spring切面使用传递给被通知方法的参数

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@Aspectpublic 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