How to load angular component by hitting URL in browser while using spring boot?

I've found an answer. Below works as expected.

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class ViewController {

   @RequestMapping({ "/dashboard", "/contacts" })   
   public String index() {
       return "forward:/index.html";
   }
}

as i understand your question just create new file named proxy.config.json and paste below code in that file, place file next to .angular-cli.json

{
  "/": {
    "target": "http://localhost:8080",
    "secure": false,
    "logLevel": "debug"
  }
}

in app.component.ts file place below code in ngOnInit()

this.http.get('/dashboard',someRequestOption).subscribe(res =>{
 ---------------
})

To prevent the spring-boot application from resolving your angular routes you can add a ViewController to redirect the routes to the angular application as explained in Springboot/Angular2 - How to handle HTML5 urls?.

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class ViewController {

   @RequestMapping({ "/dashboard" })
   public String index() {
       return "forward:/index.html";
   }
}

Angular5 app.module.js

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';

import { AppComponent } from './app.component';
import { DashboardComponent } from './dashboard/dashboard.component';

const appRoutes: Routes = [{
  path: 'dashboard',
  component: DashboardComponent
}]

@NgModule({
  declarations: [
    AppComponent,
    DashboardComponent
  ],
  imports: [
    BrowserModule,
    RouterModule.forRoot(
      appRoutes,
      { enableTracing: true },
    )
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

Dashboard component as created with ng generate component Dashboard

The angular application must be located besides the spring-boot project as requested by the resource plugin defined in the pom.xml.

|_ spring-boot

|_ angular-app