首先我們看一下我們客戶端中web.xml中的攔截器配置

    <filter>
        <filter-name>CASFilter</filter-name>
        <filter-class>org.jasig.cas.client.authentication.AuthenticationFilter</filter-class>
        <init-param>
            <param-name>casServerLoginUrl</param-name>
            <param-value
 
>http://ssocas.ane56.com:8080/cas/login</param-value>
        </init-param>
        <init-param>
            <param-name>serverName</param-name>
            <param-value>http://ptl.ane56.com:8080</param-value>
        </init-param>
    </filter>
    <filter-mapping
 
>
        <filter-name>CASFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

重要的操作無非就是客戶端jar包中的AuthenticationFilter，然後上網查了下，無非就是將這個攔截方法重寫。

反編譯一下

然後將該攔截器貼一下

package org.jasig.cas.client.authentication;

import java.io.IOException;
import javax.servlet.FilterChain;
import
 
 javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.apache.commons.logging.Log;
import org.jasig.cas.client.util.AbstractCasFilter;
import org.jasig.cas.client.util.CommonUtils;
import org.jasig.cas.client.validation.Assertion;

public class AuthenticationFilter extends AbstractCasFilter
{
  private String casServerLoginUrl;
  private boolean renew = false;

  private boolean gateway = false;

  private GatewayResolver gatewayStorage = new DefaultGatewayResolverImpl();

  protected void initInternal(FilterConfig filterConfig) throws ServletException {
    if (!isIgnoreInitConfiguration()) {
      super.initInternal(filterConfig);
      setCasServerLoginUrl(getPropertyFromInitParams(filterConfig, "casServerLoginUrl", null));
      this.log.trace("Loaded CasServerLoginUrl parameter: " + this.casServerLoginUrl);
      setRenew(parseBoolean(getPropertyFromInitParams(filterConfig, "renew", "false")));
      this.log.trace("Loaded renew parameter: " + this.renew);
      setGateway(parseBoolean(getPropertyFromInitParams(filterConfig, "gateway", "false")));
      this.log.trace("Loaded gateway parameter: " + this.gateway);

      String gatewayStorageClass = getPropertyFromInitParams(filterConfig, "gatewayStorageClass", null);

      if (gatewayStorageClass != null)
        try {
          this.gatewayStorage = ((GatewayResolver)Class.forName(gatewayStorageClass).newInstance());
        } catch (Exception e) {
          this.log.error(e, e);
          throw new ServletException(e);
        }
    }
  }

  public void init()
  {
    super.init();
    CommonUtils.assertNotNull(this.casServerLoginUrl, "casServerLoginUrl cannot be null.");
  }

  public final void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    HttpServletRequest request = (HttpServletRequest)servletRequest;
    HttpServletResponse response = (HttpServletResponse)servletResponse;
    HttpSession session = request.getSession(false);
    Assertion assertion = session != null ? (Assertion)session.getAttribute("_const_cas_assertion_") : null;

    if (assertion != null) {
      filterChain.doFilter(request, response);
      return;
    }

    String serviceUrl = constructServiceUrl(request, response);
    String ticket = CommonUtils.safeGetParameter(request, getArtifactParameterName());
    boolean wasGatewayed = this.gatewayStorage.hasGatewayedAlready(request, serviceUrl);

    if ((CommonUtils.isNotBlank(ticket)) || (wasGatewayed)) {
      filterChain.doFilter(request, response);
      return;
    }

    this.log.debug("no ticket and no assertion found");
    String modifiedServiceUrl;
    String modifiedServiceUrl;
    if (this.gateway) {
      this.log.debug("setting gateway attribute in session");
      modifiedServiceUrl = this.gatewayStorage.storeGatewayInformation(request, serviceUrl);
    } else {
      modifiedServiceUrl = serviceUrl;
    }

    if (this.log.isDebugEnabled()) {
      this.log.debug("Constructed service url: " + modifiedServiceUrl);
    }

