RESTful Web Services in ColdFusion

ColdFusion 10 lets you create and publish REST (Representational State Transfer) services that can be consumed by clients over HTTP/HTTPS request.

The following URL takes you to the Java Tutorial that provides conceptual information on REST:
http://download.oracle.com/javaee/6/tutorial/doc/gijqy.html

REST and ColdFusion

You can create REST services by defining certain attributes in the tags  cfcomponent ,  cffuntion , and  cfargument  and publish as REST resources.

• *Follows HTTP request-response model:* Beyond having HTTP as a medium, the service lets you follow all HTTP norms. The components published as REST services can be consumed over HTTP/HTTPS request. The REST services are identified with URI (Uniform Resource Identifier) and can be accessed from a web page as well as by specifying the URI in the browser's address bar.
• Supports all HTTP methods :  The REST enabled CFCs support the following HTTP methods: GET, POST, PUT, DELETE, HEAD, and OPTIONS.
• Implicit handling of serialization/deserialization: ColdFusion natively supports JSON and XML serialization/deserialization. So client applications can consume REST services by issuing HTTP/HTTPS request. The response can either be serialized to XML or JSON format.
• Publish web service as both REST service and WSDL service: You can create and publish the same ColdFusion component as a REST service and WSDL service.

Creating the REST web service

• You can create and publish a ColdFusion component or any functions in a component as REST resource.
• To create a CFC as REST web service, specify either of the following in the tag cfcomponent: restPath or rest.
• In cffunction, set the attribute access to remote for the functions that you have to expose as REST resource.

Example

Registering an application with REST service

After you create the CFC you want to REST-enable, specify the folder for registering as web service either using the function restInitAplication or in the ColdFusion Administrator.

Using ColdFusion Administrator (Data & Services > REST Services)

When you specify a folder, all CFCs in that folder or subfolders for which you have specified rest or restPath are registered.

Accessing the web service

• Use the tag  cfhttpto access the web service as shown in the following example:

• Access using the browser by providing the URL: http://localhost:8500/rest/RestTest/restService

Interpreting the URL

The URL provided in the example can be interpreted as follows:

Providing accept header

The accept header can be provided in the REST URL. The following examples illustrate this:

• For the REST URL http://localhost:8500/rest/RestTest/restService.xml, the accept parameter would be set to application\xml.
  
• Use the following header when making the rest call (instead of suffixing the URL wth .json or .xml). This is applicable for ColdFusion (2021 release) and later versions.

            <cfhttpparam type="header" name="Accept" value="application/json; charset=utf-8">

HTTP Content-type negotiation

The content-type that is returned by a RESTful web service depends on the Accept HTTP header.
Client  can set an Accept request header in the following order:

• Comma-separated list of preferred content types.
• (Followed by a semi-colon (;) A  floating point  number in the range 0 through 1 in the format q=0-1. The default value is 1.0 is the least value which indicates that the content type is not acceptable whereas 1 is the maximum value with the highest priority.
  If two types are provided the same priority, then the sequential priority is considered.

Examples

n the following example, client can use both XML and JSON format as no value is specified to indicate a priority in the Accept header:

The request in the following example specifies a priority for returning the content-type:

The order of precedence for content type is as follows:

Specifying subresources

Functions in a REST service can either be a resource function, subresource function, or subresource locator.

Resource function

The functions for which you have not specified the RestPath at function level but specified {{httpMethod.}}In this case, the resource function is invoked when URL of the CFC is accessed.

Subresource function

The functions for which you have specified both resptPath and httpMethod.
Subresource functions are used to create subresources for the resource created by CFC. If the subresource has  httpMethod  attribute in  cffunction , the function can directly handle HTTP requests as shown in the following example.

Example

Employee.cfc

In this example, httpMethod and restPath are defined. The  baseurl /hello/name is a subresource to the URL  baseurl /hello.

Subresource locator

If you have not specified the httpMethod attribute, but have specified restPath, you can dynamically resolve the component that handles the request. Any returned object is treated as a resource class instance and used to either handle the request or to further resolve the object that handles the request.

Example

In this example, StudentService.cfc and Student.cfc are the two REST resources. In StudentService.cfc the function getStudent returns a component. In the function, the object of Student is created and the values name and age are set. When the object is specified in the return type, the function defined in the object with the requested httpmethod is invoked.StudentService.cfc can be invoked directly as it has a restPath specified. Student.cfc can only be invoked through StudentService.cfc because the function getStudent in StudentService.cfc is acting as the subresource locator and returns Student.cfc.StudentService.cfc:

Student.cfc

Student.cfm

HTTP Responses

By default, ColdFusion provides default HTTP success and failure responses to the client as follows:

Success responses

Error responses

Custom responses

In addition to the default responses available with ColdFusion, you can set custom responses.
For example, assume that you have to provide a success response 201 Created. Such a default response does not exist. You can only have 200 OK or 204 No Content to send. 
In such scenarios, you can create custom responses in either of the following ways:

Send custom success responses using restSetResponse

When you define the CFC as REST service, ensure that the returnType is set to void in the cffunction(the function for which you want to send the custom response).For example,

• Create a struct for the custom response that you want to send in the cffunctionas shown in the following example:

In this example, you have set 201 as the status of the response, content that you want to send. For example, customer details and the location where you have created the resource for the POSTrequest.

