Automatic Wiring

[Raj Singh Arora]

I am very new to Spring, reading Spring in Action 4th edition. I downloaded 4.2.2 release API, and wrote some code. When I run main method of GeometryTest, it gives NullPointerException. Why automatic wiring is not working? What am I missing? Please help.

-------------------------------------------------------------------------------

package configuration;

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

@Configuration
@ComponentScan(basePackages = {"geometry"})
public class SpringConfiguration {

}

-------------------------------------------------------------------------------

package geometry;

public interface Shape {
	public void draw();
}

-------------------------------------------------------------------------------

package geometry;

import org.springframework.stereotype.Component;

@Component("circle")
public class Circle implements Shape {

	@Override
	public void draw() {
		System.out.println("drawing circle");
	}

}

-------------------------------------------------------------------------------

package geometry;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;

import configuration.SpringConfiguration;

@ContextConfiguration(classes=SpringConfiguration.class)
public class GeometryTest {
	@Autowired
	private Shape circle;
	
	public Shape getCircle() {
		return circle;
	}
	
	public void setCircle(Shape circle) {
		this.circle = circle;
	}

	public static void main(String[] args) {
		new GeometryTest().getCircle().draw();
	}
}

-------------------------------------------------------------------------------

[Jayesh A Lalwani]

Your Test class should be run from a Spring Unit Test runner.

You can't just do new GeometryTest() and expect Spring to auto-magically inject beans into a class that you instantiated. For Sprint to do it's Autowiring, Spring has to instantiate the bean. If you are instantitating a bean yourself, Spring isn't in the picture at all. For test classes, you do this by putting a @RunWith(SpringJUnit4ClassRunner.class) and adding test methods into your test class. You will be run your test through JUnit