第4章面向切面的Spring

4.1 什麼是面向切面編程

4.1.4 定義AOP術語

橫切關注點（cross-cutting concern）
通知（advice）

前置通知（Before）
後置通知（After）
返回通知（After-returning）
異常通知（After-throwing）
環繞通知（Around）

切點（pointcut）
連接點（joinpoint）
切面（Aspcet）
引入（Introduction）
織入（Weaving）

編譯期織入
類加載期織入
運行期織入

4.1.2 Spring對AOP的支持

Spring提供的4中類型的AOP支持

基於代理的經典Spring AOP（這種不介紹，因爲非常笨重和過於複雜，太老舊）
純POJO切面
@AspectJ註解驅動的切面
注入式AspectJ切面（適用於Spring各版本）

介紹的AOP方式

聲明式AOP
基於註解的AOP

Spring通知是Java編寫的

AspectJ是以JAVA語言擴展的方式實現的

Spring在運行時通知對象

SpringAOP實現的實質是代理類

Spring只支持方法級別的連接點

4.2 通過切點來選擇連接點

SpringAOP中，使用AspectJ的切點表達式語言來定義切點。 Spring僅支持AspectJ的切點指示器（pointcut designator）的一個子集。總結：SpringAOP 與 AspectJ相比弱爆了。

4.2.1 編寫切點

public interface Performance {

	void perform();
}

4.2.2 在切點中選擇bean

execution(* concert.Performance.perform(..)) and bean('woodstock')

排除!

execution(* concert.Performance.perform(..)) and !bean('woodstock')

4.3 使用註解創建切面

4.3.1 定義切面

@Aspect
public class Audience {
	
	@Before("execution(** concert.Performance.perform(..))")
	public void silenceCellPhones() {
		System.out.println("Silencing cell phones");
	}
	
	@Before("execution(** concert.Performance.perform(..))")
	public void takeSeats() {
		System.out.println("Taking seats");
	}
	
	@After("execution(** concert.Performance.perform(..))")
	public void applause() {
		System.out.println("CLAP CLAP CLAP!!!");
	}
	
	@AfterThrowing("execution(** concert.Performance.perform(..))")
	public void demandRefund() {
		System.out.println("Demanding a refund");
	}
	
}

定義切點，添加@Aspect註解

@Aspect
public class Audience {
	
	@Pointcut("execution(** concert.Performance.perform(..))")
	public void performance() {}
	
	@Before("performance()")
	public void silenceCellPhones() {
		System.out.println("Silencing cell phones");
	}
	
	@Before("performance()")
	public void takeSeats() {
		System.out.println("Taking seats");
	}
	
	@Before("performance()")
	public void applause() {
		System.out.println("CLAP CLAP CLAP!!!");
	}
	
	@AfterThrowing("performance()")
	public void demandRefund() {
		System.out.println("Demanding a refund");
	}
	
}

啓用自動代理

@Configuration
@EnableAspectJAutoProxy
@ComponentScan
public class ConcertConfig {
	
	@Bean
	public Audience audience() {
		return new Audience();
	}
}

XML啓動

<context:conponent-scan base-package="concert" />
<aop:aspectj-autoproxy />
<bean class="concert.Audience" />

4.3.2 創建環繞通知

@Aspect
public class Audience {
	
	@Pointcut("execution(** concert.Performance.perform(..))")
	public void performance() {}
	
	@Around("performance()")
	public void watchPerformance(ProceedingJoinPoint jp) {
		try {
			System.out.println("Silencing cell phones");
			System.out.println("Taking seats");
			jp.proceed();
			System.out.println("CLAP CLAP CLAP!!!");
		} catch (Throwable e) {
			System.out.println("Demanding a refund");
		}
	}
}

4.3.3 處理通知中的參數

public interface CompactDisc {
	void play();
	
	void playTrack(int trackNumber);
}


public class BlackDisc implements CompactDisc {
	
	private String title = "";
	private String artist = "";
	
	public void setTitle(String title) {
		this.title = title;
	}

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

	@Override
	public void playTrack(int trackNumber) {
		System.out.println("track " + trackNumber + " play.");
	}
	
	@Override
	public void play() {
		System.out.println("Playing " + title + " by " + artist);
	}
}

切面

@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);
	}
	
	@Before("execution(* soundsystem.CompactDisc.play(..))")
	public void countPlay() {
		System.out.println("countPlay");
	}
	
	public int getPlayCount(int trackNumber) {
		return trackCounts.containsKey(trackNumber) ? trackCounts.get(trackNumber) : 0;
	}
}

