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I've got two instances of a SessionScoped CDI bean for the same session. I was under the impression that there would be one instance generated for me by CDI, but it generated two. Am I misunderstanding how CDI works, or did I find a bug?
Here is the bean code:
package org.mycompany.myproject.session;
import java.io.Serializable;
import javax.enterprise.context.SessionScoped;
import javax.faces.context.FacesContext;
import javax.inject.Named;
import javax.servlet.http.HttpSession;
@Named @SessionScoped public class MyBean implements Serializable {
private String myField = null;
public MyBean() {
System.out.println("MyBean constructor called");
FacesContext fc = FacesContext.getCurrentInstance();
HttpSession session = (HttpSession)fc.getExternalContext().getSession(false);
String sessionId = session.getId();
System.out.println("Session ID: " + sessionId);
}
public String getMyField() {
return myField;
}
public void setMyField(String myField) {
this.myField = myField;
}
}
Here is the Facelet code:
<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core">
<f:view contentType="text/html" encoding="UTF-8">
<h:head>
<title>Test</title>
</h:head>
<h:body>
<h:form id="form">
<h:inputText value="#{myBean.myField}"/>
<h:commandButton value="Submit"/>
</h:form>
</h:body>
</f:view>
</html>
Here is the output from deployment and navigating to page:
INFO: Loading application org.mycompany_myproject_war_1.0-SNAPSHOT at /myproject
INFO: org.mycompany_myproject_war_1.0-SNAPSHOT was successfully deployed in 8,237 milliseconds.
INFO: MyBean constructor called
INFO: Session ID: 175355b0e10fe1d0778238bf4634
INFO: MyBean constructor called
INFO: Session ID: 175355b0e10fe1d0778238bf4634
Using GlassFish 3.0.1
806
Ryan, as covener already wrote, the constructor will also get called for each and every proxy for that bean. This is a standard behaviour of all proxy mechanisms which provide not only interface-proxying (like java.lang.reflect.proxy stuff) but real class-proxying.
Also imagine that the ct will also be called for each and every serialization. So if you work on a heavily load balanced cluster, you will see this lots of times. So please use @PostConstruct for beans in general.
LieGrue, strub
63
It's likely that your CDI implementation calls the underlying beans default constructor when newing up proxies to use for injection points -- this is the default behavior of javassist which is used in weld and openwebbeans.
Avoid heavy lifting in your default constructor, moving it into @PostConstruct if you can!
42
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