Can not deserialize instance of java.lang.Class out of START_OBJECT token

Question

I can't understand propperly the error I get when I run this code:

InputStream is = this.getClass().getClassLoader().getResourceAsStream(filename);  
String jsonTxt = IOUtils.toString(is);  
JSONArray json = (JSONArray) JSONSerializer.toJSON(jsonTxt);  
JSONObject metadatacontent = json.getJSONObject(0);   
ObjectMapper mapper = new ObjectMapper();  
mapper.readValue(metadatacontent.toString(), MetadataContentBean.class.getClass());

Error:

org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.lang.Class out of START_OBJECT token at [Source: java.io.StringReader@e3b895; line: 1, column: 1] at org.codehaus.jackson.map.JsonMappingException.from(JsonMappingException.java:159) at org.codehaus.jackson.map.deser.StdDeserializationContext.mappingException(StdDeserializationContext.java:192) at org.codehaus.jackson.map.deser.StdDeserializer$ClassDeserializer.deserialize(StdDeserializer.java:439) at org.codehaus.jackson.map.deser.StdDeserializer$ClassDeserializer.deserialize(StdDeserializer.java:421) at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:1588) at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1116) at com.playence.parser.JSon.Parser(JSon.java:65) at com.playence.parser.JSon.main(JSon.java:29)

What does it mean??

Maybe if I know this, I could find out my error.

Answer 1

Your problem is the last line:

MetadataContentBean.class.getClass()

This means "get me the Class object for the MetadataContentBean class, and then get me the Class object for that Class object".... if you see what I mean. So you're asking Jackson to deserialize your JSON onto a Class object, which it doesn't know how to do.

This should be just

MetadataContentBean.class

Answer 2

This is probably related to the other question, but just to complete the answer, error comes from discrepancy: type "java.lang.Class" is serialized as a JSON String (class name itself), and not as JSON object like beans are. So deserializer expects to see a JSON String, instead sees a JSON Object (which starts with START_OBJECT) and throws exception.