一、AOP介紹

AOP（Aspect Oriented Programming）意為：面向切面編程，通過(guò)預(yù)編譯方式和運(yùn)行期動(dòng)態(tài)代理實(shí)現(xiàn)程序功能的統(tǒng)一維護(hù)的一種技術(shù)编饺。AOP是OOP的延續(xù)壁酬，是軟件開(kāi)發(fā)中的一個(gè)熱點(diǎn)，也是Spring框架中的一個(gè)重要內(nèi)容酣栈，是函數(shù)式編程的一種衍生范型。利用AOP可以對(duì)業(yè)務(wù)邏輯的各個(gè)部分進(jìn)行隔離汹押，從而使得業(yè)務(wù)邏輯各部分之間的耦合度降低矿筝，提高程序的可重用性，同時(shí)提高了開(kāi)發(fā)的效率棚贾。

理解

u=2029981592,3062824930&fm=26&gp=0

1. 原理探究

AOP是Aspect Oriented Programming窖维，即面向切面編程。

那什么是AOP妙痹？

我們先回顧一下OOP：Object Oriented Programming铸史，OOP作為面向?qū)ο缶幊痰哪Ｊ剑@得了巨大的成功怯伊，OOP的主要功能是數(shù)據(jù)封裝琳轿、繼承和多態(tài)。

而AOP是一種新的編程方式，它和OOP不同崭篡，OOP把系統(tǒng)看作多個(gè)對(duì)象的交互挪哄，AOP把系統(tǒng)分解為不同的關(guān)注點(diǎn)，或者稱(chēng)之為切面（Aspect）琉闪。

要理解AOP的概念迹炼，我們先用OOP舉例，比如一個(gè)業(yè)務(wù)組件BookService颠毙，它有幾個(gè)業(yè)務(wù)方法：

• createBook：添加新的Book斯入；

• updateBook：修改Book；

• deleteBook：刪除Book吟秩。

對(duì)每個(gè)業(yè)務(wù)方法咱扣，例如，createBook()，除了業(yè)務(wù)邏輯，還需要安全檢查疚顷、日志記錄和事務(wù)處理，它的代碼像這樣：

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n30" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">public class BookService {
public void createBook(Book book) {
securityCheck();
Transaction tx = startTransaction();
try {
// 核心業(yè)務(wù)邏輯
tx.commit();
} catch (RuntimeException e) {
tx.rollback();
throw e;
}
log("created book: " + book);
}
}</pre>

繼續(xù)編寫(xiě)updateBook()偏瓤，代碼如下：

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n32" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">public class BookService {
public void updateBook(Book book) {
securityCheck();
Transaction tx = startTransaction();
try {
// 核心業(yè)務(wù)邏輯
tx.commit();
} catch (RuntimeException e) {
tx.rollback();
throw e;
}
log("updated book: " + book);
}
}</pre>

對(duì)于安全檢查、日志椰憋、事務(wù)等代碼厅克，它們會(huì)重復(fù)出現(xiàn)在每個(gè)業(yè)務(wù)方法中。使用OOP橙依，我們很難將這些四處分散的代碼模塊化证舟。

考察業(yè)務(wù)模型可以發(fā)現(xiàn)，BookService關(guān)心的是自身的核心邏輯窗骑，但整個(gè)系統(tǒng)還要求關(guān)注安全檢查女责、日志、事務(wù)等功能创译，這些功能實(shí)際上“橫跨”多個(gè)業(yè)務(wù)方法抵知，為了實(shí)現(xiàn)這些功能，不得不在每個(gè)業(yè)務(wù)方法上重復(fù)編寫(xiě)代碼软族。

