spring框架IOC原理分析代码

模拟ClasspathXmlApplication：

package junit.test;

import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.io.File;
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.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;


public class ItcastClassPathXmlApplicationContext {
    private ArrayList<BeanDefinition> beanDefinitions=new ArrayList<BeanDefinition>();
    private Map<String,Object> sigletons=new HashMap<String,Object>();
    
    public ItcastClassPathXmlApplicationContext(String filename){
        this.readXml(filename);
        this.instanceBeans();
        this.annotationInject();
        this.injectObject();
    }
    /**
     * 注解方式装载对象
     */
    private void annotationInject() {
        for(String beanName :sigletons.keySet()){
            Object bean=sigletons.get(beanName);
            if(bean!=null){
                try{
                    /*
                     * 查找方法上的注解
                     */
                    PropertyDescriptor[] ps=Introspector.getBeanInfo(bean.getClass()).getPropertyDescriptors();
                    for(PropertyDescriptor properdesc:ps){
                        Method setter=properdesc.getWriteMethod();
                        if(setter!=null && setter.isAnnotationPresent(ItcastResource.class)){
                            ItcastResource itcastResource=setter.getAnnotation(ItcastResource.class);
                            Object value=null;
                            if(itcastResource.name()!=null && !"".equals(itcastResource.name())){
                                value=sigletons.get(itcastResource.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);
                        }
                    }
                    
                    /**
                     * 查找字段上的注解
                     */
                    Field[] fields=bean.getClass().getDeclaredFields();
                    for(Field field:fields){
                        if(field.isAnnotationPresent(ItcastResource.class)){
                            ItcastResource resource=field.getAnnotation(ItcastResource.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;
                                        }
                                    }
                                }
                            }
                            String methodName="set"+field.getName().substring(0,1).toUpperCase()+field.getName().substring(1);
                            Method setter=bean.getClass().getMethod(methodName, field.getType());
                            setter.setAccessible(true);
                            setter.invoke(bean, value);
                        }
                    }
                }catch(Exception e){
                    e.printStackTrace();
                }
            }
        }
    }

    /**
     * 为bean对象的属性注入值
     */
    private void injectObject() {
        for(BeanDefinition beanDefinition: beanDefinitions){
            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
                                if(setter!=null){
                                    Object value=null;
                                    if(propertyDefinition.getRef()!=null &&!"".equals(propertyDefinition.getRef())){
                                        value=sigletons.get(propertyDefinition.getRef());
                                    }else{
                                        value=ConvertUtils.convert(propertyDefinition.getValue(), properdesc.getPropertyType());
                                    }
                                    setter.setAccessible(true);
                                    setter.invoke(bean, value);
                                    
                                }
                                break;
                                
                            }
                        }
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
                
            }
        }
    }
    /**
     * 完成bean的实例化
     */
    private void instanceBeans(){
        for(BeanDefinition bd:beanDefinitions){
            try {
                if(bd.getClassName()!=null && !"".equals(bd.getClassName().trim()))
                    sigletons.put(bd.getId(), Class.forName(bd.getClassName()).newInstance());
            } catch (Exception e) {
                e.printStackTrace();
            } 
        }
    }
    /**
     * 解析xml文件
     * @param fileName
     */
    private void readXml(String fileName) {
         File inputXml=new File(fileName);
         URL url=this.getClass().getClassLoader().getResource(fileName);
            SAXReader saxReader=new SAXReader();
            try {
                Document document=saxReader.read(url);
                Element root=document.getRootElement();
               @SuppressWarnings("unchecked")
               List<Element> beans=root.elements("bean");
               
               for(Element bean:beans){
                   String id= bean.attributeValue("id");
                   String className=bean.attributeValue("class");
                   BeanDefinition bd=new BeanDefinition(id,className);
                   @SuppressWarnings("unchecked")
                   List<Element> propertys=bean.elements("property");
                   for(Element property:propertys){
                      String propertyName = property.attributeValue("name");
                      String propertyRef = property.attributeValue("ref");
                      String propertyValue=property.attributeValue("value");
                      PropertyDefinition pd=new PropertyDefinition(propertyName, propertyRef,propertyValue);
                      bd.getPropertys().add(pd);
                   }
                   beanDefinitions.add(bd);
               }
               
            } catch (DocumentException e) {
                e.printStackTrace();
            }
    }
    
    public Object getBean(String beanName){
        return this.sigletons.get(beanName);
    }
}

存放bean信息的类：

package junit.test;

import java.util.ArrayList;
import java.util.List;

/**
 * 存放读取到的bean的信息
 * @author Administrator
 *
 */
public class BeanDefinition {
    private String id;
    private String className;
    private List<PropertyDefinition> propertys=new ArrayList<PropertyDefinition>();
    
    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;
    }

    public void setPropertys(List<PropertyDefinition> propertys) {
        this.propertys = propertys;
    }

    public List<PropertyDefinition> getPropertys() {
        return propertys;
    }

}

存放bean中属性信息的类：

package junit.test;
/**
 * 属性的定义类
 * @author Administrator
 *
 */
public class PropertyDefinition {
    
    private String name;
    private String ref;
    private String value;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public PropertyDefinition(String name, String ref,String value) {
        super();
        this.name = name;
        this.ref = ref;
        this.value=value;
    }
    public PropertyDefinition() {
        super();
    }
    public String getRef() {
        return ref;
    }
    public void setRef(String ref) {
        this.ref = ref;
    }
    public void setValue(String value) {
        this.value = value;
    }
    public String getValue() {
        return value;
    }

}

对应Resource注解：

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 ItcastResource {
    public String name() default "";
}