how tomcat works 读书笔记 十一 StandWrapper 下

StandardWrapperValve

  如果Servlet无法使用了，调用包装器的 unload 方法

// Allocate a servlet instance to process this request
try {
    if (!unavailable) {
    servlet = wrapper.allocate();
    }
}
...
// Acknowlege the request
try {
    response.sendAcknowledgement();
}
...
// Create the filter chain for this request
    ApplicationFilterChain filterChain = createFilterChain(request,servlet);
// Call the filter chain for this request// This also calls the servlet's servicet() method
try {
    String jspFile = wrapper.getJspFile();
    if (jspFile != null)
    sreq.setAttribute(Globals.JSP_FILE_ATTR, jspFile);
    else
    sreq.removeAttribute(Globals.JSP_FILE_ATTR);
    if ((servlet != null) && (filterChain != null)) {
    filterChain.doFilter(sreq, sres);
    }
    sreq.removeAttribute(Globals.JSP_FILE_ATTR);
}
...
// Release the filter chain (if any) for this request
try {
    if (filterChain != null)
        filterChain.release();
}
...
// Deallocate the allocated servlet instance
try {
    if (servlet != null) {
        wrapper.deallocate(servlet);
    }
}
...
// If this servlet has been marked permanently unavailable,
// unload it and release this instance
try {
    if ((servlet != null) && (wrapper.getAvailable() ==Long.MAX_VALUE)) {
        wrapper.unload();
    }
}

FilterDef类

    /**
     * The set of initialization parameters for this filter, keyed by
     * parameter name.
     */
    private Map<String, String> parameters = new HashMap<String, String>();

ApplicationFilterConfig类

        String filterClass = filterDef.getFilterClass();
        ClassLoader classLoader = null;
        if (filterClass.startsWith("org.apache.catalina."))
            classLoader = this.getClass().getClassLoader();
        else
            classLoader = context.getLoader().getClassLoader();
    .....
            Class<?> clazz = classLoader.loadClass(filterClass);
        this.filter = (Filter) clazz.newInstance();
        filter.init(this);
        return (this.filter);

ApplicationFilterChain类

    private ArrayList<ApplicationFilterConfig> filters = new ArrayList<ApplicationFilterConfig>();

看到了把,数组形式来存放链条。

典型的责任链模式。

public void doFilter(ServletRaquest request, ServletResponse response,FilterChain chain)
            throws java.io.IOException, ServletException
在ApplicationFilterChain的doFilter方法中，它会将自己作为第三个参数传递给它。
我们看一个Filter实现类的例子
public void doFilter(ServletRequest request, ServletResponse response,
                    FilterChain chain) throws IOException, ServletException {
    // do something here
    ...
    chain.doFilter(request, response);
}

http://blog.csdn.net/dlf123321/article/details/40078583

等所有的Filter都执行完了,就是下面的代码

           if ((request instanceof HttpServletRequest) &&
                (response instanceof HttpServletResponse)) {
                servlet.service((HttpServletRequest) request,
                                (HttpServletResponse) response);
            } else {
                servlet.service(request, response);
            }

什么时候Filter才算执行完了呢?

 private Iterator<ApplicationFilterConfig> iterator = null;

....

 if (this.iterator == null)
            this.iterator = filters.iterator();

        // Call the next filter if there is one
        if (this.iterator.hasNext()) {

                    //执行filter

       }
...
      //调用servlet的service的代码块
...

应用程序

how tomcat works 读书笔记 十一 StandWrapper 下

原文：http://blog.csdn.net/dlf123321/article/details/41260463