SpringMVC源码分析--容器初始化（三）HttpServletBean

在上一篇博客springMVC源码分析--容器初始化（二）DispatcherServlet中，我们队SpringMVC整体生命周期有一个简单的说明，并没有进行详细的源码分析，接下来我们会根据博客中提供的springMVC的生命周期图来详细的对SpringMVC的相关源码进行分析。

在上一篇博客中我们了解到，SpringMVC初始化配置是在父类HttpServletBean的init方法中，其实HttServletBean是一个比较简单的类，在这个类中并没有太复杂的功能，主要的函数是init函数中，源码如下：

主要工作就是设置我们在web.xml中配置的contextConfigLocation属性，当然这个属性是springMVC文件的配置文件地址，当然也可以不用配置，使用默认名称加载。

initBeanWrapper 函数并没有具体实现

initServletBean（）是模板方法，是在子类FrameworkServlet中实现的，接下来我们会详细分析，这样HttpServletBean的主体功能就介绍完了。

        public final void init() throws ServletException {
		if (logger.isDebugEnabled()) {
			logger.debug("Initializing servlet '" + getServletName() + "'");
		}

		// Set bean properties from init parameters.
		try {
			//获得web.xml中的contextConfigLocation配置属性，就是spring MVC的配置文件
			PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
			BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
			//获取服务器的各种信息
			ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
			bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
			//模板方法，可以在子类中调用，做一些初始化工作，bw代表DispatcherServelt
			initBeanWrapper(bw);
			//将配置的初始化值设置到DispatcherServlet中
			bw.setPropertyValues(pvs, true);
		}
		catch (BeansException ex) {
			logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
			throw ex;
		}

		// Let subclasses do whatever initialization they like.
		//模板方法，子类初始化的入口方法
		initServletBean();

		if (logger.isDebugEnabled()) {
			logger.debug("Servlet '" + getServletName() + "' configured successfully");
		}
	}

当然HttpServletBean还是提供了一些其他方法的，其实都是一些比较简单的get和set方法，就不做过多介绍了，HttpServletBean的完整源码如下：

/**
 *HttpServlet的一个简单扩展类
 */
@SuppressWarnings("serial")
public abstract class HttpServletBean extends HttpServlet
		implements EnvironmentCapable, EnvironmentAware {

	protected final Log logger = LogFactory.getLog(getClass());

	private final Set<String> requiredProperties = new HashSet<String>();

	private ConfigurableEnvironment environment;

	protected final void addRequiredProperty(String property) {
		this.requiredProperties.add(property);
	}
	@Override
	public final void init() throws ServletException {
		if (logger.isDebugEnabled()) {
			logger.debug("Initializing servlet '" + getServletName() + "'");
		}

		// Set bean properties from init parameters.
		try {
			//获得web.xml中的contextConfigLocation配置属性，就是spring MVC的配置文件
			PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
			BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
			//获取服务器的各种信息
			ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
			bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
			//模板方法，可以在子类中调用，做一些初始化工作，bw代表DispatcherServelt
			initBeanWrapper(bw);
			//将配置的初始化值设置到DispatcherServlet中
			bw.setPropertyValues(pvs, true);
		}
		catch (BeansException ex) {
			logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
			throw ex;
		}

		// Let subclasses do whatever initialization they like.
		//模板方法，子类初始化的入口方法
		initServletBean();

		if (logger.isDebugEnabled()) {
			logger.debug("Servlet '" + getServletName() + "' configured successfully");
		}
	}

	/**
	 * Initialize the BeanWrapper for this HttpServletBean,
	 * possibly with custom editors.
	 * <p>This default implementation is empty.
	 * @param bw the BeanWrapper to initialize
	 * @throws BeansException if thrown by BeanWrapper methods
	 * @see org.springframework.beans.BeanWrapper#registerCustomEditor
	 */
	protected void initBeanWrapper(BeanWrapper bw) throws BeansException {
	}

	//获取servletName
	@Override
	public final String getServletName() {
		return (getServletConfig() != null ? getServletConfig().getServletName() : null);
	}

	//获取ServletContext
	@Override
	public final ServletContext getServletContext() {
		return (getServletConfig() != null ? getServletConfig().getServletContext() : null);
	}

	protected void initServletBean() throws ServletException {
	}

	@Override
	public void setEnvironment(Environment environment) {
		Assert.isInstanceOf(ConfigurableEnvironment.class, environment);
		this.environment = (ConfigurableEnvironment) environment;
	}

	@Override
	public ConfigurableEnvironment getEnvironment() {
		if (this.environment == null) {
			this.environment = this.createEnvironment();
		}
		return this.environment;
	}

	protected ConfigurableEnvironment createEnvironment() {
		return new StandardServletEnvironment();
	}

	private static class ServletConfigPropertyValues extends MutablePropertyValues {

		public ServletConfigPropertyValues(ServletConfig config, Set<String> requiredProperties)
			throws ServletException {

			Set<String> missingProps = (requiredProperties != null && !requiredProperties.isEmpty()) ?
					new HashSet<String>(requiredProperties) : null;

			Enumeration<String> en = config.getInitParameterNames();
			while (en.hasMoreElements()) {
				String property = en.nextElement();
				Object value = config.getInitParameter(property);
				addPropertyValue(new PropertyValue(property, value));
				if (missingProps != null) {
					missingProps.remove(property);
				}
			}
			// Fail if we are still missing properties.
			if (missingProps != null && missingProps.size() > 0) {
				throw new ServletException(
					"Initialization from ServletConfig for servlet '" + config.getServletName() +
					"' failed; the following required properties were missing: " +
					StringUtils.collectionToDelimitedString(missingProps, ", "));
			}
		}
	}

}