简单的spring IOC 实现

springbean的加载 步骤为,1.配置xml文件,2.加载xml文件,并解析,3.将得到的class类保存.下面就是代码

package myc_demo.ioctest;


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;

/**
 * @program: Demo
 *
 * @description: 人间有味是清欢
 * 简单的spring ioc实现
 * @author: liuSha.pufengjun
 * @create: 2018-07-26 10:05
 **/
public class SimpleIOC {

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

    public SimpleIOC(String location) throws Exception{
        loadBeans(location);
    }

    public Object getBean(String name){
        Object bean = beanMap.get(name);
        if(null == bean){
            throw new IllegalArgumentException("there is no bean with name " +name);
        }
        return bean;
    }

    /**
     * 加载bean
     * @param location
     * @throws Exception
     */
    private void loadBeans(String location) throws Exception {
        //加载并解析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 nodes = root.getChildNodes();

        for (int i = 0 ;i < nodes.getLength(); i++){
            Node node = nodes.item(i);
            if(node instanceof Element){
                Element ele = (Element) node;
                String id = ele.getAttribute("id");
                String className = ele.getAttribute("class");

                //加载class
                Class beanClass = null;
                try {
                    beanClass = Class.forName(className);
                } catch (ClassNotFoundException e) {
                    e.printStackTrace();
                    return;
                }

                   // 创建 类
                Object bean = beanClass.newInstance();

                //遍历property标签
                NodeList propertyNodes = ele.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 相关字段访问权限设为可访问
                        Field declaredField = bean.getClass().getDeclaredField(name);
                        declaredField.setAccessible(true);

                        if (value != null && value.length() > 0) {
                            // 设置属性值
                            declaredField.set(bean, value);
                        } else {
                            String ref = propertyElement.getAttribute("ref");
                            if (null == ref && ref.length() == 0){
                                throw new IllegalArgumentException("ref config error!!");
                            }
                            // 将引用填充到相关字段中
                            declaredField.set(bean, getBean(ref));
                        }
                        //将bean注册到map中
                        registerBean(id,bean);
                    }
                }
            }

        }

    }
    //将bean添加到map中
    private  void registerBean(String id ,Object bean){
        beanMap.put(id,bean);
    }



}

实体类:

package myc_demo.ioctest;

/**
 * @program: Demo
 * @description: 人间有味是清欢
 * @author: liuSha.pufengjun
 * @create: 2018-07-26 14:04
 **/
public class Rain {
    //数量
    private String amount;
    //雨势
    private String trend ;

    public String getAmount() {
        return amount;
    }

    public void setAmount(String amount) {
        this.amount = amount;
    }

    public String getTrend() {
        return trend;
    }

    public void setTrend(String trend) {
        this.trend = trend;
    }

    @Override
    public String toString() {
        return "Wheel : {amount ["+amount+"] trend [" + trend + "] }";
    }
}

package myc_demo.ioctest;

/**
 * @program: Demo
 * @description: 人间有味是清欢
 * @author: liuSha.pufengjun
 * @create: 2018-07-26 14:03
 **/
public class Warter {
    //类型
    private String type;
    //地址
    private String address;
    //成分
    private String constituent;
    //构成
    private String take;
    private Rain rain;

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getConstituent() {
        return constituent;
    }

    public void setConstituent(String constituent) {
        this.constituent = constituent;
    }

    public String getTake() {
        return take;
    }

    public void setTake(String take) {
        this.take = take;
    }

    public Rain getRain() {
        return rain;
    }

    public void setRain(Rain rain) {
        this.rain = rain;
    }

    @Override
    public String toString() {
        return "car { type ["+ type+"] address [ " + address+ " ] constituent [" + constituent+ "] take [ " +take
                +"] wheel [" + rain.toString() + "] }";
    }
}

测试类:  这里/ioc.xml表示更目录下  不加 / 表示当前目录下

    @Test
    public void getBean() throws Exception {
        String location = SimpleIOC.class.getClassLoader().getResource("ioc.xml").getFile();
        SimpleIOC simpleIOC = new SimpleIOC(location);
        Warter warter = (Warter) simpleIOC.getBean("warter");
        System.out.println(warter);
        Rain rain = (Rain) simpleIOC.getBean("rain");
        System.out.println(rain);
    }

xml文件: ioc.xml 

<beans>
    <bean id="rain" class="myc_demo.ioctest.Rain">
        <property name="amount" value="小雨" />
        <property name="trend" value="越下越大" />
    </bean>


    <bean id="warter" class="myc_demo.ioctest.Warter">
        <property name="type" value="淡水"/>
        <property name="address" value="杭州"/>
        <property name="constituent" value="H2O2"/>
        <property name="take" value="H O N "/>
        <property name="rain" ref="rain"/>
    </bean>
</beans>

运行测试类结果: