JavaConfig simply provides another mechanism to configure the Spring
IoC container, this time in pure Java rather than requiring XML to get the job
done
But, you are still allowed to use
the classic XML way to define beans and configuration, the JavaConfig is
just another alternative solution.
See the different between classic XML
definition and JavaConfig to define a bean in Spring container.
Spring XML file:
Equivalent configuration in JavaConfig:
package com.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.HelloWorld;
import com.HelloWorldImpl;
@Configuration
public class
AppConfig {
@Bean(name="helloBean")
public
HelloWorld helloWorld() {
return
new HelloWorldImpl();
}
}
now
Spring
JavaConfig Sample Java Project-
1. We
need to write an Interface first-
package
com;
public interface EmployeeAction {
void
printHelloWorld(String msg);
}
}
2. Provide
the Implementation –
package com;
public class EmployeeActionImpl implements EmployeeAction {
private EmployeeService employeeService;
public
EmployeeActionImpl(EmployeeService employeeService) {
super();
this.employeeService = employeeService;
}
@Override
public void printHelloWorld(String msg) {
employeeService.printHelloWorld(msg);
}
}
super();
this.employeeService = employeeService;
}
@Override
public void printHelloWorld(String msg) {
employeeService.printHelloWorld(msg);
}
}
3. Interface
for Service
package
com;
public
interface EmployeeService {
void printHelloWorld(String msg);
}
4. Providing Implementation for the
above Service
package
com;
public
class EmployeeServiceImpl implements EmployeeService {
/* (non-Javadoc)
* @see com.EmployeeService#printHelloWorld(java.lang.String)
*/
@Override
public void printHelloWorld(String msg) {
System.out.println("Hello Thanooj, Welcome to " +
msg);
}
}
/**
*
Configuring JavaConfig class
*/
package
com.config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.EmployeeAction;
import com.EmployeeActionImpl;
import com.EmployeeService;
import com.EmployeeServiceImpl;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.EmployeeAction;
import com.EmployeeActionImpl;
import com.EmployeeService;
import com.EmployeeServiceImpl;
/**
* @author thanooj
*
*/
* @author thanooj
*
*/
public
@Configuration class AppConfig {
public @Bean EmployeeAction employeeAction() {
return new EmployeeActionImpl(employeeService());
}
public @Bean EmployeeService employeeService() {
return new EmployeeServiceImpl();
}
}
public @Bean EmployeeAction employeeAction() {
return new EmployeeActionImpl(employeeService());
}
public @Bean EmployeeService employeeService() {
return new EmployeeServiceImpl();
}
}
Now,
working with Client program-
package
com.client;
import
org.springframework.context.ApplicationContext;
import
org.springframework.context.annotation.AnnotationConfigApplicationContext;
import
com.EmployeeAction;
import
com.config.AppConfig;
public
class Client {
public static void main(String[] args) {
/* ApplicationContext context = new
ClassPathXmlApplicationContext("SpringBeans.xml"); */
ApplicationContext context = new
AnnotationConfigApplicationContext(AppConfig.class);
EmployeeAction empObj = (EmployeeAction) context.getBean("employeeAction");
empObj.printHelloWorld("Spring3 Java Config
world.");
}
}
output:
----------------------------------------------------------------------------------
Now
Spring
JavaConfig web based sample
package
com;
import
org.apache.commons.logging.Log;
import
org.apache.commons.logging.LogFactory;
public
class EmployeeActionImpl implements EmployeeAction {
private final Log LOGGER = LogFactory.getLog(getClass());
private EmployeeService employeeService;
public EmployeeActionImpl(EmployeeService employeeService) {
super();
this.employeeService = employeeService;
}
@Override
public String getWelcomeString() {
LOGGER.info("inside EmployeeActionImpl
getWelcomeString()");
return employeeService.getWelcomeString();
}
}
package
com;
import
org.apache.commons.logging.Log;
import
org.apache.commons.logging.LogFactory;
public
class EmployeeServiceImpl implements EmployeeService {
private final Log LOGGER = LogFactory.getLog(getClass());
@Override
public String getWelcomeString() {
LOGGER.info("inside EmployeeServiceImpl
getWelcomeString()");
return "Spring 3 MVC Hello World NEW";
}
}
package
com;
import
org.apache.commons.logging.Log;
import
org.apache.commons.logging.LogFactory;
import
org.springframework.beans.factory.annotation.Autowired;
import
org.springframework.stereotype.Controller;
import
org.springframework.web.bind.annotation.RequestMapping;
import
org.springframework.web.servlet.ModelAndView;
import
com.EmployeeAction;
@Controller
public
class HelloController {
private final Log LOGGER = LogFactory.getLog(getClass());
@Autowired
private EmployeeAction employeeAction;
@RequestMapping("/welcome")
public ModelAndView getWelcomeString() {
LOGGER.info("inside HelloController
getWelcomeString()");
String msg = employeeAction.getWelcomeString();
LOGGER.info("return value of getWelcomeString() :
"+msg);
return new ModelAndView("message",
"msg", msg);
}
}
-----------------------
package
config;
import
org.apache.commons.logging.Log;
import
org.apache.commons.logging.LogFactory;
import
org.springframework.context.annotation.Bean;
import
org.springframework.context.annotation.Configuration;
import
com.EmployeeAction;
import
com.EmployeeActionImpl;
import
com.EmployeeService;
import
com.EmployeeServiceImpl;
public
@Configuration class AppConfig {
private final Log LOGGER = LogFactory.getLog(getClass());
public @Bean EmployeeAction employeeAction() {
LOGGER.info("inside AppConfig EmployeeAction");
return new EmployeeActionImpl(employeeService());
}
public @Bean EmployeeService employeeService() {
LOGGER.info("inside AppConfig EmployeeService");
return new EmployeeServiceImpl();
}
}
------------------
mvc-dispatcher-servlet.xml
web.xml
message.jsp
output:
References:
http://www.mkyong.com/spring3/spring-3-javaconfig-example/
http://blog.springsource.org/2008/03/26/spring-java-configuration-whats-new-in-m3/
