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spring容器启动的加载过程

时间:2015-01-10 22:12:22      阅读:547      评论:0      收藏:0      [点我收藏+]

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使用spring,我们在web.xml都会配置ContextLoaderListener

  <listener>
    <listener-class>
            org.springframework.web.context.ContextLoaderListener
        </listener-class>
  </listener>
public class ContextLoaderListener extends ContextLoader implements ServletContextListener {

//由于他继承自ContextLoader,加载的时候当然会先加载他啦,那我们来看看这个类



}

 

ContextLoader这个类有一段静态代码块
private static final String DEFAULT_STRATEGIES_PATH = "ContextLoader.properties";//这个文件是在org.springframework.web.context.ContextLoader.properties他里面是

org.springframework.web.context.WebApplicationContext=org.springframework.web.context.support.XmlWebApplicationContext //这个后面再研究 以后就会把spring所有重要的东西都能看到了。
private static final Properties defaultStrategies; static { // Load default strategy implementations from properties file. // This is currently strictly internal and not meant to be customized // by application developers. try { ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, ContextLoader.class); defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);//根据上面的properties文件,就能得到一个默认的properties了。 } catch (IOException ex) { throw new IllegalStateException("Could not load ‘ContextLoader.properties‘: " + ex.getMessage()); } }

 

我们在看看ContextLoaderListener的这个方法,在容器启动的时候,他会扫描web.xml的listener配置,然后自动调用Listener的contextInitialized初始化方法。

public void contextInitialized(ServletContextEvent event) {
        this.contextLoader = createContextLoader();
        if (this.contextLoader == null) {
            this.contextLoader = this;
        }
        this.contextLoader.initWebApplicationContext(event.getServletContext());
    }

 

 

    public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
        if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) {
            throw new IllegalStateException(
                    "Cannot initialize context because there is already a root application context present - " +
                    "check whether you have multiple ContextLoader* definitions in your web.xml!");
        }

        Log logger = LogFactory.getLog(ContextLoader.class);
        servletContext.log("Initializing Spring root WebApplicationContext");
        if (logger.isInfoEnabled()) {
            logger.info("Root WebApplicationContext: initialization started");
        }
        long startTime = System.currentTimeMillis();

        try {
            // Store context in local instance variable, to guarantee that
            // it is available on ServletContext shutdown.
            if (this.context == null) {
                this.context = createWebApplicationContext(servletContext);
            }
            if (this.context instanceof ConfigurableWebApplicationContext) {
                ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context;
                if (!cwac.isActive()) {
                    // The context has not yet been refreshed -> provide services such as
                    // setting the parent context, setting the application context id, etc
                    if (cwac.getParent() == null) {
                        // The context instance was injected without an explicit parent ->
                        // determine parent for root web application context, if any.
                        ApplicationContext parent = loadParentContext(servletContext);
                        cwac.setParent(parent);
                    }
                    configureAndRefreshWebApplicationContext(cwac, servletContext);
                }
            }
            servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);

            ClassLoader ccl = Thread.currentThread().getContextClassLoader();
            if (ccl == ContextLoader.class.getClassLoader()) {
                currentContext = this.context;
            }
            else if (ccl != null) {
                currentContextPerThread.put(ccl, this.context);
            }

            if (logger.isDebugEnabled()) {
                logger.debug("Published root WebApplicationContext as ServletContext attribute with name [" +
                        WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]");
            }
            if (logger.isInfoEnabled()) {
                long elapsedTime = System.currentTimeMillis() - startTime;
                logger.info("Root WebApplicationContext: initialization completed in " + elapsedTime + " ms");
            }

            return this.context;
        }
        catch (RuntimeException ex) {
            logger.error("Context initialization failed", ex);
            servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);
            throw ex;
        }
        catch (Error err) {
            logger.error("Context initialization failed", err);
            servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, err);
            throw err;
        }
    }

 

spring容器启动的加载过程

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原文地址:http://www.cnblogs.com/hjy9420/p/4215708.html

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