Add Expression syntax to doc website repo. (#1947)
* Add Expression syntax to doc website repo. Signed-off-by: carolxob <carolxob@amazon.com> * Minor changes to headings and heading levels. Signed-off-by: carolxob <carolxob@amazon.com> * Adjusted/renamed heading levels and titles. Signed-off-by: carolxob <carolxob@amazon.com> * Minor copy edits. Signed-off-by: carolxob <carolxob@amazon.com> * Added changes from tech review. Signed-off-by: carolxob <carolxob@amazon.com> * Incorporated feedback from doc review. Signed-off-by: carolxob <carolxob@amazon.com> Signed-off-by: carolxob <carolxob@amazon.com>
This commit is contained in:
Caroline
GitHub
parent
aaad91a4ed
commit
05c94b0079
|
|
@ -0,0 +1,197 @@
|
|||
---
|
||||
layout: default
|
||||
title: Expression syntax
|
||||
nav_order: 12
|
||||
---
|
||||
|
||||
# Expression syntax
|
||||
|
||||
## Supported operators
|
||||
|
||||
Operators are listed in order of precedence (top to bottom, left to right).
|
||||
|
||||
| Operator | Description | Associativity |
|
||||
|----------------------|-------------------------------------------------------|---------------|
|
||||
| `()` | Priority Expression | left-to-right |
|
||||
| `not`<br> `+`<br> `-`| Unary Logical NOT<br>Unary Positive<br>Unary negative | right-to-left |
|
||||
| `<`, `<=`, `>`, `>=` | Relational Operators | left-to-right |
|
||||
| `==`, `!=` | Equality Operators | left-to-right |
|
||||
| `and`, `or` | Conditional Expression | left-to-right |
|
||||
|
||||
## Reserved for possible future functionality
|
||||
Reserved symbol set: `^`, `*`, `/`, `%`, `+`, `-`, `xor`, `=`, `+=`, `-=`, `*=`, `/=`, `%=`, `++`, `--`, `${<text>}`
|
||||
|
||||
## Set initializer
|
||||
Defines a set or term and/or expressions.
|
||||
|
||||
### Examples
|
||||
|
||||
#### HTTP status codes
|
||||
```
|
||||
{200, 201, 202}
|
||||
```
|
||||
#### HTTP response payloads
|
||||
```
|
||||
{"Created", "Accepted"}
|
||||
```
|
||||
|
||||
#### Handle multiple event types with different keys
|
||||
```
|
||||
{/request_payload, /request_message}
|
||||
```
|
||||
|
||||
## Priority expression
|
||||
Identifies an expression that will be evaluated at the highest priority level. Priority expression must contain an
|
||||
expression or value, empty parentheses are not supported.
|
||||
|
||||
### Examples
|
||||
|
||||
```
|
||||
/is_cool == (/name == "Steven")
|
||||
```
|
||||
|
||||
## Relational operators
|
||||
Tests the relationship of two numeric values. The operands must be numbers or JSON pointers that resolve to numbers.
|
||||
|
||||
### Syntax
|
||||
```
|
||||
<Number | JSON Pointer> < <Number | JSON Pointer>
|
||||
<Number | JSON Pointer> <= <Number | JSON Pointer>
|
||||
<Number | JSON Pointer> > <Number | JSON Pointer>
|
||||
<Number | JSON Pointer> >= <Number | JSON Pointer>
|
||||
```
|
||||
|
||||
### Examples
|
||||
```
|
||||
/status_code >= 200 and /status_code < 300
|
||||
```
|
||||
|
||||
## Equality operators
|
||||
Used to test whether two values are equivalent.
|
||||
|
||||
### Syntax
|
||||
```
|
||||
<Any> == <Any>
|
||||
<Any> != <Any>
|
||||
```
|
||||
|
||||
### Examples
|
||||
```
|
||||
/is_cool == true
|
||||
3.14 != /status_code
|
||||
{1, 2} == /event/set_property
|
||||
```
|
||||
## Using equality operators to check JSON pointer
|
||||
|
||||
Equality operators can also be used to check whether a JSON Pointer exists by comparing with `null`.
|
||||
|
||||
### Syntax
|
||||
```
|
||||
<JSON Pointer> == null
|
||||
<JSON Pointer> != null
|
||||
null == <JSON Pointer>
|
||||
null != <JSON Pointer>
|
||||
```
|
||||
|
||||
### Examples
|
||||
```
|
||||
/response == null
|
||||
null != /response
|
||||
```
|
||||
|
||||
#### Conditional expression
|
||||
Used to chain together multiple expressions and/or values.
