Spring加载过程图解

Posted 2020-10-29 南宫煌_慧

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最近看了一下Spring源码加载的简装版本，为了更好的理解，所以在绘图的基础上，进行了一些总结。（图画是为了理解和便于记忆Spring架构）

Spring的核心是IOC(控制反转)和AOP（面向切面编程），首先我们先一步一步的来了解IOC的实现：

一：首先是第一个模型：Model1：

种子 = BeanDefinition 工厂=BeanFactory

1、此处我们可以看见两个对象 BeanDefinition和BeanFactory，此处把创建对象的权限交给了BeanFactory,现在我们可以看到IOC的雏形，即把创建对象的权利交给了工厂。

public class BeanDefinition {

    private Object bean;

    public BeanDefinition(Object bean) {
        this.bean = bean;
    }

    public Object getBean() {
        return bean;
    }

}

public class BeanFactory {

    private Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>();

    public Object getBean(String name) {
        return beanDefinitionMap.get(name).getBean();
    }

    public void registerBeanDefinition(String name, BeanDefinition beanDefinition) {
        beanDefinitionMap.put(name, beanDefinition);
    }

}

二：接下來我們看第二个模型，对BeanFactory进行扩展

1、此处的BeanDefinition 进行了扩展字段，可以看做是种子有了 3 片叶子，便于记忆，分别是：

Object -> bean Class ->beanClass String ->beanClassName

2、此处的BeanFactory有了解耦的思想，使用了接口和抽象类

public class BeanDefinition {

    private Object bean;

    private Class beanClass;

    private String beanClassName;

    public BeanDefinition() {
    }

    public void setBean(Object bean) {
        this.bean = bean;
    }

    public Class getBeanClass() {
        return beanClass;
    }

    public void setBeanClass(Class beanClass) {
        this.beanClass = beanClass;
    }

    public String getBeanClassName() {
        return beanClassName;
    }

    public void setBeanClassName(String beanClassName) {
        this.beanClassName = beanClassName;
        try {
            this.beanClass = Class.forName(beanClassName);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public Object getBean() {
        return bean;
    }

}

public interface BeanFactory {

    Object getBean(String name);

    void registerBeanDefinition(String name, BeanDefinition beanDefinition);
}

此处 BeanFactory定义了获取Bean 和注册Bean的方法

public abstract class AbstractBeanFactory implements BeanFactory {

    private Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>();

    @Override
    public Object getBean(String name) {
        return beanDefinitionMap.get(name).getBean();
    }

    @Override
    public void registerBeanDefinition(String name, BeanDefinition beanDefinition) {
        Object bean = doCreateBean(beanDefinition);
        beanDefinition.setBean(bean);
        beanDefinitionMap.put(name, beanDefinition);
    }

    /**
     * 初始化bean
     * @param beanDefinition
     * @return
     */
    protected abstract Object doCreateBean(BeanDefinition beanDefinition);

}

此处实现了getBean 和registerBean的方法；另外声明了 doCreateBean的抽象方法；

public class AutowireCapableBeanFactory extends AbstractBeanFactory {

    @Override
    protected Object doCreateBean(BeanDefinition beanDefinition) {
        try {
            Object bean = beanDefinition.getBeanClass().newInstance();
            return bean;
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return null;
    }
}

最后实现类通过反射的方式，创建bean；并注册到工厂里，以便调用。

三：接下来继续完善，查看第三个模型：

1、此处 BeanDefiniton多了一个自定义的属性 propertyValues,便于属性的注入，BeanFactory方法也有所改变

1、BeanDefinition类的定义

public class BeanDefinition {

    private Object bean;

    private Class beanClass;

    private String beanClassName;

    private PropertyValues propertyValues;

    public BeanDefinition() {
    }

    public void setBean(Object bean) {
        this.bean = bean;
    }

    public Class getBeanClass() {
        return beanClass;
    }

    public void setBeanClass(Class beanClass) {
        this.beanClass = beanClass;
    }

    public String getBeanClassName() {
        return beanClassName;
    }

    public void setBeanClassName(String beanClassName) {
        this.beanClassName = beanClassName;
        try {
            this.beanClass = Class.forName(beanClassName);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public Object getBean() {
        return bean;
    }

    public PropertyValues getPropertyValues() {
        return propertyValues;
    }

    public void setPropertyValues(PropertyValues propertyValues) {
        this.propertyValues = propertyValues;
    }
}

View Code

/**
 * 用于bean的属性注入
 * @author yihua.huang@dianping.com
 */
public class PropertyValue {

    private final String name;

    private final Object value;

    public PropertyValue(String name, Object value) {
        this.name = name;
        this.value = value;
    }

    public String getName() {
        return name;
    }

    public Object getValue() {
        return value;
    }
}

import java.util.ArrayList;
import java.util.List;

