手动实现IOC

加载简单IOC容器分为四部分
1.加载xml文件，遍历其中标签
2.获取标签中的class，id，加载class属性对应的类，加载标签属性
3，利用反射遍历标签，加载属性值，填充到bean
4将bean注册到bean容器
firstIOC：IOC的实现类
firstIOCTest：IOC的测试类
Hero：测试类使用的bean
Skill：属性
ioc.xml:bean配置文件

package IOC;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import java.io.FileInputStream;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;

public class firstIOC {
    private Map<String,Object> beanMap=new HashMap<>();
    public firstIOC(String location) throws Exception{
        loadBean(location);
    }
    public Object getBean(String name){
        Object bean=beanMap.get(name);
        if(bean==null){
            throw new IllegalArgumentException("there is no bean with name:"+name);
        }
        return bean;
    }

    private void loadBean(String location) throws Exception {
        //加载xml配置文件
        InputStream inputStream=new FileInputStream(location);
        DocumentBuilderFactory factory=DocumentBuilderFactory.newInstance();
        DocumentBuilder documentBuilder=factory.newDocumentBuilder();
        Document document=documentBuilder.parse(inputStream);
        Element root=document.getDocumentElement();
        NodeList nodeList=root.getChildNodes();

        //遍历bean标签
        for (int i = 0; i <nodeList.getLength() ; i++) {
            Node node=nodeList.item(i);
            if(node instanceof Element){
                Element element= (Element) node;
                String id=element.getAttribute("id");
                String className=element.getAttribute("class");

                //加载beanClass
                Class beanClass=null;
                try{
                    beanClass=Class.forName(className);
                }catch (Exception e){
                    e.printStackTrace();
                    return;
                }
                //创建bean
                Object bean=beanClass.newInstance();
                //遍历<propery>标签
                NodeList propertyNodes=element.getElementsByTagName("property");
                for(int j=0;j<propertyNodes.getLength();j++){
                    Node propertyNode=propertyNodes.item(j);
                    if(propertyNode instanceof Element){
                        Element propertyElement= (Element) propertyNode;
                        String name=propertyElement.getAttribute("name");
                        String value=propertyElement.getAttribute("value");

                        //利用反射将bean相关字段设置为可访问
                        Field declareField=bean.getClass().getDeclaredField(name);
                        declareField.setAccessible(true);

                        if(value!=null&&value.length()!=0){
                            //将属性字段填充到相关字段
                            declareField.set(bean,value);
                        }else{
                            String ref=propertyElement.getAttribute("ref");
                            if(ref==null||ref.length()==0){
                                throw  new IllegalArgumentException("ref config error");
                            }
                            declareField.set(bean,getBean(ref));
                        }
                        //将bean注册到bean容器
                        registerBean(id,bean);
                    }
                }
            }
        }
    }

    private void registerBean(String id, Object bean) {
        beanMap.put(id,bean);
    }
}

package IOC;

public class Hero {
    private String name;
    private String old;
    private String height;
    private String location;
    private Skill skill;
}

package IOC;

public class Skill{
    private String cd;
    private String isR;
}

package IOC.ioc;
import IOC.Hero;
import IOC.Skill;
import IOC.firstIOC;
import org.junit.Test;
public class firstIOCTest {
    @Test
    public void getBean() throws Exception{
        String location= firstIOC.class.getClassLoader().getResource("ioc.xml").getFile();
        firstIOC firstIOC=new firstIOC(location);
        Skill skill= (Skill) firstIOC.getBean("skill");
        Hero hero=(Hero) firstIOC.getBean("hero");
        System.out.println(skill);
        System.out.println(hero);
    }

}

<beans>

    <bean id="skill" class="IOC.Skill">
        <property name="cd" value="69s"/>
        <property name="isR" value="is"/>

    </bean>


    <bean id="hero" class="IOC.Hero">
        <property name="name" value="盖伦"/>
        <property name="old" value="12"/>
        <property name="height" value="222"/>
        <property name="location" value="德玛西亚"/>
        <property name="skill" ref="skill "/>

    </bean>

</beans>