XOM API for Processing XML with Java

[Wolfgang Hoschek <wolfgang.hoschek AT mac.com>]

nu.xom.URIUtil.relativize(documentURL, systemID) is a bit fragile  
which in turn means that some documents can't be round-tripped. To  
start out with

1) nu.xom.URIUtil.relativize(documentURL, systemID) is a bit fragile:

String documentURL="file:///Users/hoschek/unix/devel/xom/../xom-1.2/ 
data/pe.xml"
String systemID=   "file:///Users/hoschek/unix/devel/xom-1.2/data/ 
pe.txt"
System.out.println(nu.xom.URIUtil.relativize(documentURL, systemID))

yields the following bogus output

1.2/data/pe.txt

This relative URL does not exist in the file system, of course.

2) This fragility in turn means that nu.xom.XOMHandler has an  
incompatibility bug with xerces-2.7.0 and 2.8.1 (but interestingly  
not with 2.6.2 because it reports systemIDs in a slightly different  
format) wrt. external entity declarations. To see that, add some  
print diagnostics to XOMHandler.externalEntityDecl()

    public void externalEntityDecl(String name,
       String publicID, String systemID) {
        
        System.out.println("3name="+name+", publicID="+publicID+",  
systemID="+systemID);
        if (inInternalSubset() && doctype != null) {
            internalDTDSubset.append("  <!ENTITY ");
            if (name.startsWith("%")) {
                internalDTDSubset.append("% ");
                internalDTDSubset.append(name.substring(1));
            }
            else {
                internalDTDSubset.append(name);
            }

            if (locator != null && URIUtil.isAbsolute(systemID)) {
                String documentURL = locator.getSystemId();
                System.out.println("systemID1="+systemID);
                System.out.println("docURL1="+documentURL);
                // work around Crimson style file:/root URLs
                if (documentURL != null) {
                    if (documentURL.startsWith("file:/") && ! 
documentURL.startsWith("file:///")) {
                        documentURL = "file://" +  
documentURL.substring(5);
                        System.out.println("docURL2="+documentURL);
                    }
                    if (systemID.startsWith("file:/") && ! 
systemID.startsWith("file:///")) {
                        systemID = "file://" + systemID.substring(5);
                        System.out.println("systemID2="+systemID);
                    }

                    System.out.println("normalizing (docURL,systemID) 
=\n"+documentURL+"\n"+systemID);
                    systemID = URIUtil.relativize(documentURL,  
systemID);
                    System.out.println("systemID3="+systemID);
                }
            }

            if (publicID != null) {
                internalDTDSubset.append(" PUBLIC \"");
                internalDTDSubset.append(publicID);
                internalDTDSubset.append("\" \"");
                internalDTDSubset.append(systemID);
            }
            else {
                // need to escape system ID????
                internalDTDSubset.append(" SYSTEM \"");
                internalDTDSubset.append(systemID);
            }
            internalDTDSubset.append("\">\n");

        }

    }


Now run something like this with xerces-2.8.0:

public class XOMExternalEntityTest {
        
        public static void main(String[] args) throws Exception {
                String file = args[0];
//		String file = "/Users/hoschek/unix/devel/nux/../nuxtestdata/XOM/ 
data/pe.xml";
//		String file = "/Users/hoschek/unix/devel/nux/nuxtestdata/XOM/data/ 
pe.xml";
                Document doc = new Builder().build(new File(args[0]));
                System.out.println(doc.toXML());
        }
        
}


[hoschek /Users/hoschek/unix/devel/xom]
export JAVA_OPTS='-Djava.endorsed.dirs=/Users/hoschek/unix/java/share/ 
apache/xerces-2.8.0/'

[hoschek /Users/hoschek/unix/devel/xom] fire-java  
nux.xom.sandbox.XOMExternalEntityTest /Users/hoschek/unix/devel/ 
xom/../xom-1.2/data/pe.xml
3name=%ccl, publicID=null, systemID=file:///Users/hoschek/unix/devel/ 
xom-1.2/data/pe.txt
systemID1=file:///Users/hoschek/unix/devel/xom-1.2/data/pe.txt
docURL1=file:///Users/hoschek/unix/devel/xom/../xom-1.2/data/pe.xml
normalizing (docURL,systemID)=
file:///Users/hoschek/unix/devel/xom/../xom-1.2/data/pe.xml
file:///Users/hoschek/unix/devel/xom-1.2/data/pe.txt
systemID3=1.2/data/pe.txt
<?xml version="1.0"?>
<!DOCTYPE doc SYSTEM "pe.dtd" [
  <!ENTITY % ccl SYSTEM "1.2/data/pe.txt">
]>
<doc />

[hoschek /Users/hoschek/unix/devel/xom]


3) Again, "1.2/data/pe.txt" is bogus. This in turn means that the  
document can't be round-tripped. Serializing the document and trying  
to reparse that will yield to an an exception like this:


Exception in thread "main" java.io.FileNotFoundException:
<some bogus path trailing in /1.2/data/pe.txt goes here> (No such  
file or directory)
        at java.io.FileInputStream.open(Native Method)
        at java.io.FileInputStream.<init>(FileInputStream.java:106)
        at java.io.FileInputStream.<init>(FileInputStream.java:66)
        at sun.net.www.protocol.file.FileURLConnection.connect 
(FileURLConnection.java:69)
        at sun.net.www.protocol.file.FileURLConnection.getInputStream 
(FileURLConnection.java:156)
        at org.apache.xerces.impl.XMLEntityManager.setupCurrentEntity 
(Unknown Source)
        at org.apache.xerces.impl.XMLEntityManager.startEntity 
(Unknown Source)
        at org.apache.xerces.impl.XMLEntityManager.startEntity 
(Unknown Source)
        at org.apache.xerces.impl.XMLDTDScannerImpl.startPE(Unknown  
Source)
        at org.apache.xerces.impl.XMLDTDScannerImpl.skipSeparator 
(Unknown Source)
        at org.apache.xerces.impl.XMLDTDScannerImpl.scanDecls 
(Unknown Source)
        at  
org.apache.xerces.impl.XMLDTDScannerImpl.scanDTDExternalSubset 
(Unknown Source)
        at org.apache.xerces.impl.XMLDocumentScannerImpl 
$DTDDispatcher.dispatch(Unknown Source)
        at  
org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument 
(Unknown Source)
        at org.apache.xerces.parsers.DTDConfiguration.parse(Unknown  
Source)
        at org.apache.xerces.parsers.DTDConfiguration.parse(Unknown  
Source)
        at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
        at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown  
Source)
        at nu.xom.Builder.build(Builder.java:1138)
        at nu.xom.Builder.build(Builder.java:625)


voila,
Wolfgang.