一種可行的方式是使用Proxy模式刷喜，將某個(gè)功能，例如立砸，權(quán)限檢查掖疮，放入Proxy中：

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n36" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">public class SecurityCheckBookService implements BookService {
private final BookService target;

public SecurityCheckBookService(BookService target) {
this.target = target;
}

public void createBook(Book book) {
securityCheck();
target.createBook(book);
}

public void updateBook(Book book) {
securityCheck();
target.updateBook(book);
}

public void deleteBook(Book book) {
securityCheck();
target.deleteBook(book);
}

private void securityCheck() {
...
}
}</pre>

這種方式的缺點(diǎn)是比較麻煩，必須先抽取接口仰禽，然后氮墨，針對(duì)每個(gè)方法實(shí)現(xiàn)Proxy纺蛆。

另一種方法是吐葵，既然SecurityCheckBookService的代碼都是標(biāo)準(zhǔn)的Proxy樣板代碼规揪，不如把權(quán)限檢查視作一種切面（Aspect），把日志温峭、事務(wù)也視為切面猛铅，然后，以某種自動(dòng)化的方式凤藏，把切面織入到核心邏輯中奸忽，實(shí)現(xiàn)Proxy模式。

如果我們以AOP的視角來(lái)編寫(xiě)上述業(yè)務(wù)揖庄，可以依次實(shí)現(xiàn)：

1. 核心邏輯栗菜，即BookService；

2. 切面邏輯蹄梢，即：

3. 權(quán)限檢查的Aspect疙筹；

4. 日志的Aspect；

5. 事務(wù)的Aspect禁炒。

然后而咆，以某種方式，讓框架來(lái)把上述3個(gè)Aspect以Proxy的方式“織入”到BookService中幕袱，這樣一來(lái)暴备，就不必編寫(xiě)復(fù)雜而冗長(zhǎng)的Proxy模式。

AOP原理

如何把切面織入到核心邏輯中们豌？這正是AOP需要解決的問(wèn)題涯捻。換句話(huà)說(shuō)，如果客戶(hù)端獲得了BookService的引用望迎，當(dāng)調(diào)用bookService.createBook()時(shí)障癌，如何對(duì)調(diào)用方法進(jìn)行攔截，并在攔截前后進(jìn)行安全檢查擂煞、日志混弥、事務(wù)等處理，就相當(dāng)于完成了所有業(yè)務(wù)功能对省。

在Java平臺(tái)上蝗拿，對(duì)于AOP的織入，有3種方式：

1. 編譯期：在編譯時(shí)蒿涎，由編譯器把切面調(diào)用編譯進(jìn)字節(jié)碼哀托，這種方式需要定義新的關(guān)鍵字并擴(kuò)展編譯器，AspectJ就擴(kuò)展了Java編譯器劳秋，使用關(guān)鍵字aspect來(lái)實(shí)現(xiàn)織入仓手；

2. 類(lèi)加載器：在目標(biāo)類(lèi)被裝載到JVM時(shí)胖齐，通過(guò)一個(gè)特殊的類(lèi)加載器，對(duì)目標(biāo)類(lèi)的字節(jié)碼重新“增強(qiáng)”嗽冒；

3. 運(yùn)行期：目標(biāo)對(duì)象和切面都是普通Java類(lèi)呀伙，通過(guò)JVM的動(dòng)態(tài)代理功能或者第三方庫(kù)實(shí)現(xiàn)運(yùn)行期動(dòng)態(tài)織入。

最簡(jiǎn)單的方式是第三種添坊，Spring的AOP實(shí)現(xiàn)就是基于JVM的動(dòng)態(tài)代理剿另。由于JVM的動(dòng)態(tài)代理要求必須實(shí)現(xiàn)接口，如果一個(gè)普通類(lèi)沒(méi)有業(yè)務(wù)接口贬蛙，就需要通過(guò)CGLIB或者Javassist這些第三方庫(kù)實(shí)現(xiàn)雨女。

AOP技術(shù)看上去比較神秘，但實(shí)際上阳准，它本質(zhì)就是一個(gè)動(dòng)態(tài)代理氛堕，讓我們把一些常用功能如權(quán)限檢查、日志野蝇、事務(wù)等讼稚，從每個(gè)業(yè)務(wù)方法中剝離出來(lái)。

