Navigation and Parameters problem

Question

Hey all,
I'm very new to JSF and we are attempting a very basic test app to try and get our heads round things. The app is basically a list of people, with a link to edit them, and a page which lets you edit the person and a button to save the person, after which, you will go back to the list of people.
I have a personlist.jsp page which obtains a (fixed) list of people from the PeopleDAO, using a h:dataTable to iterate and display each person. Each row has an edit link of the form "......editperson.jsp?PersonID=<number>" where number is the person ID for that person.
In the edit person page, I have a PersonBean which is used to display the person details. The person bean is specified in faces-config.xml as a managed bean, and I hook the PersonID property of the PersonBean up using a managed property linked to the PersonID param.
<managed-bean>
<managed-bean-name>personbean</managed-bean-name>
<managed-bean-class>mypackage.view.PersonBean</managed-bean-class>
<managed-bean-scope>request</managed-bean-scope>
<managed-property>
<property-name>personID</property-name>
<value>#{param.personID}</value>
</managed-property>
</managed-bean>
I have the navigation set up to go back to the personlist.jsp page once you click the save button :
<navigation-rule>
<from-view-id>/editperson.jsp</from-view-id>
<navigation-case>
<from-outcome>save</from-outcome>
<to-view-id>/personlist.jsp</to-view-id>
</navigation-case>
</navigation-rule>
On editperson.jsp, I have a commandbutton that has an action="save" (this is for simple testing since we are having problems with it) :
(in the form for editing the person)
<h:commandButton value="Update" action="save"/>
The problem is that when you click the button, it tries to reload editperson.jsp without the personID parameter, which causes an error because it is expecting a parameter as specified in the PersonBean managed bean declaration.
If I set the property to a constant value in the managed bean declaration, everything works fine, but when bound to the parameter, it causes an error.
I can see why it is an error, but I have no idea how to get around it. Am I passing parameters the wrong way, or is there some option to set a default value for the param, or am I navigating incorrectly?
Any help is appreciated,
Cheers,
Andy

Answer 1

Well, at last, it seems that after another day of testing, I have found the answer.
I'm posting back here since I found a number of people who had this problem, and none of them received an answer. Hopefully this might help some poor soul in the future.
The problem is data type conversion. When there is no person ID, the parameter is effectively a blank string, which of course cannot be converted to an integer. Even specifying the type in the managed property did not help the conversion process.
I have a mini test app that has a bean with managed int and string properties. The page renders fine when the intValue param is there, but crashes if it is not. The page doesn't give a hoot about whether the textValue parameter is there or not and will always render by substituting a blank string as the value.
I'm sure there must be some way to pass a parameter to a managed property as an integer without having the application crash if it is missing, especially considering most applications use integers for primary keys.
I have seen samples that do this, alas, since many don't compile, deploy and run out of the box, I am unable to verify whether or not they break under the same conditions.
The only thing I can think of is to have the backing bean act as a container for my real objects. I.e. PersonBean has a managed person ID string property which when set, converts the ID to an integer and loads up the person and assigns it to PersonBean.Person .
This is probably actually a better structure all round, especially if the backing bean for a view needs to contain other objects, i.e. a list of orders for that person. By adding the extra layer in there, it will make it easier to add additional model objects to the backing bean.