Spring 中DispatcherServlet初始化过程

Spring 初始化过程

Spring 初始化过程

1. javax.servlet.Servlet#public void init(ServletConfig config) 方法

public interface Servlet {
  public void init(ServletConfig config) throws ServletException;
}

2. javax.servlet.GenericServlet 抽象类

   public abstract class GenericServlet implements Servlet, ServletConfig,
           java.io.Serializable {
               
           @Override
       public void init(ServletConfig config) throws ServletException {
           this.config = config;
           this.init();
       }
        //空实现      
        public void init() throws ServletException {
           // NOOP by default
       }       
      }
   

3. javax.servlet.http.HttpServlet

   public abstract class HttpServlet extends GenericServlet {
       ...
           
           //没有init方法的实现
   }
   

4. 进入Spring的定义 org.springframework.web.servlet.HttpServletBean

   public abstract class HttpServletBean extends HttpServlet implements EnvironmentCapable, EnvironmentAware {
       
       ...
        @Override
   	public final void init() throws ServletException {
           // ...省略
           
   		// 初始化
   		initServletBean();
       }
       //空方法没有实现
       protected void initServletBean() throws ServletException {
           //...
   	}
   }
   

5. org.springframework.web.servlet.FrameworkServlet

   public abstract class FrameworkServlet extends HttpServletBean implements ApplicationContextAware {
       
       	@Override
   	protected final void initServletBean() throws ServletException {
   		getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'");
   		if (this.logger.isInfoEnabled()) {
   			this.logger.info("FrameworkServlet '" + getServletName() + "': initialization started");
   		}
   		long startTime = System.currentTimeMillis();
   
   		try {
   			this.webApplicationContext = initWebApplicationContext();
   			initFrameworkServlet();
   		}
   		catch (ServletException | RuntimeException ex) {
   			this.logger.error("Context initialization failed", ex);
   			throw ex;
   		}
   
   		if (this.logger.isInfoEnabled()) {
   			long elapsedTime = System.currentTimeMillis() - startTime;
   			this.logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +
   					elapsedTime + " ms");
   		}
   	}
   }
   

   initWebApplicationContext

   protected WebApplicationContext initWebApplicationContext() {
   		WebApplicationContext rootContext =
   				WebApplicationContextUtils.getWebApplicationContext(getServletContext());
   		WebApplicationContext wac = null;
   
   		if (this.webApplicationContext != null) {
   
   			wac = this.webApplicationContext;
   			if (wac instanceof ConfigurableWebApplicationContext) {
   				ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
   				if (!cwac.isActive()) {
   
   					if (cwac.getParent() == null) {
   
   						cwac.setParent(rootContext);
   					}
   					configureAndRefreshWebApplicationContext(cwac);
   				}
   			}
   		}
   		if (wac == null) {
   
   			wac = findWebApplicationContext();
   		}
   		if (wac == null) {
   
   			wac = createWebApplicationContext(rootContext);
   		}
   
   		if (!this.refreshEventReceived) {
   
   			onRefresh(wac);
   		}
   
   		if (this.publishContext) {
   			// Publish the context as a servlet context attribute.
   			String attrName = getServletContextAttributeName();
   			getServletContext().setAttribute(attrName, wac);
   			if (this.logger.isDebugEnabled()) {
   				this.logger.debug("Published WebApplicationContext of servlet '" + getServletName() +
   						"' as ServletContext attribute with name [" + attrName + "]");
   			}
   		}
   
   		return wac;
   	}
   

• onRefresh 方法与initFrameworkServlet方法

  protected void onRefresh(ApplicationContext context) {
  		// For subclasses: do nothing by default.
  	}
  protected void initFrameworkServlet() throws ServletException {
  	}
  

6. org.springframework.web.servlet.DispatcherServlet

   public class DispatcherServlet extends FrameworkServlet {
       	@Override
   	protected void onRefresh(ApplicationContext context) {
   		initStrategies(context);
   	}
   
   	/**
   	 * 初始化策略，之类的组件
   	 * 
   	 */
   	protected void initStrategies(ApplicationContext context) {
   		initMultipartResolver(context);
   		initLocaleResolver(context);
   		initThemeResolver(context);
   		initHandlerMappings(context);
   		initHandlerAdapters(context);
   		initHandlerExceptionResolvers(context);
   		initRequestToViewNameTranslator(context);
   		initViewResolvers(context);
   		initFlashMapManager(context);
   	}
   }
   

最后

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