板斧1:找不到action的错误
在struts.xml中参考如下配置
1 <struts> 2 3 ... 4 <package name="default" namespace="/" extends="struts-default"> 5 6 ... 7 8 <default-action-ref name="index" /> 9 10 ... 11 12 <action name="index"> 13 <result type="redirectAction"> 14 <param name="actionName">HelloWorld</param> 15 <param name="namespace">/home</param> 16 </result> 17 </action> 18 19 </package> 20 21 <include file="struts-home.xml" /> 22 23 </struts>
这样,如果输入不存在的.action 路径,会直接重定向到index这个Action上,而index中指定的HelloWorld这个Action,在struts-home.xml中
1 <?xml version="1.0" encoding="UTF-8" ?> 2 <!DOCTYPE struts PUBLIC 3 "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" 4 "http://struts.apache.org/dtds/struts-2.0.dtd"> 5 <struts> 6 7 <package name="home" namespace="/home" extends="default"> 8 9 <action name="HelloWorld_*" method="{1}" class="HelloWorldAction"> 10 <result>/WEB-INF/views/home/HelloWorld.jsp</result> 11 </action> 12 13 </package> 14 </struts>
注:struts.xml中节点出现的顺序,是有严格约定的,如果弄错顺序了,启动时,就会看到类似下面的异常
org.xml.sax.SAXParseException: The content of element type "package" must match
"(result-types?,interceptors?,default-interceptor-ref?,default-action-ref?,default-class-ref?,global-results?,global-exception-mappings?,action*)".
即各节点的顺序为:
result-types -> interceptors -> default-interceptor-ref -> default-action-ref -> default-class-ref -> global-results -> global-exception-mappings -> action
板斧2:404/500之类的常规错误
呃,这个struts2处理不了,得靠web.xml搞定
1 <error-page> 2 <error-code>404</error-code> 3 <location>/WEB-INF/common/error/404.jsp</location> 4 </error-page> 5 6 <error-page> 7 <error-code>500</error-code> 8 <location>/WEB-INF/common/error/500.jsp</location> 9 </error-page>
板斧3:业务异常/常规(运行)异常
a) 定义业务异常 (这里简单弄一个土鳖的MyException意思一下)
package com.cnblogs.yjmyzz.exception; public class MyException extends Exception { private static final long serialVersionUID = -8315871537638142775L; public MyException() { super(); } public MyException(String message) { super(message); } }
b) Action中,直接向外抛异常即可
1 public String execute() throws Exception, MyException { 2 3 //testException(); 4 5 testMyException(); 6 7 return SUCCESS; 8 } 9 10 /*private void testException() throws Exception { 11 throw new Exception("normal exception"); 12 }*/ 13 14 private void testMyException() throws MyException { 15 throw new MyException("my exception"); 16 }
c) 定义拦截器,处理异常
1 package com.cnblogs.yjmyzz.Interceptor; 2 3 import org.slf4j.Logger; 4 import org.slf4j.LoggerFactory; 5 6 import com.cnblogs.yjmyzz.exception.MyException; 7 import com.opensymphony.xwork2.ActionInvocation; 8 import com.opensymphony.xwork2.interceptor.*; 9 10 public class ExceptionInterceptor extends AbstractInterceptor { 11 12 private static final long serialVersionUID = -6827886613872084673L; 13 protected Logger logger = LoggerFactory.getLogger(this.getClass()); 14 protected Logger myexLogger = LoggerFactory.getLogger("my-exception"); 15 16 @Override 17 public String intercept(ActionInvocation ai) throws Exception { 18 String result = null; 19 try { 20 logger.debug("ExceptionInterceptor.intercept() is called!"); 21 result = ai.invoke(); 22 } catch (MyException e) { 23 // 捕获自定义异常 24 myexLogger.error(ai.toString(), e); 25 ai.getStack().push(new ExceptionHolder(e)); 26 result = "error"; 27 } catch (Exception e) { 28 // 其它异常 29 logger.error(ai.toString(), e); 30 ai.getStack().push(new ExceptionHolder(e)); 31 result = "error"; 32 } 33 return result; 34 } 35 36 }
解释一下:
ai.getStack().push(new ExceptionHolder(e)); 这一行的用途是将异常信息放入stack,这样后面的异常处理页面,就能显示异常详细信息
上面只是演示,将"业务异常MyException"与"常规异常Exception"分开处理,并且用不同的Logger实例来记录,这样就能将"业务异常"与"常规异常"分别记到不同的log文件中,对应的logback.xml参考配置:
