Shiro系列教程 AccessControlFilter源碼分析
2022-02-14 10:37:31

public abstract class AbstractFilter extends ServletContextSupport implements Filter {

    private static transient final Logger log = LoggerFactory.getLogger(AbstractFilter.class);


    protected FilterConfig filterConfig;


    public FilterConfig getFilterConfig() {
        return filterConfig;
    }


    public void setFilterConfig(FilterConfig filterConfig) {
        this.filterConfig = filterConfig;
        setServletContext(filterConfig.getServletContext());
    }

    //獲取filter的配置參數
    protected String getInitParam(String paramName) {
        FilterConfig config = getFilterConfig();
        if (config != null) {
            return StringUtils.clean(config.getInitParameter(paramName));
        }
        return null;
    }

    //filter初始化方法
    public final void init(FilterConfig filterConfig) throws ServletException {
        //設置配置信息對象FilterConfig
        setFilterConfig(filterConfig);
        try {
            //初始化完畢后回調
            onFilterConfigSet();
        } catch (Exception e) {
            if (e instanceof ServletException) {
                throw (ServletException) e;
            } else {
                if (log.isErrorEnabled()) {
                    log.error("Unable to start Filter: [" + e.getMessage() + "].", e);
                }
                throw new ServletException(e);
            }
        }
    }


    protected void onFilterConfigSet() throws Exception {
    }

}

public abstract class NameableFilter extends AbstractFilter implements Nameable {


    //給filter加了名字
    private String name;

    //獲取名字
    protected String getName() {
        //如果為空則返回web.xml filter-name的值
        if (this.name == null) {
            FilterConfig config = getFilterConfig();
            if (config != null) {
                this.name = config.getFilterName();
            }
        }

        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    protected StringBuilder toStringBuilder() {
        String name = getName();
        if (name == null) {
            return super.toStringBuilder();
        } else {
            StringBuilder sb = new StringBuilder();
            sb.append(name);
            return sb;
        }
    }

}

public abstract class OncePerRequestFilter extends NameableFilter {

    //后綴
    public static final String ALREADY_FILTERED_SUFFIX = ".FILTERED";

    //是允許此filter處理
    private boolean enabled = true; //most filters wish to execute when configured, so default to true

    public boolean isEnabled() {
        return enabled;
    }

    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }


    public final void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
            throws ServletException, IOException {
        //獲得一個key用來標識當前request(請求)已經執行過一次doFilterInternal
        String alreadyFilteredAttributeName = getAlreadyFilteredAttributeName();

        //判斷是否已經執行過doFilterInternal
        if ( request.getAttribute(alreadyFilteredAttributeName) != null ) {
            log.trace("Filter '{}' already executed.  Proceeding without invoking this filter.", getName());
            //跳過當前filter的處理，直接走后續邏輯(說白了就是脫離shiro的處理)
            filterChain.doFilter(request, response);
        } else //noinspection deprecation
            //判斷是否允許執行doFilterInternal 默認是允許的，不走下面的邏輯
            if (/* added in 1.2: */ !isEnabled(request, response) ||
                /* retain backwards compatibility: */ shouldNotFilter(request) ) {
            log.debug("Filter '{}' is not enabled for the current request.  Proceeding without invoking this filter.",
                    getName());
            filterChain.doFilter(request, response);
        } else {
            // Do invoke this filter...

            log.trace("Filter '{}' not yet executed.  Executing now.", getName());
            //設置標識
            request.setAttribute(alreadyFilteredAttributeName, Boolean.TRUE);

            //執行doFilterInternal邏輯，該方法由子類重寫來執行具體的shiro邏輯
            try {
                doFilterInternal(request, response, filterChain);
            } finally {
                // Once the request has finished, we're done and we don't
                // need to mark as 'already filtered' any more.
                request.removeAttribute(alreadyFilteredAttributeName);
            }
        }
    }


    @SuppressWarnings({"UnusedParameters"})
    protected boolean isEnabled(ServletRequest request, ServletResponse response) throws ServletException, IOException {
        return isEnabled();
    }

    protected String getAlreadyFilteredAttributeName() {
        String name = getName();
        if (name == null) {
            name = getClass().getName();
        }
        //名稱加上后綴
        return name + ALREADY_FILTERED_SUFFIX;
    }


    @Deprecated
    @SuppressWarnings({"UnusedDeclaration"})
    protected boolean shouldNotFilter(ServletRequest request) throws ServletException {
        return false;
    }

