Uses Spring to dependency inject a bean via constructor.
1. IOutputGenerator
An interface and implementation class of it.
package com.mkyong.output;
public interface IOutputGenerator{
public void generateOutput();
}
package com.mkyong.output.impl;
import com.mkyong.output.IOutputGenerator;
public class JsonOutputGenerator implements IOutputGenerator{
public void generateOutput(){
System.out.println("This is Json Output Generator");
}
}
2. Helper class
A helper class, later use Spring to DI the IOutputGenerator, via constructor.
package com.mkyong.output;
import com.mkyong.output.IOutputGenerator;
public class OutputHelper {
IOutputGenerator outputGenerator;
public void generateOutput() {
outputGenerator.generateOutput();
}
//DI via constructor
public OutputHelper(IOutputGenerator outputGenerator){
this.outputGenerator = outputGenerator;
}
}
3. Spring configuration
See below Spring bean configuration, Spring will DI above “JsonOutputGenerator” into this “OutputHelper” class, via constructor “public OutputHelper(IOutputGenerator outputGenerator)“.
<?xml version="1.0"?>
<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-2.5.xsd">
<bean id="OutputHelper" class="com.mkyong.output.OutputHelper">
<constructor-arg>
<ref bean="JsonOutputGenerator" />
</constructor-arg>
</bean>
<bean id="JsonOutputGenerator" class="com.mkyong.output.impl.JsonOutputGenerator" />
</beans>
4. Run it
Load everything, and run it.
package com.mkyong.common;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.mkyong.output.OutputHelper;
public class App {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext( "SpringBeans.xml");
OutputHelper output = (OutputHelper)context.getBean("OutputHelper");
output.generateOutput();
}
}
Output
This is Json Output Generator
