Spring 3 how to run a scheduled task with an interval from property file

Question

I am using Spring 3 to create a scheduled-task.

I have to use XML based wiring to configure it, and would like scheduled task to run with an interval that is set in a properties file.

Spring Context file:

<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://www.springframework.org/schema/beans
                       http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
                       http://www.springframework.org/schema/context
                       http://www.springframework.org/schema/context/spring-context-3.1.xsd
                       http://www.springframework.org/schema/task
                       http://www.springframework.org/schema/task/spring-task-3.1.xsd"
   xmlns:context="http://www.springframework.org/schema/context"
   xmlns:task="http://www.springframework.org/schema/task">

  <context:property-placeholder location="classpath:connector.properties"/>

  <task:scheduler id="connectorScheduler" pool-size="10"/>

  <task:scheduled-tasks scheduler="connectorScheduler">
    <task:scheduled ref="connector" method="checkConnection" fixed-rate="${connector.connectionAttemptDelayMillis}"/>
  </task:scheduled-tasks>


  <bean id="connector" class="com.test.Connector" scope="singleton">
    <constructor-arg index="0" value="${connector.user}"/>
    <constructor-arg index="1" value="${connector.password}"/>
    <constructor-arg index="2" value="${connector.connectionAttemptDelayMillis}"/>
  </bean>

</beans>

The problem is that the ${connector.connectionAttemptDelayMillis} is not allowed in the fixed-rate value. This will work fine if i was to put a number in its place, but i need this value to come from a loaded property file.

Any help is much appreciated.

Answer 1

You could do it like that (downside, you can only do your task every 1s or more):

Connector class

package com.test.Connector;

@Component
public class Connector {
    @Value("${connector.user}")
    private String user;

    @Value("${connector.password}")
    private String password;

    @Value("${connector.connectionAttemptDelayMillis:0}")
    private long attemptDelayMillis;

    @Scheduled(cron = "${connector.connectionAttemptCron}")
    public checkConnection() {
        // do the check
    }
}

Xml context

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:task="http://www.springframework.org/schema/task"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task.xsd">

    <context:annotation-config />
    <context:component-scan base-package="com.test" />

    <context:property-placeholder location="classpath:connector.properties" />

    <task:scheduler id="connectorScheduler" pool-size="10"/>
    <task:annotation-driven scheduler="connectorScheduler" />
</beans>

Properties

connector.user = someuser
connector.password = somepassword
connector.connectionAttemptDelayMillis = 5000
connector.connectionAttemptCron = */5 * * * * *

This works because cron need a string.

References

• http://static.springsource.org/spring/docs/3.0.x/reference/scheduling.html
• http://static.springsource.org/spring/docs/3.0.x/javadoc-api/org/springframework/scheduling/annotation/Scheduled.html#cron()