Struts（16）异常处理

Struts提供了一个更简单的方式来处理未捕获的异常，并将用户重定向到一个专门的错误页面。您可以轻松地Struts配置到不同的异常有不同的错误页面。

Struts的异常处理所使用的“exception”拦截容易。“exception”拦截器作为默认的栈的一部分，所以不必做任何额外的配置。它可为准备使用的盒。让我们看到了一个简单的Hello World示例进行一些修改在HelloWorldAction.java文件。在这里，我们特意推出了一个空指针异常在我们HelloWorldAction动作代码。

<span class="kwd" style="margin: 0px; padding: 0px;">package</span><span class="pln" style="margin: 0px; padding: 0px;"> com</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">yiibai</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">struts2</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="kwd" style="margin: 0px; padding: 0px;">import</span><span class="pln" style="margin: 0px; padding: 0px;"> com</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">opensymphony</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">xwork2</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="typ" style="margin: 0px; padding: 0px;">ActionSupport</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">class</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">HelloWorldAction</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">extends</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">ActionSupport</span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">private</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> name</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> execute</span><span class="pun" style="margin: 0px; padding: 0px;">(){</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> x </span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">null</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">      x </span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;"> x</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">substring</span><span class="pun" style="margin: 0px; padding: 0px;">(</span><span class="lit" style="margin: 0px; padding: 0px;">0</span><span class="pun" style="margin: 0px; padding: 0px;">);</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">return</span><span class="pln" style="margin: 0px; padding: 0px;"> SUCCESS</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> getName</span><span class="pun" style="margin: 0px; padding: 0px;">()</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">return</span><span class="pln" style="margin: 0px; padding: 0px;"> name</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="kwd" style="margin: 0px; padding: 0px;">public</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="kwd" style="margin: 0px; padding: 0px;">void</span><span class="pln" style="margin: 0px; padding: 0px;"> setName</span><span class="pun" style="margin: 0px; padding: 0px;">(</span><span class="typ" style="margin: 0px; padding: 0px;">String</span><span class="pln" style="margin: 0px; padding: 0px;"> name</span><span class="pun" style="margin: 0px; padding: 0px;">)</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;">{</span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="kwd" style="margin: 0px; padding: 0px;">this</span><span class="pun" style="margin: 0px; padding: 0px;">.</span><span class="pln" style="margin: 0px; padding: 0px;">name </span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="pln" style="margin: 0px; padding: 0px;"> name</span><span class="pun" style="margin: 0px; padding: 0px;">;</span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="pun" style="margin: 0px; padding: 0px;">}</span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="pun" style="margin: 0px; padding: 0px;">}</span>

让我们 helloWorld.jsp保持内容如下：

<span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;"><%@</span><span class="pln" style="margin: 0px; padding: 0px;"> page contentType</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"text/html; charset=UTF-8"</span><span class="pln" style="margin: 0px; padding: 0px;"> %></span><span class="pun" style="margin: 0px; padding: 0px;"><%@</span><span class="pln" style="margin: 0px; padding: 0px;"> taglib prefix</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"s"</span><span class="pln" style="margin: 0px; padding: 0px;"> uri</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"/struts-tags"</span><span class="pln" style="margin: 0px; padding: 0px;"> %></span><span class="tag" style="margin: 0px; padding: 0px;"><html></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><head></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><title></span><span class="pln" style="margin: 0px; padding: 0px;">Hello World</span><span class="tag" style="margin: 0px; padding: 0px;"></title></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></head></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><body></span><span class="pln" style="margin: 0px; padding: 0px;">   Hello World, </span><span class="tag" style="margin: 0px; padding: 0px;"><s:property</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">value</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"name"</span><span class="tag" style="margin: 0px; padding: 0px;">/></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></body></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></html></span>

以下是内容index.jsp：

<span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;"><%@</span><span class="pln" style="margin: 0px; padding: 0px;"> page language</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"java"</span><span class="pln" style="margin: 0px; padding: 0px;"> contentType</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"text/html; charset=ISO-8859-1"</span><span class="pln" style="margin: 0px; padding: 0px;">   pageEncoding</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"ISO-8859-1"</span><span class="pln" style="margin: 0px; padding: 0px;">%></span><span class="pun" style="margin: 0px; padding: 0px;"><%@</span><span class="pln" style="margin: 0px; padding: 0px;"> taglib prefix</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"s"</span><span class="pln" style="margin: 0px; padding: 0px;"> uri</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"/struts-tags"</span><span class="pln" style="margin: 0px; padding: 0px;">%>   </span><span class="dec" style="margin: 0px; padding: 0px;"><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><html></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><head></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><title></span><span class="pln" style="margin: 0px; padding: 0px;">Hello World</span><span class="tag" style="margin: 0px; padding: 0px;"></title></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></head></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><body></span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="tag" style="margin: 0px; padding: 0px;"><h1></span><span class="pln" style="margin: 0px; padding: 0px;">Hello World From Struts2</span><span class="tag" style="margin: 0px; padding: 0px;"></h1></span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="tag" style="margin: 0px; padding: 0px;"><form</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">action</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"hello"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="tag" style="margin: 0px; padding: 0px;"><label</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">for</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"name"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">Please enter your name</span><span class="tag" style="margin: 0px; padding: 0px;"></label><br/></span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="tag" style="margin: 0px; padding: 0px;"><input</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">type</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"text"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"name"</span><span class="tag" style="margin: 0px; padding: 0px;">/></span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="tag" style="margin: 0px; padding: 0px;"><input</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">type</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"submit"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">value</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"Say Hello"</span><span class="tag" style="margin: 0px; padding: 0px;">/></span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="tag" style="margin: 0px; padding: 0px;"></form></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></body></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></html></span>

