【Angular + Spring Boot】ファイルのダウンロードを実装する

import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import jakarta.servlet.http.HttpServletResponse;

@Controller
public class FileDownloadController {

    @GetMapping(value ="download-test")
    public void download(HttpServletResponse response) {
        
        try (OutputStream outputStream = response.getOutputStream();) {
            
            //ダウンロードファイルをバイト配列に変換
            Path path = Paths.get("D:/work/test.pdf");
            byte[] fileByte = Files.readAllBytes(path);

            //レスポンスヘッダに値をセット 
            response.setContentType("application/pdf");
            response.setHeader("Content-Disposition", "attachment; filename=test.pdf");
            response.setContentLength(fileByte.length);
            outputStream.write(fileByte);
            outputStream.flush();
            
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

<p>download-test works!</p>
<button (click)="download()">ダウンロード</button>

<div style="display: none;">
    <a #downloadtag [href]="safeResourceUrl" target="_blank" 
       download="test.pdf">Download</a>
</div>

import { ChangeDetectorRef, Component, ElementRef, OnInit, ViewChild } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { DomSanitizer, SafeResourceUrl } from '@angular/platform-browser';

@Component({
  selector: 'app-download-test',
  templateUrl: './download-test.component.html',
  styleUrls: ['./download-test.component.css']
})
export class DownloadTestComponent implements OnInit {

  safeResourceUrl: SafeResourceUrl;
  @ViewChild('downloadtag') downloadtag: ElementRef;

  constructor(
    private http: HttpClient,
    private sanitizer: DomSanitizer,
    private changeDetectorRef: ChangeDetectorRef,
  ) { }

  ngOnInit(): void {
  }

  download(): void {
    this.http.get("http://localhost:8080/download-test", 
                  {responseType: "blob"}).subscribe((blob) => {
      this.safeResourceUrl = this.sanitizer.bypassSecurityTrustResourceUrl(
                                            URL.createObjectURL(blob));
      const downloadtag = <HTMLLinkElement>(this.downloadtag.nativeElement);
      this.changeDetectorRef.detectChanges();
      downloadtag.click();
    })
  }
}