public class SimplePipeline implements Pipeline {

  // The basic Valve (if any) associated with this Pipeline.
  protected Valve basic = null;
  // The Container with which this Pipeline is associated.
  protected Container container = null;
  // the array of Valves
  protected Valve valves[] = new Valve[0];

  // rest of the code omitted

}

// invoke each valve in the pipeline
for (Valve valve : valves) {
    valve.invoke(...);
}
// invoke basic pipeline in the end
basic.invoke(...);

protected class SimplePipelineValveContext implements ValveContext {

  protected int stage = 0;

  public String getInfo() {
    return null;
  }

  public void invokeNext(Request request, Response response)
    throws IOException, ServletException {
    int subscript = stage;
    stage = stage + 1; // 迭代器自增1
    // Invoke the requested Valve for the current request thread
    if (subscript < valves.length) {
      valves[subscript].invoke(request, response, this);
    }
    else if ((subscript == valves.length) && (basic != null)) {
      basic.invoke(request, response, this);
    }
    else {
      throw new ServletException("No valve");
    }
  }
}

public class ClientIPLoggerValve implements Valve, Contained {

  // omitted ...

  public void invoke(Request request, Response response, ValveContext valveContext) throws IOException, ServletException {

    // Pass this request on to the next valve in our pipeline
    valveContext.invokeNext(request, response);

    // remainder omitted ...
  }
}

public class SimpleContext implements Context, Pipeline { // 本身实现了Pipeline接口
    public SimpleContext() {
      pipeline.setBasic(new SimpleContextValve());
    }
    protected HashMap children = new HashMap();
    protected Loader loader = null;
    protected SimplePipeline pipeline = new SimplePipeline(this); // 又有个Pipeline成员字段，用this去构造
    protected HashMap servletMappings = new HashMap();
    protected Mapper mapper = null;
    protected HashMap mappers = new HashMap();
    private Container parent = null;
}

public Loader getLoader() {
  if (loader != null)
    return (loader);
  if (parent != null)
    return (parent.getLoader()); // Wrapper的parent字段代表它所在的Context
  return (null);
}

Wrapper wrapper1 = new SimpleWrapper();
wrapper1.setName("Primitive");
// 必须是类的全具名
wrapper1.setServletClass("§");
Wrapper wrapper2 = new SimpleWrapper();
wrapper2.setName("Modern");
// 必须是类的全具名
wrapper2.setServletClass("com.ciaoshen.howtomcatworks.ex06.webroot.ModernServlet");

Context context = new SimpleContext();
context.addChild(wrapper1);
context.addChild(wrapper2);

public class SimpleContext implements Context, Pipeline {

  public SimpleContext() {
    pipeline.setBasic(new SimpleContextValve());
  }
  // 存放Servlet Name到Servlet程序的映射。
  // 比如拿到"Primitive"这个名字，
  // 找到叫这个名字的"com.ciaoshen.howtomcatworks.ex05.webroot.PrimitiveServlet"的类文件
  protected HashMap children = new HashMap();
  protected Loader loader = null;
  protected SimplePipeline pipeline = new SimplePipeline(this);
  // 存放URI最后指定servlet的部分，和Servlet Name之间的映射
  // 比如["/Primitive","Primitive"]
  // 从"127.0.0.1:8080/Primitive"切下"/Primitive"，映射到叫"Primitive"的Servlet程序
  protected HashMap servletMappings = new HashMap();
  protected Mapper mapper = null;
  protected HashMap mappers = new HashMap();
  private Container parent = null;

  // remainder omitted ...
}

public SimpleLoader() {
  try {
    URL[] urls = new URL[1];
    URLStreamHandler streamHandler = null;
    File classPath = new File(WEB_ROOT);
    String repository = (new URL("file", null, classPath.getCanonicalPath() + File.separator)).toString() ;
    urls[0] = new URL(null, repository, streamHandler);
    classLoader = new URLClassLoader(urls); // 直接用URLClassLoader
  }
  catch (IOException e) {
    System.out.println(e.toString() );
  }
  // remainder omitted ...
}

final class HttpProcessor implements Lifecycle, Runnable {

    // ... many code omitted

    private void process(Socket socket) {

        // ... omitted code

        // Ask our Container to process this request
        try {
            ((HttpServletResponse) response).setHeader
                ("Date", FastHttpDateFormat.getCurrentDate());
            if (ok) {
                // 实际调用容器的代码
                connector.getContainer().invoke(request, response);
            }
        } catch (ServletException e) {
            // ... omitted code
        }

        // ... omitted code    
    }
}

public synchronized void addValve(Valve valve) {
  pipeline.addValve(valve);
}

public void addServletMapping(String pattern, String name) {
  synchronized (servletMappings) {
    servletMappings.put(pattern, name);
  }
}

public String findServletMapping(String pattern) {
  synchronized (servletMappings) {
    return ((String) servletMappings.get(pattern));
  }
}

public void addMapper(Mapper mapper) {
  // this method is adopted from addMapper in ContainerBase
  // the first mapper added becomes the default mapper
  mapper.setContainer((Container) this);      // May throw IAE
  this.mapper = mapper;
  // 每个Context都有自己独立的线程，但Mapper可以多个容器共享。所以Mapper是竞态资源，Context不是。
  synchronized(mappers) {
    if (mappers.get(mapper.getProtocol()) != null)
      throw new IllegalArgumentException("addMapper:  Protocol '" +
        mapper.getProtocol() + "' is not unique");
    mapper.setContainer((Container) this);      // May throw IAE
    mappers.put(mapper.getProtocol(), mapper);
    if (mappers.size() == 1)
      this.mapper = mapper;
    else
      this.mapper = null;
  }
}

public void setLoader(Loader loader) {
  this.loader = loader;
}