RestTemplate 如何解析响应

Question

在开发spring REST Client时，出现一个问题：

1. 我有下一个 json:

{
 "return": [
 {
    "admin": false,
    "alias": "",
    "email": "",
    "emailId": {"value": 0},
    "groups": [],
    "id": {"value": 1},
    "locked": false,
    "loggedInCount": 0,
    "master": true,
    "sms": "",
    "smsId": {"value": 0},
    "type": "POWER",
    "username": "NGCP"
 },
 {
    "admin": false,
    "alias": "",
    "email": "",
    "emailId": {"value": 0},
    "groups": [{"value": 2}],
    "id": {"value": 3},
    "locked": false,
    "loggedInCount": 0,
    "master": false,
    "sms": "",
    "smsId": {"value": 0},
    "type": "POWER",
    "username": "POLICY"
 }
        ]
}

保存用户的模型类：

@JsonIgnoreProperties(ignoreUnknown = true)
public class User {

   public User(){

   }

   private boolean admin;

   private String alias;

   private String email;

   private String emailId;

   private ArrayList<String> groups;

   private String id;

   private boolean locked;

   private int loggedInCount;

   private boolean master;

   private String sms;

   private String smsId;

   private String type;

   private String userName;

//getter and setters
}

现在我正在使用“RestTemplate”来获取结果。

RestTemplate restTemplate = new RestTemplate();
ResponseEntity<User[]> response = restTemplate.exchange(URL_GET,HttpMethod.GET,request, User[].class);

并得到错误。我知道这是因为主键是“结果”，但我可以指定 restTemplate 应该从哪里解析这个 JSON 吗？

并且可以在文件上注明喜欢“emailId”以获得直接价值？一些模板？

Answer 1

1. 至于“主键是结果”：

   一个。如果您只处理一种此类 Web 服务，我将为实际有效负载创建一个包装类：

   public class Return{
       // Class property cannot be called "return" because it is Java reserved name.
       @JsonProperty("return")
       private User[] array;
       .... getter and setter
   }
   

   b.如果您处理实际有效负载位于“返回”字段中的多个 Web 服务，我将创建一个通用包装类：

   public class Return<T>{
       // Class property cannot be called "return" because it is Java reserved name.
       @JsonProperty("return")
       private T[] array;
       .... getter and setter
   }
   

   致电RestRemplate:

   ResponseEntity<Return<User>> response = restTemplate.exchange(URL_GET, 
           HttpMethod.GET, request, new ParameterizedTypeReference<Return<User>>(){});
   User[] usersArray = response2.getBody().getArray();
   

2. 对于名为“value”的 JSON 属性中的属性值，我将创建两个自定义 JsonDeserializer(s)：一个用于单个值，一个用于值数组，并在每个属性适用的地方用 @JsonDeserialize 注释：

   单值反序列化器：

   public class StringValueDeserializer  extends JsonDeserializer<String>{
   
       @Override
       public String deserialize(JsonParser parser, DeserializationContext ctxt)
               throws IOException, JsonProcessingException {
           ObjectCodec codec = parser.getCodec();
           TreeNode node = codec.readTree(parser);
           JsonNode value = (JsonNode)node.get("value");
   
           if (value != null){
               return value.asText();
           }
           return null;
       }
   }
   

   值数组解构器：

   public class StringArrayValueDeserializer  extends JsonDeserializer<List<String>>{
   
       @Override
       public List<String> deserialize(JsonParser parser, DeserializationContext ctxt)
           throws IOException, JsonProcessingException {
   
           List<String> ret = new ArrayList<>();
   
           ObjectCodec codec = parser.getCodec();
           TreeNode node = codec.readTree(parser);
   
           if (node.isArray()){
               for (JsonNode n : (ArrayNode)node){
                   JsonNode value = n.get("value");
                   if (value != null){
                       ret.add(value.asText());
                   }
               }
           }
           return ret;
       }
   }
   

   你是新来的User.class:

   public class User {
   
       private boolean admin;
   
       private String alias;
   
       private String email;
   
       @JsonDeserialize(using = StringValueDeserializer.class)
       private String emailId;
   
       @JsonDeserialize(using = StringArrayValueDeserializer.class)
       private ArrayList<String> groups;
   
       @JsonDeserialize(using = StringValueDeserializer.class)
       private String id;
   
       private boolean locked;
   
       private int loggedInCount;
   
       private boolean master;
   
       private String sms;
   
       @JsonDeserialize(using = StringValueDeserializer.class)
       private String smsId;
   
       private String type;
   
       private String username;
       .... getter and setter
   }
   

祝你好运！

Answer 2

你也可以使用JsonPath库来浏览json：

String json =  restTemplate.exchange(URL_GET,HttpMethod.GET,request, String.class);
DocumentContext document = JsonPath.parse(content, json);
List<User> users = document.read("$.return.*", new TypeRef<List<User>>() {});

Answer 3

您可以使用注释 @JsonRootName 来指定响应中的根元素。所以试试这个：

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonRootName(value ="result")
public class User {

   public User(){

   }

   private boolean admin;

   ....
}