Message Builder Policy

General Information

Policy Type

policy-message-builder

Description

Message Builder policy evaluates a list of rows sequentially. Each row reads from a source (body, header, query parameter, or context) and writes the result to a target custom variable. Template mode supports JEXL expressions and multi-line scripts with loops and conditionals.

Endpoints

List Policies

GET /apiops/projects/{projectName}/apiProxies/{apiProxyName}/policies/

Add Policy

POST /apiops/projects/{projectName}/apiProxies/{apiProxyName}/policies/{policyName}/

Update Policy

PUT /apiops/projects/{projectName}/apiProxies/{apiProxyName}/policies/{policyName}/

Delete Policy

DELETE /apiops/projects/{projectName}/apiProxies/{apiProxyName}/policies/{policyName}/

---

List Policies

Endpoint

GET /apiops/projects/{projectName}/apiProxies/{apiProxyName}/policies/

Request

Headers

Header	Value
Authorization	Bearer {token}

Path Parameters

Parameter	Type	Required	Description
projectName	string	Yes	Project name
apiProxyName	string	Yes	API Proxy name

Response

Success Response (200 OK)

{
  "status": "SUCCESS",
  "resultList": [
    {
      "apiProxy": {
        "name": "PetAPI",
        "requestPolicyList": [
          {
            "type": "policy-message-builder",
            "name": "pet-enrichment-builder",
            "description": "Enriches pet request payload with context and custom variables",
            "active": true,
            "rowList": [
              {
                "buildMode": "TEMPLATE",
                "template": "#{body.$.name}",
                "targetVariable": {
                  "name": "petName",
                  "type": "CUSTOM"
                },
                "required": false,
                "continueOnError": true,
                "defaultValue": "unknown"
              }
            ]
          }
        ],
        "responsePolicyList": [],
        "errorPolicyList": []
      }
    }
  ],
  "resultCount": 1
}

cURL Example

curl -X GET \
  "https://demo.apinizer.com/apiops/projects/MyProject/apiProxies/PetAPI/policies/" \
  -H "Authorization: Bearer YOUR_TOKEN"

---

Add Policy

Endpoint

POST /apiops/projects/{projectName}/apiProxies/{apiProxyName}/policies/{policyName}/

Request

Headers

Header	Value
Authorization	Bearer {token}
Content-Type	application/json

Path Parameters

Parameter	Type	Required	Description
projectName	string	Yes	Project name
apiProxyName	string	Yes	API Proxy name
policyName	string	Yes	Policy name

Request Body

Full JSON Body Example

The following example builds an enriched JSON payload from request body, headers, query parameters, and context variables. It also produces a nested conditional element using intermediate custom variables.