需要特別指出的是浪耘，AOP對(duì)于解決特定問(wèn)題乱灵，例如事務(wù)管理非常有用，這是因?yàn)榉稚⒃诟魈幍氖聞?wù)代碼幾乎是完全相同的七冲，并且它們需要的參數(shù)（JDBC的Connection）也是固定的痛倚。另一些特定問(wèn)題，如日志澜躺，就不那么容易實(shí)現(xiàn)蝉稳，因?yàn)槿罩倦m然簡(jiǎn)單，但打印日志的時(shí)候掘鄙，經(jīng)常需要捕獲局部變量耘戚，如果使用AOP實(shí)現(xiàn)日志，我們只能輸出固定格式的日志操漠，因此收津，使用AOP時(shí)，必須適合特定的場(chǎng)景浊伙。

2. AOP常用實(shí)現(xiàn)方式

AOP常用的實(shí)現(xiàn)方式有兩種撞秋，

1、采用聲明的方式來(lái)實(shí)現(xiàn)（基于XML）嚣鄙，

2吻贿、是采用注解的方式來(lái)實(shí)現(xiàn)（基于AspectJ）。

3. AOP中一些比較重要的概念

• 橫切關(guān)注點(diǎn)：跨越應(yīng)用程序多個(gè)模塊的方法或功能哑子。即是舅列，與我們業(yè)務(wù)邏輯無(wú)關(guān)的肌割，但是我們需要關(guān)注的部分，就是橫切關(guān)注點(diǎn)帐要。如日志 , 安全 , 緩存 , 事務(wù)等等 ....

• <mark style="box-sizing: border-box; background: rgb(255, 255, 0); color: rgb(0, 0, 0);">切面（ASPECT）</mark>：橫切關(guān)注點(diǎn) 被模塊化 的特殊對(duì)象把敞。即，它是一個(gè)類(lèi)宠叼。（把通知應(yīng)用到切入點(diǎn)的過(guò)程）

• <mark style="box-sizing: border-box; background: rgb(255, 255, 0); color: rgb(0, 0, 0);">通知/增強(qiáng)（Advice）</mark>：切面必須要完成的工作先巴。即其爵，它是類(lèi)中的一個(gè)方法冒冬。說(shuō)的通俗點(diǎn)，就是在指定切點(diǎn)上要干些什么摩渺。

  • 前置通知 Before

  • 后置通知 afterReturning

  • 環(huán)繞通知 Around

  • 異常通知 AfterThrowing

  • 最終通知 after

• 目標(biāo)（Target）：被通知對(duì)象简烤。

• 代理（Proxy）：向目標(biāo)對(duì)象應(yīng)用通知之后創(chuàng)建的對(duì)象。

• <mark style="box-sizing: border-box; background: rgb(255, 255, 0); color: rgb(0, 0, 0);">切入點(diǎn)（PointCut）</mark>：切面通知 執(zhí)行的 “地點(diǎn)”的定義摇幻。（真正被增強(qiáng)的方方法）

• <mark style="box-sizing: border-box; background: rgb(255, 255, 0); color: rgb(0, 0, 0);">連接點(diǎn)（JointPoint）</mark>：與切入點(diǎn)匹配的執(zhí)行點(diǎn)横侦。在Spring中就是某一個(gè)方法的執(zhí)行 。（簡(jiǎn)單理解：哪些方法可以被增強(qiáng)绰姻？）

注意：

在使用spring框架配置AOP的時(shí)候枉侧，不管是通過(guò)XML配置文件還是注解的方式都需要定義pointcut"切入點(diǎn)"。

<mark style="box-sizing: border-box; background: rgb(255, 255, 0); color: rgb(0, 0, 0);">execution([權(quán)限修飾符] [返回類(lèi)型] [類(lèi)全路徑] [方法名稱(chēng)] ([參數(shù)列表]))</mark>

例如定義切入點(diǎn)表達(dá)式 execution(* com.sample.service.impl..(..))

execution()是最常用的切點(diǎn)函數(shù)狂芋，其語(yǔ)法如下所示：

整個(gè)表達(dá)式可以分為五個(gè)部分：

(1)榨馁、execution(): 表達(dá)式主體。

(2)帜矾、第一個(gè)*號(hào)：表示權(quán)限修飾符翼虫，可以是public等

(3)、包名：表示需要攔截的包名屡萤，后面的兩個(gè)句點(diǎn)表示當(dāng)前包和當(dāng)前包的所有子包珍剑，com.sample.service.impl包、子孫包下所有類(lèi)的方法死陆。

