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In some cases, proxy objects are created without a target object. The most common case for this is for creating remote access and Java Management eXtension (JMX) client-side stub objects using the Spring AOP framework. This is the most likely scenario when the target object that is passed to advice objects is null.

AOP frameworks allow you to define which advice is applied to which methods. The proxy object created by ProxyFactoryBean in the previous examples calls TextMessageSendingAdvice for each method invoked, which is the default behavior. However, only when a match ends should a text message be sent. To achieve this, we can specify that the advice we re configuring should be invoked only for the endMatch() method. Specifying the advice and method involves using what AOP terms join points and pointcuts. Although the term join point has a broader meaning, Spring AOP supports only method invocations as join points. A pointcut selects zero or more join points on the target object. Spring AOP has a number of pointcut classes you can use to select join points: org.springframwork.aop.support.NameMatchMethodPointcut: Selects join points based on method names. This class matches method names using an Ant-style wildcard notation (for example, both *Match or end* select the endMatch() method name). It s used like this:

<bean id="endMatchMethodPointcut" class="org.springframework.aop.support.NameMatchMethodPointcut"> <property name="mappedName" value="endMatch"/> </bean> org.springframwork.aop.support.JdkRegexpMethodPointcut: Selects join points based on method names. This class matches method names using regular expressions and works only with Java 1.4 and newer because it uses the java.util.regexp package. org.springframwork.aop.support.Perl5RegexpMethodPointcut: Selects join points based on method names. This class matches method names using regular expressions and uses the Jakarta ORO open source regular expression library; thus, it supports Java 1.3. When using the regular expression based pointcut classes to match method names, the package name, class name, or method name can be matched, offering a more powerful selection mechanism. Here s an example of the string to match: com.apress.springbook.chapter03.TournamentMatchManager.endMatch To match the endMatch() method, use the regular expression \.endMatch$, which will select the last part of the full method name. Here s this regular expression in use: <bean id="endMatchMethodPointcut" class="org.springframework.aop.support.JdkRegExpMethodPointcut"> <property name="pattern" value="\.endMatch$"/> </bean> You should use the simplest pointcut class that works for your use case. NameMatchMethodPointcut suffices in almost all situations.

Pointcuts select zero or more join points (their selection may select no methods). You need to use them in combination with an advice to define to which methods the advice applies. An advisor takes a pointcut and an advice object and is passed to ProxyFactoryBean. Listing 3-14 shows an example. Listing 3-14. Using DefaultPointcutAdvisor to Configure a Pointcut and an Interceptor <bean id="sendTextMessageWhenMatchEnds" class="org.springframework.aop.support.DefaultPointcutAdvisor"> <property name="pointcut" ref="endMatchMethodPointcut"/> <property name="advice" ref="textMessageSendingAdvice"/> </bean> <bean id="tournamentMatchManager" class="org.springframework.aop.config.ProxyFactoryBean"> <property name="target"> <bean class="com.apress.springbook.chapter03.DefaultTournamentMatchManager"> <!-- other properties omitted --> </bean> </property> <property name="interceptorNames"> <list> <value>sendTextMessageWhenMatchEnds</value> </list> </property> </bean>

This example passes the name of the sendTextMessageWhenMatchEnds advisor to ProxyFactoryBean. This advisor applies textMessageSendingAdvice to all methods selected by the sendTextMessageWhenMatchStarts pointcut (both of which we ve configured in earlier sections). Other methods that are called on the proxy objects do not cause the advice to be invoked. Methods on proxy objects can have more than one advisor assigned to them. In this case, the order of execution is defined by the order in the XML configuration file. To control the proper ordering of multiple advisors, Spring AOP uses an advisor chain to execute all configured advisors sequentially.

Spring AOP provides convenience classes for the pointcut classes discussed earlier. These classes turn pointcut classes into advisors. Three classes are available: org.springframework.aop.support.NameMatchMethodPointcutAdvisor org.springframework.aop.support.JdkRegExpMethodPointcutAdvisor org.springframework.aop.support.Perl5RegExpMethodPointcutAdvisor These convenience classes inherit the properties defined in the pointcut class they extend and add the advice property. You should use these classes instead of a separate pointcut and an advisor class to reduce the number of lines in the XML configuration files, as shown in Listing 3-15. Listing 3-15. Using NameMatchMethodPoincutAdvisor to Simplify the XML Configuration <bean id="sendTextMessageWhenMatchStarts" class="org.springframework.aop.support.NameMatchMethodPointcutAdvisor"> <property name="mappedName" value="endMatch"/> <property name="advice" ref="textMessageSendingAdvice"/> </bean> <bean id="tournamentMatchManager" class="org.springframework.aop.config.ProxyFactoryBean"> <property name="target"> <bean class="com.apress.springbook.chapter03.DefaultTournamentMatchManager"> <!-- other properties omitted --> </bean> </property> <property name="interceptorNames"> <list> <value>sendTextMessageWhenMatchStarts</value> </list> </property> </bean> So, what happens when an advice is passed to ProxyFactoryBean without an advisor Spring AOP uses an advisor for the advice that matches all methods on the target object. As a result, an advice that is configured without an advisor will be applied to all methods of the target object.