbook.io/ji-chu/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bohans.gitbook.io/ji-chu/spring/basic/core/mian-xiang-qie-mian-bian-cheng-aop/shi-yong-zhu-jie-chuang-jian-qie-mian/chu-li-tong-zhi-zhong-de-can-shu.md).

# 处理通知中的参数

<details>

<summary><mark style="color:purple;"><strong>参数化的通知</strong></mark></summary>

```java
package soundsystem;

import java.util.HashMap;
import java.util.Map;
import org.aspect.lang.annotation.Aspect;
import org.aspect.lang.annotation.Before;
import org.aspect.lang.annotation.Pointcut;

@Aspect
public class TrackCounter {

  private Map<Integer, Integer> trackCounts = new HashMap<>();
  
  @Pointcut("execution(* soundsystem.CompactDisc.playTrack(int) " +
            "&& args(trackNumber)")
  public void trackPlayed(int trackNumber) { }

  @Before("trackPlayed(trackNumber)")
  public void countTrack(int trackNumber) {
    int currentCount = getPlayCount(trackNumber);
    trackCounts.put(trackNumber, currentCount + 1);
  }
  
  public int getPlayCount(int trackNumber) {
    return trackCounts.containsKey(trackNumber) ? 
      trackCounts.get(trackNumber) : 0;
  }
}
```

</details>

这个切面使用 **@Pointcut** 注解定义命名的切点，并使用 **@Before** 将一个方法声明为前置通知。

下图将切点表达式进行了分解，以展现参数是在什么地方指定的：

<figure><img src="/files/GHMTORAroi60PhjvOek0" alt=""><figcaption></figcaption></figure>

* <mark style="color:blue;">**切点表达式中的 args(trackNumber) 限定符表明传递给 playTrack() 方法的 int 类型参数也会传递到通知中去**</mark>。
* **参数的名称 trackNumber 也与切点方法签名中的参数相匹配。**&#x8FD9;个参数会传递到通知方法中，这个通知方法是通过 @Before 注解和命名切点 trackPlayed(trackNumber) 定义的。**切点定义中的参数与切点方法中的参数名称是一样的**，这样就完成了从命名切点到通知方法的参数转移。


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://bohans.gitbook.io/ji-chu/spring/basic/core/mian-xiang-qie-mian-bian-cheng-aop/shi-yong-zhu-jie-chuang-jian-qie-mian/chu-li-tong-zhi-zhong-de-can-shu.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.