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

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

• 代码片段

  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]

   

• 错误原因 
  fasterxml无法对这个字符串进行判断，它的处理逻辑应该是先判断这个字符串是否是boolean，因为这个字符串并不是用双引号引起来的字符串。
• 解决办法 
  String s = “testjson”;应改为String s = "\"testjson\"";，此时才可被fasterxml正确理解。