org.apache.activemq.artemis.shaded.org.jgroups.protocols.rules.Rule Maven / Gradle / Ivy
package org.apache.activemq.artemis.shaded.org.jgroups.protocols.rules;
import org.apache.activemq.artemis.shaded.org.jgroups.logging.Log;
/**
* A rule with a condition and (optional) action. When a rule is run, the condition is checked with {@link #eval()} and
* - if true - the action is triggered with {@link #trigger()}.
* @author Bela Ban
* @since 3.3
*/
public abstract class Rule implements Runnable {
protected SUPERVISOR sv; // set when rule is installed
protected Log log; // set when rule is installed
public Rule supervisor(SUPERVISOR sv) {this.sv=sv; return this;}
public Rule log(Log log) {this.log=log; return this;}
/** Returns the name of the rule. Should be unique if a rule needs to be uninstalled */
public abstract String name();
/** Describes what the rules does */
public abstract String description();
/** Called when rule is installed */
public void init() {}
/** Called when rule is uninstalled */
public void destroy() {}
/** Evaluates the condition. If true, the rule is triggered. If true, the next execution of {@link #condition()}
* should return a non-null string */
public abstract boolean eval();
/** Returns a description of the condition that led to {@link #eval()} returning true */
public abstract String condition();
/** The action of the rule. Triggered if {@link #eval()} returned true */
public abstract void trigger() throws Throwable;
public void run() {
if(!eval())
return;
try {
String condition=condition();
if(condition == null)
condition="executed rule " + name();
sv.addCondition(condition);
if(log.isTraceEnabled())
log.trace(sv.getLocalAddress() + ": executing rule " + name());
trigger();
}
catch(Throwable t) {
log.error(sv.getLocalAddress() + ": failed executiong rule " + name(), t);
}
}
}