Rollback transaction inside managed bean - jsf

I would like to rollback transaction not inside EJB but inside JSF managed bean. Inside EJB we can use SessionContext.setRollBackOnly() but what can I use in managed bean ?
#Stateless
#Local(AccountLocal.class)
public class AccountBean implements AccountLocal {
public void test1() throws CustomException(){
...
}
public void test2() throws CustomException(){
...
throw new CustomException();
}
public void test3() throws CustomException(){
...
}
public void all() throws CustomException(){
test1();
test2();
test3();
}
}
In my managed bean :
#SessionScoped
public class LoginBean implements Serializable{
public void test(){
try{
accountBean.test1();
accountBean.test2();
accountBean.test3();
}catch(CustomException e){
// WHAT HERE TO ROLLBACK TRANSACTION ?
}
}
}
EDIT : How can I ensure that if one of the test1, test2 or test3 rolls back, others will roll back too ?
I tested this code and accountBean.test1(); is validated even if accountBean.test2(); rolls back.
Could the solution be only to nest this 3 methods inside one EJB method ?
#SessionScoped
public class LoginBean implements Serializable{
public void test(){
try{
accountBean.all();
}catch(CustomException e){
...
}
}
}

Transactions are automatically rolled back by the EJB container if an unchecked exception is thrown (note that JPA's PersistenceException is such one). Your CustomException seems to be a checked exception. If changing it to extend RuntimeException as follows
public class CustomException extends RuntimeException {
// ...
}
or creating a new one is not an option, then you need to set the #ApplicationException annotation on the class with the rollback attribute set to true.
E.g.
#ApplicationException(rollback=true)
public class CustomException extends Exception {
// ...
}
Please note that the concrete problem has nothing to do with JSF. The service layer and managing transactions is completely outside the responsibility of JSF. It's the responsibility of EJB instead. JSF should merely act as "view" in this perspective.
See also:
JSF Service Layer
Handling service layer exception in Java EE frontend method

I'm playing the Devil's advocate here, since BalusC's advice that you should not let your backing beans act as services is absolutely true.
But, purely as a technical excersise, it -is- possible to start a JTA transaction in a backing bean and then control start and commit or rollback programmatically.
You can do this by injecting a UserTransaction via #Resource. Prior to calling your EJB methods, call start on this instance, and after the last call either commit or rollback.
Again, this is a purely theoretical answer. In practice, don't do this and let the backing bean call 1 EJB method that calls out to other EJB beans if needed.

Related

Extending PartialViewContext with a RequestScoped bean in JSF

In a JSF project, we wrote our own PartialViewContext to listen to some events fired by pages beans:
#RequestScoped
public class OurPartialViewContext extends PartialViewContextWrapper
{
...
// called by cdi
#SuppressWarnings("unused")
private void listenForUpdate(#Observes OurRefreshEvent event)
{
...
And we wrote the matching factory, injecting it:
public class OurPartialViewContextFactory extends PartialViewContextFactory
{
#Inject
private OurPartialViewContext customPartialViewContext;
...
Problem is that in the newest versions of JSF, the empty constructor for PartialViewContextWrapper is deprecated, asking us to use another constructor with the wrapped object in parameter.
Currently, our PartialViewContext needs to be tied to the request scope, in order to be modified during the request by the observed events and to be used by a custom PartialResponseWriter we also wrote.
So our PartialViewContext currently both:
must have an empty constructor, as it is a #RequestScoped bean;
should not have an empty constructor, as it is deprecated for PartialViewContextWrapper which it inherits from.
How could we find a solution there?
We tried to remove it from the scope and build it in the Factory with a simple new OurPartialViewContext(), but then the #Observes methods are never called.
You are required to pass the wrapped instance into the constructor and to use getWrapped() over all place in delegate methods. Otherwise your application will most probably not work when you install other JSF libraries which also ship with their own PartialViewContext implementation such as OmniFaces and PrimeFaces. You would be effectively completely skipping the functionality of their PartialViewContext implementation. This mistake was previously observed in too many custom implementations of factory-provided classes. Hence the urge to mark the default constructor as #Deprecated so that the developers are forced to use the proper design pattern.
Your specific issue can be solved by simply refactoring the listenForUpdate() method into a fullworthy request scoped CDI bean, which you then inject in the factory who in turn ultimately passes it into the constructor of your PartialViewContext implementation.
Thus, so:
#RequestScoped
public class OurEventObserver {
public void listenForUpdate(#Observes OurRefreshEvent event) {
// ...
}
}
public class OurPartialViewContextFactory extends PartialViewContextFactory {
#Inject
private OurEventObserver observer;
public OurPartialViewContextFactory(PartialViewContextFactory wrapped) {
super(wrapped);
}
#Override
public PartialViewContext getPartialViewContext(FacesContext context) {
PartialViewContext wrapped = getWrapped().getPartialViewContext(context);
return new OurPartialViewContext(wrapped, observer);
}
}
public class OurPartialViewContext extends PartialViewContextWrapper {
private OurEventObserver observer;
public OurPartialViewContext(PartialViewContext wrapped, OurEventObserver observer) {
super(wrapped);
this.observer = observer;
}
// ...
}
Inside any of the overridden methods of OurPartialViewContext you can simply access the state of the observer, provided that the listenForUpdate() modifies some instance variables representing the state.