{
  "operationMetadata": {
    "targetScope": "ALL",
    "targetPipeline": "REQUEST",
    "deploy": true,
    "deployTargetEnvironmentNameList": ["production"],
    "order": 1
  },
  "policy": {
    "type": "policy-message-builder",
    "description": "Enriches pet request payload with context and custom variables",
    "active": true,
    "rowList": [
      {
        "buildMode": "TEMPLATE",
        "template": "#{body.$.name}",
        "targetVariable": {
          "name": "petName",
          "type": "CUSTOM"
        },
        "required": false,
        "continueOnError": true,
        "defaultValue": "unknown"
      },
      {
        "buildMode": "TEMPLATE",
        "template": "#{body.$.category.name}",
        "targetVariable": {
          "name": "categoryLabel",
          "type": "CUSTOM"
        },
        "required": false,
        "continueOnError": true,
        "defaultValue": ""
      },
      {
        "buildMode": "TEMPLATE",
        "template": "#{body.$.status == 'available' ? 'AVAILABLE' : body.$.status == 'pending' ? 'PENDING' : 'SOLD'}",
        "targetVariable": {
          "name": "statusLabel",
          "type": "CUSTOM"
        },
        "required": false,
        "continueOnError": true,
        "defaultValue": ""
      },
      {
        "buildMode": "TEMPLATE",
        "template": "null",
        "targetVariable": {
          "name": "nestedObject",
          "type": "CUSTOM"
        },
        "required": false,
        "continueOnError": true,
        "defaultValue": "null"
      },
      {
        "policyCondition": {
          "conditionRuleList": [
            {
              "conditionCriteria": "AND",
              "conditionRuleList": [
                {
                  "conditionCriteria": "VALUE",
                  "firstVariable": {
                    "type": "BODY",
                    "jsonPathValue": "$.status",
                    "messageContentType": "JSON"
                  },
                  "variableDataType": "STRING",
                  "valueComparisonOperator": "EQ",
                  "secondValueSource": "VALUE",
                  "secondValue": "available"
                }
              ]
            }
          ]
        },
        "buildMode": "TEMPLATE",
        "template": "{\"displayName\":\"#{petName} - #{categoryLabel}\",\"statusLabel\":\"#{statusLabel}\"}",
        "targetVariable": {
          "name": "nestedObject",
          "type": "CUSTOM"
        },
        "required": false,
        "continueOnError": true,
        "defaultValue": "null"
      },
      {
        "buildMode": "TEMPLATE",
        "template": "{\"request\":{\"headers\":{\"contentType\":\"#{header.Content-Type}\",\"xRequestId\":\"#{header.X-Request-Id}\"},\"query\":{\"format\":\"#{query.format}\"},\"body\":{\"id\":#{body.$.id},\"name\":\"#{petName}\",\"category\":{\"id\":#{body.$.category.id},\"name\":\"#{categoryLabel}\",\"nested\":#{nestedObject}},\"photoUrls\":#{body.$.photoUrls},\"tags\":#{body.$.tags},\"status\":\"#{body.$.status}\"}},\"context\":{\"httpMethod\":\"#{context.request.httpMethod}\",\"clientIp\":\"#{context.request.remoteAddress}\",\"correlationId\":\"#{context.message.correlationId}\",\"year\":\"#{context.system.year}\",\"dateTime\":\"#{context.system.dateTime}\",\"environment\":\"#{context.environment.name}\"},\"computed\":{\"operationType\":\"#{context.request.httpMethod == 'POST' ? 'create' : context.request.httpMethod == 'PUT' ? 'update' : context.request.httpMethod == 'DELETE' ? 'delete' : 'read'}\",\"summary\":\"#{petName} (#{categoryLabel}) - #{statusLabel}\"}}",
        "targetVariable": {
          "name": "enrichedPayload",
          "type": "CUSTOM"
        },
        "required": false,
        "continueOnError": true,
        "defaultValue": "{}"
      }
    ]
  }
}

Request Body Fields

operationMetadata

Field	Type	Required	Default	Description
targetScope	string	Yes	-	Policy scope: ALL or ENDPOINT
targetEndpoint	string	No*	-	Endpoint path (required if targetScope=ENDPOINT)
targetEndpointHTTPMethod	string	No*	-	HTTP method (required if targetScope=ENDPOINT)
targetPipeline	string	Yes	-	Pipeline: REQUEST, RESPONSE, or ERROR
deploy	boolean	No	true	Whether to deploy after adding policy
deployTargetEnvironmentNameList	array	No	[]	List of environment names to deploy to
order	integer	No	null	Policy execution order (starts from 1)

Enum: targetScope

• ALL - Policy applies to all endpoints
• ENDPOINT - Policy applies only to specified endpoint

Enum: targetPipeline

• REQUEST - Executes in request pipeline
• RESPONSE - Executes in response pipeline
• ERROR - Executes in error pipeline

Enum: targetEndpointHTTPMethod

• GET, POST, PUT, DELETE, PATCH, OPTIONS, HEAD

policy

Field	Type	Required	Default	Description
type	string	Yes	-	Policy type: policy-message-builder
description	string	No	-	Policy description
active	boolean	No	true	Whether policy is active
rowList	array	Yes	-	List of message builder rows (at least one)

rowList[] (Message Builder Row)

Field	Type	Required	Default	Description
buildMode	string	Yes	-	Build mode: FORM or TEMPLATE
sourceVariable	object	Yes (FORM mode)	-	Source variable to read the value from
targetVariable	object	Yes	-	Target variable to write the result to
template	string	Yes (TEMPLATE mode)	-	Template string with #{...} expressions
required	boolean	No	false	If true, throws an error when the source value is empty
continueOnError	boolean	No	true	If true, processing continues to next row when an error occurs
defaultValue	string	No	-	Value to use when source is empty
policyCondition	object	No	-	Row-level condition; row is skipped when condition is not met

Enum: buildMode

• FORM - Copies value directly from source variable to target variable
• TEMPLATE - Evaluates #{...} template expressions (supports JEXL expressions and multi-line scripts)

variable (sourceVariable / targetVariable)

Field	Type	Required	Description
name	string	Yes (CUSTOM type)	Variable name (used to reference in templates as #{name})
type	string	Yes	Variable type (see EnumVariableType below)
headerName	string	Yes (HEADER type)	Header name (e.g., Content-Type, X-Request-Id)
paramType	string	Yes (PARAMETER type)	Parameter category: QUERY, PATH, or FORM
paramName	string	Yes (QUERY/PATH param)	Query or path parameter name
formName	string	Yes (FORM param)	Form field name
jsonPathValue	string	Yes (BODY/JSON type), Optional (CUSTOM)	JSONPath expression (e.g., $.user.name, $[0].id). For CUSTOM type, extracts a specific value from the variable's JSON content.
xpathValue	string	Yes (BODY/XML type), Optional (CUSTOM)	XPath expression (e.g., /root/user/name). For CUSTOM type, extracts a specific value from the variable's XML content.
messageContentType	string	Yes (BODY type), Optional (CUSTOM with path)	Body content type: JSON or XML. Required when using jsonPathValue or xpathValue with CUSTOM type.
contextValue	string	Yes (CONTEXT_VALUES type)	Context value enum (see EnumVariableContextValue below)

Enum: EnumVariableType

Value	Description	Required Fields
HEADER	Request or response header value	headerName
PARAMETER	Query, path, or form parameter	paramType, paramName or formName
BODY	Request or response body field	jsonPathValue or xpathValue, messageContentType
CUSTOM	Custom variable stored in the variable map. Optionally supports jsonPathValue/xpathValue with messageContentType to extract a specific value from the variable's content.	name, optionally jsonPathValue or xpathValue + messageContentType
CONTEXT_VALUES	Gateway context value (runtime metadata)	contextValue

Enum: EnumVariableParameterType

• QUERY - URL query parameter
• PATH - URL path parameter
• FORM - Form-encoded parameter

Enum: EnumMessageContentType

• JSON - JSON body (use with jsonPathValue)
• XML - XML body (use with xpathValue)

Enum: EnumVariableContextValue (contextValue)

