daffodil

Value Members

1. package sapi

   

   Provides the classes necessary to compile DFDL schemas, parse and unparse files using the compiled objects, and retrieve results and parsing diagnostics

   Provides the classes necessary to compile DFDL schemas, parse and unparse files using the compiled objects, and retrieve results and parsing diagnostics

   Overview

   The Daffodil object is a factory object to create a Compiler. The Compiler provides a method to compils a provided DFDL schema into a ProcessorFactory, which creates a DataProcessor:

   val c = Daffodil.compiler()
   val pf = c.compileFile(file)
   val dp = pf.onPath("/")

   The DataProcessor provides the necessary functions to parse and unparse data, returning a ParseResult or UnparseResult, respectively. These contain information about the parse/unparse, such as whether or not the processing succeeded any diagnostic information.

   Parse

   The DataProcessor#parse(input:java\.nio\.channels\.ReadableByteChannel,output:org\.apache\.daffodil\.sapi\.infoset\.InfosetOutputter)* method accepts input data to parse in the form of a java.nio.channels.ReadableByteChannel and an infoset.InfosetOutputter to determine the output representation of the infoset (e.g. Scala XML Nodes, JDOM2 Documents, etc.):

   val scalaOutputter = new ScalaXMLInfosetOutputter()
   val pr = dp.parse(data, scalaOutputter)
   val node = scalaOutputter.getResult

   The DataProcessor#parse(input:java\.nio\.channels\.ReadableByteChannel,output:org\.apache\.daffodil\.sapi\.infoset\.InfosetOutputter)* method is thread-safe and may be called multiple times without the need to create other data processors. However, infoset.InfosetOutputter's are not thread safe, requiring a unique instance per thread. An infoset.InfosetOutputter should call infoset.InfosetOutputter#reset before reuse (or a new one should be allocated). For example:

   val scalaOutputter = new ScalaXMLInfosetOutputter()
   files.foreach { f => {
     outputter.reset
     val pr = dp.parse(f, scalaOutputter)
     val node = scalaOutputter.getResult
   }}

   Unparse

   The same DataProcessor used for parse can be used to unparse an infoset via the DataProcessor#unparse(input* method. An infoset.InfosetInputter provides the infoset to unparse, with the unparsed data written to the provided java.nio.channels.WritableByteChannel. For example:

   val inputter = new ScalaXMLInfosetInputter(node)
   val ur = dp.unparse(inputter, wbc)

   Failures and Diagnostics

   It is possible that failures could occur during the creation of the ProcessorFactory, DataProcessor, or ParseResult. However, rather than throwing an exception on error (e.g. invalid DFDL schema, parse error, etc), these classes extend WithDiagnostics, which is used to determine if an error occurred, and any diagnostic information (see Diagnostic) related to the step. Thus, before continuing, one must check WithDiagnostics#isError. For example:

   val pf = c.compile(file)
   if (pf.isError()) {
     val diags = pf.getDiagnostics()
     diags.foreach { d =>
       System.out.println(d.toString())
     }
     return -1;
   }

   Saving and Reloading Parsers

   In some cases, it may be beneficial to save a parser and reload it. For example, when starting up, it may be quicker to reload an already compiled parser than to compile it from scratch. To save a DataProcessor:

   val dp = pf.onPath("/")
   dp.save(saveFile);

   And to restore a saved DataProcessor:

   val dp = Daffodil.reload(saveFile);
   val pr = dp.parse(data, inputter);