Spring通過構造方法依賴注入

1. IOutputGenerator

package com.zaixian.output;

public interface IOutputGenerator
{
	public void generateOutput();
}

package com.zaixian.output.impl;

import com.zaixian.output.IOutputGenerator;

public class JsonOutputGenerator implements IOutputGenerator
{
	public void generateOutput(){
		System.out.println("This is Json Output Generator");
	}
}

2. Helper類

package com.zaixian.output;

import com.zaixian.output.IOutputGenerator;

public class OutputHelper {
	IOutputGenerator outputGenerator;

	public void generateOutput() {
		outputGenerator.generateOutput();
	}

	//DI via constructor
	public OutputHelper(IOutputGenerator outputGenerator){
		this.outputGenerator = outputGenerator;
	}

}

3. Spring配置

請參閱下麵的 Spring bean 配置，Spring 將通過構造函數注入上面的 “JsonOutputGenerator” 到 “OutputHelper” 類，“public OutputHelper(IOutputGenerator outputGenerator)“.

<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.zaixian.output.OutputHelper">
		<constructor-arg>
			<ref bean="JsonOutputGenerator" />
		</constructor-arg>
	</bean>

	<bean id="JsonOutputGenerator" class="com.zaixian.output.impl.JsonOutputGenerator" />

</beans>

4.執行結果

package com.xuhuhu.common;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.zaixian.output.OutputHelper;

public class App {
	public static void main(String[] args) {
		ApplicationContext context = new ClassPathXmlApplicationContext(
				"applicationContext.xml"); OutputHelper output = (OutputHelper)context.getBean("OutputHelper");
    	        output.generateOutput();
	}
}

輸出結果

This is Json Output Generator