/**
 * 包装一个对象所有的PropertyValue。<br/>
 * 为什么封装而不是直接用List?因为可以封装一些操作。
 * @author yihua.huang@dianping.com
 */
public class PropertyValues {

    private final List<PropertyValue> propertyValueList = new ArrayList<PropertyValue>();

    public PropertyValues() {
    }

    public void addPropertyValue(PropertyValue pv) {
        //TODO:这里可以对于重复propertyName进行判断，直接用list没法做到
        this.propertyValueList.add(pv);
    }

    public List<PropertyValue> getPropertyValues() {
        return this.propertyValueList;
    }

}

View Code

2、BeanFactory的定义

/**
 * bean的容器
 * @author yihua.huang@dianping.com
 */
public interface BeanFactory {

    Object getBean(String name);

    void registerBeanDefinition(String name, BeanDefinition beanDefinition) throws Exception;
}

/**
 * @author yihua.huang@dianping.com
 */
public abstract class AbstractBeanFactory implements BeanFactory {

    private Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>();

    @Override
    public Object getBean(String name) {
        return beanDefinitionMap.get(name).getBean();
    }

    @Override
    public void registerBeanDefinition(String name, BeanDefinition beanDefinition) throws Exception {
        Object bean = doCreateBean(beanDefinition);
        beanDefinition.setBean(bean);
        beanDefinitionMap.put(name, beanDefinition);
    }

    /**
     * 初始化bean
     * @param beanDefinition
     * @return
     */
    protected abstract Object doCreateBean(BeanDefinition beanDefinition) throws Exception;

}

/**
 * 可自动装配内容的BeanFactory
 * 
 * @author yihua.huang@dianping.com
 */
public class AutowireCapableBeanFactory extends AbstractBeanFactory {

    @Override
    protected Object doCreateBean(BeanDefinition beanDefinition) throws Exception {
        Object bean = createBeanInstance(beanDefinition);
        applyPropertyValues(bean, beanDefinition);
        return bean;
    }

    protected Object createBeanInstance(BeanDefinition beanDefinition) throws Exception {
        return beanDefinition.getBeanClass().newInstance();
    }

    protected void applyPropertyValues(Object bean, BeanDefinition mbd) throws Exception {
        for (PropertyValue propertyValue : mbd.getPropertyValues().getPropertyValues()) {
            Field declaredField = bean.getClass().getDeclaredField(propertyValue.getName());
            declaredField.setAccessible(true);
            declaredField.set(bean, propertyValue.getValue());
        }
    }
}

此处增加了添加属性的方法 applyPropertyValues;

此模型可概括为：

#1.step1-最基本的容器
*step-1-container-register-and-get*

单纯的map，有get和put bean的功能

# 2.step2-将bean创建放入工厂
*step-2-abstract-beanfactory-and-do-bean-initilizing-in-it*

1. 抽象beanfactory
2. 将bean初始化放入beanfactory

# 2.step3-为bean注入属性
*step-3-inject-bean-with-property*

4、接下来我们来看第四个模型，Spring是如何实现读取配置文件的bean属性的，Model4：

从图中可以看出多了几个模块，现在分别来介绍一下：

1、BD 是简化绘制版的 BeanDefiniton

2、UR 对应下面 IO类，用于读取xml文件

RL 是ResourceLoader，用于配置文件路径

3、BDR 是用来解析XML文件的模块类

4、最后交由BeanFactory创造bean，并提供bean.

1、BeanDefinition

BeanDefiniton

/**
 * bean的内容及元数据，保存在BeanFactory中，包装bean的实体
 * 
 * @author yihua.huang@dianping.com
 */
public class BeanDefinition {

    private Object bean;

    private Class beanClass;

    private String beanClassName;

    private PropertyValues propertyValues = new PropertyValues();

    public BeanDefinition() {
    }

    public void setBean(Object bean) {
        this.bean = bean;
    }

    public Class getBeanClass() {
        return beanClass;
    }

    public void setBeanClass(Class beanClass) {
        this.beanClass = beanClass;
    }

    public String getBeanClassName() {
        return beanClassName;
    }

    public void setBeanClassName(String beanClassName) {
        this.beanClassName = beanClassName;
        try {
            this.beanClass = Class.forName(beanClassName);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public Object getBean() {
        return bean;
    }

    public PropertyValues getPropertyValues() {
        return propertyValues;
    }

    public void setPropertyValues(PropertyValues propertyValues) {
        this.propertyValues = propertyValues;
    }

