BAEL-3091: The Prototype Pattern in Java (changed code based on valid comments from a reader)

guice/README.md

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+## Google Guice
+
+This module contains articles about Google Guice
+
+### Relevant Articles
+
+- [Guide to Google Guice](https://www.baeldung.com/guice)
+- [Guice vs Spring – Dependency Injection](https://www.baeldung.com/guice-spring-dependency-injection)

guice/pom.xml

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+<?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>
+    <name>guice</name>
+    <packaging>jar</packaging>
+
+    <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>
+
+    <properties>
+        <guice.version>4.1.0</guice.version>
+    </properties>
+
+</project>

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

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+
+package com.baeldung.examples;
+
+import com.baeldung.examples.guice.Communication;
+import com.baeldung.examples.guice.binding.AOPModule;
+import com.baeldung.examples.guice.modules.BasicModule;
+import com.google.inject.Guice;
+import com.google.inject.Injector;
+import java.util.Scanner;
+
+/**
+ *
+ * @author baeldung
+ */
+public class RunGuice {
+
+    public static void main(String[] args) {
+        Injector injector = Guice.createInjector(new BasicModule(), new AOPModule());
+        Communication comms = injector.getInstance(Communication.class);
+        Scanner scanner = new Scanner(System.in);
+        while (true) {
+            String input = scanner.nextLine();
+            if (input.equalsIgnoreCase("q")) {
+                System.exit(0);
+            } else {
+                comms.sendMessage(input);
+            }
+
+        }
+
+    }
+}

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

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+package com.baeldung.examples.common;
+
+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

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+package com.baeldung.examples.common;
+
+public interface AccountService {
+
+}

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

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+package com.baeldung.examples.common;
+
+public class AccountServiceImpl implements AccountService {
+
+}

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

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+package com.baeldung.examples.common;
+
+public interface AudioBookService {
+
+}

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

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+package com.baeldung.examples.common;
+
+public class AudioBookServiceImpl implements AudioBookService {
+
+}

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

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+package com.baeldung.examples.common;
+
+public interface AuthorService {
+
+}

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

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+package com.baeldung.examples.common;
+
+public class AuthorServiceImpl implements AuthorService {
+
+}

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

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+package com.baeldung.examples.common;
+
+public interface BookService {
+
+}

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

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+package com.baeldung.examples.common;
+
+public class BookServiceImpl implements BookService {
+
+	private AuthorService authorService;
+
+}

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

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+package com.baeldung.examples.common;
+
+public interface PersonDao {
+
+}

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

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+package com.baeldung.examples.common;
+
+public class PersonDaoImpl implements PersonDao {
+
+}

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

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+
+package com.baeldung.examples.guice;
+
+import com.google.inject.Inject;
+import com.google.inject.name.Named;
+import java.util.Date;
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.logging.Logger;
+
+/**
+ *
+ * @author baeldung
+ */
+public class Communication {
+
+    final Date start = new Date();
+
+    @Inject
+    private Logger logger;
+
+    @Inject
+    private DefaultCommunicator communicator;
+
+    public Communication(Boolean keepRecords) {
+        if (keepRecords) {
+            System.out.println("keeping records");
+        }
+    }
+
+    public boolean sendMessage(String message) {
+      
+        return communicator.sendMessage(message);
+    }
+ 
+    public DefaultCommunicator getCommunicator() {
+        return this.communicator;
+    }
+
+}

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

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+
+package com.baeldung.examples.guice;
+
+import com.baeldung.examples.guice.constant.CommunicationModel;
+
+public interface CommunicationMode {
+
+    public CommunicationModel getMode();
+    
+    public boolean sendMessage(String message);
+
+}

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

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+
+package com.baeldung.examples.guice;
+
+import com.baeldung.examples.guice.marker.Communicator;
+import com.google.inject.Inject;
+import com.google.inject.name.Named;
+
+/**
+ *
+ * @author baeldung
+ */
+public class DefaultCommunicator implements Communicator {
+
+    private CommunicationMode defaultCommsMode;
+    @Inject
+    @Named("SMSComms")
+    CommunicationMode smsCommsMode;
+    @Inject
+    @Named("EmailComms")
+    CommunicationMode emailCommsMode;
+    @Inject
+    @Named("IMComms")
+    CommunicationMode imCommsMode;
+
+    protected DefaultCommunicator(CommunicationMode defaultComms) {
+        this.defaultCommsMode = defaultComms;
+    }
+
+    public DefaultCommunicator() {
+
+    }
+
+    public boolean sendMessage(String message) {
+        boolean sent = false;
+        if (defaultCommsMode != null) {
+            sent = sendMessageByDefault(message);
+        } else {
+            sent = smsCommsMode.sendMessage(message);
+        }
+        return sent;
+    }
+
+    private boolean sendMessageByDefault(String message) {
+        boolean sent = false;
+        if (message != null && !message.trim().equals("")) {
+            return defaultCommsMode.sendMessage(message);
+        }
+        return sent;
+    }
+
+}

