Help With database in Angular 4

I am developing a web app in angular, I already did the ApiRest and I tried it with Postman and good in theory (I'm not sure) all the code in angular is fine since it does not throw any errors, but the data I add from the form is not saved in the database, I mean that a new product appears on the base but emptied, on the other hand when I add products from Postman if everything is saved correctly.

This is the service code.

import { Injectable } from '@angular/core';
import { Http, Response, Headers, RequestOptions } from '@angular/http';
import 'rxjs/add/operator/map';
import {Observable} from 'rxjs/observable';
import { Producto } from '../models/producto';
import { GLOBAL } from './global';

@Injectable()
export class ProductoService{
    public url: string;

    constructor(
        public _http : Http

    ){
        this.url=GLOBAL.url;
    }
    getProductos(){
        return this._http.get(this.url+'productos').map(res => res.json());
    }

    addProducto(producto: Producto){
        let json = JSON.stringify(producto);
        let params = 'json='+json;
        let headers = new Headers({'Content-Type':'aplication/x-www-form-urlencoded'});

        return this._http.post(this.url+'productos',params,{headers:headers})
                         .map(res => res.json());

    }
}

The code of the component to add elements to the database

import { Component } from '@angular/core';
import { Router, ActivatedRoute, Params} from '@angular/router';
import { ProductoService } from '../services/producto.service';
import { Producto } from '../models/producto';

@Component({
    selector: 'producto-add',
    templateUrl: '../views/producto-add.html',
    providers: [ProductoService]
})

export class ProdcutoAddComponent{
    public titulo: string;
    public producto: Producto;

    constructor(
        private _productoService:ProductoService,
        private _route: ActivatedRoute,
        private _router: Router
    ){
        this.titulo = 'Crear un nuevo producto';
        this.producto = new Producto(0,'','',0,'');
    }
    ngOnInit(){
        console.log('El componente de agregar un producto se ha cargado correctamente');
    }
    onSubmit(){
        console.log(this.producto);
        this._productoService.addProducto(this.producto).subscribe(
            response =>{
                if(response.code == 200){
                    this._router.navigate(['/productos-list']);
                }else{
                    console.log(response);
                }

            },
            error =>{
                console.log(<any> error);

            }

        );
    }
}