Spring java configuration is not being called

Question

I started to use Spring for Dependency Injection.

I added the jar spring-context-4.0.1

I added @Configuration to a class

@Configuration
public class SpringConfig {

    @Bean
    public CategoryDAO categoryDAO() {
        return new HibernateCategoryDAO();
    }
    
}

where

public interface CategoryDAO{
}

and

public class HibernateCategoryDAO implements CategoryDAO {
}

However, when I try to @Autowired it in a Component (more precisely a Repository)

@Repository
public class MyCategoryManager implements CategoryManager {

    @Autowired
    CategoryDAO categoryDAO;

}

categoryDAO is null. Furthermore, I see stepping through the code in debug mode that it never executes the Configuration file.

What am I missing?

I don't want to use XML in Spring but do I still need to add the application-context file?

EDIT:

Following @Gummyball answer, I added the configuration. It didn't help.

I initialize MyCategoryManager class using Reflections util:

Set<?> managers = Reflections.getSubTypesOf(CategoryManager.class);

Could it be the reason? how can I overcome it?

Answer 1

Yes, you need to bootstrap Spring by adding a listener class to your web.xml. By supplying your @Configuration class (.i.e your SpringConfig class) as a context parameter, your configuration class will be picked up by Spring.

<web-app>
    <!-- Configure ContextLoaderListener to use AnnotationConfigWebApplicationContext instead of the default XmlWebApplicationContext -->
    <context-param>
        <param-name>contextClass</param-name>
        <param-value>
            org.springframework.web.context.support.AnnotationConfigWebApplicationContext
        </param-value>
    </context-param>

    <!-- Configuration locations must consist of one or more comma- or space-delimited fully-qualified @Configuration classes. Fully-qualified packages may also be specified for component-scanning -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>your.own.package.SpringConfig</param-value>
    </context-param>

    <!-- Bootstrap the root application context as usual using ContextLoaderListener -->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    // Your jersey config here
</web-app>

---

UPDATE

Based on the official Jersey Spring Example, I made this hello world example which uses Spring together with Jersey.

You'll need to have the following dependencies: spring framework, jersey-container-servlet and jersey-spring3. Or if using maven:

pom.xml

<project
    xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
    http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>
    <groupId>com.stackoverflow.question.jersey.with.spring</groupId>
    <artifactId>SpringConfig</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>
    <name>SpringConfig</name>

    <properties>
        <!-- Spring -->
        <spring-framework.version>4.0.1.RELEASE</spring-framework.version>
        <jersey.version>2.6</jersey.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>${spring-framework.version}</version>
        </dependency>
        <dependency>
            <groupId>org.glassfish.jersey.containers</groupId>
            <artifactId>jersey-container-servlet</artifactId>
            <version>${jersey.version}</version>
        </dependency>
        <dependency>
            <groupId>org.glassfish.jersey.ext</groupId>
            <artifactId>jersey-spring3</artifactId>
            <version>${jersey.version}</version>
        </dependency>
    </dependencies>
</project>

In web.xml you'll need to configure Spring and Jersey

web.xml

<web-app xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">

    <!-- Configure ContextLoaderListener to use AnnotationConfigWebApplicationContext instead of the default XmlWebApplicationContext -->
    <context-param>
        <param-name>contextClass</param-name>
        <param-value>
            org.springframework.web.context.support.AnnotationConfigWebApplicationContext
        </param-value>
    </context-param>

    <!-- Configuration locations must consist of one or more comma- or space-delimited fully-qualified @Configuration classes. -->
    <!-- Fully-qualified packages may also be specified for component-scanning -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>com.stackoverflow.question.jersey.with.spring.SpringConfig</param-value>
    </context-param>

    <!-- Bootstrap the root application context as usual using ContextLoaderListener -->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <!-- Jersey config -->
    <servlet>
        <servlet-name>SpringConfig</servlet-name>
        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>javax.ws.rs.Application</param-name>
            <param-value>com.stackoverflow.question.jersey.with.spring.MyApplication</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>SpringConfig</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
</web-app>

The trick here is to tell Jersey which package(s) to scan. Alternatively, you could use register(.class) to register each component individually.

MyApplication.java

package com.stackoverflow.question.jersey.with.spring;

import org.glassfish.jersey.server.ResourceConfig;
import org.glassfish.jersey.server.spring.scope.RequestContextFilter;

/**
 * Spring HelloWorld Web Application configuration.
 * 
 * @author Jakub Podlesak (jakub.podlesak at oracle.com)
 */
public class MyApplication extends ResourceConfig
{

    /**
     * Register JAX-RS application components.
     */
    public MyApplication()
    {
        packages(true, "com.stackoverflow.question.jersey.with.spring");
    }
}

You can tell Spring to use component scanning by supplying a package to @ComponentScan. Or, if you want more control on how Spring beans are initialized, you could use separate @Bean annotations (like you did in your question) to specify each Spring bean independently.

SpringConfig.java

package com.stackoverflow.question.jersey.with.spring;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan("com.stackoverflow.question.jersey.with.spring")
public class SpringConfig
{
}

Based on your comment about different CategoryManager implementations, I made a helper class that will return a different CategoryManager based on the enum type that you give it (which would be a user supplied value).

CategoryManagerFactory.java

package com.stackoverflow.question.jersey.with.spring;

import javax.inject.Inject;
import org.springframework.stereotype.Component;

@Component
public class CategoryManagerFactory
{
    @Inject
    private MyCategoryManager myCategoryManager;

    @Inject
    private OtherCategoryManager otherCategoryManager;

    public CategoryManager obtainCategoryManager(CategoryManagerTypes type)
    {
        switch (type) {
            case MY:
                return myCategoryManager;
            case OTHER:
                return otherCategoryManager;
            default:
                throw new IllegalArgumentException(String.format("Category %s not supported", type));
        }
    }

    public enum CategoryManagerTypes
    {
        MY, OTHER;
    }
}

MyCategoryManager.java

package com.stackoverflow.question.jersey.with.spring;

import javax.inject.Inject;
import org.springframework.stereotype.Component;

@Component
public class MyCategoryManager implements CategoryManager
{
    @Inject
    private CategoryDAO categoryDAO;

    @Override
    public String saySomething()
    {
        return "Using MyCategoryManager!";
    }
}

OtherCategoryManager.java

package com.stackoverflow.question.jersey.with.spring;

import javax.inject.Inject;
import org.springframework.stereotype.Component;

@Component
public class OtherCategoryManager implements CategoryManager
{
    @Inject
    private CategoryDAO categoryDAO;

    @Override
    public String saySomething()
    {
        return "Using OtherCategoryManager!";
    }
}

And to bring everything together, using Spring in a Jersey resource:

JerseyResource.java

package com.stackoverflow.question.jersey.with.spring;

import javax.inject.Inject;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.MediaType;
import com.stackoverflow.question.jersey.with.spring.CategoryManagerFactory.CategoryManagerTypes;

@Path("jersey-hello")
public class JerseyResource
{
    @Inject
    private CategoryManagerFactory categoryManagerFactory;

    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String getHello(@Context HttpHeaders headers, @QueryParam("category") CategoryManagerTypes category)
    {
        CategoryManager categoryManager = categoryManagerFactory.obtainCategoryManager(category);

        return categoryManager.saySomething();
    }
}

By going to http://localhost:8080/SpringConfig/jersey-hello?category=MY you'd get 'Using MyCategoryManager!'