Simple analysis of Spring core IOC container principle

The general process of parsing one side, the specific can see the source code a method of a method of the following

XmlBeanFactoryfunction is DefaultListableBeanFactory based on this basic container and implements additional functions, such as XML reads, on the basis of this basic container.

DefaultListableBeanFactoryis BeanFactory a default implementation class.

public class XmlBeanFactory extends DefaultListableBeanFactory {    private final XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(this);        /**     * Resource是Spring中对与外部资源的抽象，最常见的是对文件的抽象，特别是XML文件。     * 而且Resource里面通常保存了Spring使用者的Bean定义     * 比如applicationContext.xml在被加载时，就会被抽象为Resource来处理。     */    public XmlBeanFactory(Resource resource) throws BeansException {        this(resource, null);    }        public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {        super(parentBeanFactory);        this.reader.loadBeanDefinitions(resource);    }}

Simple example:

public class MySimpleBeanFactory {    public static void main(String[] args) {        ClassPathResource resource = new ClassPathResource("META-INF/beans.xml");        BeanFactory beanFactory = new XmlBeanFactory(resource);        User user = beanFactory.getBean("user1", User.class);        System.out.println(user.getName()+" : "+user.getAge());    }}

Steps to create a container:

1. To create an abstraction of a bean configuration fileResource
2. Created BeanFactory , for example:XmlBeanFactory
3. Parse the bean and create a BeanDefinition reader, for example XmlBeanDefinitionReader : DefaultBeanDefinitionDocumentReaderBeanDefinitionParserDelegate
4. Get BeanDefinition post-registration into DefaultListableBeanFactory :

// 最后BeanDefinition就是放到这个map里的Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>(256);

Will gradually improve in the future.

Simple analysis of Spring core IOC container principle