[QUESTION]从1.2.83升级到2.0.55之后JSONObject的toJavaObject()方法会把Map的value为null的键忽略掉怎么才能不忽略

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从1.2.83升级到2.0.55之后JSONObject的toJavaObject()方法会把Map的value为null的键忽略掉怎么才能不忽略，代码里面没有显示的设置忽略value为null的键。1.2.83版本下是可以的，升级之后就不行了。是fastjson2的默认策略有变化吗？

Start by reproducing the reported JSONObject.toJavaObject() behavior with a Map containing a null value, then compare the result between fastjson 1.2.83 and 2.0.55. Check whether the newer default strategy or an available option controls null-valued keys; done means the behavior and supported configuration are confirmed.

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