Render byte[] from Java API as an image in Angular 2

You should use responstype blob. since you return byte and not base64 string.

Because this Java getmapping tells you "byte[]"

@GetMapping("/{id}/image")
public byte[] getProductImageByProductId(@PathVariable Long id) {
    return productFacade.getProductImageByProductId(id);
}

  getProductImageByProductId(productId: number): Observable<any> {
    return this.http.get<Observable<any>>(ServiceConfig.serverBaseUrl + `/product/${productId}/image`, {responseType: 'blob'});
  } /

   export class SelectProductComponent{

    constructor(private sanitizer:DOMSanitizer, /*other params*/){}


    public someMethod(product:Product):void{
    this.productService.getProductImageByProductId(product.id).subscribe( data =>{
         var reader = new FileReader();
         const blob = new Blob([data], {
            type: 'image/jpeg'
             });
         //EDIT: Don't use function. my bad
         reader.onloadend = () => {
           const untrustedData = reader.result; 
           this.base64 = this.sanitizer.bypassSecurityTrustUrl(untrustedData);          
         } 
         reader.readAsDataURL(blob); 
         
       }
 
    }

   
       // also you can use ObjectURL if you 
      //just want the image and don't need the conversion to base64

   
        public someOtherMethod(product:Product):void{
    this.productService.getProductImageByProductId(product.id).subscribe( data =>{
            const blob = new Blob([data], {
            type: 'image/jpeg'
             });
           const objectUrl = URL.createObjectURL(blob);
           this.image = this.sanitizer.bypassSecurityTrustUrl(objectURL);
         }
       }
 
    }

}