(4)招拙、第二個(gè)號(hào)：表示類(lèi)名，號(hào)表示所有的類(lèi)措译。

(5)别凤、(..):最后這個(gè)星號(hào)表示方法名，號(hào)表示所有的方法瞳遍，后面括弧里面表示方法的參數(shù)闻妓，兩個(gè)句點(diǎn)表示任何參數(shù)。

二掠械、AOP在spring中的應(yīng)用

1. 基于XML配置的Spring AOP

1. 導(dǎo)入Aop織入依賴(lài)

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="xml" cid="n110" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>1.9.4</version>
</dependency></pre>

2. 添加業(yè)務(wù)接口

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n112" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">public interface UserService {
/**
*功能描述: 執(zhí)行查詢(xún)

• @author mfei
• @date 2021/3/12
  */
  void select();
  }</pre>

3. 業(yè)務(wù)實(shí)現(xiàn)

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n114" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">public class UserServiceImpl implements UserService {

/**

• 功能描述: 執(zhí)行查詢(xún)
• @author mfei
• @date 2022/2/12
  */
  public void select() {
  System.out.println("執(zhí)行查詢(xún)用戶(hù)的方法");
  }
  }</pre>

4. 創(chuàng)建切面類(lèi)

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n116" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">public class AopAspect {
/**

• 前置通知：目標(biāo)方法調(diào)用之前執(zhí)行的代碼
• @param jp 目標(biāo)方法
  /
  public void doBefore(JoinPoint jp){
  System.out.println("===========執(zhí)行前置通知============");
  }
  /*
• 最終通知：目標(biāo)方法調(diào)用之后執(zhí)行的代碼（無(wú)論目標(biāo)方法是否出現(xiàn)異常均執(zhí)行）
• 因?yàn)榉椒赡軙?huì)出現(xiàn)異常由缆，所以不能返回方法的返回值
• @param jp 目標(biāo)方法
  */
  public void doAfter(JoinPoint jp){
  System.out.println("===========執(zhí)行最終通知============");
  }

/**

• 環(huán)繞通知：目標(biāo)方法調(diào)用前后執(zhí)行的代碼注祖，可以在方法調(diào)用前后完成自定義的行為。
• 包圍一個(gè)連接點(diǎn)（join point）的通知均唉。它會(huì)在切入點(diǎn)方法執(zhí)行前執(zhí)行同時(shí)方法結(jié)束也會(huì)執(zhí)行對(duì)應(yīng)的部分是晨。
• 主要是調(diào)用proceed()方法來(lái)執(zhí)行切入點(diǎn)方法，來(lái)作為環(huán)繞通知前后方法的分水嶺舔箭。
• 環(huán)繞通知類(lèi)似于動(dòng)態(tài)代理的全過(guò)程：ProceedingJoinPoint類(lèi)型的參數(shù)可以決定是否執(zhí)行目標(biāo)方法罩缴。
• 而且環(huán)繞通知必須有返回值，返回值即為目標(biāo)方法的返回值
• @param pjp 目標(biāo)方法
• @return 返回值
• @throws Throwable 異常接口
  /
  public Object doAround(ProceedingJoinPoint pjp) throws Throwable{
  System.out.println("======執(zhí)行環(huán)繞通知開(kāi)始=========");
  // 調(diào)用方法的參數(shù)
  Object[] args = pjp.getArgs();
  // 調(diào)用的方法名
  String method = pjp.getSignature().getName();
  // 獲取目標(biāo)對(duì)象
  Object target = pjp.getTarget();
  // 執(zhí)行完方法的返回值
  // 調(diào)用proceed()方法层扶，就會(huì)觸發(fā)切入點(diǎn)方法執(zhí)行
  Object result=pjp.proceed();
  System.out.println("輸出,方法名：" + method + ";目標(biāo)對(duì)象：" + target + ";返回值：" + result);
  System.out.println("======執(zhí)行環(huán)繞通知結(jié)束=========");
  return result;
  }
  @AfterThrowing("execution( com.shida.dao.service.UserServiceImpl.*(..))")
  public void doAfterThrowing(){
  System.out.println("======在異常之后執(zhí)行=========");
  }
  }</pre>

