Interceptors

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

Interceptor Types

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 with Fluent API

Use the Interceptors list on an EntityDescriptor to add interceptors programmatically in your Low-Code Initializer:

AbpDynamicEntityConfig.EntityConfigurations.Configure(
    "MyApp.Organizations.Organization",
    entity =>
    {
        entity.Interceptors.Add(new CommandInterceptorDescriptor("Create")
        {
            Type = InterceptorType.Pre,
            Javascript = "if(!context.commandArgs.data['Name']) { globalError = 'Name is required!'; }"
        });

        entity.Interceptors.Add(new CommandInterceptorDescriptor("Delete")
        {
            Type = InterceptorType.Post,
            Javascript = "context.log('Deleted: ' + context.commandArgs.entityId);"
        });
    }
);

See Attributes & Fluent API for more details on Fluent API configuration.

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

JavaScript Context

Inside interceptor scripts, you have access to:

context.commandArgs

context.currentUser

context.emailSender

Logging

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