add test

hutool-core/src/main/java/cn/hutool/core/convert/ConverterRegistry.java

@@ -266,7 +266,6 @@ public class ConverterRegistry implements Serializable {
 			}
 		}
 
-
 		// 特殊类型转换，包括Collection、Map、强转、Array等
 		final T result = convertSpecial(type, rowType, value, defaultValue);
 		if (null != result) {

hutool-json/src/main/java/cn/hutool/json/JSONNull.java

@@ -7,8 +7,8 @@ import java.io.Serializable;
 /**
  * 用于定义{@code null}，与Javascript中null相对应<br>
  * Java中的{@code null}值在js中表示为undefined。
- * @author Looly
  *
+ * @author Looly
  */
 public class JSONNull implements Serializable {
 	private static final long serialVersionUID = 2633815155870764938L;

hutool-json/src/main/java/cn/hutool/json/JSONUtil.java

@@ -743,7 +743,7 @@ public class JSONUtil {
 			return jsonConfig.isIgnoreNullValue() ? null : JSONNull.NULL;
 		}
 		if (object instanceof JSON //
-				|| JSONNull.NULL.equals(object) //
+				|| ObjectUtil.isNull(object) //
 				|| object instanceof JSONString //
 				|| object instanceof CharSequence //
 				|| object instanceof Number //

hutool-json/src/test/java/cn/hutool/json/Issue2131Test.java

@@ -0,0 +1,62 @@
+package cn.hutool.json;
+
+import cn.hutool.core.collection.ListUtil;
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+import lombok.experimental.Accessors;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.beans.Transient;
+import java.util.List;
+import java.util.stream.Stream;
+
+/**
+ * https://github.com/dromara/hutool/issues/2131<br>
+ * 字段定义成final，意味着setCollections无效，因此JSON转Bean的时候无法调用setCollections注入，所以是空的。
+ */
+public class Issue2131Test {
+
+	@Test
+	public void strToBean() {
+		GoodsResponse goodsResponse = new GoodsResponse();
+		GoodsItem apple = new GoodsItem().setGoodsId(1L).setGoodsName("apple").setChannel("wechat");
+		GoodsItem pear = new GoodsItem().setGoodsId(2L).setGoodsName("pear").setChannel("jd");
+		final List<GoodsItem> collections = goodsResponse.getCollections();
+		Stream.of(apple, pear).forEach(collections::add);
+
+		String jsonStr = JSONUtil.toJsonStr(goodsResponse);
+		final JSONObject jsonObject = JSONUtil.parseObj(jsonStr);
+
+		GoodsResponse result = jsonObject.toBean(GoodsResponse.class);
+		Assert.assertEquals(0, result.getCollections().size());
+	}
+
+	@Data
+	static class BaseResponse {
+
+		@SuppressWarnings("unused")
+		@Transient
+		public final boolean successful() {
+			return code == 200 || code == 201;
+		}
+
+		private int code = 200;
+		private String message;
+	}
+
+	@EqualsAndHashCode(callSuper = true)
+	@Data
+	static class GoodsResponse extends BaseResponse {
+		// 由于定义成了final形式，setXXX无效，导致无法注入。
+		private final List<GoodsItem> collections = ListUtil.list(false);
+	}
+
+	@Data
+	@Accessors(chain = true)
+	static class GoodsItem{
+		private long goodsId;
+		private String goodsName;
+		private String channel;
+	}
+}