conditional #Autowired? - spring

Question

I have a HsqldbReconciler (for "work" with a HSQLDB database) which I autowired, like:
#Autowired
HsqldbReconciler hsqldbReconciler;
In Future there will be a OracleReconciler, MssqlReconciler, etc. I will need to use them accordingly to the type of connection a user has chosen.
How should I implement this? Usually I would have a kind of factory, which returns only the needed Reconciler. The only way in spring, I can currently imagine, is to Autowire an instance of each Reconciler, then use one of them in the code. Is there a better way?

Answer 1

make a Factory Class that will contain all your beans, e.g
#Component
class Factory{
#Autowired HsqldbReconciler hsqldb;
#Autowired OracleReconciler oracle;
#Autowired MssqlReconciler mssql;
public Object getInstance(String type){
switch(type){
case "mssql" : return mssql;
case "oracle" : return oracle;
// and so on
default : return null;
}
}
}
Now use this Factory as follows
class SomeClass{
#Autowired private Factory factory;
public Object someMethod(){
Object reconciler = factory.getInstance("mssql");
((MssqlReconciler)reconciler).someMethod();
}
}

Answer 2

Define them in your Config with the same name, but different conditions:
#Bean(name = "dbReconciler")
#Conditional(HsqldbReconcilerEnabled.class)
public ReconcilerBase getHsqldbReconciler() {
return new HsqldbReconciler();
}
#Bean(name = "dbReconciler")
#Conditional(OracleReconcilerEnabled.class)
public ReconcilerBase getOracleReconciler() {
return new OracleReconciler();
}
#Bean(name = "dbReconciler")
#Conditional(MssqlReconcilerEnabled.class)
public ReconcilerBase getMssqlReconciler() {
return new MssqlReconciler();
}
create conditions reading from app.properties:
HsqldbReconciler.enabled=true
OracleReconciler.enabled=false
MssqlReconciler.enabled=false
like this:
public class HsqldbReconcilerEnabled implements Condition {
private static final String PROP_ENABLED = "HsqldbReconciler.enabled";
#Override
public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
String property = context.getEnvironment().getProperty(PROP_ENABLED);
return Boolean.parseBoolean(property);
}
}
// etc...
use like:
#Autowired
#Qualifier("dbReconciler")
ReconcilerBase dbReconsiler;
ensure you're not enabling multiple beans at the same time.