傑克遜JSON無法反序列化哈希集

Question

我一直在尋找以下異常消息的解決方案，當我向實體發布更新時，我在spring-boot / spring-mvc項目中得到了該消息：

   o.s.w.s.m.m.a.HttpEntityMethodProcessor  : Written [{timestamp=Wed Jan 14 11:15:34 MST 2015, status=400, error=Bad Request, exception=org.springframework.http.converter.HttpMessageNotReadableException, message=Could not read JSON: Can not deserialize instance of java.util.HashSet out of START_OBJECT token

at [Source: org.apache.catalina.connector.CoyoteInputStream@7f5840c4; line: 1, column: 146] (through reference chain: com.company.product.model.people.dto.EmployeeDTO["user"]->com.company.product.security.dto.UserDTO["roles"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.HashSet out of START_OBJECT token

但是，看來我的情況與我在StackOverflow和Jackson文檔中看到的其他情況略有不同。

這是我的兩個數據結構：

public class EmployeeDTO {
   List<WorkdayDTO> workDays = new ArrayList<WorkdayDTO>();
   private UserDTO user;
   ...
   public List<WorkdayDTO> getWorkDays() {
        return workDays;
    }

    public void setWorkDays(List<WorkdayDTO> workDays) {
        this.workDays = workDays;
    }
   public UserDTO getUser() {
        return user;
    }

    public void setUser(UserDTO user) {
        this.user = user;
    }

}

和：

public class UserDTO {
    private boolean credentialsNonExpired;
    private OfficeDTO office;
    @JsonProperty("roles")  // <-- added this based on early research, hasn't helped though
    private Set<String> roles = new HashSet<String>();
    // .. standard getters & setters
}

當我執行GET時，我的json響應是這樣的：

[
   {
      "employeeId":1,
      "endDateTime":null,
      "workDays":[

      ],
      "ssn":"111-22-3333",
      "maskedSsn":null,
      "user":{
         "username":"user@test.com",
         "password":null,
         "enabled":true,
         "accountNonExpired":true,
         "accountNonLocked":true,
         "credentialsNonExpired":true,
         "office":null,
         "roles":[
            "OWNER"
         ]
      },
      "address":{
         ...
      }
   },
   {
      "employeeId":2,
      "endDateTime":null,
      "workDays":[
       ...
      ],
      "ssn":"333-44-5555",
      "maskedSsn":null,
      "user":{
         "username":"userA@test.com",
         "password":null,
         "enabled":true,
         "accountNonExpired":true,
         "accountNonLocked":true,
         "credentialsNonExpired":true,
         "office":null,
         "roles":[
            "MANAGER"
         ]
      },
      "address":{
        ...
      }
   }
]

似乎不喜歡我的employee.user.roles列表中的單個字符串，但是添加“ @JsonProperty（“ roles”）“也不起作用。

Answer 1

POST的正文格式不正確。 它包含用於roles的JSON對象。 JSON對象無法映射到HashSet ，因此失敗。 JSON中的roles必須是一個數組。