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JSON XPath

JSON XPath shard provides XPath query functionality for JSON document, it lets you extract data from JSON documents through an XPath expression.

Installation

1. Add the dependency to your shard.yml:

   dependencies:
     json-xpath:
       github: naqvis/json-xpath

2. Run shards install

Usage

require "json-xpath"

json = <<-JSON
{
 "store": {
     "book": [
         {
             "category": "reference",
             "author": "Nigel Rees",
             "title": "Sayings of the Century",
             "price": 8.95
         },
         {
             "category": "fiction",
             "author": "Evelyn Waugh",
             "title": "Sword of Honour",
             "price": 12.99
         },
         {
             "category": "fiction",
             "author": "Herman Melville",
             "title": "Moby Dick",
             "isbn": "0-553-21311-3",
             "price": 8.99
         },
         {
             "category": "fiction",
             "author": "J. R. R. Tolkien",
             "title": "The Lord of the Rings",
             "isbn": "0-395-19395-8",
             "price": 22.99
         }
     ],
     "bicycle": {
         "color": "red",
         "price": 19.95
     }
 }
}
JSON

books = JSONXPath.parse(json)

# Find authors of all books in the store
list = books.xpath_nodes("store/book/*/author")
# OR
# list = books.xpath_nodes("//author")

list.each { |a| puts a.content }
# => Nigel Rees
# => Evelyn Waugh
# => Herman Melville
# => J. R. R. Tolkien

# Find the Third book
book = books.xpath("//book/*[3]")
book.try &.children.each { |a| puts "#{a.data} : #{a.content}" }

# => author : Herman Melville
# => category : fiction
# => isbn : 0-553-21311-3
# => price : 8.99
# => title : Moby Dick

# Find the last book
book = books.xpath("//book/*[last()]")
book.try &.children.each { |a| puts "#{a.data} : #{a.content}" }

# =>  author : J. R. R. Tolkien
# =>  category : fiction
# =>  isbn : 0-395-19395-8
# =>  price : 22.99
# =>  title : The Lord of the Rings

# OR call `raw` property to retrive raw JSON
pp book.try &.raw

# => {"category" => "fiction",
# "author" => "J. R. R. Tolkien",
# "title" => "The Lord of the Rings",
# "isbn" => "0-395-19395-8",
#"price" => 22.99}

# Find all books with isbn number
list = books.xpath_nodes("//book/*[isbn]")
puts list.size # => 2

# Find all books cheaper than 10
list = books.xpath_nodes("//book/*[price<10]")
puts list.size # => 2

# Sum the price of all books
price = books.xpath_float("sum(//book/*/price)")
puts price # => 53.92

refer to spec for usage examples. And refer to Crystal XPath2 Shard for details of what functions and functionality is supported by XPath implementation.

Development

To run all tests:

crystal spec

Contributing

1. Fork it (https://github.com/naqvis/json-xpath/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• Ali Naqvi - creator and maintainer