add cache for scan result. (#7477) (#8057)

* issue: Component scan two times for @service

* add cache for scan result. (#7477)

* remove redundant comments.

Co-authored-by: zhang.jie <zhangjie@pascall.xyz>
Co-authored-by: zhang.jie <zhangjie@rivamed.cn>

dubbo-config/dubbo-config-spring/src/main/java/org/apache/dubbo/config/spring/context/annotation/DubboClassPathBeanDefinitionScanner.java

@@ -17,13 +17,15 @@
 package org.apache.dubbo.config.spring.context.annotation;
 
 import org.springframework.beans.factory.config.BeanDefinition;
-import org.springframework.beans.factory.config.BeanDefinitionHolder;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
 import org.springframework.context.annotation.ClassPathBeanDefinitionScanner;
 import org.springframework.core.env.Environment;
 import org.springframework.core.io.ResourceLoader;
 
+import java.util.Objects;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
 
 import static org.springframework.context.annotation.AnnotationConfigUtils.registerAnnotationConfigProcessors;
 
@@ -36,6 +38,10 @@
  */
 public class DubboClassPathBeanDefinitionScanner extends ClassPathBeanDefinitionScanner {
 
+    /**
+     * key is package, value is BeanDefinition
+     */
+    private final ConcurrentMap<String, Set<BeanDefinition>> beanDefinitionMap = new ConcurrentHashMap<>();
 
     public DubboClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters, Environment environment,
                                                ResourceLoader resourceLoader) {
@@ -57,14 +63,19 @@ public DubboClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, Envi
 
     }
 
-    @Override
-    public Set<BeanDefinitionHolder> doScan(String... basePackages) {
-        return super.doScan(basePackages);
-    }
-
     @Override
     public boolean checkCandidate(String beanName, BeanDefinition beanDefinition) throws IllegalStateException {
         return super.checkCandidate(beanName, beanDefinition);
     }
 
+    @Override
+    public Set<BeanDefinition> findCandidateComponents(String basePackage) {
+        Set<BeanDefinition> beanDefinitions = beanDefinitionMap.get(basePackage);
+        // if beanDefinitions size is null => scan
+        if (Objects.isNull(beanDefinitions)) {
+            beanDefinitions = super.findCandidateComponents(basePackage);
+            beanDefinitionMap.put(basePackage, beanDefinitions);
+        }
+        return beanDefinitions;
+    }
 }