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get variables from jsf query sql db display results on another jsf page [duplicate]

I have started learning JSF, but sadly most tutorials out there present only a log in or a register section.
Can you point me to some more in depth examples? One thing I'm interested in is a page presenting a list of products. I'm on page home and I press on page products so that I can see the latest products added. And every time I visit the page, the product list will be created from the latest entries in the database. How can I handle this?
One way to solve this would be to create a session scoped managed bean in which I would place different entities updated through other managed beans. I found this kind of approach in some tutorials, but it seems quite difficult and clumsy.
Which would be the best approach to solve a thing like this? What is the correct usage of session scope in two-page master-detail user interface?

What is the correct usage of session scope
Use it for session scoped data only, nothing else. For example, the logged-in user, its settings, the chosen language, etcetera.
See also:
How to choose the right bean scope?
And every time I visit the page, the product list will be created from the latest entries in the database. How can I handle this?
Typically you use the request or view scope for it. Loading of the list should happen in a #PostConstruct method. If the page doesn't contain any <h:form>, then the request scope is fine. A view scoped bean would behave like a request scoped when there's no <h:form> anyway.
All "view product" and "edit product" links/buttons which just retrieve information (i.e. idempotent) whould be just plain GET <h:link> / <h:button> wherein you pass the entity identifier as a request parameter by <f:param>.
All "delete product" and "save product" links/buttons which will manipulate information (i.e. non-idempotent) should perform POST by <h:commandLink>/<h:commandButton> (you don't want them to be bookmarkable/searchbot-indexable!). This in turn requires a <h:form>. In order to preserve the data for validations and ajax requests (so that you don't need to reload/preinitialize the entity on every request), the bean should preferably be view scoped.
Note that you should basically have a separate bean for each view and also note that those beans doesn't necessarily need to reference each other.
So, given this "product" entity:
#Entity
public class Product {
#Id
private Long id;
private String name;
private String description;
// ...
}
And this "product service" EJB:
#Stateless
public class ProductService {
#PersistenceContext
private EntityManager em;
public Product find(Long id) {
return em.find(Product.class, id);
}
public List<Product> list() {
return em.createQuery("SELECT p FROM Product p", Product.class).getResultList();
}
public void create(Product product) {
em.persist(product);
}
public void update(Product product) {
em.merge(product);
}
public void delete(Product product) {
em.remove(em.contains(product) ? product : em.merge(product));
}
// ...
}
You can have this "view products" on /products.xhtml:
<h:dataTable value="#{viewProducts.products}" var="product">
<h:column>#{product.id}</h:column>
<h:column>#{product.name}</h:column>
<h:column>#{product.description}</h:column>
<h:column>
<h:link value="Edit" outcome="/products/edit">
<f:param name="id" value="#{product.id}" />
</h:link>
</h:column>
</h:dataTable>
#Named
#RequestScoped
public class ViewProducts {
private List<Product> products; // +getter
#EJB
private ProductService productService;
#PostConstruct
public void init() {
products = productService.list();
}
// ...
}
And you can have this "edit product" on /products/edit.xhtml:
<f:metadata>
<f:viewParam name="id" value="#{editProduct.product}"
converter="#{productConverter}" converterMessage="Unknown product, please use a link from within the system."
required="true" requiredMessage="Bad request, please use a link from within the system."
/>
</f:metadata>
<h:messages />
<h:form rendered="#{not empty editProduct.product}>
<h:inputText value="#{editProduct.product.name}" />
<h:inputTextarea value="#{editProduct.product.description}" />
...
<h:commandButton value="save" action="#{editProduct.save}" />
</h:form>
#Named
#ViewScoped
public class EditProduct {
private Product product; // +getter +setter
#EJB
private ProductService productService;
public String save() {
productService.update(product);
return "/products?faces-redirect=true";
}
// ...
}
And this converter for <f:viewParam> of "edit product":
#Named
#RequestScoped
public class ProductConverter implements Converter {
#EJB
private ProductService productService;
#Override
public Object getAsObject(FacesContext context, UIComponent component, String value) {
if (value == null || value.isEmpty()) {
return null;
}
try {
Long id = Long.valueOf(value);
return productService.find(id);
} catch (NumberFormatException e) {
throw new ConverterException("The value is not a valid Product ID: " + value, e);
}
}
#Override
public String getAsString(FacesContext context, UIComponent component, Object value) {
if (value == null) {
return "";
}
if (value instanceof Product) {
Long id = ((Product) value).getId();
return (id != null) ? String.valueOf(id) : null;
} else {
throw new ConverterException("The value is not a valid Product instance: " + value);
}
}
}
You can even use a generic converter, this is explained in Implement converters for entities with Java Generics.
See also:
How to navigate in JSF? How to make URL reflect current page (and not previous one)
JSF Controller, Service and DAO
JSF Service Layer
How to inject #EJB, #PersistenceContext, #Inject, #Autowired, etc in #FacesConverter?
Communication in JSF 2.0 - Contains several examples/hints

