SSH答疑解惑系列（三）——Struts2的异常处理

女爷i 2022-08-19 04:49 165阅读 0赞

Struts2的异常采用声明式异常捕捉，具体通过拦截器来实现。

在项目中，我们可以在Action中直接抛出异常，剩下的就交给Struts2的拦截器来处理了。当然，我们需要进行相关配置。

Struts2配置了默认的拦截器，来处理异常。在struts-default.xml中，可以找到配置。有了这个配置以后，我们在项目中就方便多了。

在项目中，只需要使用exception-mapping标签来配置：

**1）全局异常**

适用对象：所有Action

<global-results >
            
            <result name="global-error">/global-error.jsp</result>
        </global-results>
    
        <global-exception-mappings>
            <exception-mapping result="global-error" exception="com.struts2.ApplicationException"></exception-mapping>
        </global-exception-mappings>

**2）局部异常**

使用对象：异常所在的Action

<action name="login" class="com.struts2.LoginAction">
    
                <exception-mapping result="error" exception="com.struts2.ApplicationException"></exception-mapping>
                <result>/success.jsp</result>
                <result name="error">/error.jsp</result>
            </action>

ApplicationException

![这里写图片描述][20160108113412087]

Throwable是所有异常的根  
Error是错误  
Exception是异常，RuntimeException是运行中的异常。

除了Struts2自带的拦截器，我们还可以自定义拦截器，覆盖底层的拦截器，使得异常的捕捉更加灵活。

自定义拦截器的配置也十分方便。

<interceptors>
                       
                       <interceptor name="errorInterceptor" class="cn.itcast.util.ErrorInterceptor" />
                       
                       <interceptor-stack name="myErrorInterceptor">
                                   <interceptor-ref name="defaultStack" />
                                   <interceptor-ref name="errorInterceptor" />
                       </interceptor-stack>
    </interceptors>
    
    <default-interceptor-ref name="myErrorInterceptor"/>
    
                <global-results>
                        <result name="errorMsg">/errorMsg.jsp</result>
                </global-results>
                <global-exception-mappings>
                        <exception-mapping result="errorMsg" exception="java.lang.Exception"></exception-mapping>
            </global-exception-mappings>

**Struts2的“错误页”**  
经常使用ssh框架开发，会发现Struts2中各种报错页面的布局和显示信息很类似。这是因为Struts2提供了一个它自己的“错误页”，在org.apache.struts2.dispatcher包下。  
  
![这里写图片描述][20160108115156661]

<html> <head> <title>Struts Problem Report</title> <style> pre { margin: 0; padding: 0; } </style> </head> <body> <h2>Struts Problem Report</h2> <p> Struts has detected an unhandled exception: </p> <#assign msgs = [] /> <#list chain as ex> <#if ex.message??> <#assign msgs = [ex.message] + msgs/> </#if> </#list> <#assign rootex = exception/> <#list chain as ex> <#if (ex.location?? && (ex.location != unknown))> <#assign rootloc = ex.location/> <#assign rootex = ex/> <#else> <#assign tmploc = locator.getLocation(ex) /> <#if (tmploc != unknown)> <#assign rootloc = tmploc/> <#assign rootex = ex/> </#if> </#if> </#list> <div id="exception-info"> <table> <tr> <td><strong>Messages</strong>:</td> <td> <#if (msgs?size > 1)> <ol> <#list msgs as msg> <#if (msg?is_method)> <li>${msg[0]}</li> <#else> <li>${msg}</li> </#if> </#list> </ol> <#elseif (msgs?size == 1)> <#if (msgs[0]?is_method)> <li>${msgs[0][0]}</li> <#else> <li>${msgs[0]}</li> </#if> </#if> </td> </tr> <#if rootloc??> <tr> <td><strong>File</strong>:</td> <td>${rootloc.URI}</td> </tr> <tr> <td><strong>Line number</strong>:</td> <td>${rootloc.lineNumber}</td> </tr> <#if (rootloc.columnNumber >= 0)> <tr> <td><strong>Column number</strong>:</td> <td>${rootloc.columnNumber}</td> </tr> </#if> </#if> </table> </div> <#if rootloc??> <#assign snippet = rootloc.getSnippet(2) /> <#if (snippet?size > 0)> <div id="snippet"> <hr /> <#list snippet as line> <#if (line_index == 2)> <#if (rootloc.columnNumber >= 3)> <pre style="background:yellow">${(line[0..(rootloc.columnNumber-3)]?html)}<span style="background:red">${(line[(rootloc.columnNumber-2)]?html)}</span><#if ((rootloc.columnNumber)<line.length())>${(line[(rootloc.columnNumber-1)..]?html)}</#if></pre> <#else> <pre style="background:yellow">${line?html}</pre> </#if> <#else> <pre>${line?html}</pre> </#if> </#list> </div> </#if> </#if> <div id="stacktraces"> <hr /> <h3>Stacktraces</h3> <#list chain as ex> <div class="stacktrace" style="padding-left: ${ex_index * 2}em"> <strong>${ex}</strong> <div> <pre> <#list ex.stackTrace as frame> ${frame} </#list> </pre> </div> </div> </#list> </div> <div class="footer"> <hr /> <p> You are seeing this page because development mode is enabled. Development mode, or devMode, enables extra debugging behaviors and reports to assist developers. To disable this mode, set: <pre> struts.devMode=false </pre> in your <code>WEB-INF/classes/struts.properties</code> file. </p> </div> </body> </html>

[20160108113412087]: /images/20220731/8c69ad6a1f2642ba92c003642c165f3e.png
[20160108115156661]: /images/20220731/5e10df0c28e742d4ad38cf61cb4f388c.png