Spring第三弹—–编码剖析Spring管理Bean的原理

先附一下编写的Spring容器的执行结果：

代码如下：

模拟的Spring容器类：

 

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package zmcSpring;   import java.net.URL; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map;   import org.dom4j.Document; import org.dom4j.Element; import org.dom4j.XPath; import org.dom4j.io.SAXReader; /* * 简单模拟Spring容器 */ public class ZmcClassPathXMLApplicationContext {      private List<BeanDefinition> beanDefines = new ArrayList<BeanDefinition>(); private Map<String,Object> sigletons = new HashMap<String,Object>();   public ZmcClassPathXMLApplicationContext(String fileName){ this.readXML(fileName); this.instanceBeans(); }   /* * 完成bean的实例化 */ private void instanceBeans(){ for(BeanDefinition beanDefinition : beanDefines){ try { sigletons.put(beanDefinition.getId(), Class.forName(beanDefinition.getClassName()).newInstance()); } catch (InstantiationException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IllegalAccessException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }   /* * 读取XMl配置文件 * @param filename */ public void readXML(String fileName){ SAXReader saxReader = new SAXReader(); Document document = null; try{ URL xmlpath = this.getClass().getClassLoader().getResource(fileName); document = saxReader.read(xmlpath); Map<String,String> nsMap = new HashMap<String,String>(); nsMap.put("ns", "http://www.springframework.org/schema/beans");//加入命名空间 XPath xsub = document.createXPath("//ns:beans/ns:bean");//创建beans/bean查询路径     xsub.setNamespaceURIs(nsMap);//设置命名空间     List<Element> beans = xsub.selectNodes(document);     for(Element element : beans){        String id = element.attributeValue("id");        String clazz = element.attributeValue("class");        BeanDefinition beanDefinition = new BeanDefinition(id,clazz);        beanDefines.add(beanDefinition);     } } catch (Exception e){ e.printStackTrace(); } }   /* * 获取bean实例 */ public Object getBean(String beanName){ return this.sigletons.get(beanName); } }

存取bean信息的类：

 

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package zmcSpring;   public class BeanDefinition { private String id; private String className;   public BeanDefinition() { super(); } public BeanDefinition(String id, String className) { super(); this.id = id; this.className = className; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getClassName() { return className; } public void setClassName(String className) { this.className = className; }   }

测试类：

 

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package Test;   import org.junit.BeforeClass; import org.junit.Test; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext;   import zmcSpring.ZmcClassPathXMLApplicationContext; import zmcjk.PersonService;   public class SpringD {   @BeforeClass public static void setUpBeforeClass() throws Exception { }   @Test public void T() { ZmcClassPathXMLApplicationContext zmc = new ZmcClassPathXMLApplicationContext("beans.xml"); PersonService ps = (PersonService) zmc.getBean("personService"); ps.save(); /*ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); PersonService ps = (PersonService) ctx.getBean("personService"); ps.save();*/ }   }

PS:配置文件及bean类都在上篇博客。