The API for Context Variables

pub.apigateway.ctxvar:getContextVariable

Use this JAVA service to retrieve a context variable’s value and assign it to a pipeline variable. All parameter names are case-sensitive.

The table lists the predefined system context variables and its syntax used to get system context variables using pub.apigateway.ctxvar:getContextVariable.

Notes on getting and setting the PROTOCOL_HEADERS

All context variable values are typed as either string or int except for the predefined context variables, PROTOCOL_HEADERS, which is of the type IData. You can set or get value for PROTOCOL_HEADERS in one of the following ways:

• set or get the entire structure.

  To set the entire structure, you must:

  • Set the varName parameter in pub.apigateway.ctxvar:setContextVariable to PROTOCOL_HEADERS.
  • Use the method ISMediatorRuntimeFacade.setContextVariableValue().

  To get the entire structure, you must:

  • Set the varName parameter in pub.apigateway.ctxvar:getContextVariable to PROTOCOL_HEADERS.
  • Use the method ISMediatorRuntimeFacade.getContextVariableValue().

  If the varName is set to PROTOCOL_HEADERS, you get or set the entire IData structure containing all of the transport headers. The key is the transport header name (for example, Content-Type) and the value is a String. The IData object for PROTOCOL_HEADERS contains a set of string values where each IData string key matches the header name in the transport headers map. The set of possible keys includes the HTTP v1.1 set of headers as well as any custom key-value pairs you might have defined.

  Alternatively, you can set the varName parameter to address a specific element in the array. For example, setting it to PROTOCOL_HEADERS[Content-Type] would apply to the Content-Type transport header.

• set or get a nested value.

  Set a nested value in one of the following ways:

  • Set the varName parameter in pub.apigateway.ctxvar:setContextVariable to PROTOCOL_HEADERS[arrayElement], where [arrayElement] refers to a specific element. For example, PROTOCOL_HEADERS[Content-Type] (to indicate the first array element in the set).
  • Alternatively, use the method ISMediatorRuntimeFacade.setContextVariableValue(). Use this method only if you are writing a JAVA service and you want to access it through the JAVA source code.

  Get a nested value in one of the following ways:

  • Set the varName parameter in pub.apigateway.ctxvar:getContextVariable to PROTOCOL_HEADERS[arrayElement], where [arrayElement] refers to a specific element. For example, PROTOCOL_HEADERS[Content-Type] (to indicate the first array element in the set).
  • Alternatively, use the method ISMediatorRuntimeFacade.getContextVariableValue(). Use this method only if you are writing a JAVA service and you want to access it through the JAVA source code.

  You can set or get a nested value inside PROTOCOL_HEADERS through an additional keyName. In this case, the object reference is not an IData object. For PROTOCOL_HEADERS, the keyName must match the transport header name in a case-sensitive manner (for example, PROTOCOL_HEADERS[Content-Type] or PROTOCOL_HEADERS[Authorization]). In this case, the Serializable value will be a string.

pub.apigateway.ctxvar:setContextVariable

Use this JAVA service to set a value on a context variable. The pipeline variable containing the context variable value should be an object reference that implements java.io.Serializable. All parameter names are case-sensitive.

pub.apigateway.ctxvar:declareContextVariable

Use this JAVA service to declare a custom context variable. All custom-defined context variables must be declared in a custom namespace that is identified by using the prefix mx (for example, mx:CUSTOM_VARIABLE). All parameter names are case-sensitive.

Note the following:

• After declaring the context variable, you can use the setContext variable to set a value on the context variable.
• You do not need to declare the following kinds of context variables:
  • The predefined context variables provided by webMethods API Gateway. If you attempt to declare an existing predefined context variable, an error will occur.
  • Any custom context variable that you define in a routing rule that you create in the conditional routing step.
• Any custom context variables that you explicitly declare in source code using the API will have a declaration scope of SESSION.
• Any custom context variable's state that is defined during the inbound request processing steps will still be available during the outbound response processing steps.
• All context variable values are typed as either string or int (excluding the PROTOCOL_HEADERS variables, which are of the type IData).
• Valid names should be upper case (by convention) and must be a valid JAVA Identifier. In general, use alpha-numerics, $ or _ symbols to construct these context names. Names with punctuation, whitespace or other characters will be considered invalid and will fail deployment.
• All custom context variables must be declared in a custom namespace that is identified by using an mx prefix (for example, mx:CUSTOM_VARIABLE).
• To reference a custom context variable in a flat string, you need to prepend a $ symbol to the context variable name to indicate that variable’s value should be referenced. Think of this usage as being similar to the & address operation for C variables.

  An expression that references a custom context variable might look like this:

  $mx:TAXID=1234 or $mx:ORDER_SYSTEM_NAME="Pluto"

  Notice that the values of the data type “int” are not enclosed in quotation marks, while the values of the data type “string” are. The quotation marks are only needed if a context variable expression (as opposed to a reference) is defined.

• Referencing an undefined context variable does not result in an error.
• Once a variable has been declared it cannot be declared again.

pub.apigateway.ctxvar:removeContextVariable

Use this JAVA service to remove a custom context variable from a request or response session. All parameter names are case-sensitive.

Sample Flow Service: Getting a Context Variable Value

This flow service sets the value of a custom context variable to be used in a response.

This flow service declares a pipeline variable named customName, which is set to the value mx:COMP_TEST.

This flow service will retrieve the context variable for customName and create an element for its context variable value in the response message return to the consumer.

You can define the customName variable value to be mx:COMP_TEST so you can use this variable to lookup the custom variable name that was seeded in the previous example.

Clicking on the customName pipeline variable displays the name.

The call to pub.mediator.ctxvar:getContextVariable retrieves the value of the custom context variable from the context variable map.

This is just a sample JAVA service that takes the context variable and creates a top-level element in the response message using the same name and value.

Sample Flow Service: Setting a Context Variable Value

This flow service sets the value of a custom context variable to be used in a response.

This flow service declares a pipeline variable named customName, which is set to the value mx:COMP_TEST.

This flow service retrieves the context variable for customName and create an element for its context variable value in the response message return to the consumer.

You define the customName variable value to be mx:COMP_TEST so you can use this variable to lookup the custom variable name that was seeded in the previous example.

Clicking on the customName pipeline variable displays the name.

The call to pub.mediator.ctxvar:getContextVariable retrieves the value of the custom context variable from the context variable map.

This is just a sample JAVA service that takes the context variable and creates a top-level element in the response message using the same name and value.