    String urlToRedirectTo = CommonUtils.constructRedirectUrl(this.casServerLoginUrl, getServiceParameterName(), modifiedServiceUrl, this.renew, this.gateway);

    if (this.log.isDebugEnabled()) {
      this.log.debug("redirecting to \"" + urlToRedirectTo + "\"");
    }

    response.sendRedirect(urlToRedirectTo);
  }

  public final void setRenew(boolean renew) {
    this.renew = renew;
  }

  public final void setGateway(boolean gateway) {
    this.gateway = gateway;
  }

  public final void setCasServerLoginUrl(String casServerLoginUrl) {
    this.casServerLoginUrl = casServerLoginUrl;
  }

  public final void setGatewayStorage(GatewayResolver gatewayStorage) {
    this.gatewayStorage = gatewayStorage;
  }
}

   我們重新定義一個類ReAuthenticationFilter，也繼承AbstractCasFilter類，在該類中完全複製AuthenticationFilter類中的內容，並在我們自己的攔截器做如下修改：

 1.增加excepPaths屬性，用於存放要排除過濾的路徑，採用陣列方式存放，應對多個url頭的攔截。

private String[] excludePaths;

 2.修改initInternal方法、從web.xml配置中解析出要排除過濾的路徑

 protected void initInternal(final FilterConfig filterConfig) throws ServletException {
        if (!isIgnoreInitConfiguration()) {
            super.initInternal(filterConfig);
            setCasServerLoginUrl(getPropertyFromInitParams(filterConfig, "casServerLoginUrl", null));
            log.trace("Loaded CasServerLoginUrl parameter: " + this.casServerLoginUrl);
            setRenew(parseBoolean(getPropertyFromInitParams(filterConfig, "renew", "false")));
            log.trace("Loaded renew parameter: " + this.renew);
            setGateway(parseBoolean(getPropertyFromInitParams(filterConfig, "gateway", "false")));
            log.trace("Loaded gateway parameter: " + this.gateway);
            final String gatewayStorageClass = getPropertyFromInitParams(filterConfig, "gatewayStorageClass", null);
            if (gatewayStorageClass != null) {
                try {
                    this.gatewayStorage = (GatewayResolver) Class.forName(gatewayStorageClass).newInstance();
                } catch (final Exception e) {
                    log.error(e,e);
                    throw new ServletException(e);
                }
            }


            //攔截器過濾修改************begin*************************
            String _excludePaths = getPropertyFromInitParams(filterConfig, "excepPaths", null);
            if(CommonUtils.isNotBlank(_excludePaths)){
             setExcludePaths(_excludePaths.trim().split(","));
            }
            //攔截器過濾修改************end************************
        }
    }

 3.修改doFilter方法、判斷請求路徑是否需要過濾

    public final void doFilter(final ServletRequest servletRequest, final ServletResponse servletResponse, final FilterChain filterChain) throws IOException, ServletException {
        final HttpServletRequest request = (HttpServletRequest) servletRequest;
        final HttpServletResponse response = (HttpServletResponse) servletResponse;
        final HttpSession session = request.getSession(false);
        final Assertion assertion = session != null ? (Assertion) session.getAttribute(CONST_CAS_ASSERTION) : null;


        //攔截器過濾修改************begin********************
        boolean isAir = request.getParameter("isAir")!=null && "true".equals(request.getParameter("isAir"));
        if (isAir ) {
            filterChain.doFilter(request, response);
        }

