代码之家 › 专栏 › 技术社区 › Koray Tugay

为什么Spring框架中的MethodMatcher接口将targetClass作为参数,而切入点已经定义了类过滤器?

spring-aop spring java

Koray Tugay · 技术社区 · 7 年前

这个 Pointcut 中的接口 Spring Framework 包括2种方法:

public interface Pointcut {

    /**
     * Return the ClassFilter for this pointcut.
     * @return the ClassFilter (never {@code null})
     */
    ClassFilter getClassFilter();

    /**
     * Return the MethodMatcher for this pointcut.
     * @return the MethodMatcher (never {@code null})
     */
    MethodMatcher getMethodMatcher();


    /**
     * Canonical Pointcut instance that always matches.
     */
    Pointcut TRUE = TruePointcut.INSTANCE;

}

这个 ClassFilter 接口已经声明,其唯一目的是确定类是否可以通过过滤器:

/**
 * Filter that restricts matching of a pointcut or introduction to
 * a given set of target classes.
 *
 * <p>Can be used as part of a {@link Pointcut} or for the entire
 * targeting of an {@link IntroductionAdvisor}.
 *
 * @author Rod Johnson
 * @see Pointcut
 * @see MethodMatcher
 */
public interface ClassFilter {

    /**
     * Should the pointcut apply to the given interface or target class?
     * @param clazz the candidate target class
     * @return whether the advice should apply to the given target class
     */
    boolean matches(Class<?> clazz);


    /**
     * Canonical instance of a ClassFilter that matches all classes.
     */
    ClassFilter TRUE = TrueClassFilter.INSTANCE;

}

我不明白的是, 为什么 MethodMatcher 接口是否再次检查课程资格?为什么这个接口的方法有targetClass参数?

public interface MethodMatcher {

    /**
     * Perform static checking whether the given method matches. If this
     * returns {@code false} or if the {@link #isRuntime()} method
     * returns {@code false}, no runtime check (i.e. no.
     * {@link #matches(java.lang.reflect.Method, Class, Object[])} call) will be made.
     * @param method the candidate method
     * @param targetClass the target class (may be {@code null}, in which case
     * the candidate class must be taken to be the method's declaring class)
     * @return whether or not this method matches statically
     */
    boolean matches(Method method, Class<?> targetClass);

    /**
     * Check whether there a runtime (dynamic) match for this method,
     * which must have matched statically.
     * <p>This method is invoked only if the 2-arg matches method returns
     * {@code true} for the given method and target class, and if the
     * {@link #isRuntime()} method returns {@code true}. Invoked
     * immediately before potential running of the advice, after any
     * advice earlier in the advice chain has run.
     * @param method the candidate method
     * @param targetClass the target class (may be {@code null}, in which case
     * the candidate class must be taken to be the method's declaring class)
     * @param args arguments to the method
     * @return whether there's a runtime match
     * @see MethodMatcher#matches(Method, Class)
     */
    boolean matches(Method method, Class<?> targetClass, Object... args);


    /**
     * Canonical instance that matches all methods.
     */
    MethodMatcher TRUE = TrueMethodMatcher.INSTANCE;

}

1 回复 | 直到 7 年前

Indra Basak 7 年前

这个 targetClass 在中指定 MethodMatcher.matches(Method method, Class<?> targetClass) 不用于检查目标调用类的合格性 .

它用于 寻找最具体的目标方法 适用于给定方法(指定为参数)的目标类。它还解决了以下问题: Java bridge methods .

这是一个样本 matches 方法来自 org.springframework.aop.aspectj.AspectJExpressionPointcut 班

public boolean matches(Method method, Class<?> targetClass, boolean beanHasIntroductions) {
    this.checkReadyToMatch();
    Method targetMethod = AopUtils.getMostSpecificMethod(method, targetClass);
    ShadowMatch shadowMatch = this.getShadowMatch(targetMethod, method);
    ...
}

这是来自 org.springframework.aop.support.AopUtils#getMostSpecificMethod

给定一个方法(可能来自接口)和使用的目标类在当前的AOP调用中,如果有对应的目标方法,请找到相应的目标方法。E、 g.该方法可以是 IFoo.bar() 目标类可能是 DefaultFoo DefaultFoo.bar() . 这样可以找到该方法上的属性。

注: 与…对比 org.springframework.util.ClassUtils#getMostSpecificMethod ,该方法解析Java 5桥接方法,以便从 起初的 方法定义。