• Use the function restSetResponseas follows:

  restSetResponse( response );

Send custom error response using cfthrow

Assume that you want to send a custom error response. For example, consider the following:method.service.cfc

In this case, you have a customer database and you are doing a GET HTTP request on /customers/123.But you find that the customer with the specified ID 123 is not available. So you want to send 404 Resource Not Found response back to the client, which is not possible by default.In this case, you can use cfthrow to send custom error response as follows:

Modifications to Application.cfc

The following enhancements have been made to Application.cfc for REST support:

Extending REST Web services

The following conditions apply when you extend the RESTful CFCs:

• You can define the REST attributes for functions in the base CFC. So all the CFCs that extend from the base CFC inherits the REST attributes.In the following example, CustomerResource. cfc extends BaseCustomerResource.cfc:BaseCustomerResource.cfc

BaseCustomerResource.cfc has all REST attributes applied to functions within the CFC. After you define BaseCustomerResource.cfc, you can define CustomerService.cfc that extends BaseCustomerResource.cfc as follows:Customerservice.cfc

BaseCustomerResource.cfm

Except the rest and restPath, no other REST attributes are required within CustomerService.cfc.

• When you inherit a RESTful CFC, you can choose to override the attributes used in the CFC that you extend. For example, the following CFC extends the BaseCustomerResource.CFC, but the function SayPlainHellooverrides the function in Base CFC.

• You have to specify the REST attributes (rest/restPath) in the derived CFC to use it as a REST service. Just that it is defined in the base CFC does not work.

REST services and data interchange formats

REST services in ColdFusion can be represented in XML or JSON formats for transmitting over the web. ColdFusion takes care of the serialization/deserialization of the ColdFusion data types used in the services to XML or JSON implicitly.
A function that is REST-enabled can take the following ColdFusion data types as arguments: query, struct, CFC type, array, array of CFCs, XML, string, numeric, boolean , date, and binary (for XML). 
ColdFusion serializes data to pre-defined formats of XML and JSON. Similarly, ColdFusion deserializes the body only if the body is in the format defined by ColdFusion.

XML serialization for REST services

Serialization specifications

• The Accept header of the request has to be either text/ xml  or application/ xml .
• There has to be a function in the service that can produce the required MIME types.
• The function has to return any of the ColdFusion supported data types.

• Cyclic arrays are not supported. You might see the serialized string published, but not with the expected output as explained in the following example:

When an array is assigned to a variable, in this case, <cfset this.arr12 = this.arr1>, you assign arr1 as the item in the second index of arr1. ColdFusion implicitly creates a new array and copies the data from arr1 to the newly created array. The newly created array is assigned to the second index of arr1. Therefore, both the instances are different, and therefore cyclic dependency is impacted.When you serialize, you get the following output:

As you can observe, the inner array gets truncated after the first element.

Deserialization specifications

• The content of the request has to be in a pre-defined format specified by ColdFusion (see details in the section Format definition).
• The content type of the request has to be either text/ xml  or application/ xml .
• There has to be a function in the service that can consume the MIME type of the request.
• cfargument  cannot have the attributes restArgSource and restArgName specified. That is, you can only send data in the body of the request.
• cfargument  type should be ColdFusion supported data type
• There can only be one argument that does not specify the restArgSource attribute. The whole body of the request is deserialized to the argument type.
• Cyclic arrays are not supported.

Format definition

Query

• The root element of the XML has to be query.
• Use the attribute ID to handle circular dependency.
• The following are the valid attribute values: string, date, boolean, numeric, document, query, struct, array, and CFC (if the value is a CFC instance).

Example

In the following example, The root query element has two child elements columnnames and rows. columnnames is the name of the columns in the query. rows can have data in multiple row elements. Here, the order of the column in the row should match the column defined in the columnames. For each column in the row, a type attribute is mandatory. The type attribute can have any of the ColdFusion data types as values.

Struct

• The root element of the XML should be struct .
• Use the attribute ID to handle circular dependency.
• The struct can have multiple entry child elements. That is, a key-value pair in the Struct instance to be serialized. entry element requires two mandatory attributes name (name of the entry) and type (the type of the value of the entry). The type attribute can have one of the ColdFusion data types as values.

