struts2 type="redirect"源码解析

首先解释一下几个名词：

request.getRequestDispatcher()是请求转发，前后页面共享一个request ;

response.sendRedirect()是重新定向，前后页面不是一个request。

RequestDispatcher.forward()是在服务器端运行;

HttpServletResponse.sendRedirect()是通过向客户浏览器发送命令来完成.

所以RequestDispatcher.forward()对于浏览器来说是“透明的”；

而HttpServletResponse.sendRedirect()则不是。

这么光说，一定很难理解，看一个例子。

情景：qq登录上，你直接点击邮箱他就会直接登录邮箱。

假如请求路径：http://localhost:8080/test/web/skiplogin.action?url=/mail/productManage.action&sessionid=1000111&&phoneId=100000

action中会把url，sessionid，phoneId解析出来，然后跳转到url，假如你是用的是

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RequestDispatcher dispatcher = request.getRequestDispatcher(url_pa); //          dispatcher.forward(request, response); //          使用这个方法转发，地址不变，这是在服务器端完成的

浏览器上的地址栏里的路径是不会变的。

假如使用response.sendRedirect(basePath+finalLocation);

浏览器上的路径就会变成：http://localhost:8080/test/mail/productManage.action。

struts2 result返回类型type="redirect"时，查看它的源代码其实就是做了一次重新跳转。

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* $Id: ServletRedirectResult.java 1188965 2011-10-25 23:19:48Z mcucchiara $   package org.apache.struts2.dispatcher;   import com.opensymphony.xwork2.ActionContext; import com.opensymphony.xwork2.ActionInvocation; import com.opensymphony.xwork2.config.entities.ResultConfig; import com.opensymphony.xwork2.inject.Inject; import com.opensymphony.xwork2.util.logging.Logger; import com.opensymphony.xwork2.util.logging.LoggerFactory; import com.opensymphony.xwork2.util.reflection.ReflectionException; import com.opensymphony.xwork2.util.reflection.ReflectionExceptionHandler; import org.apache.struts2.ServletActionContext; import org.apache.struts2.dispatcher.mapper.ActionMapper; import org.apache.struts2.dispatcher.mapper.ActionMapping; import org.apache.struts2.views.util.UrlHelper;   import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.util.*;   import static javax.servlet.http.HttpServletResponse.SC_FOUND;   /**  * <!-- START SNIPPET: description -->  *  * Calls the {<a href="http://my.oschina.net/link1212" target="_blank" rel="nofollow">@link</a>  HttpServletResponse#sendRedirect(String) sendRedirect}  * method to the location specified. The response is told to redirect the  * browser to the specified location (a new request from the client). The  * consequence of doing this means that the action (action instance, action  * errors, field errors, etc) that was just executed is lost and no longer  * available. This is because actions are built on a single-thread model. The  * only way to pass data is through the session or with web parameters  * (url?name=value) which can be OGNL expressions.  *  * <!-- END SNIPPET: description -->  * <p/>  * <b>This result type takes the following parameters:</b>  *  * <!-- START SNIPPET: params -->  *  * <ul>  *  * <li><b>location (default)</b> - the location to go to after execution.</li>  *  * <li><b>parse</b> - true by default. If set to false, the location param will  * not be parsed for Ognl expressions.</li>  *  * <li><b>anchor</b> - Optional.  Also known as "fragment" or colloquially as  * "hash".  You can specify an anchor for a result.</li>  * </ul>  *  * <p>  * This result follows the same rules from {<a href="http://my.oschina.net/link1212" target="_blank" rel="nofollow">@link</a>  StrutsResultSupport}.  * </p>  *  * <!-- END SNIPPET: params -->  *  * <b>Example:</b>  *  * <pre>  * <!-- START SNIPPET: example -->  * &lt;!--  *   The redirect URL generated will be:  *   /foo.jsp#FRAGMENT  * --&gt;  * &lt;result name="success" type="redirect"&gt;  *   &lt;param name="location"&gt;foo.jsp&lt;/param&gt;  *   &lt;param name="parse"&gt;false&lt;/param&gt;  *   &lt;param name="anchor"&gt;FRAGMENT&lt;/param&gt;  * &lt;/result&gt;  * <!-- END SNIPPET: example -->  * </pre>  *  */ public class ServletRedirectResult extends StrutsResultSupport implements ReflectionExceptionHandler {       private static final long serialVersionUID = 6316947346435301270L;       private static final Logger LOG = LoggerFactory.getLogger(ServletRedirectResult.class);       protected boolean prependServletContext = true;       protected ActionMapper actionMapper;       protected int statusCode = SC_FOUND;       protected boolean suppressEmptyParameters = false;       protected Map<String, String> requestParameters = new LinkedHashMap<String, String>();       protected String anchor;       public ServletRedirectResult() {         super();     }       public ServletRedirectResult(String location) {         this(location, null);     }       public ServletRedirectResult(String location, String anchor) {         super(location);         this.anchor = anchor;     }       @Inject     public void setActionMapper(ActionMapper mapper)     {         this.actionMapper = mapper;     }       public void setStatusCode(int code)     {         this.statusCode = code;     }       /**      * Set the optional anchor value.      *      * @param anchor      */     public void setAnchor(String anchor)     {         this.anchor = anchor;     }       /**      * Sets whether or not to prepend the servlet context path to the redirected      * URL.      *      * @param prependServletContext      *            <tt>true</tt> to prepend the location with the servlet context      *            path, <tt>false</tt> otherwise.      */     public void setPrependServletContext(boolean prependServletContext)     {         this.prependServletContext = prependServletContext;     }       public void execute(ActionInvocation invocation) throws Exception     {         if (anchor != null)         {             anchor = conditionalParse(anchor, invocation);         }           super.execute(invocation);     }       /**      * Redirects to the location specified by calling      * {<a href="http://my.oschina.net/link1212" target="_blank" rel="nofollow">@link</a>  HttpServletResponse#sendRedirect(String)}.      *      * @param finalLocation      *            the location to redirect to.      * @param invocation      *            an encapsulation of the action execution state.      * @throws Exception      *             if an error occurs when redirecting.      */     protected void doExecute(String finalLocation, ActionInvocation invocation) throws Exception     {         ActionContext ctx = invocation.getInvocationContext();         HttpServletRequest request = (HttpServletRequest) ctx.get(ServletActionContext.HTTP_REQUEST);         HttpServletResponse response = (HttpServletResponse) ctx.get(ServletActionContext.HTTP_RESPONSE);           if (isPathUrl(finalLocation))         {             if (!finalLocation.startsWith("/"))             {                 ActionMapping mapping = actionMapper.getMapping(request, Dispatcher.getInstance().getConfigurationManager());                 String namespace = null;                 if (mapping != null)                 {                     namespace = mapping.getNamespace();                 }                   if ((namespace != null) && (namespace.length() > 0) && (!"/".equals(namespace)))                 {                     finalLocation = namespace + "/" + finalLocation;                 }                 else                 {                     finalLocation = "/" + finalLocation;                 }             }               // if the URL's are relative to the servlet context, append the servlet context path             if (prependServletContext && (request.getContextPath() != null) && (request.getContextPath().length() > 0))             {                 finalLocation = request.getContextPath() + finalLocation;             }               ResultConfig resultConfig = invocation.getProxy().getConfig().getResults().get(invocation.getResultCode());             if (resultConfig != null)             {                 Map<String, String> resultConfigParams = resultConfig.getParams();                   for (Map.Entry<String, String> e : resultConfigParams.entrySet())                 {                     if (!getProhibitedResultParams().contains(e.getKey()))                     {                         String potentialValue = e.getValue() == null ? "" : conditionalParse(e.getValue(), invocation);                         if (!suppressEmptyParameters || ((potentialValue != null) && (potentialValue.length() > 0)))                         {                             requestParameters.put(e.getKey(), potentialValue);                         }                     }                 }             }               StringBuilder tmpLocation = new StringBuilder(finalLocation);             UrlHelper.buildParametersString(requestParameters, tmpLocation, "&");               // add the anchor             if (anchor != null)             {                 tmpLocation.append('#').append(anchor);             }               finalLocation = response.encodeRedirectURL(tmpLocation.toString());         }           if (LOG.isDebugEnabled())         {             LOG.debug("Redirecting to finalLocation " + finalLocation);         }           sendRedirect(response, finalLocation);//////看这个方法     }       protected List<String> getProhibitedResultParams()     {         return Arrays.asList(DEFAULT_PARAM, "namespace", "method", "encode", "parse", "location", "prependServletContext", "suppressEmptyParameters", "anchor");     }       /**      * Sends the redirection. Can be overridden to customize how the redirect is      * handled (i.e. to use a different status code)      *      * @param response      *            The response      * @param finalLocation      *            The location URI      * @throws IOException      */     protected void sendRedirect(HttpServletResponse response, String finalLocation) throws IOException     {         if (SC_FOUND == statusCode)         {             response.sendRedirect(finalLocation);//就是做了一个这样的事情         }         else         {             response.setStatus(statusCode);             response.setHeader("Location", finalLocation);             response.getWriter().write(finalLocation);             response.getWriter().close();         }       }       private static boolean isPathUrl(String url)     {         // filter out "http:", "https:", "mailto:", "file:", "ftp:"         // since the only valid places for : in URL's is before the path specification         // either before the port, or after the protocol         return (url.indexOf(':') == -1);     }       /**      * Sets the suppressEmptyParameters option      *      * @param suppressEmptyParameters      *            The new value for this option      */     public void setSuppressEmptyParameters(boolean suppressEmptyParameters)     {         this.suppressEmptyParameters = suppressEmptyParameters;     }       /**      * Adds a request parameter to be added to the redirect url      *      * @param key      *            The parameter name      * @param value      *            The parameter value      */     public ServletRedirectResult addParameter(String key, Object value)     {         requestParameters.put(key, String.valueOf(value));         return this;     }       public void handle(ReflectionException ex)     {         // Only log as debug as they are probably parameters to be appended to the url         LOG.debug(ex.getMessage(), ex);     } }