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

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+
+package com.baeldung.examples.guice;
+
+import com.baeldung.examples.guice.aop.MessageSentLoggable;
+import com.baeldung.examples.guice.constant.CommunicationModel;
+
+/**
+ *
+ * @author baeldung
+ */
+public class EmailCommunicationMode implements CommunicationMode {
+
+    @Override
+    public CommunicationModel getMode() {
+        return CommunicationModel.EMAIL;
+    }
+
+    @Override
+    @MessageSentLoggable
+    public boolean sendMessage(String Message) {
+        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
+    }
+
+}

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

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+package com.baeldung.examples.guice;
+
+public class Foo {
+}

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

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+package com.baeldung.examples.guice;
+
+import com.google.inject.Inject;
+
+public class FooProcessor {
+
+	@Inject
+	private Foo foo;
+}

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

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+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

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+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/IMCommunicationMode.java

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+
+package com.baeldung.examples.guice;
+
+import com.baeldung.examples.guice.aop.MessageSentLoggable;
+import com.baeldung.examples.guice.constant.CommunicationModel;
+import com.google.inject.Inject;
+import java.util.logging.Logger;
+
+/**
+ *
+ * @author baeldung
+ */
+public class IMCommunicationMode implements CommunicationMode {
+
+    @Inject
+    private Logger logger;
+
+    @Override
+    public CommunicationModel getMode() {
+        return CommunicationModel.IM;
+    }
+
+    @Override
+    @MessageSentLoggable
+    public boolean sendMessage(String message) {
+        logger.info("IM Message Sent");
+        return true;
+    }
+
+}

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

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+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/SMSCommunicationMode.java

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+
+package com.baeldung.examples.guice;
+
+import com.baeldung.examples.guice.aop.MessageSentLoggable;
+import com.baeldung.examples.guice.constant.CommunicationModel;
+import com.google.inject.Inject;
+import java.util.logging.Logger;
+
+/**
+ *
+ * @author baeldung
+ */
+public class SMSCommunicationMode implements CommunicationMode {
+    
+    @Inject
+    private Logger logger;
+
+    @Override
+    public CommunicationModel getMode() {
+        return CommunicationModel.SMS;
+    }
+
+    @Override
+    @MessageSentLoggable
+    public boolean sendMessage(String message) {
+        logger.info("SMS message sent");
+        return true;
+    }
+
+}

guice/src/main/java/com/baeldung/examples/guice/aop/MessageLogger.java

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+
+package com.baeldung.examples.guice.aop;
+
+import com.google.inject.Inject;
+import java.util.logging.Logger;
+import org.aopalliance.intercept.MethodInterceptor;
+import org.aopalliance.intercept.MethodInvocation;
+
+/**
+ *
+ * @author baeldung
+ */
+public class MessageLogger implements MethodInterceptor {
+
+    @Override
+    public Object invoke(MethodInvocation invocation) throws Throwable {
+        Object[] objectArray = invocation.getArguments();
+        int i = 0;
+        for (Object object : objectArray) {
+            Logger.getAnonymousLogger().info("Sending message: " + object.toString());
+        }
+        return invocation.proceed();
+    }
+}

guice/src/main/java/com/baeldung/examples/guice/aop/MessageSentLoggable.java

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+
+package com.baeldung.examples.guice.aop;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ *
+ * @author baeldung
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.METHOD)
+public @interface MessageSentLoggable {
+
+}

guice/src/main/java/com/baeldung/examples/guice/binding/AOPModule.java

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+
+package com.baeldung.examples.guice.binding;
+
+import com.baeldung.examples.guice.aop.MessageLogger;
+import com.baeldung.examples.guice.aop.MessageSentLoggable;
+import com.google.inject.AbstractModule;
+import com.google.inject.matcher.Matchers;
+
+/**
+ *
+ * @author baeldung
+ */
+public class AOPModule extends AbstractModule {
+
+    @Override
+    protected void configure() {
+        bindInterceptor(Matchers.any(),
+                Matchers.annotatedWith(MessageSentLoggable.class),
+                new MessageLogger()
+        );
+    }
+
+}