        String uri = request.getRequestURI()+request.getQueryString;
        boolean isInWhiteList = false;
        if(excludePaths!=null && excludePaths.length>0 && uri!=null){
            for(String path : excludePaths){
             if(CommonUtils.isNotBlank(path)){
              isInWhiteList = uri.indexOf(path.trim())>-1;
               if(isInWhiteList){
                 break;
               }
              }
            }
        }
        
        if(isInWhiteList){
            filterChain.doFilter(request, response);
            return;
           }
        //攔截器過濾修改************end********************************
        
        if (assertion != null) {
            filterChain.doFilter(request, response);
            return;
        }
        final String serviceUrl = constructServiceUrl(request, response);
        final String ticket = CommonUtils.safeGetParameter(request,getArtifactParameterName());
        final boolean wasGatewayed = this.gatewayStorage.hasGatewayedAlready(request, serviceUrl);
        if (CommonUtils.isNotBlank(ticket) || wasGatewayed) {
            filterChain.doFilter(request, response);
            return;
        }
        final String modifiedServiceUrl;
        log.debug("no ticket and no assertion found");
        if (this.gateway) {
            log.debug("setting gateway attribute in session");
            modifiedServiceUrl = this.gatewayStorage.storeGatewayInformation(request, serviceUrl);
        } else {
            modifiedServiceUrl = serviceUrl;
        }
        if (log.isDebugEnabled()) {
            log.debug("Constructed service url: " + modifiedServiceUrl);
        }
        final String urlToRedirectTo = CommonUtils.constructRedirectUrl(this.casServerLoginUrl, getServiceParameterName(), modifiedServiceUrl, this.renew, this.gateway);
        if (log.isDebugEnabled()) {
            log.debug("redirecting to \"" + urlToRedirectTo + "\"");
        }
        response.sendRedirect(urlToRedirectTo);
    }

   4.修改完以上方法、則web.xml中還需要修改兩點，修改後的web.xml配置如下：

    <filter>
        <filter-name>CASFilter</filter-name>
        <filter-class>org.jasig.cas.client.authentication.ReAuthenticationFilter</filter-class>
        <init-param>
            <param-name>casServerLoginUrl</param-name>
            <param-value>http://ssocas.ane56.com:8080/cas/login</param-value>
        </init-param>
        <init-param>
            <param-name>serverName</param-name>
            <param-value>http://ptl.ane56.com:8080</param-value>
        </init-param>
        <init-param>
           <description>cas not filter url</description>
           <param-name>exceptPaths</param-name>
           <param-value>isAir=true,/user/login</param-value>
        </init-param>
    </filter>

慣例圖示

從request獲取各種路徑總結 
request.getRealPath("url"); // 虛擬目錄對映為實際目錄

request.getRealPath("./");    // 網頁所在的目錄

request.getRealPath("../"); // 網頁所在目錄的上一層目錄

request.getContextPath();    // 應用的web目錄的名稱

如http://localhost:7001/bookStore/ 
/bookStore/ => [contextPath] (request.getContextPath())

獲取Web專案的全路徑 
String strDirPath = request.getSession().getServletContext().getRealPath("/");

以工程名為TEST為例：

(1)得到包含工程名的當前頁面全路徑：request.getRequestURI() 
結果：/TEST/test.jsp

(2)得到工程名：request.getContextPath() 
結果：/TEST

(3)得到當前頁面所在目錄下全名稱：request.getServletPath() 
結果：如果頁面在jsp目錄下 /TEST/jsp/test.jsp

(4)得到頁面所在伺服器的全路徑：application.getRealPath("頁面.jsp") 
結果：D:\resin\webapps\TEST\test.jsp

(5)得到頁面所在伺服器的絕對路徑：absPath=new java.io.File(application.getRealPath(request.getRequestURI())).getParent(); 
結果：D:\resin\webapps\TEST

2.在類中取得路徑：

(1)類的絕對路徑：Class.class.getClass().getResource("/").getPath() 
結果：/D:/TEST/WebRoot/WEB-INF/classes/pack/

(2)得到工程的路徑：System.getProperty("user.dir") 
結果：D:\TEST

3.在Servlet中取得路徑：

(1)得到工程目錄：request.getSession().getServletContext().getRealPath("") 引數可具體到包名。 
結果：E:\Tomcat\webapps\TEST

(3)得到相對地址：request.getRequestURI() 
結果：/TEST/test