Value	Description
REQUEST_HTTP_METHOD	HTTP method (GET, POST, PUT, DELETE, etc.)
REQUEST_REMOTE_ADDRESS	Client IP address
REQUEST_CONTENT_TYPE	Request Content-Type header
REQUEST_REQUEST_URI	Full request URI
REQUEST_QUERY_STRING	Raw query string
REQUEST_USERNAME_KEY	Authenticated username or API key
RESPONSE_STATUS_CODE	Response HTTP status code
MESSAGE_CORRELATION_ID	Unique correlation ID assigned by the gateway
ENVIRONMENT_ID	Gateway environment ID
ENVIRONMENT_NAME	Gateway environment name
APIPROXY_ID	API Proxy ID
APIPROXY_NAME	API Proxy name
APIPROXYGROUP_ID	API Proxy Group ID
APIPROXYGROUP_NAME	API Proxy Group name
APIMETHOD_ID	API Method ID
APIMETHOD_NAME	API Method name
APIMETHOD_HTTPMETHOD	API Method HTTP method
APIMETHOD_ENDPOINT	API Method endpoint path
APIMETHOD_BACKEND_HTTPMETHOD	Backend API method HTTP method
APIMETHOD_BACKEND_ENDPOINT	Backend API method endpoint path
DATETIME_YEAR	Current year (integer)
DATETIME_MONTH	Current month (integer, 1-12)
DATETIME_DAY_OF_WEEK	Day of week (integer, 1=Monday, 7=Sunday)
DATETIME_DAY_OF_MONTH	Day of month (integer, 1-31)
DATETIME_HOUR	Current hour (0-23)
DATETIME_MINUTE	Current minute (0-59)
DATETIME_SECOND	Current second (0-59)
DATETIME_EPOCH_MILLIS	Epoch milliseconds since 1970-01-01T00:00:00Z
DATETIME_FORMATTED_TEXT	Date-time in yyyy-MM-dd'T'HH:mm:ss.SSS'Z' format
DATE_FORMATTED_TEXT	Date in yyyy-MM-dd format
TIME_FORMATTED_TEXT	Time in HH:mm:ss format
CREDENTIAL_USERNAME	Authenticated credential username
CREDENTIAL_EMAIL	Authenticated credential email
CREDENTIAL_FULLNAME	Authenticated credential full name

policyCondition

The policyCondition object defines a row-level condition. The row is skipped when the condition evaluates to false.

Field	Type	Required	Description
conditionRuleList	array	Yes	List of condition rules

conditionRule fields:

Field	Type	Required	Description
conditionCriteria	string	Yes	Rule type: AND, OR, NOT, or VALUE
conditionRuleList	array	Yes (AND/OR/NOT)	Nested list of condition rules
firstVariable	object	Yes (VALUE)	Left-hand side variable for comparison
variableDataType	string	Yes (VALUE)	Data type: STRING, NUMERIC, or DATE
valueComparisonOperator	string	Yes (VALUE)	Comparison operator (see below)
secondValueSource	string	Yes (VALUE)	Right-hand side source: VALUE (literal) or VARIABLE
secondValue	string	Yes (VALUE, secondValueSource=VALUE)	Literal value to compare against
secondVariable	object	Yes (VALUE, secondValueSource=VARIABLE)	Variable to compare against

Enum: valueComparisonOperator

• EQ - Equals
• NE - Not equals
• EQ_IGNORE_CASE - Equals, case insensitive (string only)
• NE_IGNORE_CASE - Not equals, case insensitive (string only)
• LT - Less than
• LE - Less than or equal
• GT - Greater than
• GE - Greater than or equal
• CONTAINS - String contains
• NOT_CONTAINS - String does not contain
• CONTAINS_IGNORE_CASE - String contains, case insensitive
• NOT_CONTAINS_IGNORE_CASE - String does not contain, case insensitive
• STARTS_WITH - String starts with
• NOT_STARTS_WITH - String does not start with
• STARTS_WITH_IGNORE_CASE - String starts with, case insensitive
• NOT_STARTS_WITH_IGNORE_CASE - String does not start with, case insensitive
• ENDS_WITH - String ends with
• NOT_ENDS_WITH - String does not end with
• ENDS_WITH_IGNORE_CASE - String ends with, case insensitive
• NOT_ENDS_WITH_IGNORE_CASE - String does not end with, case insensitive
• IS_EXISTS - Variable exists (regardless of value)
• IS_NOT_EXISTS - Variable does not exist
• IS_NOT_EMPTY - Variable exists and is not empty
• IS_EMPTY - Variable does not exist or is empty
• EXISTS_AND_EMPTY - Variable exists but is empty
• IN - Value is in list
• NOT_IN - Value is not in list
• IN_IGNORE_CASE - Value is in list, case insensitive
• NOT_IN_IGNORE_CASE - Value is not in list, case insensitive

Response

Success Response (200 OK)

