Converter转换规则变更，空对象、空值转为Bean时，创建默认对象，而非nul

hutool-core/src/main/java/org/dromara/hutool/core/convert/CompositeConverter.java

@@ -16,6 +16,7 @@ import org.dromara.hutool.core.bean.BeanUtil;
 import org.dromara.hutool.core.bean.RecordUtil;
 import org.dromara.hutool.core.convert.impl.*;
 import org.dromara.hutool.core.lang.Opt;
+import org.dromara.hutool.core.reflect.ConstructorUtil;
 import org.dromara.hutool.core.reflect.TypeReference;
 import org.dromara.hutool.core.reflect.TypeUtil;
 import org.dromara.hutool.core.reflect.kotlin.KClassUtil;
@@ -258,6 +259,12 @@ public class CompositeConverter extends RegisterConverter {
 			return (T) ClassConverter.INSTANCE.convert(type, value);
 		}
 
+		// 空值转空Bean
+		if(ObjUtil.isEmpty(value)){
+			// issue#3649 空值转空对象，则直接实例化
+			return ConstructorUtil.newInstanceIfPossible(rowType);
+		}
+
 		// 表示非需要特殊转换的对象
 		return null;
 	}

hutool-core/src/test/java/org/dromara/hutool/core/convert/CompositeConverterTest.java

@@ -12,40 +12,52 @@
 
 package org.dromara.hutool.core.convert;
 
-import org.junit.jupiter.api.Assertions;
+import lombok.Data;
 import org.junit.jupiter.api.Test;
 
 import java.lang.reflect.Type;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
 /**
  * ConverterRegistry 单元测试
- * @author Looly
  *
+ * @author Looly
  */
 public class CompositeConverterTest {
+	@Test
+	void convertEmptyTest() {
+		final Object convert = CompositeConverter.getInstance().convert(EmptyBean.class, "");
+		assertNotNull(convert);
+		assertEquals(new EmptyBean(), convert);
+	}
+
+	@Data
+	public static class EmptyBean {}
 
 	@Test
 	public void getConverterTest() {
 		final Converter converter = CompositeConverter.getInstance().getConverter(CharSequence.class, false);
-		Assertions.assertNotNull(converter);
+		assertNotNull(converter);
 	}
 
 	@Test
-	public void customTest(){
+	public void customTest() {
 		final int a = 454553;
 		final CompositeConverter compositeConverter = CompositeConverter.getInstance();
 
 		CharSequence result = (CharSequence) compositeConverter.convert(CharSequence.class, a);
-		Assertions.assertEquals("454553", result);
+		assertEquals("454553", result);
 
 		//此处做为示例自定义CharSequence转换，因为Hutool中已经提供CharSequence转换，请尽量不要替换
 		//替换可能引发关联转换异常（例如覆盖CharSequence转换会影响全局）
 		compositeConverter.putCustom(CharSequence.class, new CustomConverter());
 		result = (CharSequence) compositeConverter.convert(CharSequence.class, a);
-		Assertions.assertEquals("Custom: 454553", result);
+		assertEquals("Custom: 454553", result);
 	}
 
-	public static class CustomConverter implements Converter{
+	public static class CustomConverter implements Converter {
 		@Override
 		public Object convert(final Type targetType, final Object value) throws ConvertException {
 			return "Custom: " + value.toString();

hutool-core/src/test/java/org/dromara/hutool/core/util/Issue3136Test.java

@@ -34,7 +34,7 @@ public class Issue3136Test {
 		final SmsRes smsRes = XmlUtil.xmlToBean(XmlUtil.parseXml(xmlStr).getDocumentElement(), SmsRes.class);
 
 		Assertions.assertEquals("02", smsRes.getCode());
-		Assertions.assertNull(smsRes.getMessage());
+		Assertions.assertEquals(new Message(), smsRes.getMessage());
 	}
 
 	@Data

hutool-json/src/main/java/org/dromara/hutool/json/convert/JSONConverter.java

@@ -293,6 +293,12 @@ public class JSONConverter implements Converter, Serializable {
 			return (T) RecordConverter.INSTANCE.convert(type, value);
 		}
 
+		// 空值转空Bean
+		if(ObjUtil.isEmpty(value)){
+			// issue#3649 空值转空对象，则直接实例化
+			return ConstructorUtil.newInstanceIfPossible(rowType);
+		}
+
 		// 表示非需要特殊转换的对象
 		return null;
 	}

hutool-json/src/test/java/org/dromara/hutool/json/Issue2564Test.java

@@ -12,8 +12,7 @@
 
 package org.dromara.hutool.json;
 
-import lombok.Getter;
-import lombok.Setter;
+import lombok.Data;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
@@ -23,14 +22,19 @@ public class Issue2564Test {
 	 * 实力类 没有get set方法，不能被认为是一个bean
 	 */
 	@Test()
-	public void emptyToBeanTest(){
-		final String x = "{}";
-		final A a = JSONUtil.toBean(x, JSONConfig.of().setIgnoreError(true), A.class);
+	public void emptyToBeanTest() {
+		// 空对象转为一个空Bean，返回默认空实例
+		String x = "{}" ;
+		A a = JSONUtil.toBean(x, JSONConfig.of().setIgnoreError(true), A.class);
+		Assertions.assertEquals(new A(), a);
+
+		// 非空对象转为一个空bean，转换失败
+		x = "{\"a\": 1}" ;
+		a = JSONUtil.toBean(x, JSONConfig.of().setIgnoreError(true), A.class);
 		Assertions.assertNull(a);
 	}
 
-	@Getter
-	@Setter
-	public static class A{
+	@Data
+	public static class A {
 	}
 }

hutool-json/src/test/java/org/dromara/hutool/json/Issue3649Test.java

@@ -0,0 +1,16 @@
+package org.dromara.hutool.json;
+
+import lombok.Data;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class Issue3649Test {
+	@Test
+	void toEmptyBeanTest() {
+		final Object bean = JSONUtil.toBean("{}", JSONConfig.of().setIgnoreError(false), EmptyBean.class);
+		Assertions.assertEquals(new EmptyBean(), bean);
+	}
+
+	@Data
+	public static class EmptyBean {}
+}