json無法解析Unrecognized token:was expecting (‘true’, ‘false’ or ‘null’)

fasterxml: Unrecognized token ‘open’: was expecting (‘true’, ‘false’ or ‘null’)

• 代碼片段

  public class JsonUtil {
      
      private static final ObjectMapper MAPPER = new ObjectMapper();
  
      public static void main(String[] args) throws Exception {
  
      String s = "testjson";
  
      String s1 = MAPPER.readValue(s, String.class);
  
      System.out.println(s1);
  }
  
  }

   

• exception

  Exception in thread "main" com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'testjson': was expecting ('true', 'false' or 'null')
   at [Source: java.io.StringReader@117c323d; line: 1, column: 9]

   

• 錯誤原因 
  fasterxml無法對這個字符串進行判斷，它的處理邏輯應該是先判斷這個字符串是否是boolean，因爲這個字符串並不是用雙引號引起來的字符串。
• 解決辦法 
  String s = “testjson”;應改爲String s = "\"testjson\"";，此時纔可被fasterxml正確理解。