java json xpath jsonpath

jsonpath和xpath语法不通http://goessner.net/articles/JsonPath/

java实现http://code.google.com/p/json-path/

google 既然搜不到,你猜我是怎么找到的?

XPath
JSONPath
Description

/
$
the root object/element

.
@
the current object/element

/
. or []
child operator

..
n/a
parent operator

//
..
recursive descent. JSONPath borrows this syntax from E4X.

*
*
wildcard. All objects/elements regardless their names.

@
n/a
attribute access. JSON structures don't have attributes.

[]
[]
subscript operator. XPath uses it to iterate over element collections and for predicates. In Javascript and JSON it is the native array operator.

|
[,]
Union operator in XPath results in a combination of node sets. JSONPath allows alternate names or array indices as a set.

n/a
[start:end:step]
array slice operator borrowed from ES4.

[]
?()
applies a filter (script) expression.

n/a
()
script expression, using the underlying script engine.

()
n/a
grouping in Xpath

XPath has a lot more to offer (Location pathes in not abbreviated syntax, operators and functions) than listed here. Moreover there is a remarkable difference how the subscript operator works in Xpath and JSONPath.

Square brackets in XPath expressions always operate on the node set resulting from the previous path fragment. Indices always start by 1.With JSONPath square brackets operate on the object or array addressed by the previous path fragment. Indices always start by 0. |2007-08-18| e3#JSONPath examples

Let's practice JSONPath expressions by some more examples. We start with a simple JSON structure built after an XML example representing a bookstore (original XML file).

{ "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 } } }

XPath
JSONPath
Result

/store/book/author
$.store.book[*].author
the authors of all books in the store

//author
$..author
all authors

/store/*
$.store.*
all things in store, which are some books and a red bicycle.

/store//price
$.store..price
the price of everything in the store.

//book[3]
$..book[2]
the third book

//book[last()]
$..book[(@.length-1)]
$..book[-1:]
the last book in order.

//book[position()<3]
$..book[0,1]
$..book[:2]
the first two books

//book[isbn]
$..book[?(@.isbn)]
filter all books with isbn number

//book[price<10]
$..book[?(@.price<10)]
filter all books cheapier than 10

//*
$..*
all Elements in XML document. All members of JSON structure


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