Dynamically load HTML template in angular2

By Robert Steers Web Design November 5, 2023

Angular is designed to work primarily as a client-side framework, and it expects templates to be static and known at compile-time. This is because Angular does template compilation during the build process to improve performance at runtime. However, for cases where you need to load dynamic templates that can change after the build process, you might need to adjust your approach.

Here’s a strategy to handle server-side dynamic templates in an Angular application:

Retrieve the Template via HTTP: Instead of compiling the template at build time, you can fetch the template at runtime from the server.
Compile the Template Dynamically: Use Angular’s Compiler API to compile the template once it’s retrieved.

Here is an example of how you could implement a component that loads and compiles a dynamic template at runtime:typescript

import { Component, OnInit, ViewChild, ViewContainerRef, Compiler, Injector, NgModule, NgModuleRef } from '@angular/core';
import { HttpClient } from '@angular/common/http';@Component({
selector: 'app-root',
template: `<div #dynamicTemplateContainer></div>`, // Placeholder for dynamic template
})
export class AppComponent implements OnInit {
title = 'app works!';
@ViewChild('dynamicTemplateContainer', { read: ViewContainerRef })
dynamicTemplateContainer: ViewContainerRef;constructor(
private http: HttpClient,
private compiler: Compiler,
private injector: Injector,
private m: NgModuleRef<any>
) {}ngOnInit() {
this.loadDynamicTemplate('https://your-server.com/template.jsp');
}loadDynamicTemplate(templateUrl: string) {
this.http.get(templateUrl, { responseType: 'text' })
.subscribe(template => {
this.dynamicTemplateContainer.clear();
const dynamicComponent = Component({ template })(class {});
const dynamicModule = NgModule({ declarations: [dynamicComponent] })(class {});this.compiler.compileModuleAndAllComponentsAsync(dynamicModule)
.then((factories) => {
const f = factories.componentFactories.find(comp => comp.componentType === dynamicComponent);
const cmpRef = this.dynamicTemplateContainer.createComponent(f);
Object.assign(cmpRef.instance, { title: this.title }); // Pass context like title
});
});
}
}

In this code snippet, the AppComponent:

Uses HttpClient to fetch the template from a server-side JSP file.
Uses Angular’s Compiler to compile the fetched template into a component dynamically.
Renders the dynamic component inside a placeholder div.

Note:

Enabling the Angular compiler in the browser adds significant overhead to your application. It’s generally not recommended for production use.
Make sure to sanitize any HTML content fetched from the server to prevent XSS (Cross-Site Scripting) attacks.
Angular’s Ahead-of-Time (AOT) compilation does not support dynamic template URLs. You will have to switch to Just-in-Time (JIT) compilation, which can increase your bundle size and affect performance.

Security Concerns:

Loading templates dynamically can expose your application to a range of security risks. Always ensure that you trust and have control over the server that provides the templates. Also, consider implementing appropriate CORS (Cross-Origin Resource Sharing) policies and use Angular’s DomSanitizer to prevent security vulnerabilities.

This approach should be used cautiously and only when necessary. If possible, it’s always better to design your application so that dynamic content is managed through data binding within a statically known template, rather than dynamically loading different templates.

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