JsonPath

导入依赖

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在build.gradle中添加依赖compile('com.jayway.jsonpath:json-path:2.1.0')。

语法

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讲解示例：

{
    "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
        }
    },
    "expensive": 10
}

表示方法

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jsonpath有两种方式表示路径：

dot notation:

$.store.book[2]

backet notation

$['store']['book'][2]

两种方式指向同样一个json子串。

运算符

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在jsonpath中有多个有效的运算符（Operator）

Operator	Description
$	The root element to query. This starts all path expressions.
@	The current node being processed by a filter predicate.
*	Wildcard. Available anywhere a name or numeric are required.
..	Deep scan. Available anywhere a name is required.
.<name>	Dot-notated child
['<name>' (, '<name>')]	Bracket-notated child or children
[<number> (, <number>)]	Array index or indexes
[start:end]	Array slice operator
[?(<expression>)]	Filter expression. Expression must evaluate to a boolean value.

方法和过滤器

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jsonpath支持多个方法：

• min()
• max()
• avg()
• stddev()
• length()

使用方法时，只能讲方法添加到json路径的末尾。

除此之外，jsonpath还支持过滤器，过滤器必须返回一个布尔类型，比如[?(@.color == ‘blue’)]，完整过滤器列表如下所示：

Operator	Description
==	left is equal to right (note that 1 is not equal to ‘1’)
!=	left is not equal to right
<	left is less than right
<=	left is less or equal to right
>	left is greater than right
>=	left is greater than or equal to right
=~	left matches regular expression [?(@.name =~ /foo.*?/i)]
in	left exists in right [?(@.size in [‘S’, ‘M’])]
nin	left does not exists in right
subsetof	left is a subset of right [?(@.sizes subsetof [‘S’, ‘M’, ‘L’])]
size	size of left (array or string) should match right
empty	left (array or string) should be empty

混合使用运算符，方法和过滤器的具体示例如下:

JsonPath	Result
$.store.book[*].author	The authors of all books
$..author	All authors
$.store.*	All things, both books and bicycles
$.store..price	The price of everything
$..book[2]	The third book
$..book[-2]	The second to last book
$..book[0,1]	The first two books
$..book[:2]	All books from index 0 (inclusive) until index 2 (exclusive)
$..book[1:2]	All books from index 1 (inclusive) until index 2 (exclusive)
$..book[-2:]	Last two books
$..book[2:]	Book number two from tail
$..book[?(@.isbn)]])	All books with an ISBN number
$.store.book[?(@.price < 10)]])	All books in store cheaper than 10
[$..book?(@.price <= $[‘expensive’])]])	All books in store that are not “expensive”
$..book[?(@.author =~ /.*REES/i)]])	All books matching regex (ignore case)
$..*	Give me every thing
$..book.length())	The number of books

操作方式

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读取一个json字符串的最简单方式如下:

String json = "...";

List<String> authors = JsonPath.read(json, "$.store.book[*].author");

如果想要提取json字符串中的部分数据：

String json = "...";

DocumentContext ctx = JsonPath.parse(json);

List<String> authorsOfBooksWithISBN = ctx.read("$.store.book[?(@.isbn)].author");


List<Map<String, Object>> expensiveBooks = JsonPath
                            .parse(json)
                            .read("$.store.book[?(@.price > 10)]", List.class);