spring实现bean对象创建代码详解

package com.jvk.ken.spring;
public class Demo {
	private String name;
	public Demo() {
		name="I'm Demo.";
	}
	public void printName() {
		System.out.println(name);
	}
	public void setName(String name) {
		this.name = name;
	}
}

<?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/context  
   http://www.springframework.org/schema/context/spring-context-3.1.xsd 
   http://www.springframework.org/schema/beans 
   http://www.springframework.org/schema/beans/spring-beans-3.1.xsd"> 
  <bean id="demo" class="com.jvk.ken.spring.DemoFactory" /> 
</beans> 

package com.jvk.ken.spring;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.ClassPathResource;
public class Test {
	public static void main(String[] args) throws Exception {
		testSpring();
	}
	private static void testSpring() throws Exception {
		BeanFactory bf = new XmlBeanFactory(new ClassPathResource("applicationContext.xml"));
		Demo bean = (Demo) bf.getBean("demo");
		System.out.println(bean.getClass());
		bean.printName();
	}
}

2012-3-28 22:18:07 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions 
信息: Loading XML bean definitions from class path resource [applicationContext.xml] 
class com.jvk.ken.spring.Demo 
I'm Demo. 

package com.jvk.ken.spring;
import java.util.HashMap;
import java.util.Map;
public class MyBeanFactory {
	// 保存bean的定义 
	Map<String, Class> beans = new HashMap<String, Class>();
	public Object getBean(String id) throws InstantiationException, 
	      IllegalAccessException {
		return beans.get(id).newInstance();
	}
	private String xmlFile;
	public MyBeanFactory(String xmlFile) throws ClassNotFoundException {
		super();
		this.xmlFile = xmlFile;
		init();
	}
	private void init() throws ClassNotFoundException {
		// 初始化与解析XML，这里略去实际解析XML的情况，使用硬编码模仿 
		System.out.println("配置文件："+xmlFile);
		String className = "com.jvk.ken.spring.Demo";
		Class<?> loadClass = this.getClass().getClassLoader().loadClass( 
		        className);
		beans.put("demo", loadClass);
	}
}

package com.jvk.ken.spring;
public class Test {
	public static void main(String[] args) throws Exception {
		testNotSpring();
	}
	private static void testNotSpring() throws Exception {
		MyBeanFactory bf = new MyBeanFactory("applicationContext.xml");
		Demo bean = (Demo) bf.getBean("demo");
		System.out.println(bean.getClass());
		bean.printName();
	}
}

配置文件：applicationContext.xml 
class com.jvk.ken.spring.Demo 
I'm Demo. 

private Demo() { 
  name="I'm Demo."; 
} 

Exception in thread "main" java.lang.IllegalAccessException: Class com.jvk.ken.spring.MyBeanFactory can not access a member of class com.jvk.ken.spring.Demo with modifiers "private" 
  at sun.reflect.Reflection.ensureMemberAccess(Reflection.java:65) 
  at java.lang.Class.newInstance0(Class.java:349) 
  at java.lang.Class.newInstance(Class.java:308) 
  at com.jvk.ken.spring.MyBeanFactory.getBean(MyBeanFactory.java:12) 
  at com.jvk.ken.spring.Test.testNotSpring(Test.java:25) 
  at com.jvk.ken.spring.Test.main(Test.java:9) 

public Object getBean(String id) throws Exception { 
    Class class1 = beans.get(id); 
    Constructor declaredConstructor = class1.getDeclaredConstructor(); 
    declaredConstructor.setAccessible(true); 
    return declaredConstructor.newInstance(); 
  } 

package com.jvk.ken.spring;
import org.springframework.beans.factory.FactoryBean;
public class DemoFactory implements FactoryBean {
	@Override 
	  public Object getObject() throws Exception {
		return new Demo();
	}
	@Override 
	  public Class getObjectType() {
		return Demo.class;
	}
	@Override 
	  public Boolean isSingleton() {
		return false;
	}
}

<bean id="demo" class="com.jvk.ken.spring.DemoFactory" />