526互联

spring（自动加载xml装载容器）

发布时间 2023-12-29 21:41:08作者: 辉辉、

1.实现将DefaultListableBeanFactory类注入到当前AbstractBeanDefinitionReader中

2.取出xml内容，并生成beanfinition实例对象，注入到DefaultListableBeanFactory类中的map中。

package org.springframework.beans.factory.xml;

import cn.hutool.core.util.StrUtil;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
import org.dom4j.util.StringUtils;
import org.springframework.beans.PropertyValue;
import org.springframework.beans.factory.BeansException;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanReference;
import org.springframework.beans.factory.supper.AbstractBeanDefinitionReader;
import org.springframework.beans.factory.supper.BeanDefinitionRegistry;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class XmlBeanDefinitionReader extends AbstractBeanDefinitionReader {
    public static final String BEAN_ELEMENT = "bean";
    public static final String PROPERTY_ELEMENT = "property";
    public static final String ID_ATTRIBUTE = "id";
    public static final String NAME_ATTRIBUTE = "name";
    public static final String CLASS_ATTRIBUTE = "class";
    public static final String VALUE_ATTRIBUTE = "value";
    public static final String REF_ATTRIBUTE = "ref";
    public static final String INIT_METHOD_ATTRIBUTE = "init-method";
    public static final String DESTROY_METHOD_ATTRIBUTE = "destroy-method";
    public static final String SCOPE_ATTRIBUTE = "scope";
    public static final String LAZYINIT_ATTRIBUTE = "lazyInit";
    public static final String BASE_PACKAGE_ATTRIBUTE = "base-package";
    public static final String COMPONENT_SCAN_ELEMENT = "component-scan";

    public XmlBeanDefinitionReader(BeanDefinitionRegistry registry) {
        super(registry);
    }

    public XmlBeanDefinitionReader(BeanDefinitionRegistry registry, ResourceLoader resourceLoader) {
        super(registry, resourceLoader);
    }


    @Override
    public void loadBeanDefinitions(Resource resource) throws BeansException {
        try {
            InputStream inputStream = resource.getInputStream();
            doLoadBeanDefinitions(inputStream);
        } catch (IOException | DocumentException ex) {
            throw new BeansException("IOException parsing XML document from " + resource, ex);
        }
    }

    @Override
    public void loadBeanDefinitions(String location) throws BeansException {
        ResourceLoader resourceLoader = getResourceLoader();
        Resource resource = resourceLoader.getResource(location);
        loadBeanDefinitions(resource);
    }

    public void doLoadBeanDefinitions(InputStream inputStream) throws DocumentException {
        SAXReader reader = new SAXReader();
        Document document = reader.read(inputStream);
        Element root = document.getRootElement();

        //自动扫描组件
        Element scanComponent = root.element(COMPONENT_SCAN_ELEMENT);
        if (scanComponent != null) {
            String backPackage = scanComponent.attributeValue(BASE_PACKAGE_ATTRIBUTE);
            if (StrUtil.isNotEmpty(backPackage)) {
                scanPackage(backPackage);
            }
        }

        //扫描bean
        List<Element> beanList = root.elements(BEAN_ELEMENT);
        for (Element bean : beanList) {
            String beanId = bean.attributeValue(ID_ATTRIBUTE);
            String beanName = bean.attributeValue(NAME_ATTRIBUTE);
            String className = bean.attributeValue(CLASS_ATTRIBUTE);
            String initMethodName = bean.attributeValue(INIT_METHOD_ATTRIBUTE);
            String destroyMethodName = bean.attributeValue(DESTROY_METHOD_ATTRIBUTE);
            String beanScope = bean.attributeValue(SCOPE_ATTRIBUTE);
            String lazyInit = bean.attributeValue(LAZYINIT_ATTRIBUTE);

            Class<?> clazz;
            try {
                //寻找class类
                clazz = Class.forName(className);
            } catch (ClassNotFoundException e) {
                throw new BeansException("Cannot find class [" + className + "]");
            }

            //ID优先name
            beanName = StrUtil.isNotEmpty(beanId) ? beanId : beanName;
            if (StrUtil.isEmpty(beanName)) {
                beanName = StrUtil.lowerFirst(clazz.getSimpleName());
            }

            //生成bean实例
            BeanDefinition beanDefinition = new BeanDefinition(clazz);

            //设置初始化init-methods
            beanDefinition.setInitMethodName(initMethodName);

            //初始化销毁方式
            beanDefinition.setDestroyMethodName(destroyMethodName);

            //设置beanScope
            if (StrUtil.isNotEmpty(beanScope)) {
                beanDefinition.setScope(beanScope);
            }

            //设置类的属性
            List<Element> propertyList = bean.elements(PROPERTY_ELEMENT);
            for (Element propertyItem : propertyList) {
                String propertyNameAttribute = propertyItem.attributeValue(NAME_ATTRIBUTE);
                String propertyValueAttribute = propertyItem.attributeValue(VALUE_ATTRIBUTE);
                String propertyRefAttribute = propertyItem.attributeValue(REF_ATTRIBUTE);

                //类设置的属性值不能为空
                if (StrUtil.isEmpty(propertyNameAttribute)) {
                    throw new BeansException("The name attribute cannot be null or empty");
                }

                //如果是实例引用，则引入对象
                Object value = propertyValueAttribute;
                if (StrUtil.isNotEmpty(propertyRefAttribute)) {
                    //组装参考示例
                    value = new BeanReference(propertyRefAttribute);
                }

                //追加bean属性内容
                PropertyValue propertyValue = new PropertyValue(propertyNameAttribute, value);
                beanDefinition.getPropertyValues().addPropertyValues(propertyValue);
            }

            //类名不能相同
            if (getRegistry().containsBeanDefinition(beanName)) {
                //beanName不能重名
                throw new BeansException("Duplicate beanName[" + beanName + "] is not allowed");
            }

            //向DefaultListableBeanFactory中的Map注册
            getRegistry().registerBeanDefinition(beanName,beanDefinition);
        }

    }

    /**
     * 自动扫描组件目录
     *
     * @param scanPath
     */
    public void scanPackage(String scanPath) {

    }

}

3.AbstractBeanDefinitionReader：实现调用注册接口去操作bean相关操作

package org.springframework.beans.factory.supper;

import org.springframework.beans.factory.BeansException;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.ResourceLoader;

public abstract class AbstractBeanDefinitionReader implements BeanDefinitionReader {
    private final BeanDefinitionRegistry registry;

    private ResourceLoader resourceLoader;

    public AbstractBeanDefinitionReader(BeanDefinitionRegistry definitionRegistry, ResourceLoader resourceLoader) {
        this.registry = definitionRegistry;
        this.resourceLoader = resourceLoader;
    }

    public AbstractBeanDefinitionReader(BeanDefinitionRegistry registry) {
        this(registry, new DefaultResourceLoader());
    }

    @Override
    public BeanDefinitionRegistry getRegistry() {
        return registry;
    }

    @Override
    public void loadBeanDefinitions(String[] locations) throws BeansException {
        for (String location : locations) {
            loadBeanDefinitions(location);
        }
    }

    public void setResourceLoader(ResourceLoader resourceLoader) {
        this.resourceLoader = resourceLoader;
    }

    @Override
    public ResourceLoader getResourceLoader() {
        return resourceLoader;
    }
}

4.测试