Spring 4 Hello World Example

Objective

Link: http://websystique.com/spring/spring-4-hello-world-example-annotation-tutorial-full-example/

This tutorial will show a spring 4 Hello World example based on spring annotation configuration, explaining the basic concepts and usage of Spring 4.

As well as providing an XML-based configuration example as a comparison, we will create a MAVEN-based project that uses the spring version of 4.0.6.

Relevant technology and development tools involved

• Spring 4.0.6.RELEASE
• Maven 3
• JDK 1.6
• Eclipse JUNO Service Release 2

Catalog of engineering Structures

The following is the final structure of the project directory:

If you want to learn how to create a maven project, please refer to the following link: Maven tutorial. It contains detailed steps to explain how to create a MAVEN project.

So, next, let's add something to the above directory structure.

Step One: Add Spring dependencies in Maven's Pom.xml

We can add all dependencies to the MAVEN project through Pom.xml, as follows:

<Projectxmlns= "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.websystique.spring</groupId>    <Artifactid>Spring4helloworldexample</Artifactid>    <version>1.0.0</version>    <Packaging>Jar</Packaging>     <name>Spring4helloworldexample</name>     <Properties>        <springframework.version>4.0.6.RELEASE</springframework.version>    </Properties>     <Dependencies>        <Dependency>            <groupId>Org.springframework</groupId>            <Artifactid>Spring-core</Artifactid>            <version>${springframework.version}</version>        </Dependency>        <Dependency>            <groupId>Org.springframework</groupId>            <Artifactid>Spring-context</Artifactid>            <version>${springframework.version}</version>        </Dependency>    </Dependencies>    <Build>        <pluginmanagement>            <Plugins>                <plugin>                    <groupId>Org.apache.maven.plugins</groupId>                    <Artifactid>Maven-compiler-plugin</Artifactid>                    <version>3.2</version>                    <Configuration>                        <Source>1.6</Source>                        <Target>1.6</Target>                    </Configuration>                </plugin>            </Plugins>        </pluginmanagement>    </Build> </Project>

For this example, we only need to add spring core and spring context dependencies, where the spring annotations are defined in Spring-context.

Step Two: Create the Pojo class

Spring advocates low-coupling and interface-based programming.

So, first we create a POJO interface and its implementation class, and this pojo will act as a spring bean.

Package publicinterface  HelloWorld {     void SayHello ( String name);}

Package publicclassimplements  helloworld{     public  void SayHello (String name) {        System.out.println ("Hello" +name);}    }

Step three: Create a spring configuration file

The spring configuration class contains definitions for some of the beans to be used in the project. @Configuration Note Declaration This class is a spring configuration class that can contain a method for @bean annotations that creates a bean to be given to spring container management.

 Packagecom.websystique.spring.configuration;ImportOrg.springframework.context.annotation.Bean;Importorg.springframework.context.annotation.Configuration;Importorg.springframework.context.annotation.Description; @Configuration Public classhelloworldconfig {@Bean (name= "Helloworldbean") @Description ("This is a sample HelloWorld Bean")     PublicHelloWorld HelloWorld () {return NewHelloworldimpl (); } }

@Description is a new annotation introduced by spring 4 to describe the definition of a bean

The above annotation-based configuration has the same effect as the following spring XML configuration (we name this file helloworld-config.xml)

<Beansxmlns= "Http://www.springframework.org/schema/beans"Xmlns:xsi= "Http://www.w3.org/2001/XMLSchema-instance"xsi:schemalocation= "Http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd">     <BeanID= "Helloworldbean"class= "Com.websystique.spring.domain.HelloWorldImpl">  </Beans>

Step four: Create the Main method to execute the program

 Packagecom.websystique.spring;ImportOrg.springframework.context.annotation.AnnotationConfigApplicationContext;ImportOrg.springframework.context.support.AbstractApplicationContext;ImportCom.websystique.spring.configuration.HelloWorldConfig;ImportCom.websystique.spring.domain.HelloWorld; Public classAppmain { Public Static voidMain (String args[]) {Abstractapplicationcontext context=NewAnnotationconfigapplicationcontext (Helloworldconfig.class); HelloWorld Bean= (HelloWorld) context.getbean ("Helloworldbean"); Bean.sayhello ("Spring 4");    Context.close (); } }

AnnotationConfigApplicationContext以我们的配置类（用@Configuration标注）作为入参创建spring应用上下文环境，在程序运行时注册所有在配置类中定义的bean。一旦我们创建了AnnotationConfigApplicationContext对象，就可以通过其getBean方法从spring容器中得到指定的bean对象，并且可以调用该The method of the Bean object performs some operations.

HelloWorld bean = (HelloWorld) context.getbean ("Helloworldbean"); Bean.sayhello ("Spring 4");

Running the above program, you will get the following results:

Hello Spring 4

If you use an XML-based configuration, the main method above should write:

 Packagecom.websystique.spring;ImportOrg.springframework.context.support.AbstractApplicationContext;ImportOrg.springframework.context.support.ClassPathXmlApplicationContext;ImportCom.websystique.spring.domain.HelloWorld; Public classAppmain { Public Static voidMain (String args[]) {Abstractapplicationcontext context=NewClasspathxmlapplicationcontext ("Helloworld-config.xml"); HelloWorld Bean= (HelloWorld) context.getbean ("Helloworldbean"); Bean.sayhello ("Spring 4");     Context.close (); } }

Where the Helloworld-config.xml file was created in step three, under engineering classpath (e.g./src/main/resources).

Conclusion

In the next article, we'll see an example of a bean's auto-detection, which is based on annotations that automatically finds all the beans in the application environment without having to declare them in a configuration class.

This example source code

http://websystique.com/?smd_process_download=1&download_id=778

Spring 4 Hello World Example