JsonPath语法详解（Java）Jayway JsonPath
A Java DSL for reading JSON documents.
Jayway JsonPath is a Java port of .
News
05 Jul 2017 - Relead JsonPath 2.4.0
26 Jun 2017 - Relead JsonPath 2.3.0
29 Feb 2016 - Relead JsonPath 2.2.0
22 Nov 2015 - Relead JsonPath 2.1.0
19 Mar 2015 - Relead JsonPath 2.0.0
11 Nov 2014 - Relead JsonPath 1.2.0
01 Oct 2014 - Relead JsonPath 1.1.0
26 Sep 2014 - Relead JsonPath 1.0.0
Getting Started
JsonPath is available at the Central Maven Repository. Maven urs add this to your POM.
<dependency>
<groupId>com.jayway.jsonpath</groupId>
<artifactId>json-path</artifactId>
<version>2.3.0</version>
</dependency>
If you need help ask questions at . Tag the question 'jsonpath' and 'java'.
JsonPath expressions always refer to a JSON structure in the same way as XPath expression are ud in combination with an XML document. The "root member object" in JsonPath is always referred to as $ regardless if it is an
object or array.
JsonPath expressions can u the dot–notation
$.store.book[0].title
or the bracket–notation
$['store']['book'][0]['title']
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Operators
Operator Description
$The root element to query. This starts all path expressions.
@The current node being procesd 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.
Functions
Functions can be invoked at the tail end of a path - the input to a function is the output of the path expression.
The function output is dictated by the function itlf.
Function Description Output
min()Provides the min value of an array of numbers Double
max()Provides the max value of an array of numbers Double
avg()Provides the average value of an array of numbers Double
stddev()Provides the standard deviation value of an array of numbers Double
length()Provides the length of an array Integer
Filter Operators
Filters are logical expressions ud to filter arrays. A typical filter would be [?(@.age > 18)] where @ reprents the current item being procesd. More complex filters can be created with logical operators && and ||. String literals must be enclod by single or double quotes ([?(@.color == 'blue')] or [?(@.color == "blue")]).
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
茶叶有保质期>left is greater than right
>=left is greater than or equal to right皮外套怎么搭配
=~left matches regular expression [?(@.name =~ /foo.*?/i)]
in left exists in right [?(@.size in ['S', 'M'])]湾组词语
nin left does not exists in right
subtof left is a subt of right [?(@.sizes subtof ['S', 'M', 'L'])]
size size of left (array or string) should match right
empty left (array or string) should be empty
Path Examples
Given the json
{
"store": {
雪花飘落的诗句"book": [
{
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
古代名医{
"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
}
JsonPath (click link to try)Result
The authors of all books
All authors
All things, both books and bicycles
The price of everything
The third book
The cond to last book
The first two books
All books from index 0 (inclusive) until index 2 (exclusive)
All books from index 1 (inclusive) until index 2 (exclusive)
Last two books
Book number two from tail
All books with an ISBN number
All books in store cheaper than 10
All books in store that are not "expensive"
All books matching regex (ignore ca)
Give me every thing
The number of books
Reading a Document
The simplest most straight forward way to u JsonPath is via the static read API.
String json = "...";
List<String> authors = ad(json, "$.store.book[*].author");
If you only want to read once this is OK. In ca you need to read an other path as well this is not the way
to go since the document will be pard every time you ad(...). To avoid the problem you can par the json first.
String json = "...";如何修改电脑开机密码
Object document = Configuration.defaultConfiguration().jsonProvider().par(json);
String author0 = ad(document, "$.store.book[0].author");
String author1 = ad(document, "$.store.book[1].author");
JsonPath also provides a fluent API. This is also the most flexible one.
String json = "...";
ReadContext ctx = JsonPath.par(json);
List<String> authorsOfBooksWithISBN = ad("$.store.book[?(@.isbn)].author");
List<Map<String, Object>> expensiveBooks = JsonPath
.using(configuration)
.par(json)
.read("$.store.book[?(@.price > 10)]", List.class);
What is Returned When?
