Merge pull request #5986 from codehunter34/BAEL-2399

BAEL-2399: Guice vs Spring - Dependency Injection

guice/pom.xml

@@ -1,29 +1,45 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<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.baeldung.examples.guice</groupId>
-    <artifactId>guice</artifactId>
-    <version>1.0-SNAPSHOT</version>
-    <packaging>jar</packaging>
-    <name>guice</name>
+<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.baeldung.examples.guice</groupId>
+	<artifactId>guice</artifactId>
+	<version>1.0-SNAPSHOT</version>
+	<packaging>jar</packaging>
+	<name>guice</name>
 
-    <parent>
-        <groupId>com.baeldung</groupId>
-        <artifactId>parent-modules</artifactId>
-        <version>1.0.0-SNAPSHOT</version>
-    </parent>
+	<parent>
+		<groupId>com.baeldung</groupId>
+		<artifactId>parent-modules</artifactId>
+		<version>1.0.0-SNAPSHOT</version>
+	</parent>
 
-    <dependencies>
-        <dependency>
-            <groupId>com.google.inject</groupId>
-            <artifactId>guice</artifactId>
-            <version>${guice.version}</version>
-        </dependency>
-    </dependencies>
+	<dependencies>
+		<dependency>
+			<groupId>com.google.inject</groupId>
+			<artifactId>guice</artifactId>
+			<version>${guice.version}</version>
+		</dependency>
 
-    <properties>
-        <guice.version>4.1.0</guice.version>
-    </properties>
+		<dependency>
+			<groupId>org.springframework</groupId>
+			<artifactId>spring-context</artifactId>
+			<version>${spring.version}</version>
+		</dependency>
+
+		<dependency>
+			<groupId>org.springframework</groupId>
+			<artifactId>spring-test</artifactId>
+			<version>${springtest.version}</version>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+
+	<properties>
+		<guice.version>4.2.2</guice.version>
+		<spring.version>5.1.3.RELEASE</spring.version>
+		<springtest.version>5.1.3.RELEASE</springtest.version>
+	</properties>
 
 </project>

guice/src/main/java/com/baeldung/examples/common/Account.java

@@ -0,0 +1,27 @@
+package com.baeldung.examples.common;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Account {
+
+	private String accountNumber;
+	private String type;
+
+	public String getAccountNumber() {
+		return accountNumber;
+	}
+
+	public void setAccountNumber(String accountNumber) {
+		this.accountNumber = accountNumber;
+	}
+
+	public String getType() {
+		return type;
+	}
+
+	public void setType(String type) {
+		this.type = type;
+	}
+
+}

guice/src/main/java/com/baeldung/examples/common/AccountService.java

@@ -0,0 +1,5 @@
+package com.baeldung.examples.common;
+
+public interface AccountService {
+
+}

guice/src/main/java/com/baeldung/examples/common/AccountServiceImpl.java

@@ -0,0 +1,8 @@
+package com.baeldung.examples.common;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class AccountServiceImpl implements AccountService {
+
+}

guice/src/main/java/com/baeldung/examples/common/AudioBookService.java

@@ -0,0 +1,5 @@
+package com.baeldung.examples.common;
+
+public interface AudioBookService {
+
+}

guice/src/main/java/com/baeldung/examples/common/AudioBookServiceImpl.java

@@ -0,0 +1,5 @@
+package com.baeldung.examples.common;
+
+public class AudioBookServiceImpl implements AudioBookService {
+
+}

guice/src/main/java/com/baeldung/examples/common/AuthorService.java

@@ -0,0 +1,5 @@
+package com.baeldung.examples.common;
+
+public interface AuthorService {
+
+}

guice/src/main/java/com/baeldung/examples/common/AuthorServiceImpl.java

@@ -0,0 +1,5 @@
+package com.baeldung.examples.common;
+
+public class AuthorServiceImpl implements AuthorService {
+
+}

guice/src/main/java/com/baeldung/examples/common/BookService.java

@@ -0,0 +1,5 @@
+package com.baeldung.examples.common;
+
+public interface BookService {
+
+}