View Code

PropertyValue

/**
 * 用于bean的属性注入
 * @author yihua.huang@dianping.com
 */
public class PropertyValue {

    private final String name;

    private final Object value;

    public PropertyValue(String name, Object value) {
        this.name = name;
        this.value = value;
    }

    public String getName() {
        return name;
    }

    public Object getValue() {
        return value;
    }
}

View Code

PropertyValues

/**
 * 包装一个对象所有的PropertyValue。<br/>
 * 为什么封装而不是直接用List?因为可以封装一些操作。
 * @author yihua.huang@dianping.com
 */
public class PropertyValues {

    private final List<PropertyValue> propertyValueList = new ArrayList<PropertyValue>();

    public PropertyValues() {
    }

    public void addPropertyValue(PropertyValue pv) {
        //TODO:这里可以对于重复propertyName进行判断，直接用list没法做到
        this.propertyValueList.add(pv);
    }

    public List<PropertyValue> getPropertyValues() {
        return this.propertyValueList;
    }

}

View Code

2、IO类

Resource

/**
 * Resource是spring内部定位资源的接口。
 * @author yihua.huang@dianping.com
 */
public interface Resource {

    InputStream getInputStream() throws IOException;
}

/**
 * @author yihua.huang@dianping.com
 */
public class UrlResource implements Resource {

    private final URL url;

    public UrlResource(URL url) {
        this.url = url;
    }

    @Override
    public InputStream getInputStream() throws IOException{
        URLConnection urlConnection = url.openConnection();
        urlConnection.connect();
        return urlConnection.getInputStream();
    }
}

ResourceLoader

/**
 * @author yihua.huang@dianping.com
 */
public class ResourceLoader {

    public Resource getResource(String location){
        URL resource = this.getClass().getClassLoader().getResource(location);
        return new UrlResource(resource);
    }
}

3、BeanDefinitionReader

/**
 * 从配置中读取BeanDefinitionReader
 * @author yihua.huang@dianping.com
 */
public interface BeanDefinitionReader {

    void loadBeanDefinitions(String location) throws Exception;
}

/**
 * 从配置中读取BeanDefinitionReader
 * 
 * @author yihua.huang@dianping.com
 */
public abstract class AbstractBeanDefinitionReader implements BeanDefinitionReader {

    private Map<String,BeanDefinition> registry;

    private ResourceLoader resourceLoader;

    protected AbstractBeanDefinitionReader(ResourceLoader resourceLoader) {
        this.registry = new HashMap<String, BeanDefinition>();
        this.resourceLoader = resourceLoader;
    }

    public Map<String, BeanDefinition> getRegistry() {
        return registry;
    }

    public ResourceLoader getResourceLoader() {
        return resourceLoader;
    }
}

XmlBeanDefinitionReader

/**
 * @author yihua.huang@dianping.com
 */
public class XmlBeanDefinitionReader extends AbstractBeanDefinitionReader {

    public XmlBeanDefinitionReader(ResourceLoader resourceLoader) {
        super(resourceLoader);
    }

    @Override
    public void loadBeanDefinitions(String location) throws Exception {
        InputStream inputStream = getResourceLoader().getResource(location).getInputStream();
        doLoadBeanDefinitions(inputStream);
    }

    protected void doLoadBeanDefinitions(InputStream inputStream) throws Exception {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder docBuilder = factory.newDocumentBuilder();
        Document doc = docBuilder.parse(inputStream);
        // 解析bean
        registerBeanDefinitions(doc);
        inputStream.close();
    }

    public void registerBeanDefinitions(Document doc) {
        Element root = doc.getDocumentElement();

        parseBeanDefinitions(root);
    }

    protected void parseBeanDefinitions(Element root) {
        NodeList nl = root.getChildNodes();
        for (int i = 0; i < nl.getLength(); i++) {
            Node node = nl.item(i);
            if (node instanceof Element) {
                Element ele = (Element) node;
                processBeanDefinition(ele);
            }
        }
    }

    protected void processBeanDefinition(Element ele) {
        String name = ele.getAttribute("name");
        String className = ele.getAttribute("class");
        BeanDefinition beanDefinition = new BeanDefinition();
        processProperty(ele,beanDefinition);
        beanDefinition.setBeanClassName(className);
        getRegistry().put(name, beanDefinition);
    }

    private void processProperty(Element ele,BeanDefinition beanDefinition) {
        NodeList propertyNode = ele.getElementsByTagName("property");
        for (int i = 0; i < propertyNode.getLength(); i++) {
            Node node = propertyNode.item(i);
            if (node instanceof Element) {
                Element propertyEle = (Element) node;
                String name = propertyEle.getAttribute("name");
                String value = propertyEle.getAttribute("value");
                beanDefinition.getPropertyValues().addPropertyValue(new PropertyValue(name,value));
            }
        }
    }
}

View Code

此文件用来定义文名，并解析xml文件

未完，待续。。。。。。

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