How to implement async calls from session bean

In the oficial Java EE documentation https://docs.oracle.com/javaee/6/tutorial/doc/gkkqg.html says "Session beans can implement asynchronous methods".
Following this tutorial I'm not able to execute a method asynchronously.
It actually Works, but like any other synchronous method. (It doesn´t start any other thread).
#ManagedBean(name = "inicioSSCCBean")
#SessionScoped
public class InicioSSCCBean implements Serializable {
...
#Asynchronous
public Future<String> sendMessage() {
String status;
try {
// Call to SAP server...
} catch (MessagingException ex) {
// Error handler
}
return new AsyncResult<String>(status);
}
public void otherMethod() {
String result = sendMessage().get(); // The result is what I expect
System.out.println(result);
}
...
}
Do anyone know how to implement an async call from a session bean?
The main goal is to make a call to a SAP service, and get the results asynchronously.
I´m using JSF 2.2, PrimeFaces.
Thanks in advance.
You misunderstood the Java EE tutorial. The term "Session bean" refers to enterprise session beans (EJBs), not to session scoped managed beans (JSF/CDI beans).
The #javax.ejb.Asynchronous annotation, as its package already hints, works only in EJBs. EJBs are recognizable by having a #javax.ejb.Xxx annotation on the class, such as #Stateless or #Stateful.
Below is the correct kickoff example:
#Stateless
public class YourService {
#Asynchronous
public void asyncDoSomething() {
// ...
}
}
#ManagedBean
public class YourBean {
#EJB
private YourService yourService;
public void submit() {
yourService.asyncDoSomething();
}
}
See also:
When is it necessary or convenient to use Spring or EJB3 or all of them together?
Is it safe to start a new thread in a JSF managed bean?
JSF Controller, Service and DAO
How can server push asynchronous changes to a HTML page created by JSF?
Aside from the fact that you're trying to use the wrong kind of bean, you'll have to understand how Future works.
When you call Future.get(), the thread will block until the Future has a result. Therefore sendMessage().get() will act exactly like a synchronous call.
However if you call sendMessage() and then perform other tasks before calling get(), it will be performed asynchronously. As you realize an asynchronous call is only useful when you don't need the result right away, making it less useful than it seems in most cases.

