Crate jlens

Extract data from JSON

This crate provides a simple domain-specific language based on method chaining to construct and run queries against serialize::json::Json objects.

An object implementing the Selector trait describes how to select a set of nodes starting at a given path in a JSON document. The most basic selector can be created with the node() function: this selector always selects precisely the path given to it. All selectors have methods such as child() and key() which return a new selector. The new selector will select nodes relative to the output of the original according to some criteria. For example, node().child() selects all children of the initial node, while node().child().child() selects all children of the children of the initial node, and so on. By continuing to chain method calls in this manner, a selector object representing a complex query expression can be built up. Example:

// Test JSON document
let json = r#"
[
   {
       "foo": ["Hello, world!", 3.14, false]
   },
   {
       "foo": [42, true]
   },
   {
       "foo": "Nope"
   },
   {
       "bar": [42, "Hello, world!"]
   }
]"#.parse::<Json>().unwrap();

// Given a list, match all objects in it that
// have a "foo" key where the value is a list
// that contains either the string "Hello, world!"
// or the u64 42
let matches = json.query(
    list().child().wherein(
        key("foo").list().child().or(
            string().equals("Hello, world!"),
            uint64().equals(42))));

// Expected matches
let match1 = r#"{"foo": ["Hello, world!", 3.14, false]}"#.parse::<Json>().unwrap();
let match2 = r#"{"foo": [42, true]}"#.parse::<Json>().unwrap();

assert_eq!(matches.len(), 2);
assert!(matches.contains(& &match1));
assert!(matches.contains(& &match2));

The JsonExt trait provides a convenience method on Json objects which runs a selector and returns a Vec<&Json> of results.

Structs

AndSel

Ascend

At

BooleanEquals

BooleanSel

Child

Descend

Diff

F64Equals

F64Sel

I64Equals

I64Sel

Intersect

Key

ListSel

Node

NullSel

ObjectSel

OrSel

Parent

StringEquals

StringSel

U64Equals

U64Sel

Union

Wherein

Enums

JsonPath

JSON node path

Traits

JsonExt

Extension trait for Json

Selector

JSON selector trait

Functions

and

Shorthand for node().and(left, right)

ascend

Shorthand for node().ascend()

at

Shorthand for node().at(index)

boolean

Shorthand for node().boolean()

child

Shorthand for node().child()

descend

Shorthand for node().descend()

diff

Shorthand for node().diff(left, right)

float64

Shorthand for node().float64()

int64

Shorthand for node().int64()

intersect

Shorthand for node().intersect(left, right)

key

Shorthand for node().key(name)

list

Shorthand for node().list()

node

Create trivial selector

null

Shorthand for node().null()

object

Shorthand for node().object()

or

Shorthand for node().or(left, right)

parent

Shorthand for node().parent()

string

Shorthand for node().string()

uint64

Shorthand for node().uint64()

union

Shorthand for node().union(left, right)

wherein

Shorthand for node().wherein(filter)