我action中写的代码：

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import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession;     @SuppressWarnings("serial") public class SkipLoginAction extends Action {           @Inject     private PhoneService phoneService;     /**      * <a href="http://my.oschina.net/u/556800" target="_blank" rel="nofollow">@return</a>      * @throws ActionException      */     public void index() throws ActionException {         try {             HttpServletRequest request =getRequest();             HttpServletResponse response =  getResponse();             AuthBean authBean = null; //          RequestDispatcher dispatcher = request.getRequestDispatcher(url_pa); //          dispatcher.forward(request, response); //          使用这个方法转发，地址不变，这是在服务器端完成的                           //客户端传来的参数             String sessionid =  request.getParameter("sessionid");             String finalLocation = request.getParameter("url");             String phoneId =  request.getParameter("phoneId");                           String contextpath = request.getContextPath();             String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + contextpath;               if(!StringUtils.isBlank(finalLocation) && !StringUtils.isBlank(sessionid) ){                                   if(!finalLocation.startsWith("/")){                     finalLocation = "/" + finalLocation;                 }                                   HttpSession session = request.getSession();                 authBean = getAuthBean();                 if(authBean!=null){                     if(phoneId.equals(authBean.getPhoneId())){                         response.sendRedirect(basePath+finalLocation);                         return;                     }                 }                 ////获得数据库中的user中的sessionid字段                 Phone phone = phoneService.findPhoneByPhoneId(phoneId);                 if(phone!=null){                     if( sessionid.equals(phone.getSessionid())){                         // 用户登陆成功                         authBean = null;                         authBean = new AuthBean();                         。。。。                         response.sendRedirect(basePath+finalLocation);                         return;                     }                 }             }             //最后不符合条件统一跳到登陆界面             finalLocation = "/web/login.index";             response.sendRedirect(basePath+finalLocation);         } catch (Exception e) {             throw new ActionException("失败");         }     } }