spring依赖注入原理剖析

 1 package junit.test;
 2 
 3 public class PropertyDefinition {
 4     private String name;
 5     private String ref;
 6     
 7     public PropertyDefinition(String name, String ref) {
 8         this.name = name;
 9         this.ref = ref;
10     }
11     
12     public String getName() {
13         return name;
14     }
15     public void setName(String name) {
16         this.name = name;
17     }
18     public String getRef() {
19         return ref;
20     }
21     public void setRef(String ref) {
22         this.ref = ref;
23     }
24     
25 }

 1 package junit.test;
 2 
 3 import java.util.ArrayList;
 4 import java.util.List;
 5 
 6 public class BeanDefinition {
 7     private String id;
 8     private String className;
 9     private List<PropertyDefinition> propertys = new ArrayList<PropertyDefinition>();
10     
11     public BeanDefinition(String id, String className) {
12         this.id = id;
13         this.className = className;
14     }
15     public String getId() {
16         return id;
17     }
18     public void setId(String id) {
19         this.id = id;
20     }
21     public String getClassName() {
22         return className;
23     }
24     public void setClassName(String className) {
25         this.className = className;
26     }
27     public List<PropertyDefinition> getPropertys() {
28         return propertys;
29     }
30     public void setPropertys(List<PropertyDefinition> propertys) {
31         this.propertys = propertys;
32     }
33     
34 }

package junit.test;

import java.beans.IntrospectionException;
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.HashSet;
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;

/**
 * 传智传客版容器
 *
 */
public class a {
    private List<BeanDefinition> beanDefines = new ArrayList<BeanDefinition>();
    private Map<String, Object> sigletons = new HashMap<String, Object>();
    
    public ItcastClassPathXMLApplicationContext(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 = sigletons.get(propertyDefinition.getRef());
                                    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");
                    PropertyDefinition propertyDefinition = new PropertyDefinition(propertyName, propertyref);
                    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);
    }
}