反射在Spring框架中的应用-IOC容器实现

IOC

• 控制翻转，它是一种设计思想，而并非实际的技术，最核心的思想就是预先将设计的对象实例创建的控制权交给程序（IOC容器）
• IOC容器的本质是一个K-V结构的map

配置文件

<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.xsd">

    
    <bean id="a" class="com.liulin.demo6.A"/>

    
    <bean id="b" class="com.liulin.demo6.A" factory-method="createBObj"/>

    
    <bean id="c" factory-bean="a" factory-method="createCObj"/>


beans>

代码

public class A {

    public A() {
        System.out.println("A 无参构造器被调用了.");
    }

    public static B createBObj() {
        System.out.println("A 的静态方法 createBObj 被调用了.");
        return new B();
    }

      public C createCObj() {
        System.out.println("A 的实例方法 createCObj 被调用了.");
        return new C();
    }

}

BeanConfig类

public class BeanConfig {

    private String id;
    private String clazz;
    private String factoryMethod;
    private String factoryBean;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getClazz() {
        return clazz;
    }

    public void setClazz(String clazz) {
        this.clazz = clazz;
    }

    public String getFactoryMethod() {
        return factoryMethod;
    }

    public void setFactoryMethod(String factoryMethod) {
        this.factoryMethod = factoryMethod;
    }

    public String getFactoryBean() {
        return factoryBean;
    }

    public void setFactoryBean(String factoryBean) {
        this.factoryBean = factoryBean;
    }
}

Init类

public class Init {

    public static void main(String[] args) throws Exception {

        //  模拟解析xml   拿到 beanConfigs
        List<BeanConfig> beanConfigs = parseXmltoBeanConfig();
        //循环
        for (BeanConfig tmpconfig : beanConfigs) {
            if (null != tmpconfig.getClazz()) {
                //拿到clazz
                Class clazz = Class.forName(tmpconfig.getClazz());
                if (null != tmpconfig.getFactoryMethod())
                {
                    //基于Class对象获取method对象
                    Method method = clazz.getDeclaredMethod(tmpconfig.getFactoryMethod());
                    IOCContainer.putBean(tmpconfig.getId(), method.invoke(null));

                } else {    //构造器创建bean实例
                    IOCContainer.putBean(tmpconfig.getId(), clazz.newInstance());
                }
            } else if(null != tmpconfig.getFactoryBean()) {
                //从容器中拿到实体bean
                Object obj = IOCContainer.getBean( tmpconfig.getFactoryBean());
                Method method = obj.getClass().getDeclaredMethod(tmpconfig.getFactoryMethod());
                IOCContainer.putBean(tmpconfig.getId(),  method.invoke(obj));
            }else{
                System.out.println("不知道在搞什么鬼.2个核心的配置都没有!");
            }
        }
    }
    
    /**
     * 模拟一个解析XML过程
     *
     * @return
     */
    private static List<BeanConfig> parseXmltoBeanConfig() {

        List<BeanConfig> beanConfigs = new ArrayList<BeanConfig>();
        BeanConfig beanConfig1 = new BeanConfig();
        beanConfig1.setClazz("com.liulin.reflect.demo6.A");
        beanConfig1.setId("a");
        beanConfigs.add(beanConfig1);

        BeanConfig beanConfig2 = new BeanConfig();
        beanConfig2.setClazz("com.liulin.reflect.demo6.A");
        beanConfig2.setId("b");
        beanConfig2.setFactoryMethod("createBObj");
        beanConfigs.add(beanConfig2);

        BeanConfig beanConfig3 = new BeanConfig();
        beanConfig3.setId("c");
        beanConfig3.setFactoryBean("a");
        beanConfig3.setFactoryMethod("createCObj");
        beanConfigs.add(beanConfig3);

        return beanConfigs;
    }
}

IOCContainer类

public class IOCContainer {

    private static HashMap container = new HashMap();

    public static void putBean(String id,Object object){
        container.put(id,object);
    }

    public static Object getBean(String id){
        return container.get(id);
    }

}