IOC Questions: question 1 to question 7

Author: momedalhouma

.gitignore

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+.idea/
+Spring5Certification.iml

lib/javax.annotation.jar

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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>java.certification.spring</groupId>
+    <artifactId>springcertification</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+
+
+    <dependencies>
+
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-core</artifactId>
+            <version>LATEST</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-context</artifactId>
+            <version>LATEST</version>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>1.18.4</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-test</artifactId>
+            <version>LATEST</version>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-web</artifactId>
+            <version>5.1.7.RELEASE</version>
+        </dependency>
+
+    </dependencies>
+
+</project>

lib/javax.ejb.jar

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+package ioc.commun;
+import lombok.*;
+
+
+@Builder
+@Setter
+@Getter
+@EqualsAndHashCode
+@ToString
+public class Person {
+
+    private String name;
+    private int age;
+    private Profession profession;
+
+
+}

lib/javax.jms.jar

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+package ioc.commun;
+
+
+import lombok.*;
+
+@Builder
+@Setter
+@Getter
+@EqualsAndHashCode
+@ToString
+public class Profession {
+    private String name;
+    private String description;
+}

lib/javax.persistence.jar

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+package ioc.question_001;
+
+
+/**
+ * What is dependency injection and what are the advantages?
+ *
+ *  Object declare their dependencies, other object(Spring container) create and inject those dependencies.
+ *  Several ways:
+ *      1- constructor injection(mandatory)
+ *      2- setter method injection
+ *      3- field injection(the worst way)
+ *
+ *  Advantages:
+ *  1-Loose coupling(between the object and its dependency)
+ *  2-coherent code
+ *  3-clean code(object creation is externalized)
+ *  4-easy testing(using mocked object)
+ *
+ *  Disadvantage
+ *  more classes and interfaces
+ */
+public class DependencyInjection {
+}

lib/javax.resource.jar

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+package ioc.question_003;
+
+
+import org.springframework.beans.factory.DisposableBean;
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.beans.factory.config.*;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
+/**
+ * What is meant by application-context?
+ *
+ *
+ * An application context is an advanced ioc container:
+ *  -Bean factory.
+ *  -Resource loader.
+ *  -Event publishing to registered listener.
+ *  -Internationalisation.
+ *
+ * The life cycle of the application context:
+ *  1-Spring IOC is instantiated.
+ *  2-Configuration bean metadata is loaded to the container.
+ *  3-Bean definition are created from the loaded metadata.
+ *  4-Bean definition are adjusted by the {@link BeanFactoryPostProcessor} (example {@link PropertySourcesPlaceholderConfigurer}).
+ *  5-Bean are created, property set.
+ *  6-{@link BeanPostProcessor#postProcessBeforeInitialization(Object, String)} are invoked.
+ *  7-methods of Aware interface are called.
+ *  8-{@link javax.annotation.PostConstruct},{@link InitializingBean#afterPropertiesSet()}, {@link Bean#initMethod()} are called.
+ *  9-{@link BeanPostProcessor#postProcessAfterInitialization(Object, String)} are invoked.
+ *  10-Applicatiuon is running.
+ *  11-Applicatiuon stop.
+ *  12-Spring Container is closed.
+ *  13-{@link javax.annotation.PreDestroy},{@link DisposableBean#destroy()}, {@link Bean#destroyMethod()} are called.
+ *
+ */
+public class SpringContainerLifeCycle {
+
+
+}

lib/javax.servlet.jar

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+package ioc.question_004;
+
+import ioc.commun.Person;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+
+/**
+ * This class create a standalone application context using the annotation config way.
+ * @todo We can use other ways like:
+ *      {@link ClassPathXmlApplicationContext}
+ *
+ */
+
+public class AppContextCreation {
+
+
+    public static void main( String[] args ) {
+        ApplicationContext apContext = new AnnotationConfigApplicationContext(MyConfiguration.class);
+        final Object pesrson = apContext.getBean("person");
+        System.out.println(pesrson);
+
+
+    }
+}

lib/javax.servlet.jsp.jar

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+package ioc.question_004;
+
+
+import ioc.commun.Person;
+import ioc.commun.Profession;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+public class MyConfiguration {
+
+    @Bean
+    public Profession profession(){
+        return Profession.builder()
+                         .name("professeur")
+                         .description("professeur a l'universite")
+                         .build();
+    }
+
+    @Bean
+    public Person person(){
+        return Person.builder()
+                     .name("wijsen")
+                     .age(52)
+                     .profession(profession())
+                     .build();
+    }
+
+}

lib/javax.servlet.jsp.jstl.jar

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+package ioc.question_005;
+import ioc.question_003.*;
+
+
+/**
+ * Can you describe the lifecycle of a Spring Bean in an ApplicationContext?
+ *
+ * 1-Bean instance is created.
+ * 2-Bean Property are set.
+ * 3-please refer to the question_003 {@link SpringContainerLifeCycle} for the steps that follows.
+ */
+public class BeanLifeCycle {
+}

lib/javax.transaction.jar

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+package ioc.question_006;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.web.WebAppConfiguration;
+
+
+/**
+ * How are you going to create an ApplicationContext in an integration test?
+ *
+ *
+ * StandAlone Application: Application Context in an integration test is loaded by {@link ContextConfiguration} annotation
+ * WebApplication : {@link ContextConfiguration } annotation along with {@link WebAppConfiguration} .
+ */
+public class MyApplicationContext {
+}

pom.xml

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+package ioc.question_007;
+
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+import org.springframework.web.context.ContextLoaderListener;
+import javax.servlet.*;
+
+/**
+ * What is the preferred way to close an application context?
+ * StandAlone application: registering a shutdownhook using  {@link ConfigurableApplicationContext}.
+ * WebApplication: automaticaly by the {@link ContextLoaderListener#contextDestroyed(javax.servlet.ServletContextEvent)}.
+ *
+ * Spring Boot closes stand-alone and web applications in the same way, but manual registering of the shutdown hook isn't
+ * required for stand-alone applications
+ */
+
+public class AppContextCreation {
+
+ public static void main( String[] args ) {
+        ApplicationContext apContext = new AnnotationConfigApplicationContext(MyConfiguration.class);
+        ((ConfigurableApplicationContext)apContext).registerShutdownHook();
+        final Object pesrson = apContext.getBean("person");
+        System.out.println(pesrson);
+
+
+
+    }
+}

src/main/java/ioc/commun/Person.java

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+package ioc.question_007;
+
+
+import ioc.commun.Person;
+import ioc.commun.Profession;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+public class MyConfiguration {
+
+    @Bean
+    public Profession profession(){
+        return Profession.builder()
+                         .name("professeur")
+                         .description("professeur a l'universite")
+                         .build();
+    }
+
+    @Bean
+    public Person person(){
+        return Person.builder()
+                     .name("wijsen")
+                     .age(52)
+                     .profession(profession())
+                     .build();
+    }
+
+}