配置

@Configuration
@EnableAspectJAutoProxy
public class TrackCounterConfig {
	
	@Bean
	public CompactDisc sgtPeppers() {
		BlackDisc cd = new BlackDisc();
		cd.setTitle("Sgt. pepper's Lonely Hearts Club Band");
		cd.setArtist("The Beatles");
		return cd;
	}
	
	@Bean
	public TrackCounter trackCounter() {
		return new TrackCounter();
	}
}

測試

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes=TrackCounterConfig.class)
public class TrackCounterTest {

	@Autowired
	private CompactDisc cd;
	
	@Autowired
	private TrackCounter counter;
	
	@Test
	public void testTrackCounter() {
		cd.playTrack(1);
		cd.playTrack(2);
		cd.playTrack(3);
		cd.playTrack(3);
		cd.playTrack(3);
		cd.playTrack(3);
		cd.playTrack(7);
		cd.playTrack(7);
		
		cd.play();
		cd.play();
		
		
		for (int i=1; i<=7; ++i) {
			int count = counter.getPlayCount(i);
			System.out.println(i + " : " + count);
		}
	}
}

4.3.4 通過註解引入新功能

新接口

public interface Encoreable {
	void performEncore();
}

切面

@Aspect
public class EncoreableIntroducer {

	@DeclareParents(value="concert.Performance+",
			defaultImpl=DefaultEncoreable.class)
	public static Encoreable encoreable;

}

4.4 在XML中聲明切面

public class Audience {
	
	public void silenceCellPhones() {
		System.out.println("Silencing cell phones");
	}
	
	public void takeSeats() {
		System.out.println("Taking seats");
	}
	
	public void applause() {
		System.out.println("CLAP CLAP CLAP!!!");
	}
	
	public void demandRefund() {
		System.out.println("Demanding a refund");
	}
}

4.4.1 聲明前置和後置通知

<aop:config>
		<aop:aspect ref="audience">
			<aop:before 
				pointcut="execution(** concert.Performance.perform(..))" 
				method="silenceCellPhones" />
			<aop:before 
				pointcut="execution(** concert.Performance.perform(..))" 
				method="takeSeats" />
			<aop:after-returning
				pointcut="execution(** concert.Performance.perform(..))" 
				method="applause" />
			<aop:after-throwing
				pointcut="execution(** concert.Performance.perform(..))" 
				method="demandRefund" />
		</aop:aspect>
	</aop:config>

定義切點

<aop:config>
		<aop:aspect ref="audience">
			<aop:pointcut 
				expression="execution(** concert.Performance.perform(..))" 
				id="performance"/>
			<aop:before 
				pointcut-ref="performance" 
				method="silenceCellPhones" />
			<aop:before 
				pointcut-ref="performance" 
				method="takeSeats" />
			<aop:after-returning
				pointcut-ref="performance" 
				method="applause" />
			<aop:after-throwing
				pointcut-ref="performance" 
				method="demandRefund" />
		</aop:aspect>
	</aop:config>

4.4.2 聲明環繞通知

public class Audience {
	
	public void watchPerformance(ProceedingJoinPoint jp) {
		try {
			System.out.println("Silencing cell phones");
			System.out.println("Taking seats");
			jp.proceed();
			System.out.println("CLAP CLAP CLAP!!!");
		} catch (Throwable e) {
			System.out.println("Demanding a refund");
		}
	}
}

    <aop:config>
		<aop:aspect ref="audience">
			<aop:pointcut 
				expression="execution(** concert.Performance.perform(..))" 
				id="performance"/>
			<aop:around 
				pointcut-ref="performance" 
				method="watchPerformance" />
		</aop:aspect>
	</aop:config>

4.4.3 爲通知傳遞參數

public interface CompactDisc {
	void playTrack(int trackNumber);
}

public class BlackDisc implements CompactDisc {
	
	private String title = "";
	private String artist = "";
	
	@Override
	public void playTrack(int trackNumber) {
		System.out.println("track " + trackNumber + " play.");
	}
	
	public void setTitle(String title) {
		this.title = title;
	}

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

	public String getArtist() {
		return artist;
	}
}

TrackCounter

public class TrackCounter {
	private Map<Integer, Integer> trackCounts = new HashMap<Integer, Integer>();
	
	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;
	}
}

XML

	<bean id="trackCounter" class="soundsystem4_4_3.TrackCounter" />
	
	<bean id="cd" class="soundsystem4_4_3.BlackDisc">
		<property name="title" value="Sgt. pepper's Lonely Hearts Club Band" />
		<property name="artist" value="The Beatles" />
	</bean>

	<aop:config>
		<aop:aspect ref="trackCounter">
			<aop:pointcut 
			expression="execution(* soundsystem4_4_3.CompactDisc.playTrack(int)) and args(trackNumber)" 
			id="trackPlayed"/>
			
