Spring 依赖注入控制反转实现，及编码解析（自制容器）
定义：
在运行期，由外部容器动态的将依赖对象动态地注入到组件中。
两种方式：
手工装配
-set方式
-构造器
-注解方式
自动装配（不推荐）
1利用构造器
2set方法注入
dao：
package dao;
public interface PersonDao {
public void add();
}
daoimpl：
package dao.impl;
import dao.PersonDao;
public class PersonDaoBean implements PersonDao{
@Override
public void add() {
System.out.println("I am person dao");
}
}
service：
package service;
public interface PersonService {
public void save();
}
serviceimpl（set实现依赖注入）：
package service.impl;
import dao.PersonDao;
import service.PersonService;
public class PersonServiceBean implements PersonService {
private PersonDao personDao;
public PersonDao getPersonDao() {
return personDao;
}
public void setPersonDao(PersonDao personDao) {
this.personDao = personDao;
}
public void save(){
personDao.add();
}
}
applicationContext.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"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.1.xsd">
<bean id = "personDao" class = "dao.impl.PersonDaoBean"></bean>
<!-- 默认构造方法 -->
<bean id = "personService" class = "service.impl.PersonServiceBean">
<property name = "personDao" ref = "personDao">
</property>
</bean>
</beans>
这样一来，dao方法会直接被spring注入到service里。运行service的save方法可以调用dao的save方法。
除了注入bean还可以注入基本属性类型，以及各种集合类。
编码剖析：
bean定义类：
package 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; } }
property定义类：
package 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; } }
自制spring容器
package test; import java.beans.Introspector; import java.beans.PropertyDescriptor; 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; public class MyClassPathXMLApplicationContext { private List<BeanDefinition> beanDefines = new ArrayList<BeanDefinition>(); private Map<String, Object> sigletons = new HashMap<String, Object>(); public MyClassPathXMLApplicationContext(String filename){ this.readXML(filename); this.instanceBeans(); this.injectObject(); } /** * 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) { } } } } /** * 完成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");//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);//获取文档下所有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); } }
