Jackson-jr閱讀多態ArrayList

Question

我使用Jackson-jr來閱讀我的JSON文件。其中之一是一個有點複雜：

[ 
{"test-1":["a","b","c","d"]}, 
{"test-2":["b","j","d"]}, 
{"test-3":["n","e","o","p","i"]}, 
{"test-4":["s","a","v","z","b","ç","x","p"]}, 
{"test-5":["d","q","u"]}, 
{"test-6":["f","b"]} 
] 

我的代碼來讀取很簡單：

InputStream inputStream = assetManager.open("test.json"); 
ArrayList<HashMap<String, ArrayList<String>>> arrays = JSON.std.beanFrom(ArrayList.class, inputStream); 

我的目的是讓每個陣列與他們每個人的工作：

arrays.get(i); 

但是，當這條線被執行時，我有一個例外：

Caused by: java.lang.ClassCastException: com.fasterxml.jackson.jr.ob.impl.DeferredMap cannot be cast to java.util.HashMap 

Jackson-jr沒有TypeFactory，TypeReference或ObjectMapper。一些鏈接，我發現答案傑克遜，而不是傑克遜JR：

ClassCastException when convert json to list of objects

Jackson custom deserializer for one field with polymorphic types

Tricky(?) JSON, polymorphic deserialization

有沒有說，在傑克遜JR來處理呢？

Answer 1

您應該編程到接口而不是實現類。由於返回的映射實現是DeferredMap而不是HashMap，因此您將獲得ClassCastException。改變分配如下

List<Map<String, List<String>>> arrays = JSON.std.beanFrom(ArrayList.class, inputStream);