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 Module. 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 — the default DB insert is skipped, only JavaScript runs
Update	Pre	Before entity update — validation, authorization
Update	Post	After entity update — sync, notifications
Update	Replace	Instead of entity update — the default DB update is skipped, only JavaScript runs
Delete	Pre	Before entity deletion — dependency checks
Delete	Post	After entity deletion — cleanup
Delete	Replace	Instead of entity deletion — the default DB delete is skipped, only JavaScript runs

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	Type	Description
data	object	Entity data dictionary (for Create/Update)
entityId	string	Entity ID (for Update/Delete)
getValue(name)	function	Get a property value
setValue(name, value)	function	Set a property value (Pre-interceptors only)

context.currentUser

Property	Type	Description
isAuthenticated	bool	Whether user is logged in
userName	string	Username
email	string	Email address
roles	string[]	User's role names
id	string	User ID

context.emailSender

Method	Description
sendAsync(to, subject, body)	Send an email

context.log(message)

Log a message (use instead of console.log).

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();\nawait db.insert('LowCodeDemo.Products.Product', data);\ncontext.log('Product created with custom code: ' + data['Code']);"
}

When Replace is used, the standard database operation does not run. You are responsible for performing any necessary persistence in your JavaScript handler.

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