5. spring配置

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="xml" cid="n118" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop.xsd">

<bean id="userService" class="com.shida.service.impl.UserServiceImpl"/>

<bean id="aspectBean" class="com.shida.aspect.AopAspect" />
<aop:config>
<aop:aspect ref="aspectBean">
<aop:pointcut id="pointcut" expression="execution(* com.shida.service.impl.UserServiceImpl..*(..))"/>
<aop:before method="doBefore" pointcut-ref="pointcut"/>
<aop:after method="doAfter" pointcut-ref="pointcut" />
<aop:around method="doAround" pointcut-ref="pointcut"/>
</aop:aspect>
</aop:config>

</beans>
</pre>

6. 測(cè)試類(lèi)

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n120" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"> @Test
public void testAop(){
ApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
UserService userService = (UserService) context.getBean("userService");
userService.select();
}</pre>

image-20210312105555314

2. 基于注解實(shí)現(xiàn)

采用注解來(lái)做aop, 主要是將寫(xiě)在spring 配置文件中的連接點(diǎn)寫(xiě)到注解里面箫章。

業(yè)務(wù)接口和業(yè)務(wù)實(shí)現(xiàn)與上邊一樣，具體切面類(lèi)如下：

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n125" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">package com.shida.aspect;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;

/**

• Description：
• @author mfei
• @date 2022/2/12
  /
  @Aspect
  public class AnnotationAopAspect {
  @Before("execution( com.shida.service.impl.UserServiceImpl.(..))")
  public void doBefore(){
  System.out.println("---------方法執(zhí)行前---------");
  }

@After("execution(* com.shida.service.impl.UserServiceImpl.*(..))")
public void doAfter(){
System.out.println("===========執(zhí)行最終通知============");
}

@Around("execution(* com.shida.service.impl.UserServiceImpl.*(..))")
public Object doAround(ProceedingJoinPoint jp) throws Throwable {
System.out.println("======執(zhí)行環(huán)繞通知開(kāi)始=========");
// 調(diào)用方法的參數(shù)
Object[] args = jp.getArgs();
// 調(diào)用的方法名
String method = jp.getSignature().getName();
// 獲取目標(biāo)對(duì)象
Object target = jp.getTarget();
// 執(zhí)行完方法的返回值
// 調(diào)用proceed()方法镜会，就會(huì)觸發(fā)切入點(diǎn)方法執(zhí)行
Object result=jp.proceed();
System.out.println("輸出,方法名：" + method + ";目標(biāo)對(duì)象：" + target + ";返回值：" + result);
System.out.println("======執(zhí)行環(huán)繞通知結(jié)束=========");
return result;
}
}</pre>

spring配置

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="xml" cid="n127" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;"><beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop.xsd">

<context:component-scan base-package="com.shida.dao"/>

<bean id="hello" class="com.shida.entity.Hello">
<property name="name" value="Spring"/>
</bean>

<bean id="userService" class="com.shida.service.impl.UserServiceImpl"/>

<bean id="annotationPointcut" class="com.shida.aspect.AnnotationPointcut"/>

<aop:aspectj-autoproxy/>

</beans></pre>

注：若有兩個(gè)增強(qiáng)類(lèi)對(duì)同一方法進(jìn)行增強(qiáng)檬寂，可以設(shè)置@Order(1) ,數(shù)字越小，執(zhí)行順序越提前

Aop底層實(shí)現(xiàn)：動(dòng)態(tài)代理

1.動(dòng)態(tài)代理：有接口的情況

JDK動(dòng)態(tài)代理實(shí)現(xiàn)戳表，創(chuàng)建接口實(shí)現(xiàn)類(lèi)的代理對(duì)象桶至，增強(qiáng)類(lèi)的方法