struts.xml 应该像这样：

<span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="pun" style="margin: 0px; padding: 0px;"><?</span><span class="pln" style="margin: 0px; padding: 0px;">xml version</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"1.0"</span><span class="pln" style="margin: 0px; padding: 0px;"> encoding</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"UTF-8"</span><span class="pun" style="margin: 0px; padding: 0px;">?></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="dec" style="margin: 0px; padding: 0px;"><!DOCTYPE struts PUBLIC   "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"   "http://struts.apache.org/dtds/struts-2.0.dtd"></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><struts></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><constant</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"struts.devMode"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">value</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"true"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="tag" style="margin: 0px; padding: 0px;">/></span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="tag" style="margin: 0px; padding: 0px;"><package</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"helloworld"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">extends</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"struts-default"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">           </span><span class="tag" style="margin: 0px; padding: 0px;"><action</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"hello"</span><span class="pln" style="margin: 0px; padding: 0px;">          </span><span class="atn" style="margin: 0px; padding: 0px;">class</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"com.yiibai.struts2.HelloWorldAction"</span><span class="pln" style="margin: 0px; padding: 0px;">          </span><span class="atn" style="margin: 0px; padding: 0px;">method</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"execute"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">         </span><span class="tag" style="margin: 0px; padding: 0px;"><result</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"success"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">/HelloWorld.jsp</span><span class="tag" style="margin: 0px; padding: 0px;"></result></span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="tag" style="margin: 0px; padding: 0px;"></action></span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="tag" style="margin: 0px; padding: 0px;"></package></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></struts></span>

现在右击项目名称，并单击Export > WAR File创建一个WAR文件。然后部署此WAR在Tomcat的webapps目录下。最后，启动Tomcat 服务器和尝试访问URL http://localhost:8080/HelloWorldStruts2/index.jsp。这会给出以下画面：

输入一个值“Struts2”，并提交页面。应该看到以下页面：

在上面的例子所示，默认的异常拦截器做了非常出色的处理异常。现在，让我们创建一个专用的错误页面，我们的例外。创建一个文件名为error.jsp 如以下内容：

<span class="pun" style="margin: 0px; padding: 0px;"><%@</span><span class="pln" style="margin: 0px; padding: 0px;"> page language</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"java"</span><span class="pln" style="margin: 0px; padding: 0px;"> contentType</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"text/html; charset=ISO-8859-1"</span><span class="pln" style="margin: 0px; padding: 0px;">pageEncoding</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"ISO-8859-1"</span><span class="pln" style="margin: 0px; padding: 0px;">%></span><span class="pun" style="margin: 0px; padding: 0px;"><%@</span><span class="pln" style="margin: 0px; padding: 0px;"> taglib prefix</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"s"</span><span class="pln" style="margin: 0px; padding: 0px;"> uri</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"/struts-tags"</span><span class="pln" style="margin: 0px; padding: 0px;">%></span><span class="dec" style="margin: 0px; padding: 0px;"><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><html></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><head></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><title></title></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></head></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><body></span><span class="pln" style="margin: 0px; padding: 0px;">   This is my custom error page</span><span class="tag" style="margin: 0px; padding: 0px;"></body></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></html></span>

Let us now configure Struts to use this this error page in case of an exception. Let us modify thestruts.xml as follows:

