Getproperty dbtype return enableddbtype null

getProperty ( "dbType" );
return ( enabledDBType != null
&& enabledDBType . equalsIgnoreCase ( "MONGODB" ));
}
}
Now we can configure both JdbcUserDAO and MongoUserDAO beans conditionally using
@Conditional as follows:
@Configuration
public class AppConfig
{
@Bean
@Conditional ( MySQLDatabaseTypeCondition . class )
public UserDAO jdbcUserDAO (){
return new JdbcUserDAO ();
}
@Bean
@Conditional ( MongoDBDatabaseTypeCondition . class )
public UserDAO mongoUserDAO (){

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return new MongoUserDAO ();
}
}
Now if we run the application like java -jar myapp.jar -DdbType=MYSQL then only JdbcUser-
DAO bean will be registered.
But if you set the System property like -DdbType=MONGODB then only MongoUserDAO bean
will be registered.
Now that we have seen how to conditionally register a bean based on System Property.
Using @Conditional based on Presence/Absence of a Java Class
Suppose we want to register MongoUserDAO bean only when MongoDB java driver class
“com.mongodb.Server” is available on classpath, if not we want to register JdbcUserDAO bean.
To accomplish that we can create Conditions to check the presence or absence of MongoDB driver
class “com.mongodb.Server” as follows:
public class MongoDriverPresentsCondition implements Condition
{
@Override
public boolean matches ( ConditionContext conditionContext ,
AnnotatedTypeMetadata metadata )
{
try {
Class . forName ( "com.mongodb.Server" );
return true ;
} catch ( ClassNotFoundException e ) {
return false ;
}
}
}
public class MongoDriverNotPresentsCondition implements Condition
{
@Override
public boolean matches ( ConditionContext conditionContext ,
AnnotatedTypeMetadata metadata )
{
try {
Class . forName ( "com.mongodb.Server" );
return false ;

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} catch ( ClassNotFoundException e ) {
return true ;
}
}
}
We just have seen how to register beans conditionally based on presence/absence of a class in
classpath.
Using @Conditional based on Configured Spring Beans
What if we want to register MongoUserDAO bean only if no other Spring bean of type UserDAO
is already registered.
We can create a Condition to check if there is any existing bean of a certain type as follows:
public class UserDAOBeanNotPresentsCondition implements Condition
{
@Override
public boolean matches ( ConditionContext conditionContext ,
AnnotatedTypeMetadata metadata )
{
UserDAO userDAO = conditionContext . getBeanFactory (). getBean ( UserDAO . clas \
s );
return ( userDAO == null );
}
}
Using @Conditional based on Properties Configuration
What if we want to register MongoUserDAO bean only if property app.dbType=MONGO is set in
properties placeholder configuration file?
We can implement that Condition as follows:

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public class MongoDbTypePropertyCondition implements Condition
{
@Override
public boolean matches ( ConditionContext conditionContext ,
AnnotatedTypeMetadata metadata )
{
String dbType = conditionContext . getEnvironment ()
. getProperty ( "app.dbType" );
return "MONGO" . equalsIgnoreCase ( dbType );
}
}
We have just seen how to implement various types of Conditions.