basics of spring autowire - first cut

spring-autowire/src/main/java/com/baeldung/autowire/sample/App.java

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+package com.baeldung.autowire.sample;
+
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+public class App {
+	public static void main(String[] args) {
+		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(AppConfig.class);
+		FooService fooService = ctx.getBean(FooService.class);
+		fooService.doStuff();
+	}
+}

spring-autowire/src/main/java/com/baeldung/autowire/sample/AppConfig.java

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+package com.baeldung.autowire.sample;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("com.baeldung.autowire.sample")
+public class AppConfig {
+
+}

spring-autowire/src/main/java/com/baeldung/autowire/sample/Bar.java

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+package com.baeldung.autowire.sample;
+
+public class Bar {
+
+}

spring-autowire/src/main/java/com/baeldung/autowire/sample/BarFormatter.java

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+package com.baeldung.autowire.sample;
+
+import org.springframework.stereotype.Component;
+
+@FormatterType("Bar")
+@Component
+public class BarFormatter implements Formatter {
+
+    public String format() {
+        return "bar";
+    }
+    
+}

spring-autowire/src/main/java/com/baeldung/autowire/sample/Foo.java

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+package com.baeldung.autowire.sample;
+
+public class Foo {
+
+}

spring-autowire/src/main/java/com/baeldung/autowire/sample/FooDAO.java

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+package com.baeldung.autowire.sample;
+
+public class FooDAO {
+
+}

spring-autowire/src/main/java/com/baeldung/autowire/sample/FooFormatter.java

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+package com.baeldung.autowire.sample;
+
+import org.springframework.stereotype.Component;
+
+@FormatterType("Foo")
+@Component
+public class FooFormatter implements Formatter {
+
+    public String format() {
+        return "foo";
+    }
+    
+}

spring-autowire/src/main/java/com/baeldung/autowire/sample/FooService.java

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+package com.baeldung.autowire.sample;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+@Component
+public class FooService {
+    
+    @Autowired
+    @FormatterType("Foo")
+    private Formatter formatter;
+    
+    public String doStuff(){
+        return formatter.format();
+    }
+    
+}

spring-autowire/src/main/java/com/baeldung/autowire/sample/Formatter.java

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+package com.baeldung.autowire.sample;
+
+public interface Formatter {
+
+	String format();
+
+}

spring-autowire/src/main/java/com/baeldung/autowire/sample/FormatterType.java

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+package com.baeldung.autowire.sample;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.beans.factory.annotation.Qualifier;
+
+@Qualifier
+@Target({ElementType.FIELD, ElementType.METHOD,ElementType.TYPE, ElementType.PARAMETER})
+@Retention(RetentionPolicy.RUNTIME)
+public @interface FormatterType {
+    
+    String value();
+
+}

spring-autowire/src/test/java/com/baeldung/autowire/sample/FooServiceTest.java

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+package com.baeldung.autowire.sample;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.support.AnnotationConfigContextLoader;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(classes=AppConfig.class, loader=AnnotationConfigContextLoader.class)
+public class FooServiceTest {
+    
+    @Autowired
+    FooService fooService;
+    
+    @Test
+    public void whenFooFormatterType_thenReturnFoo(){
+        Assert.assertEquals("foo", fooService.doStuff());
+    }
+}