底層實(shí)現(xiàn)原理：implements

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n133" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">public interface UserDao {
/**
*功能描述: 獲取用戶(hù)信息

• @author mfei
• @date 2022/2/25
  */
  void getUser();
  }</pre>

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n134" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">public class UserDaoImpl implements UserDao {

@Override
public void getUser() {
System.out.println("獲取到了用戶(hù)信息");
}
}</pre>

jdk動(dòng)態(tài)代理Proxy

Java 8 中文版 - 在線(xiàn)API中文手冊(cè) - 碼工具 (matools.com)

image-20220227113032721

參數(shù)理解：

interfaces 增強(qiáng)方法所在的類(lèi)：這個(gè)類(lèi)實(shí)現(xiàn)的接口，支持多個(gè)接口

h 實(shí)現(xiàn)接口InvocationHandler匾旭，創(chuàng)建代理對(duì)象镣屹，寫(xiě)增強(qiáng)的方法

1. 創(chuàng)建接口，實(shí)現(xiàn)方法

   <pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n144" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit;">public interface UserDao {

   int add(int a, int b);

   String getUser(String id);

   }</pre>

   <pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n145" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit;">public class UserDaoImpl implements UserDao {
   @Override
   public int add(int a, int b) {
   return a+b;
   }

   @Override
   public String getUser(String id) {
   return id;
   }
   }</pre>

2. 使用Proxy類(lèi)創(chuàng)建接口的代理對(duì)象

   <pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n148" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit;">public class JDKProxy {

   public static void main(String[] args) {
   Class[] interfaces = {UserDao.class};
   // 創(chuàng)建接口實(shí)現(xiàn)類(lèi)
   Proxy.newProxyInstance(JDKProxy.class.getClassLoader(), interfaces, new InvocationHandler() {
   // 匿名內(nèi)部類(lèi)
   @Override
   public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
   return null;
   }
   });

   }</pre>

   不適用匿名內(nèi)部類(lèi)

   完整代碼：

   <pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n151" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit;">public class JDKProxy {

   public static void main(String[] args) {
   Class[] interfaces = {UserDao.class};
   UserDaoImpl userDao = new UserDaoImpl();
   UserDao user = (UserDao) Proxy.newProxyInstance(JDKProxy.class.getClassLoader(), interfaces, new UseDaoProxy(userDao));
   int add = user.add(1, 2);
   System.out.println(add);
   }
   }
   class UseDaoProxy implements InvocationHandler{
   private Object obj;
   public UseDaoProxy(Object obj) {
   this.obj = obj;
   }

 @Override
 public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
 System.out.println("方法之前執(zhí)行"+method.getName()+"傳遞的參數(shù)"+ Arrays.toString(args));
 Object invoke = method.invoke(obj, args);
 System.out.println(invoke);
 System.out.println(obj);
 return invoke;
 }
}</pre>

2.沒(méi)有接口情況的動(dòng)態(tài)代理

底層實(shí)現(xiàn)原理：extends

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n155" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">/**

• Description：
• @author mfei
• Date: 2022/2/25 9:36
  **/
  public class UserService {

public void getUser(){
System.out.println("獲取到了用戶(hù)信息");
}
}</pre>

<pre class="md-fences md-end-block ty-contain-cm modeLoaded" spellcheck="false" lang="java" cid="n156" mdtype="fences" style="box-sizing: border-box; overflow: visible; font-family: var(--monospace); font-size: 0.9em; display: block; break-inside: avoid; text-align: left; white-space: normal; background-image: inherit; background-position: inherit; background-size: inherit; background-repeat: inherit; background-attachment: inherit; background-origin: inherit; background-clip: inherit; background-color: rgb(248, 248, 248); position: relative !important; border: 1px solid rgb(231, 234, 237); border-radius: 3px; padding: 8px 4px 6px; margin-bottom: 15px; margin-top: 15px; width: inherit; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;">public class PersonService extends UserService {

@Override
public void getUser() {
super.getUser();
// 增強(qiáng)的邏輯
}
}</pre>

通過(guò)CGLIB動(dòng)態(tài)代理

實(shí)現(xiàn)MethodInterceptor接口