Tomcat源码学习--Cookie创建和销毁

上一篇博客​​Tomcat源码学习--Session创建销毁​​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。

@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());
    }