Spring2.5学习3.2_编码剖析@Resource注解的实现原理

首先看一下J2EE提供的@Resource注解：该注解默认安照名称进行装配，名称能够通过name属性进行指定，假设没有指定name属性，当注解写在字段上时，默认取字段名进行依照名称查找，假设注解写在setter方法上默认取属性名进行装配。

当找不到与名称匹配的bean时才依照类型进行装配。可是须要注意的是，假设name属性一旦指定。就仅仅会依照名称进行装配。

这里我们模拟@Resource注解，便于理解注解的实现原理：

1.首先在前面模拟的容器中加入注入的方法annotationInject()；

XjjClassPathXMLApplicationContext.java

package junit.test;

import java.beans.Introspector;

import java.beans.PropertyDescriptor;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.net.URL;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import org.apache.commons.beanutils.ConvertUtils;

import org.dom4j.Document;

import org.dom4j.Element;

import org.dom4j.XPath;

import org.dom4j.io.SAXReader;

	/**

	 * Xjj版容器

	 *

	 */

	public class XjjClassPathXMLApplicationContext {

		private List<BeanDefinition> beanDefines = new ArrayList<BeanDefinition>();

		private Map<String, Object> sigletons = new HashMap<String, Object>();

		public XjjClassPathXMLApplicationContext(String filename){

			this.readXML(filename);

			this.instanceBeans();

			this.annotationInject();

			this.injectObject();

		}

	/**

	 * 通过注解实现注入依赖对象

	 */

	private void annotationInject() {

		for(String beanName : sigletons.keySet()){

			Object bean = sigletons.get(beanName);

			if(bean!=null){

				try {

					PropertyDescriptor[] ps = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();

					for(PropertyDescriptor properdesc : ps){

						Method setter = properdesc.getWriteMethod();//获取属性的setter方法

						if(setter!=null && setter.isAnnotationPresent(XjjResource.class)){

							XjjResource resource = setter.getAnnotation(XjjResource.class);

							Object value = null;

							if(resource.name()!=null && !"".equals(resource.name())){

								value = sigletons.get(resource.name());

							}else{

								value = sigletons.get(properdesc.getName());

								if(value==null){

									for(String key : sigletons.keySet()){

										if(properdesc.getPropertyType().isAssignableFrom(sigletons.get(key).getClass())){

											value = sigletons.get(key);

											break;

										}

									}

								}

							}

							setter.setAccessible(true);

							setter.invoke(bean, value);//把引用对象注入到属性

						}

					}

					Field[] fields = bean.getClass().getDeclaredFields();

					for(Field field : fields){

						if(field.isAnnotationPresent(XjjResource.class)){

							XjjResource resource = field.getAnnotation(XjjResource.class);

							Object value = null;

							if(resource.name()!=null && !"".equals(resource.name())){

								value = sigletons.get(resource.name());

							}else{

								value = sigletons.get(field.getName());

								if(value==null){

									for(String key : sigletons.keySet()){

										if(field.getType().isAssignableFrom(sigletons.get(key).getClass())){

											value = sigletons.get(key);

											break;

										}

									}

								}

							}

							field.setAccessible(true);//同意訪问private字段

							field.set(bean, value);

						}

					}

				} catch (Exception e) {

					e.printStackTrace();

				}

			}

		}

	}

	/**

	 * 为bean对象的属性注入值

	 */

	private void injectObject() {

		for(BeanDefinition beanDefinition : beanDefines){

			Object bean = sigletons.get(beanDefinition.getId());

			if(bean!=null){

				try {

					PropertyDescriptor[] ps = Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();

					for(PropertyDefinition propertyDefinition : beanDefinition.getPropertys()){

						for(PropertyDescriptor properdesc : ps){

							if(propertyDefinition.getName().equals(properdesc.getName())){

								Method setter = properdesc.getWriteMethod();//获取属性的setter方法 ,private

								if(setter!=null){

									Object value = null;

									if(propertyDefinition.getRef()!=null && !"".equals(propertyDefinition.getRef().trim())){

										value = sigletons.get(propertyDefinition.getRef());

									}else{

										value = ConvertUtils.convert(propertyDefinition.getValue(), properdesc.getPropertyType());

									}

									setter.setAccessible(true);

									setter.invoke(bean, value);//把引用对象注入到属性

								}

								break;

