spring源码-增强容器xml解析-3.1-白红宇

　　一、ApplicationContext的xml解析工作是通过ClassPathXmlApplicationContext来实现的，其实看过ClassPathXmlApplicationContext的xml源码解析过程的其实都应该知道，xml的解析过程基本上就是用原来的XmlBeanFactory的解析过程完成的。

　　二、为什么要拿出来单独说一下呢，其目的就是，了解怎么用同样的方式来实现xml解析过程。

　　三、xml解析过程是通过refresh下的obtainFreshBeanFactory函数实现，所以这里重点讲解obtainFreshBeanFactory的实现过程。

　　四、xml源码解析：obtainFreshBeanFactory

　　1）开端

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {        //解析过程        this.refreshBeanFactory();        //这里的beanFactory就是DefaultListableBeanFactory（后续会讲到）        ConfigurableListableBeanFactory beanFactory = this.getBeanFactory();        if (this.logger.isDebugEnabled()) {            this.logger.debug("Bean factory for " + this.getDisplayName() + ": " + beanFactory);        }        return beanFactory;    }

　　2）refreshBeanFactory

protected final void refreshBeanFactory() throws BeansException {        if (this.hasBeanFactory()) {            this.destroyBeans();            this.closeBeanFactory();        }        try {            //是不是很熟悉，这里也是通过DefaultListableBeanFactory的方式来实现的            DefaultListableBeanFactory beanFactory = this.createBeanFactory();            beanFactory.setSerializationId(this.getId());            //自定义beanFactory，处理循环依赖            //主要作用设置@Autowired和@Qualifier解析器QualifierAnnotationAutowireCandidateResolver            this.customizeBeanFactory(beanFactory);            //xml解析过程            this.loadBeanDefinitions(beanFactory);            Object var2 = this.beanFactoryMonitor;            synchronized(this.beanFactoryMonitor) {                this.beanFactory = beanFactory;            }        } catch (IOException var4) {            throw new ApplicationContextException("I/O error parsing bean definition source for " + this.getDisplayName(), var4);        }    }

　　a、DefaultListableBeanFactory继承关系

　　这里其实就可以看出ConfigurableListableBeanFactory就是这里的DefaultListableBeanFactory

　　b、customizeBeanFactory（这里不详细介绍注解的解析过程）

protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) {        if (this.allowBeanDefinitionOverriding != null) {            beanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding.booleanValue());        }        if (this.allowCircularReferences != null) {            beanFactory.setAllowCircularReferences(this.allowCircularReferences.booleanValue());        }        beanFactory.setParameterNameDiscoverer(new LocalVariableTableParameterNameDiscoverer());        beanFactory.setAutowireCandidateResolver(new QualifierAnnotationAutowireCandidateResolver());    }

　　c、loadBeanDefinitions

protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {        //是不是又很熟悉，还是基于XmlBeanDefinitionReader来进行解析了        XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);        beanDefinitionReader.setResourceLoader(this);        beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));        //解析xml        this.initBeanDefinitionReader(beanDefinitionReader);        this.loadBeanDefinitions(beanDefinitionReader);    }

protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {        Resource[] configResources = this.getConfigResources();        if (configResources != null) {            reader.loadBeanDefinitions(configResources);        }        //这里是配置方式不一样，我们是通过configLocations进行配置        String[] configLocations = this.getConfigLocations();        if (configLocations != null) {            //解析文件            reader.loadBeanDefinitions(configLocations);        }    }

public int loadBeanDefinitions(String... locations) throws BeanDefinitionStoreException {        Assert.notNull(locations, "Location array must not be null");        int counter = 0;        String[] var6 = locations;        int var5 = locations.length;        for(int var4 = 0; var4 < var5; ++var4) {            String location = var6[var4]; 　　　　　　　//主要目的计数            counter += this.loadBeanDefinitions(location);        }        return counter;    }

