Rails throws "REXML::ParseException does not have a valid root" exception

I have a JavaScript object, and converted it into JSON using Douglas Crockford's JSON utility. While sending a post AJAX request, I ge开发者_Python百科t:

REXML::ParseException does not have a valid root

REXML::ParseException (The document "{\"name\":\"asda\",\"deadline\":\"May 24, 2011\"}" does not have a valid root):

I am not able to proceed with this error.

When making your AJAX request, you're probably sending the wrong Content-Type header. If you make a request with the header Content-Type: application/xml, Rails will try to parse your request body as XML, and you'll get that error message. Instead, you'll want to use application/json or another content-type so that Rails won't try to parse it. If you're using jQuery, this is the contentType setting in $.ajax.

JSON doesn't require there to be a root element the way XML does. Try parsing it with JSON.parse(json_string), instead of with REXML.

See the below mentioned json file

{
    "glossary": {
        "title": "example glossary",
        "GlossDiv": {
            "title": "S",
            "GlossList": {
                "GlossEntry": {
                    "ID": "SGML",
                    "SortAs": "SGML",
                    "GlossTerm": "Standard Generalized Markup Language",
                    "Acronym": "SGML",
                    "Abbrev": "ISO 8879:1986",
                    "GlossDef": {
                        "para": "A meta-markup language, used to create markup languages such as DocBook.",
                        "GlossSeeAlso": ["GML", "XML"]
                    },
                    "GlossSee": "markup"
                }
            }
        }
    }
}

Here glossary is the root element which encloses the whole json similarly to xml as displayed below.

<!DOCTYPE glossary PUBLIC "-//OASIS//DTD DocBook V3.1//EN">
 <glossary><title>example glossary</title>
  <GlossDiv><title>S</title>
   <GlossList>
    <GlossEntry ID="SGML" SortAs="SGML">
     <GlossTerm>Standard Generalized Markup Language</GlossTerm>
     <Acronym>SGML</Acronym>
     <Abbrev>ISO 8879:1986</Abbrev>
     <GlossDef>
      <para>A meta-markup language, used to create markup
languages such as DocBook.</para>
      <GlossSeeAlso OtherTerm="GML">
      <GlossSeeAlso OtherTerm="XML">
     </GlossDef>
     <GlossSee OtherTerm="markup">
    </GlossEntry>
   </GlossList>
  </GlossDiv>
 </glossary>

Hence we can say that the glossary is the root and is only one tag in xml or json.

Hence you have to provide a root element in the json file which encloses the whole JSON file.