guice/src/main/java/com/baeldung/examples/common/BookServiceImpl.java

@@ -0,0 +1,10 @@
+package com.baeldung.examples.common;
+
+import org.springframework.beans.factory.annotation.Autowired;
+
+public class BookServiceImpl implements BookService {
+
+	@Autowired(required = false)
+	private AuthorService authorService;
+
+}

guice/src/main/java/com/baeldung/examples/common/PersonDao.java

@@ -0,0 +1,5 @@
+package com.baeldung.examples.common;
+
+public interface PersonDao {
+
+}

guice/src/main/java/com/baeldung/examples/common/PersonDaoImpl.java

@@ -0,0 +1,8 @@
+package com.baeldung.examples.common;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class PersonDaoImpl implements PersonDao {
+
+}

guice/src/main/java/com/baeldung/examples/guice/Foo.java

@@ -0,0 +1,4 @@
+package com.baeldung.examples.guice;
+
+public class Foo {
+}

guice/src/main/java/com/baeldung/examples/guice/FooProcessor.java

@@ -0,0 +1,12 @@
+package com.baeldung.examples.guice;
+
+import org.springframework.lang.Nullable;
+
+import com.google.inject.Inject;
+
+public class FooProcessor {
+
+	@Inject
+	@Nullable
+	private Foo foo;
+}

guice/src/main/java/com/baeldung/examples/guice/GuicePersonService.java

@@ -0,0 +1,19 @@
+package com.baeldung.examples.guice;
+
+import com.baeldung.examples.common.PersonDao;
+import com.google.inject.Inject;
+
+public class GuicePersonService {
+
+	@Inject
+	private PersonDao personDao;
+
+	public PersonDao getPersonDao() {
+		return personDao;
+	}
+
+	public void setPersonDao(PersonDao personDao) {
+		this.personDao = personDao;
+	}
+
+}

guice/src/main/java/com/baeldung/examples/guice/GuiceUserService.java

@@ -0,0 +1,19 @@
+package com.baeldung.examples.guice;
+
+import com.baeldung.examples.common.AccountService;
+import com.google.inject.Inject;
+
+public class GuiceUserService {
+
+	@Inject
+	private AccountService accountService;
+
+	public AccountService getAccountService() {
+		return accountService;
+	}
+
+	public void setAccountService(AccountService accountService) {
+		this.accountService = accountService;
+	}
+
+}

guice/src/main/java/com/baeldung/examples/guice/Person.java

@@ -0,0 +1,24 @@
+package com.baeldung.examples.guice;
+
+public class Person {
+	private String firstName;
+
+	private String lastName;
+
+	public String getFirstName() {
+		return firstName;
+	}
+
+	public void setFirstName(String firstName) {
+		this.firstName = firstName;
+	}
+
+	public String getLastName() {
+		return lastName;
+	}
+
+	public void setLastName(String lastName) {
+		this.lastName = lastName;
+	}
+
+}

guice/src/main/java/com/baeldung/examples/guice/modules/GuiceModule.java

@@ -0,0 +1,50 @@
+package com.baeldung.examples.guice.modules;
+
+import com.baeldung.examples.common.AccountService;
+import com.baeldung.examples.common.AccountServiceImpl;
+import com.baeldung.examples.common.BookService;
+import com.baeldung.examples.common.BookServiceImpl;
+import com.baeldung.examples.common.PersonDao;
+import com.baeldung.examples.common.PersonDaoImpl;
+import com.baeldung.examples.guice.Foo;
+import com.baeldung.examples.guice.Person;
+import com.google.inject.AbstractModule;
+import com.google.inject.Provider;
+import com.google.inject.Provides;
+
+public class GuiceModule extends AbstractModule {
+
+	@Override
+	protected void configure() {
+		try {
+			bind(AccountService.class).to(AccountServiceImpl.class);
+			bind(Person.class).toConstructor(Person.class.getConstructor());
+			// bind(Person.class).toProvider(new Provider<Person>() {
+			// public Person get() {
+			// Person p = new Person();
+			// return p;
+			// }
+			// });
+			bind(Foo.class).toProvider(new Provider<Foo>() {
+				public Foo get() {
+					return null;
+				}
+			});
+			bind(PersonDao.class).to(PersonDaoImpl.class);
+
+		} catch (NoSuchMethodException e) {
+			// TODO Auto-generated catch block
+			e.printStackTrace();
+		} catch (SecurityException e) {
+			// TODO Auto-generated catch block
+			e.printStackTrace();
+		}
+
+	}
+
+	@Provides
+	public BookService bookServiceGenerator() {
+		return new BookServiceImpl();
+	}
+
+}

