Passing data between managed components in JSF

Question

Is it actually possible to pass any data between managed components in JSF? If yes, how to achieve this?

Could anyone provide any sample?

Answer 1

There are several ways. If the managed beans are related to each other, cleanest way would be managed property injection. Let assume that Bean1 has the same scope or a broader scope than Bean2. First give Bean2 a Bean1 property:

public class Bean2 {
    private Bean1 bean1; // +getter +setter.
}

Then declare Bean1 in faces-config.xml to be a managed property of Bean2:

<managed-bean>
    <managed-bean-name>bean1</managed-bean-name>
    <managed-bean-class>com.example.Bean1</managed-bean-class>
    <managed-bean-scope>session</managed-bean-scope>
</managed-bean>

<managed-bean>
    <managed-bean-name>bean2</managed-bean-name>
    <managed-bean-class>com.example.Bean2</managed-bean-class>
    <managed-bean-scope>request</managed-bean-scope>
    <managed-property>
        <property-name>bean1</property-name>
        <value>#{bean1}</value>
    </managed-property>
</managed-bean>

This way the bean2 instance has instant access to the bean1 instance.

If you don't want to use managed property injection for some reasons, then you can also grab Application#evaluateExpressionGet() to access it programmatically. Here's an example of retrieving Bean1 inside Bean2:

FacesContext context = FacesContext.getCurrentInstance();
Bean1 bean1 = (Bean1) context.getApplication().evaluateExpressionGet(context, "#{bean1}", Bean1.class);

The Bean1 must however already be declared as managed bean bean1 in faces-config.xml.

For more info and hints about passing data around inside JSF, you may find this article useful.

Answer 2

To add to BalusC's answer, if you are using a dependency-injection framework (spring, guice, etc.), or if using JSF 2.0, you can have one managed bean set into the other using just:

@Inject
private Bean2 bean2;

(or the appropriate annotation based on your DI framework)