Hijacker

Hijacker is a develoment too meant to proxy to an existing API while being able to mock and modify specific requests via rules.

• Get Started
  • Install
  • Create Config
  • Run
• Config
  • Config
  • Rule
  • Base Rule
  • Rule Types
  • Logger
• Extending Hijacker
  • Plugins
  • Custom Rule Types
  • Hooks

Get Started

Install

Locally

npm i -D @hijacker/core

Globally

npm i -g @hijacker/core

Create Config

Create config file named hijacker.config.js with the following:

module.exports = {
  port: 3000,
  baseRule: {
    baseUrl: '<YOUR_API_URL>'
  },
  rules: []
}

View Config for more information.

Run

Add a hijacker script to your package.json file: "hijacker": "hijacker".

Then run the following command in the directory with your config file:

npm run hijacker

Your hijacker instance should now be running at http://localhost:3000 with the interface available at http://localhost:3000/hijacker.

Config

Config

Property	Descripton	Type	Required	Default
port	Port that you want the hijacker instance to run on	number	yes
baseRule	Base rule that other rules will inhert from. See Base Rule	Partial<Rule>	yes
rules	Array of hijacker rules. See Rule	Partial<Rule>[]	yes
logger	Logger configuration options. See Logger	LoggerOptions	no

Rule

A tells hijacker how to handle certain requests. If no matching rule is found, hijacker will proxy the request to the API server.

Property	Description	Type	Required	Default
name	Rule name. Used for display purposes only	string	no
disabled	If rule is disabled it can't be matched	boolean	no	false
type	Rule type. Used to determine which RuleType to use for matching and handling the request	string	rest
baseUrl	Base URL for API you want to point hijacker at for specific rule	string	no

Base Rule

The base rule allows you set default values for the

Rule Types

By default hijacker includes Rest and a GraphQL rule types. Each rule type can have additional properties that build upon the base rule properties. Each rule will be merged with the Base Rule and use it's values unless overridden in the rule.

The base rule has the same values as Rules. The only difference is that baseUrl is required so that requests that have no matching rule will be able to be proxied.

Rest Rule

The rest rule type is meant for REST APIs, and will be used for rule's where type is set to rest. The rest rule type has the same properties as the Rule, as well as the following:

Property	Description	Type	Required	Default
skipApi		boolean	no	false
method	HTTP method of the request to match on.	GET | HEAD | POST | PUT | DELETE | OPTIONS | TRACE | PATCH | ALL	no	ALL
body	Response body to send back when a rule matches	any	no	undefined
path	URL path of request to match on.	string	yes
statusCode	Status code you would like hijacker return for a request	number	no
routeTo	Path to redirect request to at the API url	string	no

GraphQL Rule

The GraphQL rule type expands on the Rest Rule but adds matching that works for GraphQL queries. Right now the GraphQL rule type only matches on the operation name.

Property	Description	Type	Required	Default
operationName	Operation to match in graphql query	string	yes

Example:

query TestQuery {
  posts {
    name
    id
  }
}

For the above query, TestQuery is the operationName that should be used to match query in a rule.

Logger

Settings for built in logger. This may eventually get changed to accepting a custom logger.

Property	Description	Type	Required	Default
level	Max log level that you wan't logged to the console.	SILLY | DEBUG | HTTP | INFO | WARN | ERROR | NONE	no	INFO

Extending Hijacker

Hijacker was made with extensibility in mind. There are a two ways Hijacker can be extended: custom rule types and hooks.

Plugins

Plugins are how hooks and rule types are packaged up to be added to a config for a hijacker user to use.

Property	Description	Type	Required	Default
name	Name of plugin	string	yes
initPlugin	Function called to initialize plugin and pass HijackerContext	(context: HijackerContext) => void	no
hooks	Array of hook names that the plugin allows to be hooked into	string[]	no
handlers	List of hook handlers for plugin	Record<string, function>	no
ruleTypes	Array of custom rule types	RuleType[]	no

Custom Rule Types

It is possible to create custom rule types, that allow for request matching and handling. You can view RestRule and GraphqlRule for examples.

Property	Description	Type	Required	Default
type	Rule type used to match rules	string	yes
createRule	Create rule object used for the handler	(rule: Partial<Rule<T>>) => Rule<T>	yes
isMatch	Used to determine if request matches a rule	(request: HijackerRequest, rule: Rule<T>) => boolean	yes
handler	Request handler for rule type	(request: Request<T>, baseRule: Partial<Rule<T>>, context: HijackerContext) => Promise<HijackerResponse>	yes

Hooks

Hooks allow plugins to listen and modify objects at specific points in the request lifecycle. Hook handlers are passed an object that they can modify and return an object of the same shape. Right now Hijacker has hooks for the following events:

Hook Name	Type	Description	Synchronous
HIJACKER_START	Config	Executed when hijacker starts up and allows modifying the hijacker config	yes
HIJACKER_REQUEST	HijackerRequst	Begining of request. Called before rule matched	no
HIJACKER_RESPONSE	HijackerResponse	Called after request handler, before response returned to client	no

Plugins are able to add additional hooks using the HookManager which allow other plugins to modify their functionality.