							}

						}

					}

				} catch (Exception e) {

				}

			}

		}

	}

	/**

	 * 完毕bean的实例化

	 */

	private void instanceBeans() {

		for(BeanDefinition beanDefinition : beanDefines){

			try {

				if(beanDefinition.getClassName()!=null && !"".equals(beanDefinition.getClassName().trim()))

					sigletons.put(beanDefinition.getId(), Class.forName(beanDefinition.getClassName()).newInstance());

			} catch (Exception e) {

				e.printStackTrace();

			}

		}

	}

	/**

	 * 读取xml配置文件

	 * @param filename

	 */

	private 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");//增加命名空间

	         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);//获取文档下全部bean节点

	         for(Element element: beans){

	            String id = element.attributeValue("id");//获取id属性值

	            String clazz = element.attributeValue("class"); //获取class属性值

	            BeanDefinition beanDefine = new BeanDefinition(id, clazz);

	            XPath propertysub =  element.createXPath("ns:property");

	            propertysub.setNamespaceURIs(nsMap);//设置命名空间

	            List<Element> propertys = propertysub.selectNodes(element);

	            for(Element property : propertys){

	            	String propertyName = property.attributeValue("name");

	            	String propertyref = property.attributeValue("ref");

	            	String propertyValue = property.attributeValue("value");

	            	PropertyDefinition propertyDefinition = new PropertyDefinition(propertyName, propertyref, propertyValue);

	            	beanDefine.getPropertys().add(propertyDefinition);

	            }

	            beanDefines.add(beanDefine);

	         }

	        }catch(Exception e){

	            e.printStackTrace();

	        }

	}

	/**

	 * 获取bean实例

	 * @param beanName

	 * @return

	 */

	public Object getBean(String beanName){

		return this.sigletons.get(beanName);

	}

}

实现注解用的类型：@XjjResource

XjjResource.java

package junit.test;

import java.lang.annotation.ElementType;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)

@Target({ElementType.FIELD, ElementType.METHOD})

public @interface XjjResource {

	public String name() default "";

}

BeanDefinition.java

package junit.test;

import java.util.ArrayList;

import java.util.List;

public class BeanDefinition {

	private String id;

	private String className;

	private List<PropertyDefinition> propertys = new ArrayList<PropertyDefinition>();

	public BeanDefinition(String id, String className) {

		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;

	}

	public List<PropertyDefinition> getPropertys() {

		return propertys;

	}

	public void setPropertys(List<PropertyDefinition> propertys) {

		this.propertys = propertys;

	}

}

PropertyDefinition.java

package junit.test;

public class PropertyDefinition {

	private String name;

	private String ref;

	private String value;

	public String getValue() {

		return value;

	}

	public void setValue(String value) {

		this.value = value;

	}

	public PropertyDefinition(String name, String ref, String value) {

		this.name = name;

		this.ref = ref;

		this.value = value;

	}

	public String getName() {

		return name;

	}

	public void setName(String name) {

		this.name = name;

	}

	public String getRef() {

		return ref;

	}

	public void setRef(String ref) {

		this.ref = ref;

	}

}

PersonServiceBean.java对PersonDao进行注解方式注入

package xjj.service.impl;

import junit.test.XjjResource;

import xjj.dao.PersonDao;

import xjj.service.PersonService;

public class PersonServiceBean implements PersonService {

	@XjjResource private PersonDao personDao;

	private String name;	

	public void setPersonDao(PersonDao personDao) {

		this.personDao = personDao;

	}

	public PersonServiceBean(){}

	public PersonServiceBean(PersonDao personDao, String name) {

		this.personDao = personDao;

		this.name = name;

	}

	public void save(){

		//System.out.println(name);

		personDao.add();

	}

}

beans.xml

<?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/beans

           http://www.springframework.org/schema/beans/spring-beans-2.5.xsd

           http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd">

          <context:annotation-config/>

          <bean id="personDaoxxxx" class="xjj.dao.impl.PersonDaoBean"></bean>

          <bean id="personService" class="xjj.service.impl.PersonServiceBean">

          </bean>

</beans>

SpringTest2.java

package junit.test;

import org.junit.BeforeClass;

import org.junit.Test;

import xjj.service.PersonService;

public class SpringTest2 {

	@BeforeClass

	public static void setUpBeforeClass() throws Exception {

	}

	@Test public void instanceSpring(){

		XjjClassPathXMLApplicationContext ctx = new XjjClassPathXMLApplicationContext("beans.xml");

		PersonService personService = (PersonService)ctx.getBean("personService");

		personService.save();

	}

}

模拟结果：成功注入了PersonDaoBean

巴特西

Spring2.5学习3.2_编码剖析@Resource注解的实现原理

最新文章

热门文章