　　public int loadBeanDefinitions(String location) throws BeanDefinitionStoreException {        return this.loadBeanDefinitions(location, (Set)null);    }    public int loadBeanDefinitions(String location, Set
     
       actualResources) throws BeanDefinitionStoreException {        ResourceLoader resourceLoader = this.getResourceLoader();        if (resourceLoader == null) {            throw new BeanDefinitionStoreException("Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");        } else {            int loadCount;            if (!(resourceLoader instanceof ResourcePatternResolver)) {                Resource resource = resourceLoader.getResource(location);                loadCount = this.loadBeanDefinitions((Resource)resource);                if (actualResources != null) {                    actualResources.add(resource);                }                if (this.logger.isDebugEnabled()) {                    this.logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");                }                return loadCount;            } else {                try {                    Resource[] resources = ((ResourcePatternResolver)resourceLoader).getResources(location);                    //包装成Resource，进行解析                    loadCount = this.loadBeanDefinitions(resources);                    if (actualResources != null) {                        Resource[] var9 = resources;                        int var8 = resources.length;                        for(int var7 = 0; var7 < var8; ++var7) {                            Resource resource = var9[var7];                            actualResources.add(resource);                        }                    }                    if (this.logger.isDebugEnabled()) {                        this.logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");                    }                    return loadCount;                } catch (IOException var10) {                    throw new BeanDefinitionStoreException("Could not resolve bean definition resource pattern [" + location + "]", var10);                }            }        }    }

public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {        Assert.notNull(resources, "Resource array must not be null");        int counter = 0;        Resource[] var6 = resources;        int var5 = resources.length;        for(int var4 = 0; var4 < var5; ++var4) {            Resource resource = var6[var4];            //单独解析没一个resource            counter += this.loadBeanDefinitions((Resource)resource);        }        return counter;    }

　　d、loadBeanDefinitions（这里是不是很熟悉，这里的解析过程就是XmlBeanFactory里面的xml的核心解析过程）

public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {        return this.loadBeanDefinitions(new EncodedResource(resource));    }    public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {        Assert.notNull(encodedResource, "EncodedResource must not be null");        if (this.logger.isInfoEnabled()) {            this.logger.info("Loading XML bean definitions from " + encodedResource.getResource());        }        Set
     
       currentResources = (Set)this.resourcesCurrentlyBeingLoaded.get();        if (currentResources == null) {            currentResources = new HashSet(4);            this.resourcesCurrentlyBeingLoaded.set(currentResources);        }        if (!((Set)currentResources).add(encodedResource)) {            throw new BeanDefinitionStoreException("Detected cyclic loading of " + encodedResource + " - check your import definitions!");        } else {            int var6;            try {                InputStream inputStream = encodedResource.getResource().getInputStream();                try {                    InputSource inputSource = new InputSource(inputStream);                    if (encodedResource.getEncoding() != null) {                        inputSource.setEncoding(encodedResource.getEncoding());                    }                    var6 = this.doLoadBeanDefinitions(inputSource, encodedResource.getResource());                } finally {                    inputStream.close();                }            } catch (IOException var15) {                throw new BeanDefinitionStoreException("IOException parsing XML document from " + encodedResource.getResource(), var15);            } finally {                ((Set)currentResources).remove(encodedResource);                if (((Set)currentResources).isEmpty()) {                    this.resourcesCurrentlyBeingLoaded.remove();                }            }            return var6;        }    }

　　e、剩下的部分参考：的源码解析部分第4）点

　　五、分析一下流程

　　1）通过ClassPathXmlApplicationContext来进行xml的解析工作

　　2）首先进行赋值到configLocations的属性上面

　　3）xml解析过程还是通过XmlBeanDefinitionReader来实现解析

　　4）xml解析不同的地方：

　　a、新增解析增加计数

　　b、返回类型使用接口ConfigurableListableBeanFactory

　　c、增加string的配置方式，代码编写感觉更好。

　　d、解析之前和之后，都做了很多其他工作。相比之下拓展了很多其他功能。