{
  "status": "SUCCESS",
  "deploymentResult": {
    "success": true,
    "deploymentResults": [
      {
        "environmentName": "production",
        "success": true,
        "message": "Deployment successful"
      }
    ]
  }
}

cURL Example

curl -X POST \
  "https://demo.apinizer.com/apiops/projects/MyProject/apiProxies/PetAPI/policies/pet-enrichment-builder/" \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "operationMetadata": {
      "targetScope": "ALL",
      "targetPipeline": "REQUEST",
      "deploy": true,
      "deployTargetEnvironmentNameList": ["production"],
      "order": 1
    },
    "policy": {
      "type": "policy-message-builder",
      "description": "Enriches pet request payload",
      "active": true,
      "rowList": [
        {
          "buildMode": "TEMPLATE",
          "template": "#{body.$.name}",
          "targetVariable": {
            "name": "petName",
            "type": "CUSTOM"
          },
          "required": false,
          "continueOnError": true,
          "defaultValue": "unknown"
        },
        {
          "buildMode": "TEMPLATE",
          "template": "{\"id\":#{body.$.id},\"name\":\"#{petName}\",\"status\":\"#{body.$.status}\",\"method\":\"#{context.request.httpMethod}\",\"correlationId\":\"#{context.message.correlationId}\"}",
          "targetVariable": {
            "name": "enrichedPayload",
            "type": "CUSTOM"
          },
          "required": false,
          "continueOnError": true,
          "defaultValue": "{}"
        }
      ]
    }
  }'

---

Update Policy

Endpoint

PUT /apiops/projects/{projectName}/apiProxies/{apiProxyName}/policies/{policyName}/

Request

Headers

Header	Value
Authorization	Bearer {token}
Content-Type	application/json

Path Parameters

Parameter	Type	Required	Description
projectName	string	Yes	Project name
apiProxyName	string	Yes	API Proxy name
policyName	string	Yes	Policy name

Request Body

Same structure as Add Policy request body.

Full JSON Body Example

{
  "operationMetadata": {
    "targetScope": "ALL",
    "targetPipeline": "REQUEST",
    "deploy": true,
    "deployTargetEnvironmentNameList": ["production"]
  },
  "policy": {
    "type": "policy-message-builder",
    "description": "Updated: Enriches pet payload with JEXL script for tags",
    "active": true,
    "rowList": [
      {
        "buildMode": "TEMPLATE",
        "template": "#{body.$.name}",
        "targetVariable": {
          "name": "petName",
          "type": "CUSTOM"
        },
        "required": false,
        "continueOnError": true,
        "defaultValue": "unknown"
      },
      {
        "buildMode": "TEMPLATE",
        "template": "#{body.$.status == 'available' ? 'AVAILABLE' : body.$.status == 'pending' ? 'PENDING' : 'SOLD'}",
        "targetVariable": {
          "name": "statusLabel",
          "type": "CUSTOM"
        },
        "required": false,
        "continueOnError": true,
        "defaultValue": ""
      },
      {
        "buildMode": "TEMPLATE",
        "template": "#{\n  var out = '[';\n  var first = true;\n  for (item : body.$.tags) {\n    if (!first) { out = out + ','; }\n    out = out + '{\"id\":' + item.id + ',\"label\":\"' + item.name + '\"}';\n    first = false;\n  }\n  out + ']'\n}",
        "targetVariable": {
          "name": "tagList",
          "type": "CUSTOM"
        },
        "required": false,
        "continueOnError": true,
        "defaultValue": "[]"
      },
      {
        "buildMode": "TEMPLATE",
        "template": "{\"name\":\"#{petName}\",\"status\":\"#{statusLabel}\",\"tags\":#{tagList},\"correlationId\":\"#{context.message.correlationId}\"}",
        "targetVariable": {
          "name": "enrichedPayload",
          "type": "CUSTOM"
        },
        "required": false,
        "continueOnError": true,
        "defaultValue": "{}"
      }
    ]
  }
}

Response

Success Response (200 OK)

