The first thing necessary for a relationship it to define a relationship type in the system. We have an MBean that creates a binary relationship (two roles) on start and removes the relationship when stopped. The following is a complete MBean declaration (note: all attributes other then the name are optional)
<mbean code="org.apache.geronimo.jmx.Relationship" name="geronimo.test:role=Relationship,name=Twins">
<attribute name="Name">Twins</attribute>
<attribute name="LeftRoleName">Good</attribute>
<attribute name="LeftRoleClass"> some.good.BeanMBean</attribute>
<attribute name="LeftRoleMinimum">1</attribute>
<attribute name="LeftRoleMaximum">1</attribute>
<attribute name="LeftRoleDescription">This is the Good Twin</attribute>
<attribute name="RightRoleName">Evil</attribute>
<attribute name="RightRoleClass"> some.evil.BeanBean</attribute>
<attribute name="RightRoleMinimum">1</attribute>
<attribute name="RightRoleMaximum">1</attribute>
<attribute name="RightRoleDescription">This is the Evil Twin</attribute>
</mbean>
The default is for a relationship with two roles, "left" and "right", where each role is r/w, can have zero or more elements and can only contains MBeans of type "java.lang.Object" (anything).
We also now support MBean relationship declaration in our MBean deployment descriptor. You can declare an MBean as follows.
<mbean code="some.good.Bean" name="geronimo.test:alignment=Good">
<attribute name="Interval">3000000</attribute>
</mbean><mbean code="some.evil.Bean" name="geronimo.test:alignment=Evil">
<attribute name="Interval">30000</attribute>
<relationship
name="basic good and evil"
role="Evil"
type="Twins"
target="geronimo.test:alignment=Good"
targetRole="Good"/>
</mbean>The name and role attributes are required. The type, target and target role attributes are only used if the relationship is not found. In the case where the relationship is not found, we create a new one of the specified type and assign the target to the target role. The target and targetRole attributes are really only necessary for blind relationships or if the relationship has a minimal cardinality of 1.
Finally, I added the RelationshipMBeanProxyFactory creates a dynamic proxy to an MBean based on a relationship end point. The interface type, relationship existience, and object existance is not enforced during construction. Instead, if a method is invoked on the proxy and there is no relationship registered with the specified id or if the target role does not conatin any objects, an InvocationTargetException is thrown, which contains an IllegalStateException. If an interface method that is not implemented by the MBean is invoked, an InvocationTargetException is thrown, which contains an NoSuchMethodException.
To invoke a method based on the above relationship you can simply do this:
some.evil.BeanMBean evil = (some.evil.BeanMBean) RelationshipMBeanProxyFactory.getProxy(
some.evil.Bean.class,
server,
"basic good and evil",
"Evil");
evil.doSomethingEvil();
There is also a overloaded method which does not take the interface class, but looks at the RoleInfo to determine the interface class. This only works if the role is defined in terms of interfaces and not classes.
I'm going to keep working on this, as this is a path to a simple dependency management system. I'm not sure exactly how it will work, but I plan on having a special "Must be started" relationship which contains the object names of the MBeans that must be started before the an MBean is started. I'm avoiding details, because I just don't know exactly how it will work. BTW, I just writing the easy dependancy system, not the final dependancy startup/management system, so please don't worry we can rewrite it later (think XP -- something for today).
-dain
/************************* * Dain Sundstrom * Partner * Core Developers Network *************************/
