fix from dubbo:master, 2.5.7 : GenericJSONConverter主要是用在日志部分输出，所以当我们输出locale对象时就发生stack溢出。
```
java.lang.StackOverflowError
	at com.alibaba.dubbo.common.json.JSONWriter.valueString(JSONWriter.java:189)
	at com.alibaba.dubbo.common.json.GenericJSONConverter$7.encode(GenericJSONConverter.java:100)
	at com.alibaba.dubbo.common.json.GenericJSONConverter.writeValue(GenericJSONConverter.java:338)
	at com.alibaba.dubbo.common.json.GenericJSONConverter.writeValue(GenericJSONConverter.java:347)
	at com.alibaba.dubbo.common.json.GenericJSONConverter.writeValue(GenericJSONConverter.java:395)
	at com.alibaba.dubbo.common.json.GenericJSONConverter.writeValue(GenericJSONConverter.java:347)
	at com.alibaba.dubbo.common.json.GenericJSONConverter.writeValue(GenericJSONConverter.java:395)
```
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 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
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 *     http://www.apache.org/licenses/LICENSE-2.0
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package com.alibaba.dubbo.common.json;
import junit.framework.Assert;
import org.junit.Test;
import java.io.StringReader;
import java.io.StringWriter;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import static org.junit.Assert.assertEquals;
@Deprecated