guice/src/main/java/com/baeldung/examples/spring/SpringBeansConfig.java

@@ -0,0 +1,17 @@
+package com.baeldung.examples.spring;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import com.baeldung.examples.common.AudioBookService;
+import com.baeldung.examples.common.AudioBookServiceImpl;
+
+@Configuration
+public class SpringBeansConfig {
+
+	@Bean
+	public AudioBookService audioBookServiceGenerator() {
+		return new AudioBookServiceImpl();
+	}
+
+}

guice/src/main/java/com/baeldung/examples/spring/SpringMainConfig.java

@@ -0,0 +1,21 @@
+package com.baeldung.examples.spring;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+
+import com.baeldung.examples.common.BookService;
+import com.baeldung.examples.common.BookServiceImpl;
+
+@Configuration
+@Import({ SpringBeansConfig.class })
+@ComponentScan("com.baeldung.examples")
+public class SpringMainConfig {
+
+	@Bean
+	public BookService bookServiceGenerator() {
+		return new BookServiceImpl();
+	}
+
+}

guice/src/main/java/com/baeldung/examples/spring/SpringPersonService.java

@@ -0,0 +1,22 @@
+package com.baeldung.examples.spring;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+import com.baeldung.examples.common.PersonDao;
+
+@Component
+public class SpringPersonService {
+
+    @Autowired
+    private PersonDao personDao;
+
+    public PersonDao getPersonDao() {
+        return personDao;
+    }
+
+    public void setPersonDao(PersonDao personDao) {
+        this.personDao = personDao;
+    }
+
+}

guice/src/main/java/com/baeldung/examples/spring/UserService.java

@@ -0,0 +1,22 @@
+package com.baeldung.examples.spring;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+import com.baeldung.examples.common.AccountService;
+
+@Component
+public class UserService {
+
+	@Autowired
+	private AccountService accountService;
+
+	public AccountService getAccountService() {
+		return accountService;
+	}
+
+	public void setAccountService(AccountService accountService) {
+		this.accountService = accountService;
+	}
+
+}

guice/src/test/java/com/baeldung/examples/GuiceUnitTest.java

@@ -0,0 +1,61 @@
+package com.baeldung.examples;
+
+import static org.junit.Assert.assertNotNull;
+
+import org.junit.Test;
+
+import com.baeldung.examples.common.BookService;
+import com.baeldung.examples.guice.FooProcessor;
+import com.baeldung.examples.guice.GuicePersonService;
+import com.baeldung.examples.guice.GuiceUserService;
+import com.baeldung.examples.guice.Person;
+import com.baeldung.examples.guice.modules.GuiceModule;
+import com.google.inject.Guice;
+import com.google.inject.Injector;
+
+public class GuiceUnitTest {
+
+	@Test
+	public void givenAccountServiceInjectedInGuiceUserService_WhenGetAccountServiceInvoked_ThenReturnValueIsNotNull() {
+		Injector injector = Guice.createInjector(new GuiceModule());
+		GuiceUserService guiceUserService = injector.getInstance(GuiceUserService.class);
+		assertNotNull(guiceUserService.getAccountService());
+	}
+
+	@Test
+	public void givenBookServiceIsRegisteredInModule_WhenBookServiceIsInjected_ThenReturnValueIsNotNull() {
+		Injector injector = Guice.createInjector(new GuiceModule());
+		BookService bookService = injector.getInstance(BookService.class);
+		assertNotNull(bookService);
+	}
+
+	@Test
+	public void givenMultipleBindingsForPerson_WhenPersonIsInjected_ThenTestFailsByProvisionException() {
+		Injector injector = Guice.createInjector(new GuiceModule());
+		Person person = injector.getInstance(Person.class);
+		assertNotNull(person);
+	}
+
+	@Test
+	public void givenFooInjectedToFooProcessorAsOptionalDependency_WhenFooProcessorIsRetrievedFromContext_ThenCreationExceptionIsNotThrown() {
+		Injector injector = Guice.createInjector(new GuiceModule());
+		FooProcessor fooProcessor = injector.getInstance(FooProcessor.class);
+		assertNotNull(fooProcessor);
+	}
+
+	@Test
+	public void givenGuicePersonServiceConstructorAnnotatedByInject_WhenGuicePersonServiceIsInjected_ThenInstanceWillBeCreatedFromTheConstructor() {
+		Injector injector = Guice.createInjector(new GuiceModule());
+		GuicePersonService personService = injector.getInstance(GuicePersonService.class);
+		assertNotNull(personService);
+	}
+
+	@Test
+	public void givenPersonDaoInjectedToGuicePersonServiceBySetterInjection_WhenGuicePersonServiceIsInjected_ThenPersonDaoInitializedByTheSetter() {
+		Injector injector = Guice.createInjector(new GuiceModule());
+		GuicePersonService personService = injector.getInstance(GuicePersonService.class);
+		assertNotNull(personService);
+		assertNotNull(personService.getPersonDao());
+	}
+
+}

