詳解spring切面使用傳遞給被通知方法的參數

本文介紹了詳解spring切面使用傳遞給被通知方法的參數，分享給大家，具體如下：

場景：

BlankDisc代表CD實體，可以通過playTrack()方法直接播放某一個磁道中的歌曲。

需求是記錄每個磁道被播放的次數。

一種方法就是修改playTrack()方法，直接在每次調用的時候記錄這個數量。但是，記錄磁道的播放次數與播放本身是不同的關注點，因此不應該屬於playTrack()方法。這應該是切面要完成的任務。

CompactDisc接口

public interface CompactDisc { //播放某一個磁道中的歌曲void playTrack(String track); }

實現類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); } }

切麵類TraceCount

 /** * 切麵類的任務：記錄每個磁道被播放的次數* 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，為該磁道計數@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" > <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> <!-- 開啟aop註解--> <aop:aspectj-autoproxy/>

測試

@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")); } }

測試結果3，2，1，0

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