Why the injection of Session beans gives null pointer exception? - jsf

Question

I have a very simple JSF 2.2 ( hibernate 4.3 ) application that has 2 pages.
first page is login.xhtml which is bound to below session bean
import javax.inject.Named;
import java.io.Serializable;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.enterprise.context.SessionScoped;
import javax.faces.application.FacesMessage;
import javax.faces.context.FacesContext;
#Named(value = "loginBean")
#SessionScoped
public class LoginBean implements Serializable {
/**
* Creates a new instance of LoginBean
*/
Company company;
private static final long serialVersionUID = 1520318172495977648L;
public String Login() {
CompanyHelper companyHelper = new CompanyHelper();
company = companyHelper.Login(this.loginName, this.password);
if (company != null) {
return "";
} else {
FacesMessage msg = new FacesMessage("Failed", "Wrong Usernames or password.");
msg.setSeverity(FacesMessage.SEVERITY_ERROR);
FacesContext.getCurrentInstance().addMessage(null, msg);
return "";
}
}
}
It just validate the Username and password from the DB and returns the company object
the second page delivery.xhtml which bound to view bean. Inside this bean I have injected the login bean but it returns null every time I use Company object. However, when I go to login.xhtml I found that company object is not null.
Below is the delivery bean.
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.PostConstruct;
import javax.faces.model.SelectItem;
import javax.inject.Named;
import javax.faces.view.ViewScoped;
import javax.inject.Inject;
#Named(value = "deliveryBean")
#ViewScoped
public class DeliveryBean implements Serializable {
/**
* Creates a new instance of DeliveryBean
*/
#Inject
private LoginBean loginBean;
#PostConstruct
public void init() {
// returns null pointer exception
Logger.getLogger(LoginBean.class.getName()).log(Level.SEVERE, loginBean.company);
}
public String SendItem() {
// reutn null point exception
String personName=deliverRequest.setDeliverFrom(loginBean.company.getContactPersonName());
return "";
}
}
here is the pom.xml
<dependencies>
<!-- https://mvnrepository.com/artifact/org.primefaces/primefaces -->
<dependency>
<groupId>org.primefaces</groupId>
<artifactId>primefaces</artifactId>
<version>6.1</version>
</dependency>
<dependency>
<groupId>javax</groupId>
<artifactId>javaee-web-api</artifactId>
<version>7.0</version>
<scope>provided</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/javax.validation/validation-api -->
<dependency>
<groupId>javax.validation</groupId>
<artifactId>validation-api</artifactId>
<version>1.1.0.Final</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>4.3.11.Final</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.40</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.12</version>
</dependency>
I am deploying the application on Glassfish 4.1

Answer 1

#Inject
private LoginBean loginBean;
The way injection works is first it creates a proxy object in the loginBean field. CDI doesn't create or lookup a LoginBean instance immediately. Instead it waits until you call a method on the proxy in the loginBean field. CDI calls this a contextual reference - the instance that you'll get depends on the context in which you asked for it.
But you don't call a method:
loginBean.company.toString()
You access the company field directly - CDI can't intercept this. So you get a useless null value from the proxy.
The solution is to not access managed beans' fields directly. Instead make company private and create a getter:
public class LoginBean implements Serializable {
private Company company;
public Company getCompany() {
return company;
}
And call this getter in the DeliveryBean.