如何反序列化此动态值JSON？

You cannot have POJOs here (in sane sense), but people tend to use POJO-generators that do not do ahead analysis even for dynamic objects. "Dynamic" objects should be typically mapped using java.util.Map (ordered implementation) + unique values can be mapped using java.util.Set (ordered implementation). Thus, if you have a custom enumeration for the currencies, say something like

enum Currency {

    BRL,
    CNY,
    EUR,
    INR,
    JPY,
    USD,

}

then you can easily define the mapping without any POJOs that do not look applicable here at all:

private static final Type exchangesType = new TypeToken<Map<String, Map<Currency, Set<Currency>>>>() {
}.getType();

final Map<String, Map<Currency, Set<Currency>>> exchanges = gson.fromJson(jsonReader, exchangesType);
System.out.println(exchanges);

So the trivial toString() output will be as follows:

{Exchange1={EUR=[CNY, USD], INR=[USD, CNY]}, Exchange2={BRL=[EUR, USD, INR], JPY=[USD, EUR, CNY]}}

如果您不喜欢Currency枚举的想法（必须始终使用最新的枚举进行更新，等等），那么您可以简单地将货币标记声明为java.lang.String并获得相同的结果：

private static final Type exchangesType = new TypeToken<Map<String, Map<String, Set<String>>>>() {
}.getType();

final Map<String, Map<String, Set<String>>> exchanges = gson.fromJson(jsonReader, exchangesType);
System.out.println(exchanges);