SpEL unable to access the instance variable

Question

I am trying to make use of Spring Boot AutoConfigured @EnableScheduling to create a cron job. Job triggers perfectly fine if the fixedRateString is hardcoded. However it does not succeed if I try to make use of SpEL to supply the value.

//Bean Instantiation in JavaConfig

@Bean
public AlertbotJob2 getAlertJob2() {
    AlertbotJob2 alertbotJob2 = new AlertbotJob2("alertId", "alertName", "alertSubject", "6000", true);
    return alertbotJob2;
}

Bean Definition

public class AlertbotJob2 {

String alertId;
String alertName;
String alertSubject;
public String cronPattern;
boolean isActive;

public AlertbotJob2() {
}

public AlertbotJob2(String alertId, String alertName, String alertSubject, String cronPattern, boolean isActive) {
    super();
    this.alertId = alertId;
    this.alertName = alertName;
    this.alertSubject = alertSubject;
    this.cronPattern = cronPattern;
    this.isActive = isActive;
}

@Scheduled(initialDelay = 60000, fixedRateString = "#{this.cronPattern}")
public void doTheJob() {
    System.out.println("DoSomething");
}

}

Exception is :: Expression parsing failed; nested exception is org.springframework.expression.spel.SpelEvaluationException: EL1008E: Property or field 'this' cannot be found on object of type 'org.springframework.beans.factory.config.BeanExpressionContext' - maybe not public?

I am just trying to set the trigger values dynamically. Please help.

Mark Bramnik · Accepted Answer · 2017-12-18 20:43:10Z

1

I don't think you can use SpEL like this. Maybe the better approach is to define your cron pattern in some property like:

myapp.scheduler.cronPattern=...

And then use the following syntax:

@Scheduled(cron = "${myapp.scheduler.cronPattern}")
public void doTheJob() {
    ...
}

answered Dec 18, 2017 at 20:43

Mark Bramnik

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Comments

Gary Russell · Accepted Answer · 2017-12-18 20:43:13Z

1

You can't use this there.

You have to do it by bean name @someBean.cronPattern.

answered Dec 18, 2017 at 20:43

Gary Russell

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2 Comments

zikzakjack Over a year ago

Well, I tried that approach but did not work well. As I am programmatic ally creating the beans after reading database configurations. Need to figure out if @someBean.cronPattern can be created with prototype scope ..

Gary Russell Over a year ago

No; there is no way for the SpEL expression to directly refer to the instance of the class in which the annotation resides.

zikzakjack · Accepted Answer · 2018-01-30 21:42:32Z

Solution 1: use the hardcoded pattern if its already known @Scheduled(cron = "0 0/5 * * * MON-FRI")

Solution 2: If the pattern is available in some property @Scheduled(cron = "${myapp.scheduler.cronPattern}")

Solution 3 : This approach does not use annotation. Instead the Beans are just implemented as runnables And then override the SchedulingConfigurer.configureTasks() to dynamically set the schedules using taskRegistrar.addCronTask(urRunnableJob, urCronPatternFromDB); . Cron pattern is stored in database table, initialize it as properties as below.

class AppConfig { 

    @Autowired
    ConfigurableEnvironment environment;

    private void initPropertiesMap() {
        environment.getPropertySources()
            .addLast(new MapPropertySource("myAppProperties", myAppProperties.getProperties())); // Prior DAO call required to read the configs from database
    }

    @PostConstruct
    public void postConstruct() {
        initPropertiesMap();
    }

}

Akinfemiwa olayode · Accepted Answer · 2022-07-04 16:47:17Z

0

you can try this:

   e.g @Value("#{T(com.someName.ClassName).cronPattern}")

I reference this Accessing static variable in spring annotations using spel

answered Jul 4, 2022 at 16:47

Akinfemiwa olayode

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