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)