Lazy Initalizing Beans

A questions on the OTN JDeveloper & ADF forum asked how to initialize attributes with data in a bean before showing the attributes.
The first solution which comes to mind is to initialize attributes and data in the constructor of the bean. This however is not a wise thing to do as you can’t predict when the constructor is called and in which phase of the life cycle you are (as it depends on the scope of the bean).
Here you can use a solution I call lazy initializing the data of a bean. It’s based on the assumption that once the page tries to get an attribute from the bean, the life cycle already has done all other initializations (like bindings). Now if we defer the init of the bean data until a (or the first) getter is called we are save.
To implement this we set an attribute to null and check if it’s null in the getter of the attribute. If we find it’s still null, we init the data and set the attribute to a not null value. Here is the sample code:


import javax.faces.context.FacesContext;
import javax.faces.event.ActionEvent;

import javax.servlet.ServletContext;

import oracle.adf.model.BindingContext;
import oracle.adf.share.logging.ADFLogger;

import oracle.binding.AttributeBinding;
import oracle.binding.BindingContainer;

public class LazyInitBean {
    private static transient final ADFLogger LOGGER = ADFLogger.createADFLogger(LazyInitBean.class);

    private String myName;

    public void setMyName(String myName) {"set data: " + myName);
        this.myName = myName;

    public String getMyName() {
        // lazy init the data only when it's null
        if (myName == null) {
  "init data through layz init");
        return myName;

    public LazyInitBean() {"LazyInitBean: c'tor");

    private void initData() {"data intialized");
        // this method inits the beans attributes (only one here)!
        myName = "just init myself";
        //Get ServlerContexct
        FacesContext ctx = FacesContext.getCurrentInstance();
        ServletContext servletContext = (ServletContext) ctx.getExternalContext().getContext();
        // get the binding container
        BindingContainer bindings = BindingContext.getCurrent().getCurrentBindingsEntry();

        // get an ADF attributevalue from the ADF page definitions
        AttributeBinding attr = (AttributeBinding) bindings.getControlBinding("myTestValue1");
        if (attr != null) {
            String old = (String) attr.getInputValue();
            attr.setInputValue("NEW DEFAULT VALUE");
  "LazyInitBean: setnew default value to 'NEW DEFAULT VALUE' old: " + old);
        } else {
  "LazyInitBean: bindings not present!");

     * Force the init of the beans attributes
    public void resetData() {"LazyInitBean: reset!");
        // setting the myName to null causes a re initialization
        myName = null;
        // you can call initData() here too;

    public void buttonListener(ActionEvent actionEvent) {"Action initData");

Now, whenever in a page or fragment the getter to the bean parameter is called (this can be the getter to every property of a component which can have EL) the bean is checkes if the attribute is already initialized and if not calls the initData() method in the bean. If a value is present, the getter returns the value. The initData() method show that attributes in the binding layer can initialized this way too. This is shown with the myTestValue1 attribute which is defined as pageDef variable. You can overwrite the text in the inputText and when you click the button ‘Clear Data’ the data is initialized again removing the data from the inputText and setting it back to the initial values.
Below is a sample of a fragment which uses the bean to lazy initialize the attribute.

<?xml version='1.0' encoding='UTF-8'?>
<ui:composition xmlns:ui="" xmlns:af="">
    <af:panelGridLayout id="pgl1">
        <af:gridRow height="100%" id="gr1">
            <af:gridCell width="100%" halign="stretch" valign="stretch" id="gc1">
                <!-- Content -->
                <af:panelGroupLayout id="pgl2" layout="vertical">
                    <af:outputText value="Lazy Region" id="ot1" inlineStyle="font-size:large;"/>
                    <af:inputText label="Name:" id="it1" value="#{backingBeanScope.LazyInitBean.myName}" partialTriggers="b1 b2"/>
                    <af:outputText value="Hello: #{backingBeanScope.LazyInitBean.myName}!" id="ot2" partialTriggers="b2 b1"/>
                    <af:button text="ShowMessage" id="b2"/>
                    <af:button text="Clear Data" id="b1" actionListener="#{backingBeanScope.LazyInitBean.buttonListener}"/>
                    <af:inputText label="MyTestValue" id="it2" value="#{bindings.myTestValue1.inputValue}" partialTriggers="b1"/>

Be aware of the fact, that this solution depends on the component(s) which calls the getter which in due course init the data. As the getter methods of the components are called in the order they appear in the component tree you have be careful which getter you use. It should be the first if you want to setup everything up front, but use the last if you want to load data at the end of the page render cycle (e.g. to get more data from a web service but already see the page).

In a comment Aino Andriessen mentioned that you can use the @PostConstruct annotation on a method which then will be called whenever the bean is constructed after all other injections are done. That is the difference to lazy init method. The method is called every time after all other injections are done. If you only want to setup data if the data is really needed this is not possible this way. Nevertheless, to make the sample application show the @PostConstruct method too, I added a method postconstructMethod() in the bean, which writes a log message.

    public void postconstructMethod() {"PostConstruct Called!");
        // init everything here which can be done quickly and is needed to init UI components before showing them
        // or call initData() from here

You can download the sample workspace from the ADF-EMG Sample Project page of get it from GitHub. The sample does not need a DB. The samples are updated to show the @PostConstruct technique.