guice/src/test/java/com/baeldung/examples/SpringUnitTest.java

@@ -0,0 +1,63 @@
+package com.baeldung.examples;
+
+import static org.junit.Assert.assertNotNull;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import com.baeldung.examples.common.AudioBookService;
+import com.baeldung.examples.common.BookService;
+import com.baeldung.examples.spring.SpringMainConfig;
+import com.baeldung.examples.spring.SpringPersonService;
+import com.baeldung.examples.spring.UserService;
+
+@RunWith(SpringRunner.class)
+@ContextConfiguration(classes = { SpringMainConfig.class })
+public class SpringUnitTest {
+	@Autowired
+	ApplicationContext context;
+
+	@Test
+	public void givenAccountServiceAutowiredToUserService_WhenGetAccountServiceInvoked_ThenReturnValueIsNotNull() {
+		UserService userService = context.getBean(UserService.class);
+		assertNotNull(userService.getAccountService());
+	}
+
+	@Test
+	public void givenBookServiceIsRegisteredAsBeanInContext_WhenBookServiceIsRetrievedFromContext_ThenReturnValueIsNotNull() {
+		BookService bookService = context.getBean(BookService.class);
+		assertNotNull(bookService);
+	}
+
+	@Test
+	public void givenBookServiceIsRegisteredAsBeanInContextByOverridingAudioBookService_WhenAudioBookServiceIsRetrievedFromContext_ThenNoSuchBeanDefinitionExceptionIsThrown() {
+		BookService bookService = context.getBean(BookService.class);
+		assertNotNull(bookService);
+		AudioBookService audioBookService = context.getBean(AudioBookService.class);
+		assertNotNull(audioBookService);
+	}
+
+	@Test
+	public void givenAuthorServiceAutowiredToBookServiceAsOptionalDependency_WhenBookServiceIsRetrievedFromContext_ThenNoSuchBeanDefinitionExceptionIsNotThrown() {
+		BookService bookService = context.getBean(BookService.class);
+		assertNotNull(bookService);
+	}
+
+	@Test
+	public void givenSpringPersonServiceConstructorAnnotatedByAutowired_WhenSpringPersonServiceIsRetrievedFromContext_ThenInstanceWillBeCreatedFromTheConstructor() {
+		SpringPersonService personService = context.getBean(SpringPersonService.class);
+		assertNotNull(personService);
+	}
+
+	@Test
+	public void givenPersonDaoAutowiredToSpringPersonServiceBySetterInjection_WhenSpringPersonServiceRetrievedFromContext_ThenPersonDaoInitializedByTheSetter() {
+		SpringPersonService personService = context.getBean(SpringPersonService.class);
+		assertNotNull(personService);
+		assertNotNull(personService.getPersonDao());
+	}
+
+}