Question

I have following situation
– Have a MongoService class, which reads host, port, database from file

xml configuration

<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-3.0.xsd">

    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations">
            <list>
                <value>file:///storage/local.properties</value>
            </list>
        </property>
    </bean>
</beans>  

The local.properties looks like

### === MongoDB interaction === ###
host="127.0.0.1"
port=27017
database=contract

and MongoService Class as

@Service
public class MongoService {

    private final Mongo mongo;
    private final String database;
    private static final Logger LOGGER = LoggerFactory.getLogger(MongoService.class);

    public MongoService(@Nonnull final @Value("#{ systemProperties['host']}") String host, @Nonnull final @Value("#{ systemProperties['port']}") int port, @Nonnull final @Value("#{ systemProperties['database']}") String db) throws UnknownHostException {
        LOGGER.info("host=" + host + ", port=" + port + ", database=" + db);
        mongo = new Mongo(host, port);
        database = db;
    }
}

When I want to test that bean is fine, I do the following in
MongoServiceTest.java

public class MongoServiceTest {

    @Autowired
    private MongoService mongoService;

}

It complains saying that can not identify bean for MongoService .

Then I add the following to above xml

<bean id="mongoService" class="com.business.persist.MongoService"></bean>

Then it complains saying "No Matching Constructor found"

What I want to do

a.) MongoService should be @Autowired and reads configuration params from <value>file:///storage/local.properties</value>

Question

a.) Is accessing values in constructor are correct? (file name is local.properties and I am using @Value("#{ systemProperties['host']}") syntax)

b.) What is that I need to make it work so that @Autowired private MongoService mongoService loads correctly and reads value off local.properties file.

P.S. I am very new to Spring and don’t really know how to make this work

Thanks much for your help in advance

Answer 1

I think , You have to add constructor-arg to config xml as follows.

<bean id="mongoService" class="com.business.persist.MongoService">

        <constructor-arg type="java.lang.String">
            <value>host</value>
        </constructor-arg>

        <constructor-arg type="int">
            <value>port</value>
        </constructor-arg>

        <constructor-arg type="java.lang.String">
            <value>database</value>
        </constructor-arg>

    </bean>

I am not sure,Bst way could be adding java based bean config. Remove the bean definition from xml and add java-based congfig as follows

@Service
public class MongoService {

    private final Mongo mongo;
    private final String database;
    private static final Logger LOGGER = LoggerFactory.getLogger(MongoService.class);

@bean
    public MongoService(@Nonnull final @Value("#{ systemProperties['host']}") String host, @Nonnull final @Value("#{ systemProperties['port']}") int port, @Nonnull final @Value("#{ systemProperties['database']}") String db) throws UnknownHostException {
        LOGGER.info("host=" + host + ", port=" + port + ", database=" + db);
        mongo = new Mongo(host, port);
        database = db;
    }
}

HTH