將JSON字符串反序列化為POJO列表

Question

這是我的代碼，用於反序列化從Google App Engine Cloud Endpoint得到的響應：

String jsonString = IOUtils.toString(
    httpResponse.getEntity().getContent(), "UTF-8");

ObjectMapper mapper = new ObjectMapper();
ArrayList<myPOJO> myList= 
    mapper.readValue(jsonString, new TypeReference<ArrayList<MyPOJO>>(){});

jsonString看起來像這樣：

{
  "items" : [ {
    "id" : "12345",
    "name" : "test1"
  }, {
    "id" : "121212",
    "name" : "test2"
  } ]
}

但我收到此錯誤：

org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token at [Source: java.io.StringReader@547a7880; line: 1, column: 1]

用Jackson將這個JSON反序列化為POJO列表的正確方法是什么？

Answer 1

您必須為您的JSON根對象創建根POJO 。 例如：

class Root {

    private List<Entity> items;

    //getters, setters, toString, etc
}

class Entity {

    private long id;
    private String name;

    //getters, setters, toString, etc
}

簡單的應用程序：

ObjectMapper mapper = new ObjectMapper();
Root list = mapper.readValue(json, Root.class);
System.out.println(list);

印刷品：

Root [items=[Entity [id=12345, name=test1], Entity [id=121212, name=test2]]]

Answer 2

嘗試直接使用映射器反序列化

String jsonString = IOUtils.toString(
        httpResponse.getEntity().getContent(), "UTF-8");

    ObjectMapper mapper = new ObjectMapper();

    List<MyPOJO> myList= mapper.convertValue(jsonString, mapper.getTypeFactory().constructCollectionType(List.class, MyPOJO.class));