!926 【轻量级 PR】：fix: convertXxxByFlatMap, 当map后内容为null时, flatMap会出现NPE

Merge pull request !926 from dhb52/N/A

yudao-framework/yudao-common/src/main/java/cn/iocoder/yudao/framework/common/util/collection/CollectionUtils.java

@@ -78,7 +78,7 @@ public class CollectionUtils {
         if (CollUtil.isEmpty(from)) {
             return new ArrayList<>();
         }
-        return from.stream().flatMap(func).filter(Objects::nonNull).collect(Collectors.toList());
+        return from.stream().filter(Objects::nonNull).flatMap(func).filter(Objects::nonNull).collect(Collectors.toList());
     }
 
     public static <T, U, R> List<R> convertListByFlatMap(Collection<T> from,
@@ -87,7 +87,7 @@ public class CollectionUtils {
         if (CollUtil.isEmpty(from)) {
             return new ArrayList<>();
         }
-        return from.stream().map(mapper).flatMap(func).filter(Objects::nonNull).collect(Collectors.toList());
+        return from.stream().map(mapper).filter(Objects::nonNull).flatMap(func).filter(Objects::nonNull).collect(Collectors.toList());
     }
 
     public static <K, V> List<V> mergeValuesFromMap(Map<K, List<V>> map) {
@@ -123,7 +123,7 @@ public class CollectionUtils {
         if (CollUtil.isEmpty(from)) {
             return new HashSet<>();
         }
-        return from.stream().flatMap(func).filter(Objects::nonNull).collect(Collectors.toSet());
+        return from.stream().filter(Objects::nonNull).flatMap(func).filter(Objects::nonNull).collect(Collectors.toSet());
     }
 
     public static <T, U, R> Set<R> convertSetByFlatMap(Collection<T> from,
@@ -132,7 +132,7 @@ public class CollectionUtils {
         if (CollUtil.isEmpty(from)) {
             return new HashSet<>();
         }
-        return from.stream().map(mapper).flatMap(func).filter(Objects::nonNull).collect(Collectors.toSet());
+        return from.stream().map(mapper).filter(Objects::nonNull).flatMap(func).filter(Objects::nonNull).collect(Collectors.toSet());
     }
 
     public static <T, K> Map<K, T> convertMap(Collection<T> from, Function<T, K> keyFunc) {
@@ -315,4 +315,4 @@ public class CollectionUtils {
         return list.stream().flatMap(Collection::stream).collect(Collectors.toList());
     }
 
-}
+}