详解spring切面使用传递给被通知方法的参数

本文介绍了详解spring切面使用传递给被通知方法的参数，分享给大家，具体如下：

场景：

blankdisc代表cd实体，可以通过playtrack()方法直接播放某一个磁道中的歌曲。

需求是记录每个磁道被播放的次数。

一种方法就是修改playtrack()方法，直接在每次调用的时候记录这个数量。但是，记录磁道的播放次数与播放本身是不同的关注点，因此不应该属于playtrack()方法。这应该是切面要完成的任务。

compactdisc接口

public interface compactdisc { 
 
  //播放某一个磁道中的歌曲 
  void playtrack(string track); 
 
} 

实现类blankdisc

public class blankdisc implements compactdisc { 
 
  private string title; 
  private string artist; 
  private list<string> tracks; 
 
  public void settitle(string title) { 
    this.title = title; 
  } 
 
  public void setartist(string artist) { 
    this.artist = artist; 
  } 
 
  public void settracks(list<string> tracks) { 
    this.tracks = tracks; 
  } 
 
  @override 
  public void playtrack(string track) { 
    system.out.println("-track: " + track); 
  } 
 
} 

切面类tracecount 

/** 
 * 切面类的任务：记录每个磁道被播放的次数 
 * created by administrator on 2017/12/1. 
 */ 
@component 
@aspect 
public class trackcounter { 
 
  private map<string, integer> trackcounts = new hashmap<>(); 
 
  @pointcut("execution(* chapter04.aop_args.blankdisc.playtrack(string)) && args(track)") 
  public void trackplayed(string track) { 
  } 
 
  //在播放前，为该磁道计数 
  @before("trackplayed(track)") 
  public void counttrack(string track) { 
    int currentcount = getplaycount(track); 
    trackcounts.put(track, currentcount + 1); 
  } 
 
  public int getplaycount(string track) { 
    return trackcounts.containskey(track) ? trackcounts.get(track) : 0; 
  } 
} 

applicationcontext.xml配置文件

<context:component-scan base-package="aop_test,chapter04"/> 
 
<bean id="compactdisc" 
   class="chapter04.aop_args.blankdisc"> 
  <property name="title" value="sgt. pepper's lonely hearts club band" /> 
  <property name="artist" value="the beatles" /> 
  <property name="tracks"> 
    <list> 
      <value>sgt. pepper's lonely hearts club band</value> 
      <value>with a little help from my friends</value> 
      <value>lucy in the sky with diamonds</value> 
      <value>getting better</value> 
      <value>fixing a hole</value> 
      <value>she's leaving home</value> 
      <value>being for the benefit of mr. kite!</value> 
      <value>within you without you</value> 
      <value>when i'm sixty-four</value> 
      <value>lovely rita</value> 
      <value>good morning good morning</value> 
      <value>sgt. pepper's lonely hearts club band (reprise)</value> 
      <value>a day in the life</value> 
    </list> 
  </property> 
</bean> 
 
<!-- 开启aop注解 --> 
<aop:aspectj-autoproxy/> 

测试

@runwith(springjunit4classrunner.class) 
@contextconfiguration("classpath:applicationcontext.xml") 
public class test_aop_args { 
 
  @autowired 
  compactdisc cd; 
 
  @autowired 
  trackcounter trackcounter; 
 
  @test 
  public void test(){ 
    cd.playtrack("sgt. pepper's lonely hearts club band"); 
    cd.playtrack("with a little help from my friends"); 
    cd.playtrack("lucy in the sky with diamonds"); 
    cd.playtrack("sgt. pepper's lonely hearts club band"); 
    cd.playtrack("with a little help from my friends"); 
    cd.playtrack("sgt. pepper's lonely hearts club band"); 
 
    system.out.println(trackcounter.getplaycount("sgt. pepper's lonely hearts club band")); 
    system.out.println(trackcounter.getplaycount("with a little help from my friends")); 
    system.out.println(trackcounter.getplaycount("lucy in the sky with diamonds")); 
    system.out.println(trackcounter.getplaycount("getting better")); 
  } 
} 

测试结果 3，2，1，0

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。