guice/src/main/java/com/baeldung/examples/guice/binding/BasicModule.java

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+
+package com.baeldung.examples.guice.binding;
+
+import com.baeldung.examples.guice.Communication;
+import com.baeldung.examples.guice.CommunicationMode;
+import com.baeldung.examples.guice.DefaultCommunicator;
+import com.baeldung.examples.guice.EmailCommunicationMode;
+import com.baeldung.examples.guice.IMCommunicationMode;
+import com.baeldung.examples.guice.SMSCommunicationMode;
+import com.google.inject.AbstractModule;
+import com.google.inject.name.Names;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+/**
+ *
+ * @author baeldung
+ */
+public class BasicModule extends AbstractModule {
+
+    @Override
+    protected void configure() {
+        try {
+            bind(Communication.class).toConstructor(Communication.class.getConstructor(Boolean.TYPE));
+        } catch (NoSuchMethodException ex) {
+            Logger.getLogger(BasicModule.class.getName()).log(Level.SEVERE, null, ex);
+        } catch (SecurityException ex) {
+            Logger.getLogger(BasicModule.class.getName()).log(Level.SEVERE, null, ex);
+        }
+        bind(DefaultCommunicator.class).annotatedWith(Names.named("AnotherCommunicator")).to(DefaultCommunicator.class).asEagerSingleton();
+
+        bind(CommunicationMode.class).annotatedWith(Names.named("IMComms")).to(IMCommunicationMode.class);
+        bind(CommunicationMode.class).annotatedWith(Names.named("EmailComms")).to(EmailCommunicationMode.class);
+        bind(CommunicationMode.class).annotatedWith(Names.named("SMSComms")).to(SMSCommunicationMode.class);
+    }
+
+}

guice/src/main/java/com/baeldung/examples/guice/constant/CommunicationModel.java

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+
+package com.baeldung.examples.guice.constant;
+
+/**
+ *
+ * @author baeldung
+ */
+public enum CommunicationModel {
+
+    EMAIL("Email"), SMS("SMS"), IM("IM"), PHONE("Phone");
+
+    final String name;
+
+    CommunicationModel(String name) {
+        this.name = name;
+    }
+}

guice/src/main/java/com/baeldung/examples/guice/marker/Communicator.java

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+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package com.baeldung.examples.guice.marker;
+
+/**
+ *
+ * @author Tayo
+ */
+public interface Communicator {
+    
+}

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

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+
+package com.baeldung.examples.guice.modules;
+
+import com.baeldung.examples.guice.Communication;
+import com.baeldung.examples.guice.CommunicationMode;
+import com.baeldung.examples.guice.DefaultCommunicator;
+import com.baeldung.examples.guice.EmailCommunicationMode;
+import com.baeldung.examples.guice.IMCommunicationMode;
+import com.baeldung.examples.guice.SMSCommunicationMode;
+import com.google.inject.AbstractModule;
+import com.google.inject.name.Names;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+/**
+ *
+ * @author baeldung
+ */
+public class BasicModule extends AbstractModule {
+
+    @Override
+    protected void configure() {
+        try {
+            bind(Communication.class).toConstructor(Communication.class.getConstructor(Boolean.class));
+            bind(Boolean.class).toInstance(true);
+        } catch (NoSuchMethodException ex) {
+            Logger.getLogger(com.baeldung.examples.guice.binding.BasicModule.class.getName()).log(Level.SEVERE, null, ex);
+        } catch (SecurityException ex) {
+            Logger.getLogger(com.baeldung.examples.guice.binding.BasicModule.class.getName()).log(Level.SEVERE, null, ex);
+        }
+        bind(DefaultCommunicator.class).annotatedWith(Names.named("AnotherCommunicator")).to(DefaultCommunicator.class).asEagerSingleton();
+
+        bind(CommunicationMode.class).annotatedWith(Names.named("IMComms")).to(IMCommunicationMode.class);
+        bind(CommunicationMode.class).annotatedWith(Names.named("EmailComms")).to(EmailCommunicationMode.class);
+        bind(CommunicationMode.class).annotatedWith(Names.named("SMSComms")).to(SMSCommunicationMode.class);
+    }
+
+}

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

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+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 new Foo();
+				}
+			});
+			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/resources/logback.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

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());
+	}
+
+}