Why I can't inject (using @Autowired) a service class into the Main class (the class that contains the main() method) in this Spring application?

Question

I am pretty new in Spring and I have the following problem.

I am implement a Spring console application (this is not a web app) that perform some query on the database and I have the following configuration:

A beans.xml file containing the beans definition:

 <context:component-scan base-package="it.mycompany.myapp.profilatura.service" />

 <!-- bean definitions here -->
 <bean id="helloWorld" class="HelloWorld">
    <property name="message" value="Hello World!"/>
 </bean>

As you can see in this file I have also specified that the application have tho scan the it.mycompany.myapp.profilatura.service package that will contain classes annoted with @Service annotation, by this line:

<context:component-scan base-package="it.mycompany.myapp.profilatura.service" />

So this is my MainApp class that contain the main() method and that start the application:

public class MainApp {
    
    @Autowired
    private static UtenteLoggatoService utenteLoggatoService;
    
    public static void main(String[] args) {
       
        ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
      
        HelloWorld obj = (HelloWorld) context.getBean("helloWorld");

        obj.getMessage();
        
        utenteLoggatoService.getInfoUtenteLoggato();
   }
}

As you can see, at the end, it perform this method call:

utenteLoggatoService.getInfoUtenteLoggato();

and this is the autowired UtenteLoggatoService class:

@Service
@Transactional(rollbackFor={Exception.class})
public class UtenteLoggatoService {
    
    public String getInfoUtenteLoggato() {
        return "TEST";
    }

}

The problem is that when I perform this application I obtain this error message into my stacktrace:

Exception in thread "main" org.springframework.beans.factory.xml.XmlBeanDefinitionStoreException: Line 8 in XML document from class path resource [Beans.xml] is invalid; nested exception is org.xml.sax.SAXParseException; lineNumber: 8; columnNumber: 74; The prefix "context" for element "context:component-scan" is not bound.
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:399)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:336)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:304)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:181)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:217)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:188)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:252)
    at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:127)
    at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:93)
    at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:129)
    at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:537)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:452)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
    at MainApp.main(MainApp.java:14)
Caused by: org.xml.sax.SAXParseException; lineNumber: 8; columnNumber: 74; The prefix "context" for element "context:component-scan" is not bound.
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:203)
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:177)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:400)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:327)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:284)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:290)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2787)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:606)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:118)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:510)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:848)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:777)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
    at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:243)
    at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:339)
    at org.springframework.beans.factory.xml.DefaultDocumentLoader.loadDocument(DefaultDocumentLoader.java:76)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadDocument(XmlBeanDefinitionReader.java:429)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:391)
    ... 14 more

What am I missing? How can I solve this issue and use the UtenteLoggatoService into the MainApp class?

The exception you're receiving is unrelated to the question you're asking. — Sotirios Delimanolis, Nov 19 '15 at 15:39

AndreaNobili · Answer 1 · 2015-11-19T15:56:14.123

I soled by myself looking at the documentation:

So I have this beans.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd">


    <context:component-scan base-package="it.mycompany.myproject.profilatura.app" />
    <context:component-scan base-package="it.hp.miur.profilatura.service" />

    <!-- bean definitions here -->
    <bean id="helloWorld" class="it.mycompany.myproject.profilatura.app.HelloWorld">
       <property name="message" value="Hello World!"/>
    </bean>

</beans>

And this MainApp class:

@Component
public class MainApp {

    @Autowired
    private UtenteLoggatoService utenteLoggatoService;

    public static void main(String[] args) {

        ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");

        MainApp app = context.getBean(MainApp.class);

        app.start();

        //HelloWorld obj = (HelloWorld) context.getBean("helloWorld");

        //obj.getMessage();


   }  

    private void start() {
        System.out.println("APPLICATION STARTED");
        System.out.println(utenteLoggatoService.getInfoUtenteLoggato());
    }

}

So it work, I think that it is the most common solution

Doing in this way the MainApp class is a Spring component and I instanciate it as a Spring bean so I can autowire another bean (as UtenteLoggatoService utenteLoggatoService) that is inside the context taking it from the context.

Why does this fix anything? What part of the documentation lead you to this solution? — Sotirios Delimanolis, Nov 19 '15 at 15:40
Because doing in this way the MainApp class is a Spring component and I instanciate it as a bean so I can autowire another bean inside the context. It work fine — AndreaNobili, Nov 19 '15 at 15:53

Why I can't inject (using @Autowired) a service class into the Main class (the class that contains the main() method) in this Spring application?

1 Answers1