Spring AOP : APC 自动代理创建器 DefaultAdvisorAutoProxyCreator

概述

DefaultAdvisorAutoProxyCreator是Spring AOP内置的一个APC,它在容器每个bean初始化的后置处理阶段，从容器中找到所有的Spring Advisor bean,然后检测这些Advisor bean是否需要包裹到容器正在初始化的bean上。

DefaultAdvisorAutoProxyCreator要用的拦截器都来自于容器中匹配的Spring Advisors,而不考虑其他方式定义的aspects。

DefaultAdvisorAutoProxyCreator过滤某个Spring Advisor是否符合条件的方法isEligibleAdvisorBean覆盖了基类中的缺省实现。它有两种工作模式 :

1. 不使用Advisor bean名称前缀匹配方式 : 这种方式下认为每个Advisor都符合条件;
2. 使用Advisor bean名称前缀匹配方式 : 这种方式下认为仅仅Advisor bean名称符合指定前缀的Advisor才符合条件;

当前，符合以上isEligibleAdvisorBean条件的Advisor并不是都会应用到该APC当前所处理的bean上，还会根据bean类/方法上的注解考虑是否包裹一个Advisor。

源代码

源代码版本 : spring-aop-5.1.5.RELEASE

package org.springframework.aop.framework.autoproxy;

import org.springframework.beans.factory.BeanNameAware;
import org.springframework.lang.Nullable;

/**
 * BeanPostProcessor implementation that creates AOP proxies based on all
 * candidate Advisors in the current BeanFactory. This class is
 * completely generic; it contains no special code to handle any particular aspects,
 * such as pooling aspects.
 *
 * It's possible to filter out advisors - for example, to use multiple post processors
 * of this type in the same factory - by setting the usePrefix property to true,
 * in which case only advisors beginning with the DefaultAdvisorAutoProxyCreator's bean
 * name followed by a dot (like "aapc.") will be used. This default prefix can be changed
 * from the bean name by setting the advisorBeanNamePrefix property.
 * The separator (.) will also be used in this case.
 *
 * @author Rod Johnson
 * @author Rob Harrop
 */
@SuppressWarnings("serial")
public class DefaultAdvisorAutoProxyCreator extends AbstractAdvisorAutoProxyCreator implements BeanNameAware {

	/** Separator between prefix and remainder of bean name. */
	public static final String SEPARATOR = ".";


	private boolean usePrefix = false;

	@Nullable
	private String advisorBeanNamePrefix;


	/**
	 * Set whether to only include advisors with a certain prefix in the bean name.
	 * Default is false, including all beans of type Advisor.
	 * @see #setAdvisorBeanNamePrefix
	 */
	public void setUsePrefix(boolean usePrefix) {
		this.usePrefix = usePrefix;
	}

	/**
	 * Return whether to only include advisors with a certain prefix in the bean name.
	 */
	public boolean isUsePrefix() {
		return this.usePrefix;
	}

	/**
	 * Set the prefix for bean names that will cause them to be included for
	 * auto-proxying by this object. This prefix should be set to avoid circular
	 * references. Default value is the bean name of this object + a dot.
	 * @param advisorBeanNamePrefix the exclusion prefix
	 */
	public void setAdvisorBeanNamePrefix(@Nullable String advisorBeanNamePrefix) {
		this.advisorBeanNamePrefix = advisorBeanNamePrefix;
	}

	/**
	 * Return the prefix for bean names that will cause them to be included
	 * for auto-proxying by this object.
	 */
	@Nullable
	public String getAdvisorBeanNamePrefix() {
		return this.advisorBeanNamePrefix;
	}

	@Override
	public void setBeanName(String name) {
		// If no infrastructure bean name prefix has been set, override it.
		if (this.advisorBeanNamePrefix == null) {
			this.advisorBeanNamePrefix = name + SEPARATOR;
		}
	}


	/**
	 * Consider Advisor beans with the specified prefix as eligible, if activated.
	 * @see #setUsePrefix
	 * @see #setAdvisorBeanNamePrefix
	 */
	@Override
	protected boolean isEligibleAdvisorBean(String beanName) {
       // 使用该方法判断某个 Spring Advisor bean, bean 名称为 beanName 是否是符合条件的
       // Advisor
		if (!isUsePrefix()) {
          // 如果不使用前缀匹配机制，则认为 beanName 对应的 Advisor 总是符合条件
			return true;
		}
       
       // 如果使用前缀匹配机制，则仅在前缀匹配时才认为当前 Advisor bean 符合条件
		String prefix = getAdvisorBeanNamePrefix();
		return (prefix != null && beanName.startsWith(prefix));
	}

}

参考文章

• Spring AOP : APC 自动代理创建器 AbstractAutoProxyCreator