JSONSVR - THE API SERVER MOCKUP TOOL

JSONSVR enables you to quickly provide a mockup server that serves RESTful protocols. You write the API in service.json and then provide corresponding responses for each API there. The responses can be read from .json files, .html files, .txt, or even provided as a string. You can write Javascript expressions in the .json or .html files as well to create a template that could provide dynamic responses.

Content

• Running the JSON server
• Configure the server using config.json
• Writing service.json
• API Definition
• JavaScript Expressions
• JSON template
• HTML template
• Support of S3 Hosted Files
• The Test Library API Reference

Running the JSON server

npm install -g jsonsvr
jsonsvr --init
jsonsvr

Configure the server using config.json

To configure the JSON server, write or modify the config.json file. You can pull the bootstraping config.json file using the jsonsvr --init command.

You may specify the path for your configuration file using the --config parameter.

jsonsvr --config /path/to/config.json

The config.json file example:

{
  "port": "port number for the server to serve",
  "imports": {
    "module identifier": "module name"
  },
  "serviceDescriptor": "./data/service.json",
  "noDefaultIndexPage": false,
  "accessLog": "./access.log"
}

Port

The port number to which the server is served on.

Imports

An optional imports configuration allows you to load the node modules specified by module name. Once successfully imported at startup, you may refer to this module inside the .json or .html files using the module identifier. For example:

in config.json:

{
  ...
  "modules": {
    "moment": "moment",
    "uu": "uuid",
    "lo": "lodash"
  }
}

in orders.json:

{
  "trackingId": "$ctx.trackingId = uu.v4()",
  "created": "$moment()",
  "expire": "$moment().add(30, 'days')",
  "$exec": "$ctx.orderIndex.push(ctx.trackingId); ctx.orderIndex = lo.uniq(ctx.orderIndex)"
}

Note: You'll need to issue npm install <module> to install external modules before being able to import them to the service.

serviceDescriptor

You may specify the location of the service descriptor file using the serviceDescriptor configuration parameter in config.json file. The content of this parameter can be

• An absolute path on local machine
• A relative path against the current working directory
• A URI describing S3 object (see S3 Support for more detail)

The bootstraping template for service.json can be generated using the jsonsvr --init command.

noDefaultIndexPage

By default, the server will be started with the root path / being a documentation page (this document) if the root path was not defined in service.json file. You can disable this behavior by setting the noDefaultIndexPage to true, in which the server will return 404-Not Found.

Access Log

Set the accessLog to the path of a log file or a special keyword console to enable the full dump of requests and responses made by JSON server. In latter case, the access log is printed on the console.

Writing service.json

You create service.json file to define APIs. The service.json file is loaded when the server starts. It is located at ./data/services.json by default. However, you can specify the different location in serviceDescriptor property on the config.json file. You may need to restart the server if you made changes to the service descriptor file.

To define an API, use the route path as a key. Under the route path key, defines the HTTP methods, i.e. GET, POST, PUT, DELETE, OPTIONS, PATCH, HEAD etc. A special method * can also be specified if you want the route path to serve for every HTTP methods.

{
  "/api/orders": {
    "GET": {
      "response": "./data/orders.json"
    },
    "POST": {
      "response": "./data/orders_result.json"
    }
  },

  "/api/users": {
    "GET": {
      "response": "./data/users.json"
    }
  }
}

The route path may contain parameters. JSON server uses the path parameter syntax used in express.js, which uses a colon-leaded parameter names within the route path. The parameter can later be accessed in the scripts using ctx.request.params.<parameter>

{
  "/api/users/:userId": {
    "GET": {
      "response": "./data/user.json"
    }
  }
}

in user.json:

{
  "userId": "${ctx.request.params.userId}"
}

You may use the variables in service definition file, such as in path.

{
  "/api/users/:userId": {
    "GET": {
      "response": "./data/${ctx.request.params.userId}/user.json"
    }
  }
}

API definition

Several ways to define a response for an API described in service.json file. You must define one of the following response types for an API in order to get it to function.

• response - read from a file
• errorResponse - respond with HTTP status code
• redirect - respond with 301 status code with redirect URL
• textResponse - response with the given text
• proxy - forward the request to the specified URL and respond with the response from such URL

Note: The response types are mutual exclusive. They cannot be used together in a single API method.

response

Respond with the content of the specified file. The currently supported files are: .json, .html, and .txt.

{
  "GET": {
    "response": "./data/response.json"
  }
}

errorResponse

Respond with the given HTTP status code.

{
  "GET": {
    "errorResponse": "500"
  }
}

redirect

Direct the browser to the redirected URL for this API. The redirect parameter defines the target URL to redirect to. No query string are being carried over from the original URL unless the redirectQueryString parameter is set to true. See redirectQueryString option for more information.

{
  "GET": {
    "redirect": "http://www.google.com"
  }
}

redirectQueryString

Carry over the query string from the request to the redirected URI. Note that all the query strings from the redirect parameter will be replaced.

