JSF :: What Causes Backing Bean Return Null

I tried to create my first javaweb project. However when some action were being invoke I received an error. Here is what I did:

Person.javapackage org.javaeesample.entities;
import java.io.Serializable;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;

[Code].....

When tried to run my project what happened were:

1. When i clicked the link from show.xhtml

<h:link value="#{p.name}" outcome="details">
<f:param name="pid" value="#{p.id}"/>
</h:link>

It output the page but without data being displayed.

but on the url it shows: [URL] .....

1. When i clicked 'Save' button in create.xhtml here is the error i received:

An Error Occurred: