Make DocumentBuilder.parse ignore DTD references

Question

When I parse my xml file (variable f) in this method, I get an error

C:\Documents and Settings\joe\Desktop\aicpcudev\OnlineModule\map.dtd (The system cannot find the path specified)

I know I do not have the dtd, nor do I need it. How can I parse this File object into a Document object while ignoring DTD reference errors?

private static Document getDoc(File f, String docId) throws Exception{
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    DocumentBuilder db = dbf.newDocumentBuilder();
    Document doc = db.parse(f);


    return doc;
}

Masseur

Answer 1

A similar approach to the one suggested by @anjanb

    builder.setEntityResolver(new EntityResolver() {
        @Override
        public InputSource resolveEntity(String publicId, String systemId)
                throws SAXException, IOException {
            if (systemId.contains("foo.dtd")) {
                return new InputSource(new StringReader(""));
            } else {
                return null;
            }
        }
    });

I found that simply returning an empty InputSource worked just as well?

Groat

Setting the features on DocumentBuilderFactory worked for me. The solution in this post did not work. – Tetrafluoroethylene

This also worked perfectly for me, even though I thought I didn't use SAX – Heck

Sadly this didn't work for me. I still got the error. @jt did it for me though. – Offprint

Thanks for the solution, this is the approach recommended by org.xml I think. It looks like there is a lot of material on this topic. see xerces.apache.org/xml-commons/components/resolver/…, or en.wikipedia.org/wiki/XML_Catalog and the javadoc saxproject.org/apidoc/org/xml/sax/EntityResolver.html and saxproject.org/apidoc/org/xml/sax/ext/EntityResolver2.html – Pop

Answer 2

Try setting features on the DocumentBuilderFactory:

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

dbf.setValidating(false);
dbf.setNamespaceAware(true);
dbf.setFeature("http://xml.org/sax/features/namespaces", false);
dbf.setFeature("http://xml.org/sax/features/validation", false);
dbf.setFeature("http://apache.org/xml/features/nonvalidating/load-dtd-grammar", false);
dbf.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);

DocumentBuilder db = dbf.newDocumentBuilder();
...

Ultimately, I think the options are specific to the parser implementation. Here is some documentation for Xerces2 if that helps.

Comb

the last one (load-external-dtd) did the trick for me - thanks. – Urogenous

While trying this, I got a DOMException: NAMESPACE_ERR: An attempt is made to create or change an object in a way which is incorrect with regard to namespaces.. I fixed this with dbf.setNamespaceAware(true); – Ochoa

Just to let you know, the last feature setting (as stated by @Amarghosh) works great with a SAXParserFactory. – Moskva

For me the load-external-dtd setting was enough. – Flaunch

Using all the above features also makes the code to fail. Just using the last two feature(nonvalidating) makes my code work. – Tremendous

Per the most upvoted comment, load-external-dtd was the trick. Thanks! I was surprised that a feature with http://apache.org/... in the name fixes Java DTD parsing errors, but happy to have a fix that doesn't involve exceptions or XML modification. In my case, this fixed some intermittent failures when parsing Apple PLIST files and when either apple.com was unreachable or when apple.com couldn't respond to the HTTP request. Much obliged. :) – Razz

Answer 3

I found an issue where the DTD file was in the jar file along with the XML. I solved the issue based on the examples here, as follows: -

DocumentBuilder db = dbf.newDocumentBuilder();
db.setEntityResolver(new EntityResolver() {
    public InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException {
        if (systemId.contains("doc.dtd")) {
             InputStream dtdStream = MyClass.class
                     .getResourceAsStream("/my/package/doc.dtd");
             return new InputSource(dtdStream);
         } else {
             return null;
         }
      }
});

Errand

Answer 4

Source XML (With DTD)

<!DOCTYPE MYSERVICE SYSTEM "./MYSERVICE.DTD">
<MYACCSERVICE>
   <REQ_PAYLOAD>
      <ACCOUNT>1234567890</ACCOUNT>
      <BRANCH>001</BRANCH>
      <CURRENCY>USD</CURRENCY>
      <TRANS_REFERENCE>201611100000777</TRANS_REFERENCE>
   </REQ_PAYLOAD>
</MYACCSERVICE>