{
  "GET": {
    "redirect": "http://www.google.com/",
    "redirectQueryString": true
  }
}

textResponse

Respond with the given text

{
  "GET": {
    "textResponse": "Hello"
  }
}

You may use javascript expression in textResponse. See javascript expression for more details.

proxy

Forward the request to the specified URL and respond with the response from such URL

{
  "GET": {
    "proxy": "http://www.google.com"
  }
}

condition

Only use this particular method definition if the condition is met, i.e. the expression returns true or a javascript truthly value. Otherwise, return 404 or the other method definition that has its condition matched. In the latter case, an array of method definitions has to be given instead of an method definition content.

{
  "GET": {
    "condition": "ctx.request.params.userId === '2931'",
    "response": "./data/user2931.json"
  }
}

From the example above, if the user ID does not equal 2931, a 404 error returns.

{
  "GET": [
    {
      "condition": "ctx.request.params.userType === 'individual'",
      "response": "./data/individual.json"
    },
    {
      "condition": "ctx.request.params.userType === 'juristic'",
      "response": "./data/juristic.json"
    },
    {
      "response": "./data/default.json"
    }
  ]
}

From the example above, the condition is provided such that the given method definition would handle the matched case. The last definition, however, does not provide a condition. In such case the server assumes the true condition. The evaluation starts from the first element of the method defition array. The first method definition that either not have condition or having the condition returns true, will be used. Others will be neclected for the particular request.

Note that giving an array of more than one method definitions does not make sense when all method definitions do not define condition. Doing so, only the first defition will always be excuted.

headers

Define response headers

{
  "GET": {
    "headers": {
      "Content-type": "text/html",
      "Set-cookie": "session=29222"
    }
  }
}

preScript

Provide Javascript to run before response is sent. The script is provided as a string.

Note: You do not need to use expression directive ${...} in the preScript value.

{
  "/api/query": {
    "*": {
      "preScript": "ctx.data.queries = []",
      "response": "./data/query-result.json"
    }
  }
}

PreScript supports mutilple statements using array.

postScript

Provide Javascript to run after the response is sent. The script is provided as a string.

Note: You do not need to use expression directive ${...} in the postScript value.

{
  "/api/product": {
    "*": {
      "response": "./data/product.json",
      "postScript": "ctx.data.summary = Math.round(ctx.data.price)"
    }
  }
}

PostScript supports mutilple statements using array.

Initialization Script

There are cases when initialization has to take place in order to prepare environments -- e.g. data structures -- for further usages. Such situations can be written as an $init script in the service descriptor file.

For example, to initialize the users array:

{
  "$init": "ctx.data.users = []"
}

The $init allows multiple statements. They can be written as an array:

{
  "$init": [
    "ctx.data.users = []",
    "ctx.data.sessionIndex = {}",
    "ctx.data.count = 0"
  ]
}

The initialization script runs only when the server starts, i.e. when the service.json is loaded.

Javascript Expression

To allow dynamic generation of content or configuration, you may use javascript expression in your json values. The expression can be defined inside ${...} directive and can be used in mixed with the string value.

The following is an example of how expressions can be used:

{
  "values": "${a}, ${b}, ${c}",
  "average": "${(a + b + c)/3}"
}

Note: If the expression spans an entire string value, the type of result will be that of the result of the expression. For example, if your expression returns a number, the property value will be a number. If you need the expression that returns numeric (or other primitive types such as boolean, null, or undefined) to be represented as a string, use the String(...) function. For example, "values": "${String(true)}" would be interpolated to "values": "true", while the "values":"${true}" results in "value": true.

JSON template

The JSON files you defined in the service.json file as the values to the response property are JSON templates. A JSON template can be a static content, having no expressions or directives, or dynamic, with expressions and/or directives within them. The dynamic generation of JSON file according to the template is a powerful feature of JSON server, which enables you to generate test cases that work for you.

Use of Variables in Javascript Expressions

The Context variable

The context variable can be accessed in the expression as a ctx variable. There are useful properties of this context variable that you can use. They are:

• ctx.req represents the current request. It is a Request instance from expressjs framework. Interesting properties are:
  • ctx.req.body provides the parsed body value. If the Content-type is application/json then the body is a Javascript object represents that JSON. If the Content-type is form-data, the body is key-value pair of param and value.
  • ctx.req.headers provides the HTTP request headers in key-value pairs.
  • ctx.req.params provides the named URI component in the route. For example, /api/users/:username route will have ctx.req.params.username be that third element of the route.
  • ctx.req.query provides the key-value pairs of the parsed query strings from the URI.
• ctx.data represents the globally accessible data where you can declare variables to use with the other APIs.

JSON Directives

In JSON templates, you can use JSON Server directive to control the fields. The JSON directive is described as a JSON object literal with the key (property name) beginning with a dollar sign ($) denoting the command.

$array directive

Used to create an array of repeating element based on the given template.

