Spring AOP 处理通知中的参数

1. 切面

切点表达式中使用了 args(trackNumber) 限定符指定参数，参数名称要与切点方法中的参数名一致。

package soundsystem;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;

import java.util.HashMap;
import java.util.Map;

/**
* Created by liujiajia on 2017/3/28.
*/
@Aspect
public class TrackCounter {
    private Map<Integer, Integer> trackCounts = new HashMap<Integer, Integer>();

    @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;
    }
}

2. 切点

package soundsystem;

/**
* Created by liujiajia on 2017/3/7.
*/
public interface CompactDisc {
    void playTrack(int trackNumber);
}

3. 切点的实现

package soundsystem;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import java.util.List;

/**
* Created by liujiajia on 2017/3/8.
*/
public class BlankDisc implements CompactDisc {
    public BlankDisc() {
    }

    public BlankDisc(@Value("${disc.title}") String title, @Value("${disc.artist}") String artist) {
        this.title = title;
        this.artist = artist;
    }

    private String title;

    private String artist;

    private List<String> tracks;

    public void playTrack(int trackNumber) {
        System.out.println(tracks.get(trackNumber - 1));
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getArtist() {
        return artist;
    }

    public void setArtist(String artist) {
        this.artist = artist;
    }

    public List<String> getTracks() {
        return tracks;
    }

    public void setTracks(List<String> tracks) {
        this.tracks = tracks;
    }
}

4. 配置类

package soundsystem;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;

import java.util.ArrayList;
import java.util.List;

/**
* Created by liujiajia on 2017/3/28.
*/
@Configuration
@EnableAspectJAutoProxy
public class TrackCounterConfig {
    @Bean
    public CompactDisc sgtPeppers() {
        BlankDisc cd = new BlankDisc();
        cd.setTitle("Sgt. Pepper's Lonely Hearts Club Band");
        cd.setArtist("The Beatles");
        List<String> tracks = new ArrayList<String>();
        tracks.add("Sgt. Pepper's Lonely Hearts Club Band");
        tracks.add("With a Little Help from My Friends");
        tracks.add("Lucy in the Sky with Diamonds");
        tracks.add("Getting Better");
        tracks.add("Fixing a Hole");
        cd.setTracks(tracks);
        return cd;
    }

    @Bean
    public TrackCounter trackCounter() {
        return new TrackCounter();
    }
}

5. 测试类

package soundsystem;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import static org.junit.Assert.assertEquals;

/**
* Created by liujiajia on 2017/3/28.
*/
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = TrackCounterConfig.class)
public class TrackCounterTest {
    @Autowired
    private CompactDisc cd;

    @Autowired
    private TrackCounter counter;

    @Test
    public void testTrackerCounter() {
        cd.playTrack(1);
        cd.playTrack(2);
        cd.playTrack(3);
        cd.playTrack(3);
        cd.playTrack(3);
        cd.playTrack(3);
        cd.playTrack(5);
        cd.playTrack(5);

        assertEquals(1, counter.getPlayCount(1));
        assertEquals(1, counter.getPlayCount(2));
        assertEquals(4, counter.getPlayCount(3));
        assertEquals(0, counter.getPlayCount(4));
        assertEquals(2, counter.getPlayCount(5));
    }
}