<span class="pun" style="margin: 0px; padding: 0px;"><?</span><span class="pln" style="margin: 0px; padding: 0px;">xml version</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"1.0"</span><span class="pln" style="margin: 0px; padding: 0px;"> encoding</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"UTF-8"</span><span class="pun" style="margin: 0px; padding: 0px;">?></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="dec" style="margin: 0px; padding: 0px;"><!DOCTYPE struts PUBLIC   "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"   "http://struts.apache.org/dtds/struts-2.0.dtd"></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><struts></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><constant</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"struts.devMode"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">value</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"true"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="tag" style="margin: 0px; padding: 0px;">/></span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="tag" style="margin: 0px; padding: 0px;"><package</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"helloworld"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">extends</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"struts-default"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">         </span><span class="tag" style="margin: 0px; padding: 0px;"><action</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"hello"</span><span class="pln" style="margin: 0px; padding: 0px;">          </span><span class="atn" style="margin: 0px; padding: 0px;">class</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"com.yiibai.struts2.HelloWorldAction"</span><span class="pln" style="margin: 0px; padding: 0px;">          </span><span class="atn" style="margin: 0px; padding: 0px;">method</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"execute"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">         </span><span class="tag" style="margin: 0px; padding: 0px;"><exception-mapping</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">exception</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"java.lang.NullPointerException"</span><span class="pln" style="margin: 0px; padding: 0px;">         </span><span class="atn" style="margin: 0px; padding: 0px;">result</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"error"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="tag" style="margin: 0px; padding: 0px;">/></span><span class="pln" style="margin: 0px; padding: 0px;">         </span><span class="tag" style="margin: 0px; padding: 0px;"><result</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"success"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">/HelloWorld.jsp</span><span class="tag" style="margin: 0px; padding: 0px;"></result></span><span class="pln" style="margin: 0px; padding: 0px;">         </span><span class="tag" style="margin: 0px; padding: 0px;"><result</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"error"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">/Error.jsp</span><span class="tag" style="margin: 0px; padding: 0px;"></result></span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="tag" style="margin: 0px; padding: 0px;"></action></span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="tag" style="margin: 0px; padding: 0px;"></package></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></struts></span>

在上面的例子所示，现在我们已经配置 Struts使用专用error.jsp的NullPointerException异常。如果现在重新运行该程序，现在看到下面的输出：

此外，Struts2 框架自带的“日志”拦截记录异常。使记录器记录的未捕获异常，我们可以很容易地看堆栈跟踪和工作出了什么错误。

全局异常映射：

我们已经看到了我们可以处理特定的异常行动。我们可以设置一个例外，全局将适用于所有的行动。例如，要捕获 NullPointerException异常，我们可以添加<global-exception-mappings...>标签里面<package...>标签和其<result...>标签应加在<行动.. >标记在struts.xml文件如下： 

<span class="pun" style="margin: 0px; padding: 0px;"><?</span><span class="pln" style="margin: 0px; padding: 0px;">xml version</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"1.0"</span><span class="pln" style="margin: 0px; padding: 0px;"> encoding</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="str" style="margin: 0px; padding: 0px;">"UTF-8"</span><span class="pun" style="margin: 0px; padding: 0px;">?></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="dec" style="margin: 0px; padding: 0px;"><!DOCTYPE struts PUBLIC   "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"   "http://struts.apache.org/dtds/struts-2.0.dtd"></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><struts></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"><constant</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"struts.devMode"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">value</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"true"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="tag" style="margin: 0px; padding: 0px;">/></span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="tag" style="margin: 0px; padding: 0px;"><package</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"helloworld"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">extends</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"struts-default"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="tag" style="margin: 0px; padding: 0px;"><global-exception-mappings></span><span class="pln" style="margin: 0px; padding: 0px;">         </span><span class="tag" style="margin: 0px; padding: 0px;"><exception-mapping</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">exception</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"java.lang.NullPointerException"</span><span class="pln" style="margin: 0px; padding: 0px;">         </span><span class="atn" style="margin: 0px; padding: 0px;">result</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"error"</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="tag" style="margin: 0px; padding: 0px;">/></span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="tag" style="margin: 0px; padding: 0px;"></global-exception-mappings></span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="tag" style="margin: 0px; padding: 0px;"><action</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"hello"</span><span class="pln" style="margin: 0px; padding: 0px;">          </span><span class="atn" style="margin: 0px; padding: 0px;">class</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"com.yiibai.struts2.HelloWorldAction"</span><span class="pln" style="margin: 0px; padding: 0px;">          </span><span class="atn" style="margin: 0px; padding: 0px;">method</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"execute"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">         </span><span class="tag" style="margin: 0px; padding: 0px;"><result</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"success"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">/HelloWorld.jsp</span><span class="tag" style="margin: 0px; padding: 0px;"></result></span><span class="pln" style="margin: 0px; padding: 0px;">         </span><span class="tag" style="margin: 0px; padding: 0px;"><result</span><span class="pln" style="margin: 0px; padding: 0px;"> </span><span class="atn" style="margin: 0px; padding: 0px;">name</span><span class="pun" style="margin: 0px; padding: 0px;">=</span><span class="atv" style="margin: 0px; padding: 0px;">"error"</span><span class="tag" style="margin: 0px; padding: 0px;">></span><span class="pln" style="margin: 0px; padding: 0px;">/Error.jsp</span><span class="tag" style="margin: 0px; padding: 0px;"></result></span><span class="pln" style="margin: 0px; padding: 0px;">      </span><span class="tag" style="margin: 0px; padding: 0px;"></action></span><span class="pln" style="margin: 0px; padding: 0px;">   </span><span class="tag" style="margin: 0px; padding: 0px;"></package></span><span class="pln" style="margin: 0px; padding: 0px;"></span><span class="tag" style="margin: 0px; padding: 0px;"></struts></span>