Initialization of List in a JSF Managed bean

I' have a question about initialization of List in the POJO as it follows the next code:
public class Person {
//other fields...
private List<String> friends=new ArrayList<>();
public List<String> getFriends() {
return friends;
}
public void setFriends(List<String> friends) {
this.friends = friends;
}
}
OR is it better like this and have initalization in other class(like for example Bean(JSF))
public class Person {
//other fields...
private List<String> friends;
public List<String> getFriends() {
return friends;
}
public void setFriends(List<String> friends) {
this.friends = friends;
}
}
So my question is what approach is better?
If it's a managed bean as you say, you should do this in a method annotated with #PostConstruct
public class Person {
private List<String> friends;
#PostConstruct
public void init(){
friends = new ArrayList<String>();
}
//getter and setter...
}
The practice of doing any initialization in the getter and setter is generally frowned upon within the context of JSF. See Why JSF calls getters multiple times
Also, per the API for #PostConstruct, the contract specifies safety features and guarantees that if an exception is thrown in a method annotated as such, the bean should not be put into service. There are no such guarantees on a plain constructor.
In a managed bean, injection happens immediately after construction. This means that any operations you're carrying out in the constructor cannot depend on any injected resources (via #ManagedProperty). Whereas in a #PostConstruct method, you'll have access to all the resources declared on the managed bean
EDIT: It's important to note that there can be only one #PostConstruct for any #ManagedBean, so all important initializations should happen in there.
It's also worthwhile to note that, while the #PostConstruct method is the ideal place to initialize a backing bean variable/List, there are implications regarding the scope of the managed bean
#RequestScoped: In a managed bean with this annotation, the method will be called per submit of the JSF view concerned. A #RequestScoped bean is destroyed and recreated with every request, The implication of this is that depending on your setup, the list initialized in the #PostConstruct may be reset to empty or default values during each request. Under certain circumstances, conversion errors may occur as a result of the re-initialization of the list mid-JSF request.
#ViewScoped: In a managed bean with this annotation, you're guaranteed to have the #PostConstruct method run once, if and only if you're dealing with the same instance of the #ViewScoped bean. If the viewscoped bean is destroyed and recreated, the #PostConstruct method will run again.
#SessionScoped: A bean with this annotation is created once and stays alive until the user's HTTP session ends. In this scenario, the #PostConstruct method is guaranteed to run once and only once until the bean is destroyed
See also
https://stackoverflow.com/a/3406631/1530938
I would suggest this:
public class Person {
//other fields...
private List<String> friends=new ArrayList<>();
// returns a copy to protect original list
public List<String> getFriends() {
Collections.unmodifiableList(new ArrayList<>(friends));
}
public void addFriend(String> friend) {
this.friends.add(friend);
}
public void addFriends(List<String> friends) {
this.friends.addAll(friends);
}
}
In my opinion it would be best to handle that in the constructors. If a default constructor is used, initialize the list in the constructor.
public Person() {
friends = new ArrayList<>();
}
If a constructor which accepts parameters is used, let the calling class pass in a list.
public Person(ArrayList<> friends) {
this.friends = friends;//friends
}
My suggestion, add a null check in the getter:
public class Person {
//other fields...
private List<String> friends;
public List<String> getFriends() {
if (this.friends == null) friends = new ArrayList<String>();
return friends;
}
}
But also notice I have omitted the setter. Instead, in any client code, call like this:
personInstance.getFriends().add("Some Item");
Or if you have a full list to add:
personInstance.getFriends().addAll(someStringCollection);
It depends. Usually first way preferable because you may want to add something to collection later. If you won't know was your collection initialized or not you must check it every time.

How do I force a managed bean to initialize first?

I have a navigation managed bean for each user.
and I need it to initialize first before any other bean because a value is required from the bean.
May I know how do I perform that?
I have tried eager="true" but it doesn't work.
any quick and easy solution via faceconfig would be greatly appreciated.
Just perform the desired initialization job in bean's #PostConstruct.
#PostConstruct
public void init() {
// Here.
}
It'll be invoked when the bean is injected/referenced from another bean for the first time.
The eager=true works only on application scoped beans.
From what I see you should reference the other bean. Let's assume a have a utility class that can pull a bean from the context.
Basically ->
//Bean A
public void doSomething()
{
String required = Utility.getBeanB().getRequiredValue();
use(required);
}
...
//Bean B
public String getRequiredValue()
{
return "Hi, I'm a required value";
}
I have several large web apps that have a "Session Bean" that stores stuff like user preferences, shared objects etc... and this method works perfectly. By using a reference to the bean you eliminate the need to chain the initialization. That method will always DEPEND on the method in the other bean, thus guaranteeing the order of initialization.
There's a variety of ways to access the bean but I usually go through the EL route ->
Get JSF managed bean by name in any Servlet related class
Best of luck, I try to stay "functionally pure" when I can--and I hope that get's a laugh considering the language!
Here's some cool hax for ya, in case other solutions aren't working for you due to various circumstances...
Let's say I have a class Alpha that I want initialized first:
public class Alpha {
#PostConstruct
public void init() {
}
}
I can put the following method in Alpha:
#ManagedBean(name = "Alpha", eager = true)
public class Alpha {
public static void requireAlpha() {
FacesContext context = FacesContext.getCurrentInstance();
Object alpha = context.getApplication().evaluateExpressionGet(context, "#{Alpha}", Object.class);
System.out.println("Alpha required: " + alpha.toString());
}
#PostConstruct
public void init() {
}
}
Then, in any classes that are initializing too early, simply call:
Alpha.requireAlpha();
// ...
// (Code that requires Alpha to be initialized first.)
And if there's a ChildAlpha class that extends Alpha that you really want to be initialized (rather than the parent), make sure to use "ChildAlpha" instead, in both the name="" and the EL Expression ("#{}").
See here for more infos: Get JSF managed bean by name in any Servlet related class

