[jboss-dev-forums] [Design the new POJO MicroContainer] - Re: Property lookup interceptors

[adrian@jboss.org]

This is the wrong approach. The system property stuff is legacy from the MBean days.
It's certainly the wrong api to be extending, we need to let it die. :-)

The correct approach is should be to create your own ValueMetaData


  | <deployment xmlns="urn:jboss:bean-deployer:2.0" xmlns:ldap="urn:jboss:ldap:1.0">
  | 
  | <bean name="LDAPLookUp" ...>
  |    <!-- ldap config here -->
  | </bean>
  | 
  | <bean name="blah">
  |    <property name="x"><ldap:property bean="LDAPLookUp" key="ldapkeyhere" default="...">
  | </deployment>
  | 

The ldap:property parses to an implementation of ValueMetaData,
something similar to the inject value metadata (AbstractDependencyValueMetaData),
except it gets the value from the LDAPLookUp bean.

(untested code)

  |    public Object getValue(TypeInfo info, ClassLoader cl) throws Throwable
  |    {
  |       ControllerState state = dependentState;
  |       if (state == null)
  |          state = ControllerState.INSTALLED;
  |       Controller controller = context.getController();
  |       ControllerContext lookup = controller.getContext(getUnderlyingValue(), state);
  | 
  |       if (isLookupValid(lookup) == false)
  |          throw new Error("Should not be here - dependency failed - " + this);
  | 
  |       if (lookup == null)
  |          return null;
  | 
  |       Object ldap = lookup.getTarget();
  |       if (result instanceof LDAPLookup == false)
  |          throw new IllegalStateException("Not an LDAPLookup: " + ldap);
  |       LDAPLookup ldapLookup = (LDAPLookup) ldap;
  |       Object result = ldapLookup.lookup(key);
  |       if (result == null)
  |          return defaultValue;
  |       return result;
  |    }
  | 

But it is not documented how to do this, the only close example
is the javabean namespace but that just creates objects directly from the xml.

There maybe a case for abstracting this such that a bean could
implement a "ValueFactory" interface

  | public interface ValueFactory
  | {
  |    Object getValue(String key);
  | }
  | 
and us including a generic piece of xml in our schema to enable its use

  | <property name="x"><value-factory bean="LDAPLookup" key="..." default="..."/></property>
  | 

Which would probably cover most simple use cases?

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