			<aop:before pointcut-ref="trackPlayed" method="countTrack" />
		</aop:aspect>
	</aop:config>

test

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations= {"classpath:soundsystem4_4_3/trackconfig.xml"})
public class TrackCounterTest {

	@Autowired
	private CompactDisc cd;
	
	@Autowired
	private TrackCounter counter;
	
	@Test
	public void testTrackCounter() {
		cd.playTrack(1);
		cd.playTrack(2);
		cd.playTrack(3);
		cd.playTrack(3);
		cd.playTrack(3);
		cd.playTrack(3);
		cd.playTrack(7);
		cd.playTrack(7);

		for (int i=1; i<=7; ++i) {
			int count = counter.getPlayCount(i);
			System.out.println(i + " : " + count);
		}
	}
}

4.4 通過切面引入新的功能

    <aop:config>
		<aop:aspect>
			<aop:declare-parents 
				types-matching="concert.Performance+"
				implement-interface="concert.Encoreable" 
				default-impl="concert.DefaultEncoreable" />
		</aop:aspect>
	</aop:config>

方法2：delegate-ref

<bean id="encoreableDelegate" class="concert.DefaultEncoreable" />
	
	<aop:config>
		<aop:aspect>
			<aop:declare-parents 
				types-matching="concert.Performance+"
				implement-interface="concert.Encoreable" 
				delegate-ref="encoreableDelegate" />
		</aop:aspect>
	</aop:config>

4.5 注入AspectJ切面

public aspect CriticAspect {
	public CriticAspect() {}
	
	pointcut performance() : execution(* perform(..));
	
	before():performance() {
		System.out.println(criticismEngine.getCriticism());
	}
	
	private CriticismEngine criticismEngine;
	
	public void setCriticismEngine(CriticismEngine criticismEngine) {
		this.criticismEngine = criticismEngine;
	}
}

public interface CriticismEngine {
	String getCriticism();
}

public class CriticismengineImpl implements CriticismEngine {

	@Override
	public String getCriticism() {
		int i = (int)(Math.random() * criticismPool.length);
		return criticismPool[i];
	}

	private String[] criticismPool;
	public void setCriticismPool(String[] criticismPool) {
		this.criticismPool = criticismPool;
	}
}

XML 注意 factory-method="aspectOf"

<bean id="criticismEngine" class="concert.CriticismengineImpl">
		<property name="criticismPool">
			<list>
				<value>Wrost perforamance ever.</value>
				<value>Wrost perforamance ever.</value>
				<value>Wrost perforamance ever.</value>
			</list>
		</property>
	</bean>
	
	<bean class="concert.CriticAspect" factory-method="aspectOf">
		<property name="criticismEngine" ref="criticismEngine"></property>
	</bean>

Spring實戰（第4版）Spring In Action - 第4章面向切面的Spring

第4章面向切面的Spring

4.1 什麼是面向切面編程

4.1.4 定義AOP術語

4.1.2 Spring對AOP的支持

4.2 通過切點來選擇連接點

4.2.1 編寫切點

4.2.2 在切點中選擇bean

4.3 使用註解創建切面

4.3.1 定義切面

4.3.2 創建環繞通知

4.3.3 處理通知中的參數

4.3.4 通過註解引入新功能

4.4 在XML中聲明切面

4.4.1 聲明前置和後置通知

4.4.2 聲明環繞通知

4.4.3 爲通知傳遞參數

4.4 通過切面引入新的功能

2020年上半年數據庫系統工程師考試

Future.get拋出TimeoutException，並不會中斷或者取消任務

AutoCloseable使用與注意，try-with-resources（推薦）

千萬不要再構造函數調用重載函數，非要調用函數請使用final函數

Java 8 實戰腦圖

UnPooled.copiedBuffer與wrappedBuffer的使用

https://yachay.unat.edu.pe/blog/index.php?comment_area=format_blog&comment_component=blog&comment_co

linux以太網驅動總結

Spring實戰（第4版）Spring In Action - 第4章 面向切面的Spring

第4章 面向切面的Spring

4.1 什麼是面向切面編程

4.1.4 定義AOP術語

4.1.2 Spring對AOP的支持

4.2 通過切點來選擇連接點

4.2.1 編寫切點

4.2.2 在切點中選擇bean

4.3 使用註解創建切面

4.3.1 定義切面

4.3.2 創建環繞通知

4.3.3 處理通知中的參數

4.3.4 通過註解引入新功能

4.4 在XML中聲明切面

4.4.1 聲明前置和後置通知

4.4.2 聲明環繞通知

4.4.3 爲通知傳遞參數

4.4 通過切面引入新的功能

Spring實戰（第4版）Spring In Action - 第4章面向切面的Spring

第4章面向切面的Spring