As a small improvement to what BalusC recommended, sometimes you can remove the required / requiredMessage part from the <f:viewParam> of your "details" screen and instead use the conditional rendering of the editing form (as BalusC did) with a reverse condition for recommending a specific link for the "list/master" screen or, even use a viewAction that would test the param and force a redirect to that list.

jsf : passing a selected hyperlink as a query argument

I have a mySql table of PROJECTS, which I am displaying as a list in the index.xhtml. The projectid column contains hyperlinks. When they're clicked I would like the specific projectid row selected to be passed as the query argument into another jsf file (ListProjects.xhtml) which displays all the project values referring to the projectid selected in the index.xhtml. The index.xhtml page seems to pass the values correctly (when hovering over the selection the url displays the right id value). When actually clicking the selction I get a blank page in the resulting ListPprojects.xhtml:
I'm not sure if it's my choice of tags on index.xhtml where should be replaced by another tag like CommandLink which maps to a bean action.
Alternatively, is tag in the result page (ListProject.xhtml) the right tag to use to retrieve the projectid value as the query argument?
Also if the projectid is an int, should this first be converted to String by using parseInt or other method?
Is the problem in one of the session beans where projectid is resulting in a null value which causes the result page to render blank records? Any advice is greatly appreciated. Thanks in advance!
The named query in the entity bean (projects.java) is:
#NamedQuery(name = "Projects.findByProjectid", query = "SELECT p FROM Projects p WHERE p.projectid = :projectid")
In the index.xhtml I use the following tag to display the hyperlink:
<h:link value="#{item.projectid}" outcome="ListProject">
<f:param name="projectid" value="#{item.projectid}"/>
</h:link>
The ListProjects.xhtml is the page where I would like to display the project details based on the projectid selected in the index.xhtml (and here's where I start getting confused):
<h:column>
<f:facet name="header">
<h:outputText value="Countryid"/>
</f:facet>
<h:commandLink action="#{selProjectMgtBean.selProjectList}" value="#{item.projectid}"/>
</h:column>
My session bean:
#Stateless
public class ProjectSelectedBean implements ProjectSelectedBeanLocal {
#PersistenceContext(unitName = "QueryTrialNoMavenPU")
private EntityManager em;
#Override
public List<Projects> getSelectedProjects(String projectid) {
HttpServletRequest request = (HttpServletRequest) FacesContext.getCurrentInstance().getExternalContext().getRequest();
projectid=request.getParameter(projectid);
return em.createNamedQuery("Projects.findByProjectid", Projects.class).setParameter ("projectid", projectid).getResultList();
}
}
Finally the calls the methods for rendering the selection:
package com.manaar.beans;
imports....
#Named(value = "selProjectMgtBean")
#RequestScoped
public class SelProjectMgtBean {
#ManagedProperty(value="#{item.projectid}")
private String projectid;
private List<Projects> selProjectList;
#EJB
private ProjectSelectedBeanLocal projectSelectedBeanLocal;
#PostConstruct
public void init() {
HttpServletRequest request = (HttpServletRequest) FacesContext.getCurrentInstance ().getExternalContext().getRequest();
projectid=request.getParameter("projectid");
selProjectList = projectSelectedBeanLocal.getSelectedProjects();
}
public List<Projects> getSelProjectList() {
return selProjectList;
}
public void setSelProjectList(List<Projects> selProjectList) {
this.selProjectList = selProjectList;
}
}

you didn't set :projectId in query:
you can change code as follow:
public List<Projects> getSelectedProjects(String projectId) {
return em.createNamedQuery("Projects.findByProjectid", Projects.class).setParameter("projectId" , projectId).getResultList();
}

Regarding one of your questions:
Use h:link for pure navigational purposes (with the outcome parameter) and h:commandLink to invoke an action directly (with the action parameter). The called method in this case should return a String telling JSF where to navigate next.

