【spring-boot】spring-boot学习之ImportSelector接口

ImportSelector接口是至spring中导入外部配置的核心接口，在SpringBoot的自动化配置和@EnableXXX(功能性注解)都有它的存在，关于SpringBoot的分析可以参考:https://www.cnblogs.com/niechen/p/9027804.html

其主要作用是收集需要导入的配置类，如果该接口的实现类同时实现EnvironmentAware， BeanFactoryAware ，BeanClassLoaderAware或者ResourceLoaderAware，那么在调用其selectImports方法之前先调用上述接口中对应的方法，如果需要在所有的@Configuration处理完在导入时可以实现DeferredImportSelector接口。

在这里我举个Spring中的实例来看一下：

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(TransactionManagementConfigurationSelector.class)
public @interface EnableTransactionManagement {

    /**
     * Indicate whether subclass-based (CGLIB) proxies are to be created ({@code true}) as
     * opposed to standard Java interface-based proxies ({@code false}). The default is
     * {@code false}. <strong>Applicable only if {@link #mode()} is set to
     * {@link AdviceMode#PROXY}</strong>.
     * <p>Note that setting this attribute to {@code true} will affect <em>all</em>
     * Spring-managed beans requiring proxying, not just those marked with
     * {@code @Transactional}. For example, other beans marked with Spring's
     * {@code @Async} annotation will be upgraded to subclass proxying at the same
     * time. This approach has no negative impact in practice unless one is explicitly
     * expecting one type of proxy vs another, e.g. in tests.
     */
    boolean proxyTargetClass() default false;

    /**
     * Indicate how transactional advice should be applied. The default is
     * {@link AdviceMode#PROXY}.
     * @see AdviceMode
     */
    AdviceMode mode() default AdviceMode.PROXY;

    /**
     * Indicate the ordering of the execution of the transaction advisor
     * when multiple advices are applied at a specific joinpoint.
     * The default is {@link Ordered#LOWEST_PRECEDENCE}.
     */
    int order() default Ordered.LOWEST_PRECEDENCE;

}

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