Referring to a local DTD in Java

Question

I have some XML that I'm parsing with a SAX parser in Java. It starts with this preamble:

<!DOCTYPE math 
    PUBLIC "-//W3C//DTD MathML 3.0//EN"
           "http://www.w3.org/Math/DTD/mathml3/mathml3.dtd">

How do I change this to use a local DTD?

I suppose I could do something like this:

<!DOCTYPE math 
    PUBLIC "-//W3C//DTD MathML 3.0//EN"
           "file:///c:/MathML/mathml3.dtd">

Not exactly like that, but something like that. However, I need the path to be independent of the user's system.

How do I use a local DTD with a path relative to the class path?

Solution 1

Take a look at this article on using XML catalogs to resolve DTDs locally without having to modify your XML source. The basic steps are:

1. create an XML file that maps system IDs to local DTDs
2. modify your code to instantiate and configure a CatalogResolver
3. provide the CatalogResolver to the XML Reader (obtained from the parser)

Solution 2

When dealing with Web Apps, you can put the dtd in the lib folder and refer to it like:

<!DOCTYPE name PUBLIC 
    "-//CMP//DTD dtdName 1.0//EN"
        "/WEB-INF/lib/dtdName.dtd">

Solution 3

The solution is to provide the DTD file location in the system using classpath. So the DocType that worked offline would be:

<!DOCTYPE hibernate-configuration SYSTEM 
    "classpath://org/hibernate/hibernate-configuration-3.0.dtd">

Comments

[mounaim]

this is simpler than the first answer !! Thanks Hitham

[Mo Beigi]

Hacky but works, don't forget the port number if you have one (localhost:8080)

[Vadzim]

This works only with special org.hibernate.util.DTDEntityResolver.

[Sully]

I posted the answer as a web app solution and not for simplicity

[Jerry]

java.net.MalformedURLException: unknown protocol: classpath I am getting this exception

[Mehdi]

lib folder should contain "only" libraries.

[Sully]

@Mehdi, DTDs are usually inside JARs, which are in the lib folder. You just have to reference them differently as jar:file: <absolute-path>/log4j.jar!/org/apache/log4j/xml/log4j.dtd

[Mehdi]

Didn't know you can reference a dtd inside a jar, but it's a file appart, why not to place it in a path like conf/dtd and keep the lib folder for jars as possible.