|
||||
|
||||
#### Syntax
|
||||
```
|
||||
<Any> and <Any>
|
||||
<Any> or <Any>
|
||||
not <Any>
|
||||
```
|
||||
|
||||
### Examples
|
||||
```
|
||||
/status_code == 200 and /message == "Hello world"
|
||||
/status_code == 200 or /status_code == 202
|
||||
not /status_code in {200, 202}
|
||||
/response == null
|
||||
/response != null
|
||||
```
|
||||
|
||||
## Definitions
|
||||
|
||||
### Literal
|
||||
A fundamental value that has no children.
|
||||
- Float _(Supports values from 3.40282347 × 10<sup>38</sup> to 1.40239846 × 10<sup>−45)</sup>_
|
||||
- Integer _(Supports values from −2,147,483,648 to 2,147,483,647)_
|
||||
- Boolean _(Supports true or false)_
|
||||
- JSON Pointer _(See JSON Pointer section for details)_
|
||||
- String _(Supports valid Java strings)_
|
||||
- Null _(Supports null check to see whether a JSON pointer exists)_
|
||||
|
||||
### Expression string
|
||||
The string that will be parsed for evaluation. Expression string is the highest level of a Data Prepper expression. Only supports one expression string resulting in a return value. An _expression string_ is not the same as an _expression_.
|
||||
|
||||
### Statement
|
||||
The highest level component of the expression string.
|
||||
|
||||
### Expression
|
||||
A generic component that contains a _Primary_ or an _Operator_. Expressions may contain expressions. An expressions imminent children can contains 0-1 _Operators_.
|
||||
|
||||
### Primary
|
||||
|
||||
- _Set_
|
||||
- _Priority Expression_
|
||||
- _Literal_
|
||||
|
||||
### Operator
|
||||
Hard coded token that identifies the operation used in an _expression_.
|
||||
|
||||
### JSON pointer
|
||||
A Literal used to reference a value within the Event provided as context for the _Expression String_. JSON Pointers are identified by a
|
||||
leading `/` containing alphanumeric character or underscores, delimited by `/`. JSON Pointers can use an extended character set if wrapped
|
||||
in double quotes (`"`) using the escape character `\`. Note, JSON Pointer require `~` and `/` that should be used as part of the path and
|
||||
not a delimiter to be escaped.
|
||||
|
||||
- `~0` representing `~`
|
||||
- `~1` representing `/`
|
||||
|
||||
#### Shorthand syntax (Regex, `\w` = `[A-Za-z_]`)
|
||||
```
|
||||
/\w+(/\w+)*
|
||||
```
|
||||
|
||||
##### Shorthand example
|
||||
```
|
||||
/Hello/World/0
|
||||
```
|
||||
|
||||
##### Escaped syntax example
|
||||
```
|
||||
"/<Valid String Characters | Escaped Character>(/<Valid String Characters | Escaped Character>)*"
|
||||
```
|
||||
|
||||
#### Escaped example
|
||||
```
|
||||
# Path
|
||||
# { "Hello - 'world/" : [{ "\"JsonPointer\"": true }] }
|
||||
"/Hello - 'world\//0/\"JsonPointer\""
|
||||
```
|
||||
|
||||
## White space
|
||||
### Operators
|
||||
White space is **optional** surrounding Relational Operators, Regex Equality Operators, Equality Operators and commas.
|
||||
White space is **required** surrounding Set Initializers, Priority Expressions, Set Operators, and Conditional Expressions.
|
||||
|
||||
### Reference table
|
||||
|
||||
| Operator | Description | White Space Required | ✅ Valid Examples | ❌ Invalid Examples |
|
||||
|----------------------|--------------------------|----------------------|----------------------------------------------------------------|---------------------------------------|
|
||||
| `{}` | Set Initializer | Yes | `/status in {200}` | `/status in{200}` |
|
||||
| `()` | Priority Expression | Yes | `/a==(/b==200)`<br>`/a in ({200})` | `/status in({200})` |
|
||||
| `in`, `not in` | Set Operators | Yes | `/a in {200}`<br>`/a not in {400}` | `/a in{200, 202}`<br>`/a not in{400}` |
|
||||
| `<`, `<=`, `>`, `>=` | Relational Operators | No | `/status < 300`<br>`/status>=300` | |
|
||||
| `=~`, `!~` | Regex Equality Operators | No | `/msg =~ "^\w*$"`<br>`/msg=~"^\w*$"` | |
|
||||
| `==`, `!=` | Equality Operators | No | `/status == 200`<br>`/status_code==200` | |
|
||||
| `and`, `or`, `not` | Conditional Operators | Yes | `/a<300 and /b>200` | `/b<300and/b>200` |
|
||||
| `,` | Set Value Delimiter | No | `/a in {200, 202}`<br>`/a in {200,202}`<br>`/a in {200 , 202}` | `/a in {200,}` |
|
||||
Loading…
Reference in New Issue