大體思路：

1、選擇BeanDefinition的實現類，並例項化BeanDefinition

2、註冊BeanDefinition

3、獲取Bean，看看是不是正常工作的。

非抽象的實現類主要有三個

1、GenericBeanDefinition，這個也是官方推薦使用的，註釋裡提到可以動態設定parentbeandefinition等。

2、RootBeanDefinition，這個跟@Configuration註解有關。
3、ChildBeanDefinition，這個也可以實現設定parentbeandefinition，不過它是預先定義parent/child關係，官方也不推薦使用了，看註釋可以知道，從spring2.5開始

GenericBeanDefinition已經替代ChildBeanDefinition了。

基於以上思路，我們選擇GenericBeanDefinition

public class GenericBeanDefinition extends AbstractBeanDefinition {

    @Nullable
    private String parentName;


    /**
     * Create a new GenericBeanDefinition, to be configured through its bean
     * properties and configuration methods.
     * 
 
@see #setBeanClass
     * @see #setScope
     * @see #setConstructorArgumentValues
     * @see #setPropertyValues
     */
    public GenericBeanDefinition() {
        super();
    }

    /**
     * Create a new GenericBeanDefinition as deep copy of the given
     * bean definition.
     * @param original the original bean definition to copy from
     
 
*/
    public GenericBeanDefinition(BeanDefinition original) {
        super(original);
    }


    @Override
    public void setParentName(@Nullable String parentName) {
        this.parentName = parentName;
    }

    @Override
    @Nullable
    public String getParentName() {
        return this.parentName;
    }


    @Override
    public AbstractBeanDefinition cloneBeanDefinition() {
        return new GenericBeanDefinition(this);
    }

    @Override
    public boolean equals(@Nullable Object other) {
        if (this == other) {
            return true;
        }
        if (!(other instanceof GenericBeanDefinition)) {
            return false;
        }
        GenericBeanDefinition that = (GenericBeanDefinition) other;
        return (ObjectUtils.nullSafeEquals(this.parentName, that.parentName) && super.equals(other));
    }

    @Override
    public String toString() {
        if (this.parentName != null) {
            return "Generic bean with parent '" + this.parentName + "': " + super.toString();
        }
        return "Generic bean: " + super.toString();
    }

}

框架裡面一般是怎麼使用GenericBeanDefinition的呢？

一般是在BeanDefinitionBuilder裡面，或者是BeanDefinitionReaderUtils，我記得是這個，由於這個筆記本不好用，簡單搜下

然後就是註冊BeanDefinition了

找一個beanFactory，

public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory
        implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {

不只實現了ConfigurableListableBeanFactory，還實現了BeanDefinitionRegistry

public interface BeanDefinitionRegistry extends AliasRegistry {

    /**
     * Register a new bean definition with this registry.
     * Must support RootBeanDefinition and ChildBeanDefinition.
     * @param beanName the name of the bean instance to register
     * @param beanDefinition definition of the bean instance to register
     * @throws BeanDefinitionStoreException if the BeanDefinition is invalid
     * @throws BeanDefinitionOverrideException if there is already a BeanDefinition
     * for the specified bean name and we are not allowed to override it
     * @see GenericBeanDefinition
     * @see RootBeanDefinition
     * @see ChildBeanDefinition
     */
    void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
            throws BeanDefinitionStoreException;

    ..........

}

所以，我們只要呼叫這個beanFactory的註冊方法即可。

生成beanName

BeanNameGenerator介面，有兩個實現類

public interface BeanNameGenerator {

    /**
     * Generate a bean name for the given bean definition.
     * @param definition the bean definition to generate a name for
     * @param registry the bean definition registry that the given definition
     * is supposed to be registered with
     * @return the generated bean name
     */
    String generateBeanName(BeanDefinition definition, BeanDefinitionRegistry registry);

}

AnnatationBeanNameGenerator就是我們平時使用的註解方式@Autowired，的一個這樣的格式，而預設的beanName則是，類名稱+#+0（com.spring.learn.service.impl.TestServiceImpl#0）這樣的。

bean之間的依賴

通過constructor，或者property方式注入

之前不是說過BeanDefinition接口裡面有兩個引數，一個是關於建構函式，一個是關於屬性set方法注入的。

構造器注入程式碼

 GenericBeanDefinition controllerBeanDefinition = (GenericBeanDefinition) BeanDefinitionBuilder.
                genericBeanDefinition(TestControllerWithConstructor.class)
                .addConstructorArgValue("controller name is TestController")
                .addConstructorArgReference(testServiceName)
                .getBeanDefinition();

屬性值注入程式碼

        GenericBeanDefinition propertyControllerBeanDefinition = (GenericBeanDefinition) BeanDefinitionBuilder
                .genericBeanDefinition(TestControllerWithProperty.class)
                .addPropertyValue("name","name is property controller")
                .addPropertyReference("testService",testServiceName).getBeanDefinition();

完成注入程式碼：

 public static void main(String[] args) {
//        SpringApplication.run(SpringLearnApplication.class, args);
        //建立一個工廠來
        DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
        //建立beanDefinition
        GenericBeanDefinition beanDefinition = (GenericBeanDefinition) BeanDefinitionBuilder.genericBeanDefinition(TestServiceImpl.class)
                .getBeanDefinition();
        //建立beanDefinition Name
        String testServiceName = AnnotationBeanNameGenerator.INSTANCE.generateBeanName(beanDefinition,beanFactory);
        //注入到spring 工廠裡
        beanFactory.registerBeanDefinition(testServiceName,beanDefinition);

        //建立controller，這個builder模式裡邊，要呼叫constructor的方法
        GenericBeanDefinition controllerBeanDefinition = (GenericBeanDefinition) BeanDefinitionBuilder.
                genericBeanDefinition(TestControllerWithConstructor.class)
                .addConstructorArgValue("controller name is TestController")
                .addConstructorArgReference(testServiceName)
                .getBeanDefinition();
        String controllerBeanName = AnnotationBeanNameGenerator.INSTANCE.generateBeanName(controllerBeanDefinition,beanFactory);
        beanFactory.registerBeanDefinition(controllerBeanName,controllerBeanDefinition);

        //---------------------------------------------
        //注入之後，再取出來，將controller裡面service和 spring裡面的service作對比是不是一樣的。
        TestControllerWithConstructor testController = (TestControllerWithConstructor) beanFactory.getBean(controllerBeanName);
        TestService testService = (TestService) beanFactory.getBean(testServiceName);
        Assert.isTrue(testController.getTestService()==testService,"他們不相等，有問題");


        //__________________________________________________
        //這個是通過屬性值property注入到DefaultListableBeanFactory
        GenericBeanDefinition propertyControllerBeanDefinition = (GenericBeanDefinition) BeanDefinitionBuilder
                .genericBeanDefinition(TestControllerWithProperty.class)
                .addPropertyValue("name","name is property controller")
                .addPropertyReference("testService",testServiceName).getBeanDefinition();
        String propertyControllerName = AnnotationBeanNameGenerator.INSTANCE.generateBeanName(propertyControllerBeanDefinition,beanFactory);
        beanFactory.registerBeanDefinition(propertyControllerName,propertyControllerBeanDefinition);
        //注入進去之後，再取出propertyController
        TestControllerWithProperty propertyController = (TestControllerWithProperty) beanFactory.getBean(propertyControllerName);
        System.out.println(propertyController.getName());
        Assert.isTrue(propertyController.getTestService()==testService,"他們不相等，有問題");

    }

https://www.cnblogs.com/grey-wolf/p/12070377.html

今天就到這了，我去看別的了，