如何将 json 字符串反序列化为不同的特定 java 对象？

Question

I managed to serialize an extreme complex class (which nests 50-some customize java object) to json string using gson. Here is a piece of my object:

public class myComplexObject{
     private int a;
     private String b;
     private myclassA c;
     private myclassB d;
     ...
     private map<String, Object> x;
}

please note the field private map<String, Object> x , the VALUE Object could be Integer , Double , String , myClassC ,... it works well when serializing, but when deserializing, gson could not convert the json string as my expectation. eg for the json string

{
"keyA":"1",
}

I expect that gson could convert it to Integer , but gson recognize it as Double .Which will lead exception in later process.

So, my question is, what should I do to let the serializer(not limited to gson) know that when deserializing a json string to a java Object class like this, which should be convert to Integer , which should be convert to Double ...

Answer 1

When deserializing a JSON number with Gson as Object , it defaults to deserializing the JSON value as Java Double (as you have seen). Recently in Gson 2.8.9 a new feature has been added which allows specifying a ToNumberStrategy . This allows you to more easily influence how Gson deserializes JSON numbers. Some default implementations are provided by the ToNumberPolicy enum. The one closest to your requirement is ToNumberPolicy.LONG_OR_DOUBLE . If you really need Integer as value type, you can try writing your own implementation similar to Gson's one .