{
  "status": "SUCCESS",
  "deploymentResult": {
    "success": true,
    "deploymentResults": [
      {
        "environmentName": "production",
        "success": true,
        "message": "Deployment successful"
      }
    ]
  }
}

cURL Example

curl -X PUT \
  "https://demo.apinizer.com/apiops/projects/MyProject/apiProxies/PetAPI/policies/pet-enrichment-builder/" \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "operationMetadata": {
      "targetScope": "ALL",
      "targetPipeline": "REQUEST",
      "deploy": true,
      "deployTargetEnvironmentNameList": ["production"]
    },
    "policy": {
      "type": "policy-message-builder",
      "description": "Updated: Enriches pet payload",
      "active": true,
      "rowList": [
        {
          "buildMode": "TEMPLATE",
          "template": "#{body.$.name}",
          "targetVariable": { "name": "petName", "type": "CUSTOM" },
          "required": false,
          "continueOnError": true,
          "defaultValue": "unknown"
        }
      ]
    }
  }'

---

Delete Policy

Endpoint

DELETE /apiops/projects/{projectName}/apiProxies/{apiProxyName}/policies/{policyName}/

Request

Headers

Header	Value
Authorization	Bearer {token}

Path Parameters

Parameter	Type	Required	Description
projectName	string	Yes	Project name
apiProxyName	string	Yes	API Proxy name
policyName	string	Yes	Policy name

Response

Success Response (200 OK)

{
  "status": "SUCCESS",
  "deploymentResult": {
    "success": true
  }
}

cURL Example

curl -X DELETE \
  "https://demo.apinizer.com/apiops/projects/MyProject/apiProxies/PetAPI/policies/pet-enrichment-builder/" \
  -H "Authorization: Bearer YOUR_TOKEN"

---

Template Syntax Reference

Simple Variable Access

Syntax	Description
#{body.$.field}	JSON body field via JSONPath
#{body.$[0].field}	JSON array body — first element field
#{body./root/field}	XML body field via XPath
#{header.Header-Name}	Request header value
#{query.paramName}	URL query parameter
#{path.paramName}	URL path parameter
#{form.fieldName}	Form-encoded parameter
#{customVarName}	Custom variable from current row chain

Region-Aware Variable Access

Syntax	Description
#{request.body.$.field}	Request body field (explicit region)
#{request.header.Name}	Request header (explicit region)
#{response.body.$.field}	Response body field (explicit region)
#{response.header.Name}	Response header (explicit region)
#{request.body./root/field}	Request body XPath (explicit region)
#{response.body./root/field}	Response body XPath (explicit region)

Custom Variable Path (JSONPath/XPath on variable content)

Syntax	Description
#{myVar.$.user.name}	JSONPath on custom variable's JSON content
#{myVar./root/element}	XPath on custom variable's XML content
#{myVar./bookstore/book[1]/title}	XPath with predicate on custom variable

Context Variable Syntax

Syntax	contextValue Enum
#{context.request.httpMethod}	REQUEST_HTTP_METHOD
#{context.request.remoteAddress}	REQUEST_REMOTE_ADDRESS
#{context.message.correlationId}	MESSAGE_CORRELATION_ID
#{context.apiProxy.name}	APIPROXY_NAME
#{context.apiMethod.httpMethod}	APIMETHOD_HTTPMETHOD
#{context.system.year}	DATETIME_YEAR
#{context.system.dateTime}	DATETIME_FORMATTED_TEXT
#{context.environment.name}	ENVIRONMENT_NAME
#{context.credential.username}	CREDENTIAL_USERNAME

JEXL Expression Examples

#{body.$.price * 1.18}
#{body.$.firstName + ' ' + body.$.lastName}
#{body.$.status == 'available' ? 'IN_STOCK' : 'OUT_OF_STOCK'}
#{context.request.httpMethod == 'POST' ? 'create' : 'read'}

JEXL Script (Multi-Line) Example

#{
  var out = '[';
  var first = true;
  for (item : body.$.tags) {
    if (!first) { out = out + ','; }
    out = out + '{"id":' + item.id + ',"name":"' + item.name + '"}';
    first = false;
  }
  out + ']'
}

The return keyword is not used in JEXL Script. The value of the last evaluated expression is returned automatically.