When using JsonPath in java its important to know what type you expect in your result. JsonPath will automatically
try to cast the result to the type expected by the invoker.
//Will throw an java.lang.ClassCastException
List<String> list = JsonPath.par(json).read("$.store.book[0].author")
//Works fine
String author = JsonPath.par(json).read("$.store.book[0].author")
When evaluating a path you need to understand the concept of when a path is definite. A path is indefinite if it contains: .. - a deep scan operator
(<expression>) - an expression
[<number>, <number> (, <number>)] - multiple array indexes
Indefinite paths always returns a list (as reprented by current JsonProvider).
By default a simple object mapper is provided by the MappingProvider SPI. This allows you to specify the return type you want and the MappingProvider will
try to perform the mapping. In the example below mapping between Long and Date is demonstrated.
String json = "{\"date_as_long\" : 1411455611975}";
Date date = JsonPath.par(json).read("$['date_as_long']", Date.class);
If you configure JsonPath to u JacksonMappingProvider or GsonMappingProvider` you can even map your JsonPath output directly into POJO's. Book book = JsonPath.par(json).read("$.store.book[0]", Book.class);
To obtainin full generics type information, u TypeRef.
TypeRef<List<String>> typeRef = new TypeRef<List<String>>() {};
List<String> titles = JsonPath.par(JSON_DOCUMENT).read("$.store.book[*].title", typeRef);
Predicates
There are three different ways to create filter predicates in JsonPath.
Inline Predicates
Inline predicates are the ones defined in the path.
List<Map<String, Object>> books = JsonPath.par(json)
.read("$.store.book[?(@.price < 10)]");
You can u && and || to combine multiple predicates [?(@.price < 10 && @.category == 'fiction')] ,
[?(@.category == 'reference' || @.price > 10)].
You can u ! to negate a predicate [?(!(@.price < 10 && @.category == 'fiction'))].
最美夕阳红Filter Predicates
Predicates can be built using the Filter API as shown below:
import static com.jayway.jsonpath.JsonPath.par;
import static com.jayway.jsonpath.Criteria.where;
import static com.jayway.jsonpath.Filter.filter;
...
.
..
Filter cheapFictionFilter = filter(
where("category").is("fiction").and("price").lte(10D)
);
List<Map<String, Object>> books =
par(json).read("$.store.book[?]", cheapFictionFilter);
Notice the placeholder ? for the filter in the path. When multiple filters are provided they are applied in order where the number of placeholders must match
the number of provided filters. You can specify multiple predicate placeholders in one filter operation [?, ?], both predicates must match.
Filters can also be combined with 'OR' and 'AND'
Filter fooOrBar = filter(
where("foo").exists(true)).or(where("bar").exists(true)
);
Filter fooAndBar = filter(
where("foo").exists(true)).and(where("bar").exists(true)
);
Roll Your Own
Third option is to implement your own predicates
Predicate booksWithISBN = new Predicate() {
@Override
public boolean apply(PredicateContext ctx) {
return ctx.item(Map.class).containsKey("isbn");
}
};
List<Map<String, Object>> books =
Path vs Value
In the Goessner implementation a JsonPath can return either Path or Value. Value is the default and what all the examples above are returning. If you rather have the path of the elements our query is hitting this can be acheived with an option.
Configuration conf = Configuration.builder()
.options(Option.AS_PATH_LIST).build();
List<String> pathList = using(conf).par(json).read("$..author");
asrtThat(pathList).containsExactly(
"$['store']['book'][0]['author']",
"$['store']['book'][1]['author']",
"$['store']['book'][2]['author']",
"$['store']['book'][3]['author']");
Tweaking Configuration
Options
When creating your Configuration there are a few option flags that can alter the default behaviour.
DEFAULT_PATH_LEAF_TO_NULL
This option makes JsonPath return null for missing leafs. Consider the following json
[
{
"name" : "john",
"gender" : "male"
},
{
"name" : "ben"