Example

CFC Component

• The root element of the XML has to be  component .
• ID  attribute is used to handle circular dependency.
• The name attribute has to provide the fully qualified name of the CFC from webroot .
• A component element can contain multiple property child elements.
• The property elements are the  cfproperty  values defined in  cfcomponent .
• The name attribute of the property corresponds to the name of the  cfproperty  defined.
• type  attribute specifies the type of the  cfproperty .
• If, in the component, any property has a null value, then it does not appear in the serialized format. This applies also for deserialization.

Example

Student.cfc

In the following example,  testrest .student means the CFC Student.cfc is placed in the testrest directory under webroot.

Format for array and array of cfcomponent

• The root element has to be  array .
• size attribute specifies the length of the array.
• The type attribute is not mandatory for the array element whereas for item element, it is mandatory.
• If the array is a  cfcomponent  array, then the type attribute of array element should have the fully qualified name of the CFC.
• The array element contains multiple item child elements. Only the non-null items in the array are serialized.
• The item element has two attributes:  index  that specifies that index of the item in the array and type.

Example

The following example shows an array containing two struct objects:

Example: Array of CFC Serialization

The following example illustrates serializing array of CFC to XML and JSON formats.

Example: Array of CFC: Deserialization

The following example illustrates deserializing array of CFC from XML format.

string, boolean, numeric, binary, and date

Specify the values directly in the body of the request.

Handling cyclic dependency

In ColdFusion, cyclic dependency is handled using the ID reference. All ColdFusion complex data types have unique IDs when serialized. If the same object has to be serialized elsewhere, instead of serializing the object again, a reference is made to the already serialized data using its ID. In the following example, the main object is a struct. The struct contains an array of objects. The array has two elements and both the elements are the same instance of a struct. During serialization, the first element in the array is serialized as it is. The ID of the serialized struct is 2. Instead of serializing the second element, as that object is already serialized, IDREF attribute is used to refer to the already serialized struct instance.

JSON serialization and REST services

Serialization specifications

• The content type of the Accept header of the request has to be text/JSON, application/JSON, or text/plain.
• REST service should have a function that can handle the required MIME types.
• Function has to return any of the ColdFusion supported data types other than binary.

• Cyclic behavior is unsupported. But in the case of arrays, you might see the serialized string published, but not with expected output as explained in the following example:

When an array is assigned to a variable (in this case) <cfset this.arr12 = this.arr1>, you assign arr1 as the item in the second index of arr1. ColdFusion implicitly creates a new array and copies the data from arr1 to the newly created array. The newly created array is assigned to the second index of arr1. Therefore, both the instances are different, and therefore cyclic dependency is impacted.When you serialize, you get the following output:

• As you can observe, the inner array gets truncated after the first element.

Deserialization specifications

• The content of the request is in a predefined format specified by ColdFusion.
• The content type of the request is text/JSON, application/JSON, or text/plain.
• A function in the service consumes the MIME type of the request.
• cfargument does not have the attributes restargsource and restargname specified.
• cfargument type is ColdFusion supported data type other than binary or CFC definition.
• Only one argument has no restAargSource attribute specified. The whole body of the request is deserialized to the argument type.
• Cyclic behavior is unsupported. But in the case of cyclic arrays, you might see the deserialized array published, but not giving expected output.

Format definitions

Format for query

Format for struct

Format for component

Format for array

string, boolean, numeric, and date

Specify the values directly in the body of the request. ----

Support for GZip encoding

If the request contains a Content-Encoding header of "gzip" then the request entity (if any) is uncompressed using the gzip algorithm. If the request contains an Accept-Encoding header containing "gzip" and an "If-None-Match" Header, entitytag value is checked: if it contains the -gzip suffix, remove this suffix, otherwise, completely remove the "if-none-match" header.

If the request contains a Accept-Encoding header that contains "gzip", then the response entity (if any) is compressed using gzip and a Content-Encoding header of "gzip" is added to the response. As this filter is active, the resource representation can be compressed. the value "Accept-Encoding" is so added to the Vary header. If any entityTag is used and content may be gzipped, the "-gzip" suffix is added to entitytag value.

Site-level REST application support

In ColdFusion 10, multiple applications cannot have the same name, even if the applications are residing in different hosts. With the enhanced ColdFusion 11 REST feature, you can have multiple applications with the same name but available in different hosts. Also, you can set one default application (containing the REST service) for each virtual host. 

You can register the directory containing the REST service by using any one of the following options:

• autoregister Application Setting
• ColdFusion Administrator console
• ColdFusion Admin API
• restInitApplication method

Option 1: autoregister Application Setting

A new Application setting autoregister is introduced in ColdFusion 11.

