cyclic managebean detection error in JSF

Question

I have to pages A and B, I want to navigate from A to B and back from B to A in JSF. I set managed property B in managed bean of A and visa versa but problem is i got an error like MANAGED BEAN CYCLIC DETECTION.

  <managed-bean>
      <managed-bean-name>viewBulkMetalIssueBean</managed-bean-name>
      <managed-bean-class>com.cc.jas.web.manufacturing.bulkmetalissue.ViewBulkMetalIssueBean</managed-bean-class>
      <managed-bean-scope>request</managed-bean-scope>
      <managed-property>
       <property-name>viewJobcardBean</property-name>
       <property-class>com.cc.jas.web.manufacturing.jobcard.ViewJobcardBean</property-class>
       <value>#{viewJobcardBean}</value>
       </managed-property>


     </managed-bean>


    <managed-bean>
      <managed-bean-name>viewJobcardBean</managed-bean-name>
      <managed-bean-class>com.cc.jas.web.manufacturing.jobcard.ViewJobcardBean</managed-bean-class>
      <managed-bean-scope>request</managed-bean-scope>
    <managed-property>
       <property-name>viewBulkMetalIssueBean</property-name>
       <property-class>com.cc.jas.web.manufacturing.bulkmetalissue.ViewBulkMetalIssueBean</property-class>
       <value>#{viewBulkMetalIssueBean}</value>
       </managed-property>


      </managed-bean>

Is there any solution or alternate solution for this problem ?

score 14 · Accepted Answer · answered Nov 24 '10 at 10:43

That's indeed not possible. Without this detection, it would only lead to an infinite loop of managed property setting.

To go around this, just let the "parent" bean set itself in the "child" bean when it has been injected.

public class Parent {
    private Child child;

    public void setChild(Child child) {
        this.child = child;
        this.child.setParent(this);
    }

    // ...
}

With

<managed-bean>
    <managed-bean-name>parent</managed-bean-name>
    <managed-bean-class>com.example.Parent</managed-bean-class>
    <managed-bean-scope>request</managed-bean-scope>
    <managed-property>
        <property-name>child</property-name>
        <property-class>com.example.Child</property-class>
        <value>#{child}</value>
    </managed-property>
</managed-bean>

<managed-bean>
    <managed-bean-name>child</managed-bean-name>
    <managed-bean-class>com.example.Child</managed-bean-class>
    <managed-bean-scope>request</managed-bean-scope>
</managed-bean>

It will throws null pointer exception when i navigate to parent from child. from parent to child works fine — chetan, Nov 24 '10 at 11:44
Apparently you're doing this too early. Do it in `@PostConstruct` or later, not in constructor, simply because the setter isn't called yet. You would by the way have exactly the same problem when cyclic injection was allowed like that :) — BalusC, Nov 24 '10 at 11:46

score 4 · Answer 2 · answered Nov 24 '10 at 06:24

You can't have cyclic injections in your JSF managed beans. This is explained nicely in the MyFaces wiki.

An alternate solution is to look up the reference from java code within your managed bean using an EL resolver (for JSF 1.2):

ELContext elContext = FacesContext.getCurrentInstance().getELContext();
NeededBean neededBean = (NeededBean) FacesContext.getCurrentInstance().getApplication()
    .getELResolver().getValue(elContext, null, "neededBean");

See the MyFaces wiki entry for further explanation, and implementations for other JSF versions.

can i know what is middle value of getValue() method ? – chetan Jul 19 '11 at 06:46 — chetan, Jul 19 '11 at 06:46

cyclic managebean detection error in JSF

2 Answers2