「推荐收藏！」【Spring源码探究】（一）MVC容器初始化🏅彻底让你明白运行原理和源码流程

package org.springframework.web.servlet;
import javax.servlet.http.HttpServletRequest;
public interface HandlerMapping {
    String PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE = HandlerMapping.class.getName() + ".pathWithinHandlerMapping";
    String BEST_MATCHING_PATTERN_ATTRIBUTE = HandlerMapping.class.getName() + ".bestMatchingPattern";
    String INTROSPECT_TYPE_LEVEL_MAPPING = HandlerMapping.class.getName() + ".introspectTypeLevelMapping";
    String URI_TEMPLATE_VARIABLES_ATTRIBUTE = HandlerMapping.class.getName() + ".uriTemplateVariables";
    String PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE = HandlerMapping.class.getName() + ".producibleMediaTypes";
    HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;
}
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HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;
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/**
 * Return the HandlerExecutionChain for this request.
 * <p>Tries all handler mappings in order.
 * @param request current HTTP request
 * @return the HandlerExecutionChain, or <code>null</code> if no handler could be found
 */
 protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
    for (HandlerMapping hm : this.handlerMappings) {
      if (logger.isTraceEnabled()) {
        logger.trace("Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");
      }
      HandlerExecutionChain handler = hm.getHandler(request);
      if (handler != null) {
        return handler;
      }
    }
    return null;
}
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package org.springframework.web.servlet;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.springframework.util.CollectionUtils;
public class HandlerExecutionChain {
  private final Object handler;
  private HandlerInterceptor[] interceptors;
  private List<HandlerInterceptor> interceptorList;
  public HandlerExecutionChain(Object handler) {
    this(handler, null);
  }
  public HandlerExecutionChain(Object handler, HandlerInterceptor[] interceptors) {
    if (handler instanceof HandlerExecutionChain) {
      HandlerExecutionChain originalChain = (HandlerExecutionChain) handler;
      this.handler = originalChain.getHandler();
      this.interceptorList = new ArrayList<HandlerInterceptor>();
      CollectionUtils.mergeArrayIntoCollection(originalChain.getInterceptors(), this.interceptorList);
      CollectionUtils.mergeArrayIntoCollection(interceptors, this.interceptorList);
    }
    else {
      this.handler = handler;
      this.interceptors = interceptors;
    }
  }
  public Object getHandler() {
    return this.handler;
  }
  public void addInterceptor(HandlerInterceptor interceptor) {
    initInterceptorList();
    this.interceptorList.add(interceptor);
  }
  public void addInterceptors(HandlerInterceptor[] interceptors) {
    if (interceptors != null) {
      initInterceptorList();
      this.interceptorList.addAll(Arrays.asList(interceptors));
    }
  }
  private void initInterceptorList() {
    if (this.interceptorList == null) {
      this.interceptorList = new ArrayList<HandlerInterceptor>();
    }
    if (this.interceptors != null) {
      this.interceptorList.addAll(Arrays.asList(this.interceptors));
      this.interceptors = null;
    }
  }
  public HandlerInterceptor[] getInterceptors() {
    if (this.interceptors == null && this.interceptorList != null) {
      this.interceptors = this.interceptorList.toArray(new HandlerInterceptor[this.interceptorList.size()]);
    }
    return this.interceptors;
  }
  @Override
  public String toString() {
    if (this.handler == null) {
      return "HandlerExecutionChain with no handler";
    }
    StringBuilder sb = new StringBuilder();
    sb.append("HandlerExecutionChain with handler [").append(this.handler).append("]");
    if (!CollectionUtils.isEmpty(this.interceptorList)) {
      sb.append(" and ").append(this.interceptorList.size()).append(" interceptor");
      if (this.interceptorList.size() > 1) {
        sb.append("s");
      }
    }
    return sb.toString();
  }
}
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private final Object handler;
private HandlerInterceptor[] interceptors;
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package org.springframework.web.servlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public interface HandlerInterceptor {
    boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)throws Exception;
    void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)throws Exception;
    void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)throws Exception;
}
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package org.springframework.web.servlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public interface HandlerAdapter {
  boolean supports(Object handler); 
  ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;
  long getLastModified(HttpServletRequest request, Object handler);
}
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/** List of HandlerMappings used by this servlet */
    private List<HandlerMapping> handlerMappings;
/** List of HandlerAdapters used by this servlet */
    private List<HandlerAdapter> handlerAdapters;
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/**
   * Return the HandlerAdapter for this handler object.
   * @param handler the handler object to find an adapter for
   * @throws ServletException if no HandlerAdapter can be found for the handler. This is a fatal error.
   */
  protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
    for (HandlerAdapter ha : this.handlerAdapters) {
      if (logger.isTraceEnabled()) {
        logger.trace("Testing handler adapter [" + ha + "]");
      }
      if (ha.supports(handler)) {
        return ha;
      }
    }
    throw new ServletException("No adapter for handler [" + handler +
        "]: Does your handler implement a supported interface like Controller?");
  }
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package org.springframework.web.servlet;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public interface View {
  String RESPONSE_STATUS_ATTRIBUTE = View.class.getName() + ".responseStatus";
  String PATH_VARIABLES = View.class.getName() + ".pathVariables";
  String getContentType();
  void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception;
}
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