    //由子類重寫,這個方法最多被執行一次
    protected abstract void doFilterInternal(ServletRequest request, ServletResponse response, FilterChain chain)
            throws ServletException, IOException;
}

//一個AOP的類，在執行chain.doFilter(request, response); 添加了前置 后置 最終三個環繞方法.
public abstract class AdviceFilter extends OncePerRequestFilter {


    //AOP方法
    protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {
        return true;
    }


    //AOP方法
    @SuppressWarnings({"UnusedDeclaration"})
    protected void postHandle(ServletRequest request, ServletResponse response) throws Exception {
    }


    AOP方法
    @SuppressWarnings({"UnusedDeclaration"})
    public void afterCompletion(ServletRequest request, ServletResponse response, Exception exception) throws Exception {
    }


    protected void executeChain(ServletRequest request, ServletResponse response, FilterChain chain) throws Exception {
        chain.doFilter(request, response);
    }

    public void doFilterInternal(ServletRequest request, ServletResponse response, FilterChain chain)
            throws ServletException, IOException {

        Exception exception = null;

        try {

            //執行前置AOP方法 根據返回值continueChain覺得是否繼續執行chain.doFilter(request, response);
            boolean continueChain = preHandle(request, response);
            if (log.isTraceEnabled()) {
                log.trace("Invoked preHandle method.  Continuing chain?: [" + continueChain + "]");
            }

            //如果preHandle返回true則執行
            if (continueChain) {
                executeChain(request, response, chain);
            }

            //如果不出異常則執行postHandle
            postHandle(request, response);
            if (log.isTraceEnabled()) {
                log.trace("Successfully invoked postHandle method");
            }

        } catch (Exception e) {
            exception = e;
        } finally {
            //異常與否都在最后執行
            cleanup(request, response, exception);
        }
    }

    protected void cleanup(ServletRequest request, ServletResponse response, Exception existing)
            throws ServletException, IOException {
        Exception exception = existing;
        try {
            //AOP方法
            afterCompletion(request, response, exception);
            if (log.isTraceEnabled()) {
                log.trace("Successfully invoked afterCompletion method.");
            }
        } catch (Exception e) {
            if (exception == null) {
                exception = e;
            } else {
                log.debug("afterCompletion implementation threw an exception.  This will be ignored to " +
                        "allow the original source exception to be propagated.", e);
            }
        }
        //如果executeChain方法出現異常則在這里拋出
        if (exception != null) {
            if (exception instanceof ServletException) {
                throw (ServletException) exception;
            } else if (exception instanceof IOException) {
                throw (IOException) exception;
            } else {
                if (log.isDebugEnabled()) {
                    String msg = "Filter execution resulted in an unexpected Exception " +
                            "(not IOException or ServletException as the Filter API recommends).  " +
                            "Wrapping in ServletException and propagating.";
                    log.debug(msg);
                }
                throw new ServletException(exception);
            }
        }
    }
}

public abstract class PathMatchingFilter extends AdviceFilter implements PathConfigProcessor {

    //路徑匹配器
    //匹配規則http://blog.csdn.net/nimasike/article/details/70739982
    protected PatternMatcher pathMatcher = new AntPathMatcher();

    //這里存的內容是 例如:
    // /login.jsp [anon]
    // /index.jsp [bar, baz]
    protected Map<String, Object> appliedPaths = new LinkedHashMap<String, Object>();

    //假設你的配置是 /user/** = user, roles[admin, foo]
    //如果這個類是roles path為/user/**   config為admin, foo
    //如果這個類是user path為/user/**  config為null
    public Filter processPathConfig(String path, String config) {
        String[] values = null;
        if (config != null) {
            values = split(config);
        }

        this.appliedPaths.put(path, values);
        return this;
    }


    //獲得請求路徑
    //假設請求http://localhost/index.jsp?id=18
    //則返回值為/index.jsp
    protected String getPathWithinApplication(ServletRequest request) {
        return WebUtils.getPathWithinApplication(WebUtils.toHttp(request));
    }

    //請求路徑與path匹配
    protected boolean pathsMatch(String path, ServletRequest request) {
        String requestURI = getPathWithinApplication(request);
        log.trace("Attempting to match pattern '{}' with current requestURI '{}'...", path, requestURI);
        return pathsMatch(path, requestURI);
    }


    protected boolean pathsMatch(String pattern, String path) {
        return pathMatcher.matches(pattern, path);
    }


