Tomcat源码学习--Cookie创建和销毁

谁践踏了优雅 2022-06-06 05:26 226阅读 0赞

上一篇博客[Tomcat源码学习--Session创建销毁][Tomcat_--Session]中我们学习了Session创建、使用和销毁的操作，接下来我们看看Tomcat中对Cookie是如何做处理的。首先我们要了解Cookie是由浏览器创建、管理和销毁操作的，Tomcat只能获取浏览器请求过来的cookie值，或者创建cookie。

#### 一、获取Cookie ####

1、通过request获取cookie

Cookie [] cookies = request.getCookies();

在Request的外观类RequestFacade类中提供getCookies（）方法

@Override
        public Cookie[] getCookies() {
    
            if (request == null) {
                throw new IllegalStateException(
                                sm.getString("requestFacade.nullRequest"));
            }
    
            Cookie[] ret = null;
    
            /*
             * Clone the returned array only if there is a security manager
             * in place, so that performance won't suffer in the non-secure case
             */
            if (SecurityUtil.isPackageProtectionEnabled()){
                ret = AccessController.doPrivileged(
                    new GetCookiesPrivilegedAction());
                if (ret != null) {
                    ret = ret.clone();
                }
            } else {
                ret = request.getCookies();
            }
    
            return ret;
        }

在tomcat的类Rquest中提供getCookies()方法，cookiesConverted会将浏览器发送过来的cookie数据进行解析

@Override
        public Cookie[] getCookies() {
            if (!cookiesConverted) {
                convertCookies();
            }
            return cookies;
        }

covertCookies中会对cookie进行转换并返回

protected void convertCookies() {
            if (cookiesConverted) {
                return;
            }
    
            cookiesConverted = true;
    
            if (getContext() == null) {
                return;
            }
    		//解析cookie，浏览器将cookie数据添加到header中发送到后端
            parseCookies();
    
            ServerCookies serverCookies = coyoteRequest.getCookies();
            CookieProcessor cookieProcessor = getContext().getCookieProcessor();
    
            int count = serverCookies.getCookieCount();
            if (count <= 0) {
                return;
            }
    
            cookies = new Cookie[count];
    		//获取解析后的cookie并组装后返回
            int idx=0;
            for (int i = 0; i < count; i++) {
                ServerCookie scookie = serverCookies.getCookie(i);
                try {
                    /*
                    we must unescape the '\\' escape character
                    */
                    Cookie cookie = new Cookie(scookie.getName().toString(),null);
                    int version = scookie.getVersion();
                    cookie.setVersion(version);
                    scookie.getValue().getByteChunk().setCharset(cookieProcessor.getCharset());
                    cookie.setValue(unescape(scookie.getValue().toString()));
                    cookie.setPath(unescape(scookie.getPath().toString()));
                    String domain = scookie.getDomain().toString();
                    if (domain!=null)
                     {
                        cookie.setDomain(unescape(domain));//avoid NPE
                    }
                    String comment = scookie.getComment().toString();
                    cookie.setComment(version==1?unescape(comment):null);
                    cookies[idx++] = cookie;
                } catch(IllegalArgumentException e) {
                    // Ignore bad cookie
                }
            }
            if( idx < count ) {
                Cookie [] ncookies = new Cookie[idx];
                System.arraycopy(cookies, 0, ncookies, 0, idx);
                cookies = ncookies;
            }
        }

parseCookies()方法会将浏览器发送过来的header中的cookie提取出来

protected void parseCookies() {
            if (cookiesParsed) {
                return;
            }
    
            cookiesParsed = true;
    
            ServerCookies serverCookies = coyoteRequest.getCookies();
            serverCookies.setLimit(connector.getMaxCookieCount());
            CookieProcessor cookieProcessor = getContext().getCookieProcessor();
            cookieProcessor.parseCookieHeader(coyoteRequest.getMimeHeaders(), serverCookies);
        }

CookieProcessor的实现类Rfc6265CookieProcessor会根据一定的规则对头部的cookie解析并转换为Cookie数组

在浏览器发送到后台的数据中Cookie是一个字符串，通过；分好进行数据分割。

![Image 1][]

@Override
        public void parseCookieHeader(MimeHeaders headers,
                ServerCookies serverCookies) {
    
            if (headers == null) {
                // nothing to process
                return;
            }
    
            // process each "cookie" header
    		//查找头部中key为Cookie的值
            int pos = headers.findHeader("Cookie", 0);
            while (pos >= 0) {
                MessageBytes cookieValue = headers.getValue(pos);
    
                if (cookieValue != null && !cookieValue.isNull() ) {
                    if (cookieValue.getType() != MessageBytes.T_BYTES ) {
                        if (log.isDebugEnabled()) {
                            Exception e = new Exception();
                            // TODO: Review this in light of HTTP/2
                            log.debug("Cookies: Parsing cookie as String. Expected bytes.", e);
                        }
                        cookieValue.toBytes();
                    }
                    if (log.isDebugEnabled()) {
                        log.debug("Cookies: Parsing b[]: " + cookieValue.toString());
                    }
                    ByteChunk bc = cookieValue.getByteChunk();
    
                    Cookie.parseCookie(bc.getBytes(), bc.getOffset(), bc.getLength(),
                            serverCookies);
                }
    
                // search from the next position
                pos = headers.findHeader("Cookie", ++pos);
            }
        }

这样就可以从头部中获取所有的Cookie数据，并返回Cookie的数组集合。

#### 二、Cookie销毁 ####

cookie会有日期生存时间，cookie的销毁操作是浏览器来实现的，tomcat无法完成cookie销毁操作。

#### 三、Cookie创建 ####

cookie创建简单来说就是tomcat通过设置一定的key、value和生存时间让浏览器来创建cookie。

调用HttpServletResponse的addCookie来创建cookie

Cookie testCookie = new Cookie("test", "test");
    testCookie.setMaxAge(30);
    response.addCookie(testCookie);

HttpServletResponse的实现类ResponseFacade调用addCookie

@Override
        public void addCookie(Cookie cookie) {
    
            if (isCommitted()) {
                return;
            }
    
            response.addCookie(cookie);
    
        }

Response的addCookie中会将cookie对象转为String数据并添加到头部中

@Override
        public void addCookie(final Cookie cookie) {
    
            // Ignore any call from an included servlet
            if (included || isCommitted()) {
                return;
            }
    
            cookies.add(cookie);
    	//将cookie对象转为String头部数据
            String header = generateCookieString(cookie);
            //if we reached here, no exception, cookie is valid
            // the header name is Set-Cookie for both "old" and v.1 ( RFC2109 )
            // RFC2965 is not supported by browsers and the Servlet spec
            // asks for 2109.
    	//将cookie值添加到头部中
            addHeader("Set-Cookie", header, getContext().getCookieProcessor().getCharset());
        }

[Tomcat_--Session]: http://blog.csdn.net/qq924862077/
[Image 1]: