How to detect trailing garbage using Jackson ObjectMapper

Question

Say I have a class

class A {
    public int x;
}

Then a valid json can be parsed as follows:

ObjectMapper mapper = new Obje         


        

Answer 1

You can have something like below. Basically loop through the tokens before you readValue. JsonParser#nextToken() validates if your String is a proper JSON.

Here is the code:

public static void main(String[] args) throws JsonParseException, IOException  {

        ObjectMapper mapper = new ObjectMapper();

        String str = "{\"x\" : 3} garbage";

        JsonParser x = mapper.getJsonFactory().createJsonParser(str);
        while(x.nextToken()!=null){

        }
    A a =   mapper.readValue(str, A.class);

        System.out.println(a);
    }

console output:

Exception in thread "main" org.codehaus.jackson.JsonParseException: Unexpected character ('g' (code 103)): expected a valid value (number, String, array, object, 'true', 'false' or 'null')
 at [Source: java.io.StringReader@65faba46; line: 1, column: 12]
    at org.codehaus.jackson.JsonParser._constructError(JsonParser.java:1432)
    at org.codehaus.jackson.impl.JsonParserMinimalBase._reportError(JsonParserMinimalBase.java:385)
    at org.codehaus.jackson.impl.JsonParserMinimalBase._reportUnexpectedChar(JsonParserMinimalBase.java:306)
    at org.codehaus.jackson.impl.ReaderBasedParser._handleUnexpectedValue(ReaderBasedParser.java:1192)
    at org.codehaus.jackson.impl.ReaderBasedParser.nextToken(ReaderBasedParser.java:479)
    at example.JsonParse.main(JsonParse.java:21)