The sort answer is yes. This is more general spring/design pattern issue rater then Spring Batch.
The Spring Batch tricky parts are the configuration and understanding scope of bean creation.
Let’s assume all your Strategies implement Strategy interface that looks like:
interface Strategy {
int execute(int a, int b);
};
Every strategy should implements Strategy and use @Component annotation to allow automatic discovery of new Strategy. Make sure all new strategy will placed under the correct package so component scan will find them.
For example:
@Component
public class StrategyA implements Strategy {
@Override
public int execute(int a, int b) {
return a+b;
}
}
The above are singletons and will be created on the application context initialization.
This stage is too early to use @Value("#{jobParameters['strategy']}") as JobParameter wasn't created yet.
So I suggest a locator bean that will be used later when myTasklet is created (Step Scope).
StrategyLocator class:
public class StrategyLocator {
private Map<String, ? extends Strategy> strategyMap;
public Strategy lookup(String strategy) {
return strategyMap.get(strategy);
}
public void setStrategyMap(Map<String, ? extends Strategy> strategyMap) {
this.strategyMap = strategyMap;
}
}
Configuration will look like:
@Bean
@StepScope
public MyTaskelt myTasklet () {
MyTaskelt myTasklet = new MyTaskelt();
//set the strategyLocator
myTasklet.setStrategyLocator(strategyLocator());
return myTasklet;
}
@Bean
protected StrategyLocator strategyLocator(){
return = new StrategyLocator();
}
To initialize StrategyLocator we need to make sure all strategy were already created. So the best approach would be to use ApplicationListener on ContextRefreshedEvent event (warning in this example strategy names start with lower case letter, changing this is easy...).
@Component
public class PlugableStrategyMapper implements ApplicationListener<ContextRefreshedEvent> {
@Autowired
private StrategyLocator strategyLocator;
@Override
public void onApplicationEvent(ContextRefreshedEvent contextRefreshedEvent) {
ApplicationContext applicationContext = contextRefreshedEvent.getApplicationContext();
Map<String, Strategy> beansOfTypeStrategy = applicationContext.getBeansOfType(Strategy.class);
strategyLocator.setStrategyMap(beansOfTypeStrategy);
}
}
The tasklet will hold a field of type String that will be injected with Strategy enum String using @Value and will be resolved using the locator using a "before step" Listener.
public class MyTaskelt implements Tasklet,StepExecutionListener {
@Value("#{jobParameters['strategy']}")
private String strategyName;
private Strategy strategy;
private StrategyLocator strategyLocator;
@BeforeStep
public void beforeStep(StepExecution stepExecution) {
strategy = strategyLocator.lookup(strategyName);
}
@Override
public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception {
int executeStrategyResult = strategy.execute(1, 2);
}
public void setStrategyLocator(StrategyLocator strategyLocator) {
this.strategyLocator = strategyLocator;
}
}
To attach the listener to the taskelt you need to set it in your step configuration:
@Bean
protected Step myTaskletstep() throws MalformedURLException {
return steps.get("myTaskletstep")
.transactionManager(transactionManager())
.tasklet(deleteFileTaskelt())
.listener(deleteFileTaskelt())
.build();
}
