saveXML: Output internal XML Tree

Description

Methods for writing the representation of an XML tree to a string or file. Originally this was intended to be used only for DOMs (Document Object Models) stored in internal memory created via xmlTree, but methods for XMLNode, XMLInternalNode and XMLOutputStream objects (and others) allow it to be generic for different representations of the XML tree.

Note that the indentation when writing an internal C-based node (XMLInternalNode) may not be as expected if there are text nodes within the node.

Also, not all the parameters are meaningful for all methods. For example, compressing when writing to a string is not supported.

Usage

saveXML(doc, file=NULL, compression=0, indent=TRUE, prefix = '',
        doctype = NULL, encoding = getEncoding(doc), ...)
## S3 method for class 'XMLInternalDocument':
saveXML(doc, file=NULL, compression=0, indent=TRUE, prefix = '\n',
                            doctype = NULL, encoding =  getEncoding(doc), ...)
## S3 method for class 'XMLInternalDOM':
saveXML(doc, file=NULL, compression=0, indent=TRUE, prefix = '\n',
                       doctype = NULL, encoding =  getEncoding(doc), ...)
## S3 method for class 'XMLNode':
saveXML(doc, file=NULL, compression=0, indent=TRUE, prefix = '\n',
                 doctype = NULL, encoding = getEncoding(doc), ...)
## S3 method for class 'XMLOutputStream':
saveXML(doc, file=NULL, compression=0, indent=TRUE, prefix = '\n',
                         doctype = NULL, encoding = getEncoding(doc), ...)
doc{the document object representing the XML document.}
  file{the name of the file to which the contents of the XML
    nodes will be serialized.}
  compression{an integer value between 0 and 9 indicating the
    level of compression to use when saving the file. Higher values
    indicate increased compression and hence smaller files
    at the expense of computational time to do the compression and decompression.}
  indent{a logical value indicating whether to indent
    the nested nodes when serializing to the stream.}
  prefix{a string that is written to the stream/connection before
     the XML is output. If this is NULL, it is ignored. This allows us to
     put the XML introduction/preamble at the beginning of the document
     while allowing it to be omitted when we are outputting multiple
     "documents" within a single stream.}
  doctype{an object identifying the elements for the DOCTYPE in the output.
    This can be a string or an object of class Doctype.}
  encoding{a string indicating which encoding style to use.  This
  is currently ignored except in the method in Sxslt for saving a
  document generated by applying an XSL style sheet to an XML document.}
  ...{extra parameters for specific methods}
One can create an internal XML tree (or DOM)
 using newXMLDoc and newXMLNode.
 saveXML allows one to generate a textual representation of
 that DOM in human-readable and reusable XML format.
 saveXML is a generic function that allows one to call
 the rendering operation with either the top-level node
 of the DOM or of the document object (of class XMLInternalDocument
 that is used to 
 accumulate the nodes and with which the developer 
 adds nodes.
If file is not specified, the result is a character string containing
 the resulting XML content.
 If file is passed in the call,
http://www.w3.org/XML, http://www.omegahat.org/RSXML
[object Object]
newXMLDoc
newXMLNode
xmlOutputBuffer
xmlOutputDOM
b = newXMLNode("bob")
 saveXML(b)
 f = tempfile()
 saveXML(b, f)
 doc = xmlInternalTreeParse(f)
 saveXML(doc)

con <- xmlOutputDOM()
con$addTag("author", "Duncan Temple Lang")
con$addTag("address",  close=FALSE)
con$addTag("office", "2C-259")
con$addTag("street", "Mountain Avenue.")
con$addTag("phone", close=FALSE)
con$addTag("area", "908", attrs=c(state="NJ"))
con$addTag("number", "582-3217")
con$closeTag() # phone
con$closeTag() # address
saveXML(con$value(), file="out.xml")

# Work with entities
 f = system.file("exampleData", "test1.xml", package = "XML")
 doc = xmlRoot(xmlTreeParse(f))
 outFile = tempfile()
 saveXML(doc, outFile)
 alt = xmlRoot(xmlTreeParse(outFile))
 if(! identical(doc, alt) )
  stop("Problems handling entities!")
 con = textConnection("test1.xml", "w")
 saveXML(doc, con)
 close(con)
 alt = get("test1.xml")
 identical(doc, alt)
 x = newXMLNode("a", "some text", newXMLNode("c", "sub text"), "more text")
 cat(saveXML(x), "")
 cat(as(x, "character"), "")

     # Showing the prefix parameter
  doc = newXMLDoc()
  n = newXMLNode("top", doc = doc)
  b = newXMLNode("bar", parent = n)
     # suppress the 
  saveXML(doc, prefix = character())
     # put our own comment in
  saveXML(doc, prefix = "")
     # or use a comment node.
  saveXML(doc, prefix = newXMLCommentNode("This is an alternative prefix"))
IO
file

Description

Usage

Arguments