{
  "data": {
    "$array": {
      "count": 10,
      "element": "${ctx.i}"
    }
  }
}

The element template can include dynamic expressions as same as that applies with the JSON templates. A special variable ctx.i is available in the context for the element template, which contains the current iteration number.

Properties

• count The number of generated elements
• element The element template.

$exec directive

Used to execute a Javascript statements without generating values in any outputs to the target field.

For example, for this json template:

{
  "field": { "$exec": "ctx.lastCall = new Date()" }
}

Generates the output as:

{}

For multiple statements, use array.

{
  "field": { "$exec": [
    "ctx.data.today = moment()",
    "ctx.data.tomorrow = ctx.data.today.add(1, 'days')"
  ]}
}

$csv directive

Reads records in a CSV file to create an array of templated elements.

{
  "$csv": {
    "file": "file path",
    "element": "string, object, or any types",
    "firstLineHeader": false,
    "headers": "optional string array of header variable names, defined in the same sequence againt columns",
    "delimiter": "optional delimiter. Default to comma"
  }
}

parameters:

• file Specifies path to the CSV file.
• element Defines the element template. Can be a string (with expressions), object, or any types.
• firstLineHeader Set to true if the first line on the CSV file defines header. If so, the headers will be used as a subscript to col in the context variable. Default to false.
• headers Array of header names to override CSV file header, or when they are absent. The headers will be used as a subscript to col in the context variable.
• delimiter A field delimiter for this CSV file.

$if directive

Conditionally return the element defined in then property if the condition implies JavaScript truthly value. Otherwise, the else element is returned, if defined. Otherwise, the target field is eliminated.

Note: You need to use Javascript expression ${...} for condition if you plan to provide expression to evaluate rather than a constant string or a value.

{
  "pricing": { 
    "$if": {
      "condition": "${data.price > 200}",
      "then": "expensive",
      "else": "inexpensive"
    } 
  },

  "errorMessage": { 
    "$if": { 
      "condition": "${data.error}",
      "then": "${data.errmsg}" 
      }
    }
}

Note: Unlike the full-fleged languages, JSON-server DSL does not defer the evaluation of then statements to when the condition is true, as well as for an else when the condition evalues to false. JSON server pre-evaluates the entire JSON structure before directive evaluation so all expressions are evaluated regardless of the condition resulting value.

HTML template

The current version does not support dynamic HTML content generation.

Support of S3 Hosted Files

JSON Server supports AWS S3 hosted files in most of the configuration and descriptors that require file path. To refer to S3 stored content, simply use s3:// URI scheme in place of the path.

For example, in config.json you may use:

{
  "serviceDescriptor": "s3://your-s3-bucket-name/path/to/object.json"
}

The Test Library API Reference

Utilities that are commonly required for convenience in creating mock API are preloaded by default. This bundle of utilities can be accessed under lib namespace. They can be used in any expression evaluations on both service definition file and the template files.

lib.condition()

Use as an expression in place of if statement. Condition returns the then evaluation if the condition is true. Otherwise, it returns the result of else evaluation.

Note: The if and the conditional expression in Javascript can also be used. This interface is just provided for convenience.

Declaration:

lib.condition(condition: boolean, then: () => any, else: () => any): any

example

{
  "days": "${lib.condition(ctx.days > 30, () => days - 10, () => days + 20)}"
}

lib.randomDigits()

Returns a random number or letters in the given character class as string for the given number of digits. Useful for generating random fix-length string IDs.

Declaration

lib.randomDigits(len: number = 8, charClass: string = lib.CC_NUMBERS): string

Parameters

• len optional number of digits to be returned
• charClass optional string of available characters to pick at random
  • The library has provided constant strings for mostly used character classes
    • lib.CC_ALPHANUM for Alphanumeric (numbers and capital letters, 0-9 A-Z)
    • lib.CC_MIX_ALPHANUM for Alphanumeric with mixed character cases (0-9 A-Z a-z)
    • lib.CC_NUMBERS for numeric digits (0-9)
    • lib.CC_CAPITALS for capital letters (A-Z)
    • lib.CC_LOWERCASES for lowercase letters (a-z)
    • You can also use them in mix, for example lib.CC_LOWERCASES + lib.CC_CAPITALS.

Example

{
  "username": "${lib.randomDigits(lib.randomNumber(15,3), lib.CC_CAPITALS)}", 
  "password": "${lib.randomDigits(16, lib.CC_MIX_ALPHANUM + '!@#$%^&*()_-+=\\/.\\'\"<>?{}[]')"
}

lib.randomNumber

Returns the random number in the range of the given [max, min] inclusive.

Declaration

lib.randomNumber(max: number = 100, min: number = 0)

Parameters

• max optional maximum possible number to return, inclusive. Default to 100
• min optional minimum possible number to return, inclusive. Default to 0

Example

{
  "price": "USD ${lib.randomNumber(100)}",
  "height": "${lib.randomNumber(210, 140)} cm"
}