Multiple log statements from single println

Question

I am writing the size of my arraylist just for debugging purposes but I notices that I get the value multiple times in the log window in Eclipse. It is different for each time, and it applies other places where I debug with System.out.println(..) Any reason why this happens?

---

Log window

INFO: 4
INFO: 4
INFO: 4
INFO: 4

View

<f:metadata>
    <f:event listener="#{defaultNewQuestionHandler.init}" type="preRenderView" />
</f:metadata>

Backingbean

import java.io.Serializable;
import java.util.ArrayList;

import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;

@ViewScoped
@ManagedBean
public class DefaultNewQuestionHandler extends QuestionHandler implements Serializable {

    private static final long serialVersionUID = -6986655384538762284L;

    @Override
    public void init() {
        answers = new ArrayList<Answer>();

        for (int i = 0; i < 4; i++) {
            addAnswerAlternative();
        }

        System.out.println(answers.size());
    }
}

Answer 1

You get the value multiple times in the log due to JSF's Request Respond Lifecycle. The initial request results in 4 log entries because JSF executes the Restore View, Apply Request Values, Process Events and Render Response phase.

Answer 2

JSF tends to call methods on the backing bean more than once (as mentioned eg in this Seam performance tips article). It's generally a good idea to calculate the result, stick it in a field, and have the JSF page reference a method that just returns the field value.