Spring 条件装配 Condition 分析

1. 条件装配 Condition

三个过滤器：OnClassCondition, OnBeanCondition, OnWebApplicationCondition

顶层接口Condition

@FunctionalInterface
public interface Condition {
    boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata);
}

条件装配 AutoConfigurationImportSelector.ConfigurationClassFilter#filter

public class AutoConfigurationImportSelector implements DeferredImportSelector, BeanClassLoaderAware,
        ResourceLoaderAware, BeanFactoryAware, EnvironmentAware, Ordered {

    private static class ConfigurationClassFilter {

        private final List<AutoConfigurationImportFilter> filters;

        List<String> filter(List<String> configurations) {
            // ...
            for (AutoConfigurationImportFilter filter : this.filters) {
                boolean[] match = filter.match(candidates, this.autoConfigurationMetadata);
                // ...
        }
    }
}

public interface AutoConfigurationImportFilter {
    boolean[] match(String[] autoConfigurationClasses, AutoConfigurationMetadata autoConfigurationMetadata);
}

具体实现

abstract class FilteringSpringBootCondition extends SpringBootCondition
        implements AutoConfigurationImportFilter, BeanFactoryAware, BeanClassLoaderAware {

    @Override
    public boolean[] match(String[] autoConfigurationClasses, AutoConfigurationMetadata autoConfigurationMetadata) {
        ConditionEvaluationReport report = ConditionEvaluationReport.find(this.beanFactory);
        ConditionOutcome[] outcomes = getOutcomes(autoConfigurationClasses, autoConfigurationMetadata);
        boolean[] match = new boolean[outcomes.length];
        for (int i = 0; i < outcomes.length; i++) {
            match[i] = (outcomes[i] == null || outcomes[i].isMatch());
            if (!match[i] && outcomes[i] != null) {
                logOutcome(autoConfigurationClasses[i], outcomes[i]);
                if (report != null) {
                    report.recordConditionEvaluation(autoConfigurationClasses[i], this, outcomes[i]);
                }
            }
        }
        return match;
    }
}