JSF2: How to initiate services at deployment [duplicate]

This question already has an answer here:
Using special auto start servlet to initialize on startup and share application data
(1 answer)
Closed 7 years ago.
For university project I am developing a webapplication with JSF. My excercise is to do the frontend. A fellow studend is supposed to do backend stuff. Both parts are designed to be seerate applications. Both communicate through RMI. I want to open the connection once at deployment.
I am at the point to settle up the connection now. I tried to do that with a #ApplicationScoped ManagedBean:
//Constructor of ApplicationScoped ManagedBean
public Communication() {
this.connect();
}
Is that way possible? I tried it but the managedBean seems not to be called..
Can you advice a Best Practice?
#Brian: Unfortunately I don't use EJB at all -.-
#BalusC's pot:
I created a communicationbean:
#ManagedBean(name="communication")
#ApplicationScoped
public class Communication {
public static FrontendCommInterface server;
public Communication() {
this.connect();
}
Then I created the LoginBean:
#ManagedBean
#ViewScoped
public class Login {
#ManagedProperty(value="#{communication}")
private Communication communicationBean;
public FrontendCommInterface server;
private String username;
private String password;
public Login() {
server = communicationBean.getConnection();
}
public String login(){
HttpSession session = (HttpSession) FacesContext.getCurrentInstance().getExternalContext().getSession(true);
String sessionId = session.getId();
try {
server.login(getUsername(), getPassword(), sessionId);
return "start.xhtml";
} catch (RemoteException e) {
e.printStackTrace();
FacesContext.getCurrentInstance().addMessage(null, new FacesMessage(FacesMessage.SEVERITY_ERROR,"Anmeldung nicht erfolgreich: ", getUsername()+", "+getPassword()+", "+sessionId));
return "login.xhtml";
}
}
But unfortunately it throws exceptions:
com.sun.faces.mgbean.ManagedBeanCreationException: Klasse org.dhbw.stg.wwi2008c.mopro.ui.managedBeans.Login can not be instanciated.
java.lang.NullPointerException
org.dhbw.stg.wwi2008c.mopro.ui.managedBeans.Login.<init>(Login.java:28)
After debuging I found out that my ManagedProperty is Null ! It hasn't been created! How to do that? I thought referencing via managedproperty would create it -.-
The managed bean is only auto-created whenever it's been referenced by EL #{managedBeanName}, which can happen by either accessing as-is in view, or by being injected as managed property of another bean, or being manually EL-resolved by e.g. Application#evaluateExpressionGet().
In your particular case, you actually want to intialize some stuff during webapp's startup. You rather want to use ServletContextListener for this.
#WebListener
public class Config implements ServletContextListener {
public void contextInitialized(ServletContextEvent event) {
// Do stuff during webapp's startup.
}
public void contextDestroyed(ServletContextEvent event) {
// Do stuff during webapp's shutdown.
}
}
You could even pre-create an application scoped managed bean there whenever necessary (if your intent is to be able to access it from other beans by #ManagedProperty).
public void contextInitialized(ServletContextEvent event) {
event.getServletContext().setAttribute("bean", new Bean());
}
JSF stores application scoped beans as an attribute of the ServletContext and JSF won't auto-create another one when one is already present, so the one and the same as created by the above code example will be used by JSF as well.
If you can use EJB 3.1 lite {1} in your web app, then you can use a Singleton Session Bean, annotated with #Startup, and a #PostConstruct method. I have one that looks like:
#Singleton
#Startup
public class CachePrimer {
#PostConstruct
public void loadOpenRequests() {
...
}
}
{1}: EJB 3.1 lite is included in the Web Profile of JavEE 6, and is provided by web profile servers like Glassfish, JBoss 6, and Resin. When using such a web profile server, you simply include your EJBs in your .war file, no additional work is required.

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