I have an e-store application and I want to pass item id to the action every time the button for that item is pressed.

my jsp :

<s:submit  value="addToCart" action="addToCart" type="submit">
<s:param name="id" value="%{#cpu.id}" />
</s:submit>

action:

public class ProductsCPU extends BaseAction implements Preparable, SessionAware {
private static final long serialVersionUID = 2124421844550008773L;

private List colors = new ArrayList<>();
private List cpus;
private String id;

public String getId() {
    return id;
}

public void setId(String id) {
    this.id = id;
}

When I print id to console, it has the NULL value. What is the problem?