How to POST with Postman to an API in Java?

I tried to create a small API to do tests, my Java code seems OK, with Postman when I want to do a GET my list of products is fine for me, on the other hand when I want to do a POST, I have a 400 Bad Request.

Here is my code:

// Produits
    @GetMapping(value = "/Produits")
    public List<Product> listeProduits() {
        return productDao.findAll();
    }

    // Récupère un produit par son ID
    @GetMapping(value = "/Produits/{id}")
    public Product afficherUnProduit(@PathVariable int id) {
        return productDao.findById (id);
    }

    @PostMapping(value = "Produits/")
    public void ajouterProduit(@RequestBody @Validated Product product, final HttpServletRequest request, Error filterError) {
        productDao.save(product);
    }

In Postman, in my body I have the content-type: application / json of filled in.

Where can this problem come from?

Thanks

I looked at you project. Everything is working ok.
But you have "bad" POST url - "/Produits/" <--- last slash can be reason for the long not-understanding and "Why this is not working!!". Because in Postman you also must call url -> "localhost:8080/Produits/" <-- here also need last slash.

I've started your project and it works well with this setting of Postman (picrures below). Please look carefully, every symbol is might be a reason.

After POST and save I was able to get entity through GET method

I tried to reproduce getting 400 bad request, but I failed.

Based on your code, I can access to (you might try this)

localhost:8080/Produits/

but

localhost:8080/Produits

returned 404 not found.

Maybe you can add more information, which might be helpful. Thanks.

400 is Bad request. Maybe you do wrong POST request instead GET. Because only "ajouterProduit" method has validation.

Also yeah check your url- if you have "Produits/" set the same in Postman
http://localhost:8080/Produits/

And you can check you service through curl if you has Linux or Mac:
curl http://localhost:8080/Produits/
It will help you understand - you doing wrong Postman request or service has some different url or something

And more code :

@Override
    public List<Product> findAll () {
        return products;
    }

    @Override
    public Product findById (int id) {
        for (Product product : products) {
            if (product.getId () == id) {
                return product;
            }
        }
        return null;
    }


    @Override
    public Product save (Product product) {
        products.add(product);
        return product;
    }

And Postman screen :

The Product Class :

public class Product {
private int id;
private String nom;
private int prix;
private int dureeDeVie;
public Product() {
}
public Product (int id, String nom, int prix, int dureeDeVie) {
this.id = id;
this.nom = nom;
this.prix = prix;
this.dureeDeVie = dureeDeVie;
}
public int getId () {
return id;
}
public void setId (int id) {
this.id = id;
}
public String getNom () {
return nom;
}
public void setNom (String nom) {
this.nom = nom;
}
public int getPrix () {
return prix;
}
public void setPrix (int prix) {
this.prix = prix;
}
public int getDureeDeVie () {
return dureeDeVie;
}
public void setDureeDeVie (int dureeDeVie) {
this.dureeDeVie = dureeDeVie;
}
@Override
public String toString () {
return "Product{" +
"id=" + id +
", nom='" + nom + '\'' +
", prix=" + prix +
", dureeDeVie=" + dureeDeVie +
'}';
}
}