• You can set the auto register to true if you want to enable the auto registration for the application: 

• Specifying the  servicemapping  is optional. If  servicemapping  is not specified, the "this.name"/application name will be taken as default.

• Specify the  usehost  or hostname, If  usehost  attribute is set to true, then the host name is parsed from the URL. usehost="True" is the default value for REST service registration. If usehost=true, the host name will be taken from the URL. The host name will be used for registration. If no hosts are specified, that is, usehost="False", all applications without a host name and all requests from any host will be serviced.

• Explicitly naming the host name will make the host name. If the host name is not mentioned, then the  usehost  name will  be defaulted .

• Set isDefault to true and the application will be made as default app. 

When the first request comes to the application and if that request is  non-REST  request, the application will be started and registered. If both  usehost  and host are not specified, the apps will be registered without  host  name. 

Option 2: Registering a REST application using ColdFusion Administrator console

• Use the Administrator console to register a directory containing REST-enabled CF components. Select Adobe ColdFusion 11 Administrator console > Data & Services > REST services.
• Browse and select the root path (or the application path) where ColdFusion will search for the directory containing a set of REST enabled CF components. 
  (Optional) In the Service Mapping section, specify the virtual mapping in place of application name. If the folder has an Application.cfc file and an application name, use the application name to identify the REST services in the directory. 
  (Optional) Enter the Host Name. This will enable the mapping of the selected application with the host. Each host can have a default application and multiple applications with the same application name can be mapped to different hosts.
• Set the REST application as a default application by selecting the option Set as default application. By selecting this option, you omit the need to specify the service mapping or the application name in the URI.
• Click the Add Service button to complete registration of the directory.
• View the Active ColdFusion REST Services display table to view the list of active service mappings. You can use the same to edit or delete the service mappings in future.

Option 3: Registering a REST application using the ColdFusion Admin API

You can use functions defined in CFIDE. adminapi .extensions CFC to manage a REST application. The functions are:

• registerRESTService(path[,serviceMapping[,host[,isdef]]]: This function registers the REST application. The root path specifies the directory containing REST-enabled CF component. Optionally, the service mapping for the REST application,  host name , and  isdefault  can be specified.
• getRESTServices(): This function returns an array of REST services registered with the ColdFusion Administrator.
• deleteRESTService(rootPath): This function deletes the specified REST application registered with the ColdFusion Administrator.
• refreshRESTService(rootPath): If you make any changes to the REST-enabled CF component, you can refresh the registered application by calling this function.
• getDefaultRestService(): Returns the  server wide  default REST application.
• getAllDefaultRESTServices: Returns all the default REST services. It is an array of path – host pair.

Option 4: Registering a REST application using the restInitApplication method

You can also register a REST application by calling the method restInitApplication

The syntax is:

The options are an optional argument. In the options struct you can pass the:

• Host
• useHost
• isDefault

For registering by specifying the host explicitly:

For registering by specifying the UseHost attribute: The host name will be extracted from the request URL and will be used for registration.

• In the options you can specify host, useHost and isDefault. The option usage is same as autoRegister feature.
• If you have already registered the application using the Administrator module, call restInitApplication to refresh the REST service.
• Use the restDeleteApplication function to delete the REST service. The syntax is restDeleteApplication(rootPath)

Support for pluggable serializer and deserializer

In the application.cfc, you can register your own handler for serializing and deserializing the complex types. If the serializer is not specified, ColdFusion uses the default mechanism for serialization.

Example: If you have a phone directory to be serialized on the following parameters:

• The main data structure is an Array. 
• Each element of the array is a struct. 
• The Struct contains 2 elements. 
• The first is the name of the contact and the second is the struct which contains the code and the phone number.

Array

And in this example, you want to serialize only struct in a simple format and want the result as follows:

With the enhanced ColdFusion 11 REST feature, the user can use the plugged-in custom serializer instead of using the default serialization function. The custom serializer has four functions:

• CanSerialize - Returns a boolean value and takes the "Accept Type" of the request as the argument. You can return true if you want the customserialzer to serialize the data to the passed argument type. 
• Serialize - The main serialization logic must be implemented in this function. If canSerialize returns "True" for a request, then ColdFusion will use this function to serialize. If canSerialize returns false, then ColdFusion will use the default serialization to serialize.
• CanDeserialize - Returns a boolean value and takes the " Content Type " of the request as the argument. You can return true if you want the customserialzer to deserialize the data.
• DeSerialize - The main deserialization logic must be implemented in this function. If canDeSerialize returns "True" for a request, then ColdFusion will use this function to deserialize. If canDeSerialize returns false, then ColdFusion will use the default de-serialization to deserialize.

The below CustomSerializer code sample will help you to achieve the result for the scenario explained above (Customizing serialization /deserialization of phone directory):

The CustomSerializer that you have implemented can be specified through application.cfc.