这里有一种方法：（略）

public class Test {
    public static void main(String args[]) throws IOException {
        String json = "{\"integer_value\":null}";
        Moshi moshi = new Moshi.Builder().add(new ZeroWhenNullAdapter()).build();
        JsonAdapter<Data> jsonAdapter = moshi.adapter(Data.class);
        Data data = jsonAdapter.fromJson(json);
    }
}

@Retention(RetentionPolicy.RUNTIME)
public @interface Nullable { // you can use any annotation named 'Nullable'
}

@Retention(RUNTIME)
@JsonQualifier
public @interface ZeroWhenNull {}

public class Data {
    @ZeroWhenNull
    int integer_value = 0;
}

public class ZeroWhenNullAdapter {
    // this isn't really needed, but Moshi insists that adapters work both
    // ways as far as I can tell
    @ToJson
    String toJson(@ZeroWhenNull int n) {
        return Integer.toString(n);
    }

    @FromJson
    @ZeroWhenNull
    int fromJson(@Nullable String n) {
        return n == null ? 0 : Integer.parseInt(n);
    }
}

这不是使用默认值，而是显式地将字段设置为零。