    //這個方法返回false則請求會被中斷
    protected boolean preHandle(ServletRequest request, ServletResponse response) throws Exception {

        if (this.appliedPaths == null || this.appliedPaths.isEmpty()) {
            if (log.isTraceEnabled()) {
                log.trace("appliedPaths property is null or empty.  This Filter will passthrough immediately.");
            }
            return true;
        }

        //首先進行路徑匹配
        for (String path : this.appliedPaths.keySet()) {
            // If the path does match, then pass on to the subclass implementation for specific checks
            //(first match 'wins'):
            if (pathsMatch(path, request)) { 
                //匹配到路徑執行isFilterChainContinued
                log.trace("Current requestURI matches pattern '{}'.  Determining filter chain execution...", path);
                Object config = this.appliedPaths.get(path);
                return isFilterChainContinued(request, response, path, config);
            }
        }

        //如果沒有匹配允許執行
        return true;
    }


    @SuppressWarnings({"JavaDoc"})
    private boolean isFilterChainContinued(ServletRequest request, ServletResponse response,
                                           String path, Object pathConfig) throws Exception {

        //這里判斷是否允許shiro執行 默認允許
        if (isEnabled(request, response, path, pathConfig)) { //isEnabled check added in 1.2
            if (log.isTraceEnabled()) {
                log.trace("Filter '{}' is enabled for the current request under path '{}' with config [{}].  " +
                        "Delegating to subclass implementation for 'onPreHandle' check.",
                        new Object[]{getName(), path, pathConfig});
            }
            //則執行onPreHandle,根據返回值來決定是否繼續允許執行后續的filter
            //所有shiro-fiter都會重寫此方法，如果返回false 則請求會被中斷
            return onPreHandle(request, response, pathConfig);
        }

        if (log.isTraceEnabled()) {
            log.trace("Filter '{}' is disabled for the current request under path '{}' with config [{}].  " +
                    "The next element in the FilterChain will be called immediately.",
                    new Object[]{getName(), path, pathConfig});
        }

        return true;
    }


    protected boolean onPreHandle(ServletRequest request, ServletResponse response, Object mappedValue) throws Exception {
        return true;
    }


    @SuppressWarnings({"UnusedParameters"})
    protected boolean isEnabled(ServletRequest request, ServletResponse response, String path, Object mappedValue)
            throws Exception {
        return isEnabled(request, response);
    }
}

public abstract class AccessControlFilter extends PathMatchingFilter {

    //默認登錄頁
    public static final String DEFAULT_LOGIN_URL = "/login.jsp";

    public static final String GET_METHOD = "GET";

    public static final String POST_METHOD = "POST";

    private String loginUrl = DEFAULT_LOGIN_URL;

    public String getLoginUrl() {
        return loginUrl;
    }

    public void setLoginUrl(String loginUrl) {
        this.loginUrl = loginUrl;
    }

    protected Subject getSubject(ServletRequest request, ServletResponse response) {
        return SecurityUtils.getSubject();
    }

    //子類根據業務規則覺得是否中斷請求
    protected abstract boolean isAccessAllowed(ServletRequest request, ServletResponse response, Object mappedValue) throws Exception;

    protected boolean onAccessDenied(ServletRequest request, ServletResponse response, Object mappedValue) throws Exception {
        return onAccessDenied(request, response);
    }

    protected abstract boolean onAccessDenied(ServletRequest request, ServletResponse response) throws Exception;

    //這里調用的isAccessAllowed
    public boolean onPreHandle(ServletRequest request, ServletResponse response, Object mappedValue) throws Exception {
        return isAccessAllowed(request, response, mappedValue) || onAccessDenied(request, response, mappedValue);
    }

    protected boolean isLoginRequest(ServletRequest request, ServletResponse response) {
        return pathsMatch(getLoginUrl(), request);
    }

    //保存請求路徑調轉到登錄頁面
    protected void saveRequestAndRedirectToLogin(ServletRequest request, ServletResponse response) throws IOException {
        saveRequest(request);
        redirectToLogin(request, response);
    }

    //保存請求路徑
    protected void saveRequest(ServletRequest request) {
        WebUtils.saveRequest(request);
    }

    //跳轉到登錄頁
    protected void redirectToLogin(ServletRequest request, ServletResponse response) throws IOException {
        String loginUrl = getLoginUrl();
        WebUtils.issueRedirect(request, response, loginUrl);
    }

}