add converter for json

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

@@ -29,9 +29,6 @@ import cn.hutool.core.convert.impl.XMLGregorianCalendarConverter;
 import cn.hutool.core.convert.impl.ZoneIdConverter;
 import cn.hutool.core.date.DateTime;
 import cn.hutool.core.lang.Opt;
-import cn.hutool.core.reflect.ClassUtil;
-import cn.hutool.core.reflect.TypeUtil;
-import cn.hutool.core.util.ServiceLoaderUtil;
 
 import javax.xml.datatype.XMLGregorianCalendar;
 import java.io.Serializable;
@@ -78,6 +75,25 @@ import java.util.concurrent.atomic.AtomicReference;
 public class RegisterConverter implements Converter, Serializable {
 	private static final long serialVersionUID = 1L;
 
+	/**
+	 * 类级的内部类，也就是静态的成员式内部类，该内部类的实例与外部类的实例 没有绑定关系，而且只有被调用到才会装载，从而实现了延迟加载
+	 */
+	private static class SingletonHolder {
+		/**
+		 * 静态初始化器，由JVM来保证线程安全
+		 */
+		private static final CompositeConverter INSTANCE = new CompositeConverter();
+	}
+
+	/**
+	 * 获得单例的 ConverterRegistry
+	 *
+	 * @return ConverterRegistry
+	 */
+	public static CompositeConverter getInstance() {
+		return RegisterConverter.SingletonHolder.INSTANCE;
+	}
+
 	/**
 	 * 默认类型转换器
 	 */
@@ -92,7 +108,6 @@ public class RegisterConverter implements Converter, Serializable {
 	 */
 	public RegisterConverter() {
 		registerDefault();
-		registerCustomBySpi();
 	}
 
 	@Override
@@ -233,20 +248,4 @@ public class RegisterConverter implements Converter, Serializable {
 		defaultConverterMap.put(Optional.class, new OptionalConverter());// since 5.0.0
 		defaultConverterMap.put(Opt.class, new OptConverter());// since 5.7.16
 	}
-
-	/**
-	 * 使用SPI加载转换器
-	 */
-	private void registerCustomBySpi() {
-		ServiceLoaderUtil.load(Converter.class).forEach(converter -> {
-			try {
-				final Type type = TypeUtil.getTypeArgument(ClassUtil.getClass(converter));
-				if (null != type) {
-					putCustom(type, converter);
-				}
-			} catch (final Exception ignore) {
-				// 忽略注册失败的
-			}
-		});
-	}
 }

hutool-core/src/main/java/cn/hutool/core/convert/impl/MapConverter.java

@@ -67,7 +67,7 @@ public class MapConverter implements Converter, Serializable {
 			// 二次转换，转换键值类型
 			map = convert(targetType, keyType, valueType, map);
 		} else {
-			throw new UnsupportedOperationException(StrUtil.format("Unsupport toMap value type: {}", value.getClass().getName()));
+			throw new UnsupportedOperationException(StrUtil.format("Unsupported toMap value type: {}", value.getClass().getName()));
 		}
 		return map;
 	}

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

@@ -7,6 +7,7 @@ import cn.hutool.core.convert.impl.DateConverter;
 import cn.hutool.core.convert.impl.TemporalAccessorConverter;
 import cn.hutool.core.reflect.TypeUtil;
 import cn.hutool.core.text.StrUtil;
+import cn.hutool.json.convert.JSONConverter;
 
 import java.io.Serializable;
 import java.time.temporal.TemporalAccessor;
@@ -59,6 +60,12 @@ public class JSONConfig implements Serializable {
 	 */
 	private Converter converter = (type, value)->{
 		final Class<?> rawType = TypeUtil.getClass(type);
+		if(null == rawType){
+			return value;
+		}
+		if(JSON.class.isAssignableFrom(rawType)){
+			return JSONConverter.INSTANCE.toJSON(value);
+		}
 		if(Date.class.isAssignableFrom(rawType) || TemporalAccessor.class.isAssignableFrom(rawType)){
 			// 用户指定了日期格式，获取日期属性时使用对应格式
 			final String valueStr = Convert.convertWithCheck(String.class, value, null, isIgnoreError());

hutool-json/src/main/java/cn/hutool/json/convert/JSONConverter.java

@@ -4,6 +4,7 @@ import cn.hutool.core.bean.BeanUtil;
 import cn.hutool.core.bean.copier.BeanCopier;
 import cn.hutool.core.convert.ConvertException;
 import cn.hutool.core.convert.Converter;
+import cn.hutool.core.convert.RegisterConverter;
 import cn.hutool.core.convert.impl.ArrayConverter;
 import cn.hutool.core.convert.impl.CollectionConverter;
 import cn.hutool.core.convert.impl.MapConverter;
@@ -42,6 +43,11 @@ import java.util.Map;
 public class JSONConverter implements Converter {
 	public static final JSONConverter INSTANCE = new JSONConverter(null);
 
+	static {
+		RegisterConverter.getInstance().putCustom(JSONObject.class, INSTANCE);
+		RegisterConverter.getInstance().putCustom(JSONArray.class, INSTANCE);
+	}
+
 	/**
 	 * 创建JSON转换器
 	 *
@@ -141,6 +147,12 @@ public class JSONConverter implements Converter {
 			return result;
 		}
 
+		// 标准转换器
+		final Converter converter = RegisterConverter.getInstance().getConverter(targetType, true);
+		if (null != converter) {
+			return (T) converter.convert(targetType, json);
+		}
+
 		// 尝试转Bean
 		if (BeanUtil.isBean(rawType)) {
 			return BeanCopier.of(json,

hutool-json/src/test/java/cn/hutool/json/Issue2555Test.java

@@ -1,3 +1,5 @@
+package cn.hutool.json;
+
 import cn.hutool.json.JSON;
 import cn.hutool.json.JSONObject;
 import cn.hutool.json.JSONUtil;