Fast & easy command line tool for converting XML files to JSON.
The output is designed to be easy to store and process using JSON-based databases, such as mongoDB and CouchDB. In fact, the original motivation for xml-to-json was to store and query a large (~10GB) XML-based dataset, using an off-the-shelf scalable JSON database.
Currently the tool processes XMLs according to lossy rules designed to produce sensibly minimal output. If you need to convert without losing information at all consider something like the XSLT offered by the jsonml project. Unlike jsonml, this tool - xml-to-json - produces json output similar (but not identical) to the xml2json-xslt project.
xml-to-json is implemented in Haskell. Currently the implementation is minimal - for example, the core translation functionality is not exported as a library. If you want to use it as a library, open an issue on this project (or better yet - do it and submit a pull request).
As of this writing, xml-to-json uses hxt with the expat-based hxt-expat parser. The pure Haskell parsers for hxt all seem to have memory issues which hxt-expat doesn't.
Just run the tool with the filename as a single argument, and direct the stdout to a file or a pipe:
xml-to-json myfile.xml > myfile.js
Use the --help
option to see the full command line options.
Here's a (possibly outdated) snapshot of the --help
output:
Usage: xml-to-json [OPTION...] files...
-h --help Show this help
-t TAG --tag-name=TAG Start conversion with nodes named TAG (ignoring all parent nodes)
-s --skip-roots Ignore the selected nodes, and start converting from their children
(can be combined with the 'start-tag' option to process only children of the matching nodes)
-m --multiline Output each of the top-level converted json objects on a seperate line
-n --ignore-nulls Ignore nulls (do not output them) in the top-level output objects
-a --as-array Output the resulting objects in a top-level JSON array
Input file:
<?xml version="1.0"?>
<!DOCTYPE Test>
<Tests>
<Test Name="The First Test">
<Description Format="FooFormat">
Just a dummy
<!-- comment -->
Xml file.
</Description>
</Test>
<Test Name="Second"/>
</Tests>
JSON output (formatted for readability - actual output a single line):
{
"Tests" : {
"Test" : [
{ "Name" : "The First Test",
"Description" : {
"Format" : "FooFormat",
"value" : "Just a dummy\n\nXml file."
}
},
{ "Name" : "Second" }
]
}
}
For large XML files, the speed on a core-i5 machine is about 2MB of xml / sec, with a 100MB XML file resulting in a 56MB json output. It took about 10 minutes to process 1GB of xml data. The main performance limit is memory - only one single-threaded process was running since every single large file (tens of megabytes) consumes a lot of memory - about 50 times the size of the file.
A few simple tests have shown this to be at least twice as fast as jsonml's xlst-based converter (however, the outputs are not similar, as stated above).
Currently the program processes files serially. If run in parallel on many small XML files (<5MB) the performance becomes cpu-bound and processing may be much faster, depending on the architecture.