JSF primefaces showing list of object not list of string

I already tried to search through this site, but maybe I'm not getting understand well.
Please kindly advice for my cases..
I'm using Netbeans 7.3 + Primefaces + Hibernate.
I want to show a list from my query.
My query already in.. and there's no error showup, but the display is not what I want (I think it returning an object or something, not sure).
Please kindly correct me if I'm missed something.
Here's my PtlLovBean
#ManagedBean(name = "ptlLovBean")
#SessionScoped
public class PtlLovBean implements Serializable {
private static final String FLIGHT = "LOV_FLIGHT";
private List lovFlight;
public List getLovFlight() {
PtlLovDao ptlLovDao = new PtlLovDaoImpl();
return ptlLovDao.getByKey(FLIGHT);
}
}
Here's ptlLovDao
public interface PtlLovDao {
public List getByKey(String key);
}
Here's PtlLovDaoImpl
public class PtlLovDaoImpl implements PtlLovDao {
#Override
public List getByKey(String key) {
Session session = HibernateUtil.getSessionFactory().openSession();
Query query = session.createQuery("from PtlLov where LOV_KEY = :param");
query.setParameter("param", key);
return query.list();
}
}
Here's my JSF :
<p:selectOneMenu id="flightName" value="#{wizard.user.selectedFlightName}">
<f:selectItem itemLabel="Select Flight" itemValue="" />
<f:selectItems value="#{ptlLovBean.lovFlight}" />
</p:selectOneMenu>
Display after Code:
Sorry I'm not capable to insert picture, so here's the image link :
http://i117.photobucket.com/albums/o56/po_se_for/PIC_zps88ec4983.png

You can either override the toString method in your PtlLov class or define itemValue and itemLabel properties in your f:selectItems tag.
Something like this:
<f:selectItems value="#{ptlLovBean.lovFlight}" var="flight"
itemValue="#{flight}" itemLabel="#{flight.description}" />

When/where do entities get created on a Java EE web application?

When or where do entities get created?
Do they get created when the XHTML page loads and accesses the entities via the managed bean?
Or do they get automatically created in the managed bean?
Do we need to manually create it from the managed bean's constructor?
Please see the code below (some necessary code might not have been copied.)
The entity would be:
public class PersonalInfo implements Serializable {
#Size(max = 50)
#Column(name = "FIRST_NAME", length = 50)
private String firstName;
// some getters and setters
}
the web page would be:
<h:form>
<h:outputText value="first name"/>
<h:inputText value="#{personalInforController.personalInfo.firstName}" />
<h:commandButton value="hit me"
action="#{personalInforController.create}"
immediate="true"/>
</h:form>
and the backing bean would be:
#Named(value = "personalInfoController")
#SessionScoped
public class PersonalInforController {
#EJB
PersonalInfoFacade ejbFacade;
PersonalInfo personalInfo;
String defaultPage = "index";
public String create() {
try {
ejbFacade.create(personalInfo);
return "prepareCreate";
} catch (Exception e) {
return "success";
}
}
}

In the example code given, the create action indeed doesn't seem to be able to work. The entity must be created by the backing bean before that.
If it's a simple entity, either the constructor or an #PostConstruct method would work. For instance:
#Named(value = "personalInfoController")
#SessionScoped
public class PersonalInforController {
#EJB
PersonalInfoFacade ejbFacade;
PersonalInfo personalInfo;
String defaultPage = "index";
#PostConstruct
public void init() {
personalInfo = new PersonalInfo();
}
public String create() {
try {
ejbFacade.create(personalInfo);
return "prepareCreate";
} catch (Exception e) {
return "success";
}
}
Some notes about the code. It's highly suspicious, and most likely plain wrong, to declare your bean to be #SessionScoped. If personalInfo is being edited in two tabs or windows you'll be in a world of hurt. I suggest making your bean #ViewScoped (for CDI, there's a separate extension made by the Seam3 that enables this, if you can't/won't use this extension consider using #ManagedBean instead of #Named).
Also, you might want to declare your instance variables to be private and give ejbFacade a better name (e.g. personalInfoFacade). I also doubt whether immediate is necessary on the commandButton, and since the outputText is obviously a label for the given inputText, you might want to consider using outputLabel and the for attribute.

jsf dynamic change of managedbean

How can I dynamically change managed bean of "value" attribute? For example, I have h:inputText and, depending on typed-in text, managed bean must be #{studentBean.login} or #{lecturerBean.login}. In a simplified form:
<h:inputText id="loginField" value="#{'nameofbean'.login}" />
I tried to embed another el-expression instead of 'nameofbean':
value="#{{userBean.specifyLogin()}.login}"
but it doesn't worked out.

Polymorphism should rather be done in the model, not in the view.
E.g.
<h:inputText value="#{person.login}" />
with
public interface Person {
public void login();
}
and
public class Student implements Person {
public void login() {
// ...
}
}
and
public class Lecturer implements Person {
public void login() {
// ...
}
}
and finally in the managed bean
private Person person;
public String login() {
if (isStudent) person = new Student(); // Rather use factory.
// ...
if (isLecturer) person = new Lecturer(); // Rather use factory.
// ...
person.login();
// ...
return "home";
}
Otherwise you have to change the view everytime when you add/remove a different type of Person. This is not right.

Another way:
<h:inputText id="loginField1" value="#{bean1.login}" rendered="someCondition1"/>
<h:inputText id="loginField2" value="#{bean2.login}" rendered="someCondition2"/>