BAEL-2921 Understanding getBean

spring-core/src/main/java/com/baeldung/getbean/AnnotationConfig.java

@@ -0,0 +1,22 @@
+package com.baeldung.getbean;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Scope;
+
+@Configuration
+class AnnotationConfig {
+
+    @Bean(name = {"tiger", "kitty"})
+    @Scope(value = "prototype")
+    Tiger getTiger(String name) {
+        return new Tiger(name);
+    }
+
+    @Bean(name = "lion")
+    Lion getLion() {
+        return new Lion("Hardcoded lion name");
+    }
+
+    interface Animal {}
+}

spring-core/src/main/java/com/baeldung/getbean/Lion.java

@@ -0,0 +1,13 @@
+package com.baeldung.getbean;
+
+class Lion implements AnnotationConfig.Animal {
+    private String name;
+
+    Lion(String name) {
+        this.name = name;
+    }
+
+    String getName() {
+        return name;
+    }
+}

spring-core/src/main/java/com/baeldung/getbean/Tiger.java

@@ -0,0 +1,13 @@
+package com.baeldung.getbean;
+
+class Tiger implements AnnotationConfig.Animal {
+    private String name;
+
+    Tiger(String name) {
+        this.name = name;
+    }
+
+    String getName() {
+        return name;
+    }
+}

spring-core/src/test/java/com/baeldung/getbean/GetBeanByNameAndTypeUnitTest.java

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+package com.baeldung.getbean;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.springframework.beans.factory.BeanNotOfRequiredTypeException;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+class GetBeanByNameAndTypeUnitTest {
+    private ApplicationContext context;
+
+    @BeforeAll
+    void setup() {
+        context = new AnnotationConfigApplicationContext(AnnotationConfig.class);
+    }
+
+    @Test
+    void whenSpecifiedMatchingNameAndType_thenShouldReturnRelatedBean() {
+        Lion lion = context.getBean("lion", Lion.class);
+
+        assertEquals("Hardcoded lion name", lion.getName());
+    }
+
+    @Test
+    void whenSpecifiedNotMatchingNameAndType_thenShouldThrowException() {
+        assertThrows(BeanNotOfRequiredTypeException.class, () -> context.getBean("lion", Tiger.class));
+    }
+}

spring-core/src/test/java/com/baeldung/getbean/GetBeanByNameUnitTest.java

@@ -0,0 +1,40 @@
+package com.baeldung.getbean;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.springframework.beans.factory.NoSuchBeanDefinitionException;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+class GetBeanByNameUnitTest {
+    private ApplicationContext context;
+
+    @BeforeAll
+    void setup() {
+        context = new AnnotationConfigApplicationContext(AnnotationConfig.class);
+    }
+
+    @Test
+    void whenGivenExistingBeanName_shouldReturnThatBean() {
+        Object requestedBean = context.getBean("lion");
+
+        assertEquals(requestedBean.getClass(), Lion.class);
+    }
+
+    @Test
+    void whenGivenNonExistingBeanName_shouldThrowException() {
+        assertThrows(NoSuchBeanDefinitionException.class, () -> context.getBean("non-existing"));
+    }
+
+    @Test
+    void whenCastingToWrongType_thenShouldThrowException() {
+        assertThrows(ClassCastException.class, () -> {
+            Tiger tiger = (Tiger) context.getBean("lion");
+        });
+    }
+}

spring-core/src/test/java/com/baeldung/getbean/GetBeanByNameWithConstructorParametersUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.getbean;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.springframework.beans.factory.UnsatisfiedDependencyException;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+class GetBeanByNameWithConstructorParametersUnitTest {
+    private ApplicationContext context;
+
+    @BeforeAll
+    void setup() {
+        context = new AnnotationConfigApplicationContext(AnnotationConfig.class);
+    }
+
+    @Test
+    void whenGivenCorrectNameOrAlias_shouldReturnBeanWithSpecifiedName() {
+        Tiger tiger = (Tiger) context.getBean("tiger", "Cutie");
+        Tiger tigerSecond = (Tiger) context.getBean("tiger", "Striped");
+        Tiger tigerViaAlias = (Tiger) context.getBean("kitty", "Siberian");
+        assertEquals("Cutie", tiger.getName());
+        assertEquals("Striped", tigerSecond.getName());
+        assertEquals("Siberian", tigerViaAlias.getName());
+    }
+
+    @Test
+    void whenNoArgumentSpecifiedForPrototypeBean_thenShouldThrowException() {
+        assertThrows(UnsatisfiedDependencyException.class, () -> {
+            Tiger tiger = (Tiger) context.getBean("tiger");
+        });
+    }
+}

spring-core/src/test/java/com/baeldung/getbean/GetBeanByTypeUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.getbean;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.springframework.beans.factory.NoUniqueBeanDefinitionException;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+class GetBeanByTypeUnitTest {
+    private ApplicationContext context;
+
+    @BeforeAll
+    void setup() {
+        context = new AnnotationConfigApplicationContext(AnnotationConfig.class);
+    }
+
+    @Test
+    void whenGivenExistingUniqueType_thenShouldReturnRelatedBean() {
+        Lion lion = context.getBean(Lion.class);
+
+        assertNotNull(lion);
+    }
+
+    @Test
+    void whenGivenAmbiguousType_thenShouldThrowException() {
+        assertThrows(NoUniqueBeanDefinitionException.class, () -> context.getBean(AnnotationConfig.Animal.class));
+    }
+}

spring-core/src/test/java/com/baeldung/getbean/GetBeanByTypeWithConstructorParametersUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.getbean;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+class GetBeanByTypeWithConstructorParametersUnitTest {
+    private ApplicationContext context;
+
+    @BeforeAll
+    void setup() {
+        context = new AnnotationConfigApplicationContext(AnnotationConfig.class);
+    }
+
+    @Test
+    void whenGivenExistingTypeAndValidParameters_thenShouldReturnRelatedBean() {
+        Tiger tiger = context.getBean(Tiger.class, "Shere Khan");
+
+        assertEquals("Shere Khan", tiger.getName());
+    }
+}