Java DOM implementation for accepting above XML as String and removing DTD declaration

public Document removeDTDFromXML(String payload) throws Exception {

    System.out.println("### Payload received in XMlDTDRemover: " + payload);

    Document doc = null;
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    try {

        dbf.setValidating(false);
        dbf.setNamespaceAware(true);
        dbf.setFeature("http://xml.org/sax/features/namespaces", false);
        dbf.setFeature("http://xml.org/sax/features/validation", false);
        dbf.setFeature("http://apache.org/xml/features/nonvalidating/load-dtd-grammar", false);
        dbf.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);

        DocumentBuilder db = dbf.newDocumentBuilder();

        InputSource is = new InputSource();
        is.setCharacterStream(new StringReader(payload));
        doc = db.parse(is); 

    } catch (ParserConfigurationException e) {
        System.out.println("Parse Error: " + e.getMessage());
        return null;
    } catch (SAXException e) {
        System.out.println("SAX Error: " + e.getMessage());
        return null;
    } catch (IOException e) {
        System.out.println("IO Error: " + e.getMessage());
        return null;
    }
    return doc;

}

Destination XML (Without DTD)

<MYACCSERVICE>
   <REQ_PAYLOAD>
      <ACCOUNT>1234567890</ACCOUNT>
      <BRANCH>001</BRANCH>
      <CURRENCY>USD</CURRENCY>
      <TRANS_REFERENCE>201611100000777</TRANS_REFERENCE>
   </REQ_PAYLOAD>
</MYACCSERVICE> 

Obstetrics

Answer 5

I know I do not have the dtd, nor do I need it.

I am suspicious of this statement; does your document contain any entity references? If so, you definitely need the DTD.

Anyway, the usual way of preventing this from happening is using an XML catalog to define a local path for "map.dtd".

Overall

Answer 6

here's another user who got the same issue : http://forums.sun.com/thread.jspa?threadID=284209&forumID=34

user ddssot on that post says

myDocumentBuilder.setEntityResolver(new EntityResolver() {
          public InputSource resolveEntity(java.lang.String publicId, java.lang.String systemId)
                 throws SAXException, java.io.IOException
          {
            if (publicId.equals("--myDTDpublicID--"))
              // this deactivates the open office DTD
              return new InputSource(new ByteArrayInputStream("<?xml version='1.0' encoding='UTF-8'?>".getBytes()));
            else return null;
          }
});

The user further mentions "As you can see, when the parser hits the DTD, the entity resolver is called. I recognize my DTD with its specific ID and return an empty XML doc instead of the real DTD, stopping all validation..."

Hope this helps.

Palmar

Answer 7

I'm working with sonarqube, and sonarlint for eclipse showed me Untrusted XML should be parsed without resolving external data (squid:S2755)

I managed to solve it using:

    factory = DocumentBuilderFactory.newInstance();

    factory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);

    // If you can't completely disable DTDs, then at least do the following:
    // Xerces 1 - http://xerces.apache.org/xerces-j/features.html#external-general-entities
    // Xerces 2 - http://xerces.apache.org/xerces2-j/features.html#external-general-entities
    // JDK7+ - http://xml.org/sax/features/external-general-entities
    factory.setFeature("http://xml.org/sax/features/external-general-entities", false);

    // Xerces 1 - http://xerces.apache.org/xerces-j/features.html#external-parameter-entities
    // Xerces 2 - http://xerces.apache.org/xerces2-j/features.html#external-parameter-entities
    // JDK7+ - http://xml.org/sax/features/external-parameter-entities
    factory.setFeature("http://xml.org/sax/features/external-parameter-entities", false);

    // Disable external DTDs as well
    factory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);

    // and these as well, per Timothy Morgan's 2014 paper: "XML Schema, DTD, and Entity Attacks"
    factory.setXIncludeAware(false);
    factory.setExpandEntityReferences(false);

Obstinate