There are three ways to provide the configuration metadata to Spring container. Below are the more details about them.
1. Xml based configuration file
<?xml version=”1.0″ encoding=”UTF-8″?>
<beans xmlns=”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-3.0.xsd”>
<!– A simple bean definition –>
<bean id=”…” class=”…”>
<!– collaborators and configuration for this bean go here –>
</bean>
<!– A bean definition with lazy init set on –>
<bean id=”…” class=”…” lazy-init=”true”>
<!– collaborators and configuration for this bean go here –>
</bean>
<!– A bean definition with initialization method –>
<bean id=”…” class=”…” init-method=”…”>
<!– collaborators and configuration for this bean go here –>
</bean>
<!– A bean definition with destruction method –>
<bean id=”…” class=”…” destroy-method=”…”>
<!– collaborators and configuration for this bean go here –>
</bean>
<!– more bean definitions go here –>
</beans>
2. Annotation based configuration
<?xml version=”1.0″ encoding=”UTF-8″?>
<beans xmlns=”http://www.springframework.org/schema/beans”
xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance”
xmlns:context=”http://www.springframework.org/schema/context”
xsi:schemaLocation=”http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd”>
<context:annotation-config/>
<!– bean definitions go here –>
<bean id=”empAddress” class=”in.malliktalksjava.spring.samples.EmployeeAddress” />
</beans>
Once <context:annotation-config/> is configured, you can start annotating your code to indicate that Spring should automatically wire values into properties, methods, and constructors. Once you add the annotation config, you can use @Autowired annotation as below on setter methods to get rid of the <property> element in XML configuration file. When Spring finds an @Autowired annotation used with setter methods, it tries to perform byType autowiring on the method.
Employee.java:
package in.malliktalksjava.spring.samples;
public class Employee{
@Autowired
public EmployeeAddress empAddress;
public void test(){
System.out.println(empAddress.getStreet());
System.out.println(empAddress.getPostalCode());
}
}
EmployeeAddress.java:
package in.malliktalksjava.spring.samples;
public class EmployeeAddress{
private String street;
private String postalCode;
public void setStreet(String street){
this.street = street;
}
public String getStreet(){
return street;
}
public void setPostalCode(String postalCode)
this.postalCode = postalCode;
}
public String getPostalCode(){
return postalCode;
}
}
3. Java based configuration
Java based configuration option enables you to write most of your Spring configuration without XML but with the help of few Java-based annotations. Annotating a class with the @Configuration indicates that the class can be used by the Spring IoC container as a source of bean definitions. The @Bean annotation tells Spring that a method annotated with @Bean will return an object that should be registered as a bean in the Spring application context.
HelloWorldConfig.java
package in.malliktalksjava.spring.samples;
import org.springframework.context.annotation.*;
@Configuration
public class HelloWorldConfig {
@Bean
public HelloWorld helloWorld(){
return new HelloWorld();
}
}
HelloWorld.java
package in.malliktalksjava.spring.samples;
public class HelloWorld {
private String message;
public void setMessage(String message){
this.message = message;
}
public void getMessage(){
System.out.println(” Message is : ” + message);
}
}
MainApp.java:
package in.malliktalksjava.spring.samples;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.*;
public class MainApp {
public static void main(String[] args) {
ApplicationContext ctx =
new AnnotationConfigApplicationContext(HelloWorldConfig.class);
HelloWorld helloWorld = ctx.getBean(HelloWorld.class);
helloWorld.setMessage(“Hello World!”);
helloWorld.getMessage();
}
}
Complete application has been created without writing any configuration file.
</> MV Techbytes 