abp/docs/en/low-code/interceptors.md

//[doc-seo]
{
    "Description": "Add custom business logic to dynamic entity CRUD operations using Interceptors in the ABP Low-Code System. Validate, transform, and react to data changes with JavaScript."
}

Interceptors

Interceptors allow you to run custom JavaScript code before, after, or instead of Create, Update, and Delete operations on dynamic entities.

Interceptor Types

Command	Type	When Executed
Create	Pre	Before entity creation — validation, default values
Create	Post	After entity creation — notifications, related data
Create	Replace	Instead of entity creation — must return the new entity's Id (see below)
Update	Pre	Before entity update — validation, authorization
Update	Post	After entity update — sync, notifications
Update	Replace	Instead of entity update — no return value needed
Delete	Pre	Before entity deletion — dependency checks
Delete	Post	After entity deletion — cleanup
Delete	Replace	Instead of entity deletion — no return value needed

Defining Interceptors with Attributes

Use the [DynamicEntityCommandInterceptor] attribute on a C# class:

[DynamicEntity]
[DynamicEntityCommandInterceptor(
    "Create",
    InterceptorType.Pre,
    "if(!context.commandArgs.data['Name']) { globalError = 'Name is required!'; }"
)]
[DynamicEntityCommandInterceptor(
    "Create",
    InterceptorType.Post,
    "context.log('Entity created: ' + context.commandArgs.entityId);"
)]
public class Organization
{
    public string Name { get; set; }
}

The Name parameter must be one of: "Create", "Update", or "Delete". The InterceptorType can be Pre, Post, or Replace. When Replace is used, the default database operation is completely skipped and only your JavaScript handler executes. Multiple interceptors can be added to the same class (AllowMultiple = true).

Defining Interceptors in model.json

Add interceptors to the interceptors array of an entity:

{
  "name": "LowCodeDemo.Customers.Customer",
  "interceptors": [
    {
      "commandName": "Create",
      "type": "Pre",
      "javascript": "if(context.commandArgs.data['Name'] == 'Invalid') {\n  globalError = 'Invalid Customer Name!';\n}"
    }
  ]
}

Interceptor Descriptor

Field	Type	Description
commandName	string	"Create", "Update", or "Delete"
type	string	"Pre", "Post", or "Replace"
javascript	string	JavaScript code to execute

JavaScript Context

Inside interceptor scripts, you have access to:

context.commandArgs

Property / Method	Type	Description
data	object	Entity data dictionary (for Create/Update)
entityId	string	Entity ID (for Update/Delete)
commandName	string	Command name ("Create", "Update", or "Delete")
entityName	string	Full entity name
getValue(name)	function	Get a property value
setValue(name, value)	function	Set a property value (Pre-interceptors only)
hasValue(name)	function	Check if a property exists in the data
removeValue(name)	function	Remove a property from the data

context.currentUser

Property / Method	Type	Description
isAuthenticated	bool	Whether user is logged in
id	string	User ID
userName	string	Username
email	string	Email address
name	string	First name
surName	string	Last name
phoneNumber	string	Phone number
phoneNumberVerified	bool	Whether phone is verified
emailVerified	bool	Whether email is verified
tenantId	string	Tenant ID (for multi-tenant apps)
roles	string[]	User's role names
isInRole(roleName)	function	Check if user has a specific role

context.emailSender

Property / Method	Description
isAvailable	Whether the email sender is configured and available
sendAsync(to, subject, body)	Send a plain-text email
sendHtmlAsync(to, subject, htmlBody)	Send an HTML email

Logging

Method	Description
context.log(message)	Log an informational message
context.logWarning(message)	Log a warning message
context.logError(message)	Log an error message

Use these methods instead of console.log (which is blocked in the sandbox).

db (Database API)

Full access to the Scripting API for querying and mutating data.

globalError

Set this variable to a string to abort the operation and return an error:

globalError = 'Cannot delete this entity!';

Examples

Pre-Create: Validation

{
  "commandName": "Create",
  "type": "Pre",
  "javascript": "if(!context.commandArgs.data['Name']) {\n  globalError = 'Organization name is required!';\n}"
}

Post-Create: Email Notification

{
  "commandName": "Create",
  "type": "Post",
  "javascript": "if(context.currentUser.isAuthenticated && context.emailSender) {\n  await context.emailSender.sendAsync(\n    context.currentUser.email,\n    'New Order Created',\n    'Order total: $' + context.commandArgs.data['TotalAmount']\n  );\n}"
}

Pre-Update: Role-Based Authorization

{
  "commandName": "Update",
  "type": "Pre",
  "javascript": "if(context.commandArgs.data['IsDelivered']) {\n  if(!context.currentUser.roles.includes('admin')) {\n    globalError = 'Only administrators can mark orders as delivered!';\n  }\n}"
}

Pre-Delete: Business Rule Check

{
  "commandName": "Delete",
  "type": "Pre",
  "javascript": "var project = await db.get('LowCodeDemo.Projects.Project', context.commandArgs.entityId);\nif(project.Budget > 100000) {\n  globalError = 'Cannot delete high-budget projects!';\n}"
}

Pre-Update: Negative Value Check

{
  "commandName": "Update",
  "type": "Pre",
  "javascript": "if(context.commandArgs.data['Quantity'] < 0) {\n  globalError = 'Quantity cannot be negative!';\n}"
}

Replace-Create: Custom Insert Logic

When you need to completely replace the default create operation with custom logic:

{
  "commandName": "Create",
  "type": "Replace",
  "javascript": "var data = context.commandArgs.data;\ndata['Code'] = 'PRD-' + Date.now();\nvar result = await db.insert('LowCodeDemo.Products.Product', data);\ncontext.log('Product created with custom code: ' + data['Code']);\nreturn result.Id;"
}

Important: Replace-Create interceptors must return the new entity's Id (Guid). The system uses this value to fetch and return the created entity. Use return result.Id; after db.insert(...).

Replace-Update and Replace-Delete interceptors do not need to return a value.

Pre-Update: Self-Reference Check

{
  "commandName": "Update",
  "type": "Pre",
  "javascript": "if(context.commandArgs.data.ParentCategoryId === context.commandArgs.entityId) {\n  globalError = 'A category cannot be its own parent!';\n}"
}

See Also

• Scripting API
• model.json Structure
• Custom Endpoints