1 <?xml version="1.0" encoding="UTF-8" ?> 2 <configuration scan="true" scanPeriod="1800 seconds" 3 debug="false"> 4 5 <property name="USER_HOME" value="logs" /> 6 <property scope="context" name="FILE_NAME" value="test-logback" /> 7 8 <timestamp key="byDay" datePattern="yyyy-MM-dd" /> 9 10 <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender"> 11 <encoder> 12 <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n 13 </pattern> 14 </encoder> 15 </appender> 16 17 <appender name="file" 18 class="ch.qos.logback.core.rolling.RollingFileAppender"> 19 <file>${USER_HOME}/${FILE_NAME}.log</file> 20 21 <rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy"> 22 <fileNamePattern>${USER_HOME}/${byDay}/${FILE_NAME}-${byDay}-%i.log.zip 23 </fileNamePattern> 24 <minIndex>1</minIndex> 25 <maxIndex>10</maxIndex> 26 </rollingPolicy> 27 28 <triggeringPolicy 29 class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy"> 30 <maxFileSize>5MB</maxFileSize> 31 </triggeringPolicy> 32 <encoder> 33 <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %-4relative [%thread] %-5level 34 %logger{150} - %msg%n 35 </pattern> 36 </encoder> 37 </appender> 38 39 40 <appender name="exception-file" 41 class="ch.qos.logback.core.rolling.RollingFileAppender"> 42 <file>${USER_HOME}/${FILE_NAME}_myexception.log</file> 43 44 <rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy"> 45 <fileNamePattern>${USER_HOME}/${byDay}/${FILE_NAME}-${byDay}-%i.log.zip 46 </fileNamePattern> 47 <minIndex>1</minIndex> 48 <maxIndex>10</maxIndex> 49 </rollingPolicy> 50 51 <triggeringPolicy 52 class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy"> 53 <maxFileSize>5MB</maxFileSize> 54 </triggeringPolicy> 55 <encoder> 56 <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %-4relative [%thread] %-5level 57 %logger{150} - %msg%n 58 </pattern> 59 </encoder> 60 </appender> 61 62 <logger name="com.cnblogs.yjmyzz" level="error" additivity="true"> 63 <appender-ref ref="file" /> 64 </logger> 65 66 <logger name="my-exception" level="error" additivity="true"> 67 <appender-ref ref="exception-file" /> 68 </logger> 69 70 <root level="error"> 71 <appender-ref ref="STDOUT" /> 72 </root> 73 </configuration>
运行后,会生成二个日志文件,类似下图:(业务日志记录在test-logback_myexception.log中,常规运行异常记录在test-logback.log中)
tips:如果还有更多的异常类型要处理(比如:SQL异常、Spring异常、网络连接异常等,参考上面的处理)。另:如果把3.b)中Action方法里的testMyException()注释掉,换成testException(),即抛出普通异常,则异常信息将记录到test-logback.log中
d) struts中拦截器配置,以及全局异常处理页面
struts2中所有action的方法执行会先经常拦截器,所以拦截器是处理异常的好机机(比如:记录异常到日志文件、转换成友好异常信息)
1 <?xml version="1.0" encoding="UTF-8" ?> 2 <!DOCTYPE struts PUBLIC 3 "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN" 4 "http://struts.apache.org/dtds/struts-2.3.dtd"> 5 6 <struts> 7 8 <constant name="struts.enable.DynamicMethodInvocation" value="false" /> 9 <constant name="struts.devMode" value="true" /> 10 11 <package name="default" namespace="/" extends="struts-default"> 12 13 <interceptors> 14 <interceptor name="myinterceptor" 15 class="com.cnblogs.yjmyzz.Interceptor.ExceptionInterceptor"> 16 </interceptor> 17 18 <interceptor-stack name="myStack"> 19 <interceptor-ref name="myinterceptor" /> 20 </interceptor-stack> 21 </interceptors> 22 23 <default-interceptor-ref name="myStack" /> 24 <default-action-ref name="index" /> 25 26 <global-results> 27 <result name="error">/WEB-INF/common/error.jsp</result> 28 </global-results> 29 30 <global-exception-mappings> 31 <exception-mapping exception="java.lang.Exception" 32 result="error" /> 33 </global-exception-mappings> 34 35 <action name="index"> 36 <result type="redirectAction"> 37 <param name="actionName">HelloWorld</param> 38 <param name="namespace">/home</param> 39 </result> 40 </action> 41 42 </package> 43 44 <include file="struts-home.xml" /> 45 <include file="struts-mytatis.xml" /> 46 47 </struts>
e) 通用error.jsp 代码
1 <%@ page contentType="text/html;charset=UTF-8" language="java" %> 2 <%@ taglib prefix="s" uri="/struts-tags" %> 3 4 <html> 5 <head><title>Simple jsp page</title></head> 6 <body> 7 <h3>Exception:</h3> 8 <s:property value="exception"/> 9 10 <h3>Stack trace:</h3> 11 <pre> 12 <s:property value="exceptionStack"/> 13 </pre> 14 </body> 15 </html>
这样运行时,就会显示给用户一个很"低俗但通用"的错误页面:
显然,直接把底层异常展示给用户是不好的做法(相当于直接告诉你底裤的颜色),可以稍微装饰一下,只要改下拦截器:
1 package com.cnblogs.yjmyzz.Interceptor; 2 3 import org.slf4j.Logger; 4 import org.slf4j.LoggerFactory; 5 6 import com.cnblogs.yjmyzz.exception.MyException; 7 import com.opensymphony.xwork2.ActionInvocation; 8 import com.opensymphony.xwork2.interceptor.*; 9 10 public class ExceptionInterceptor extends AbstractInterceptor { 11 12 private static final long serialVersionUID = -6827886613872084673L; 13 protected Logger logger = LoggerFactory.getLogger(this.getClass()); 14 protected Logger myexLogger = LoggerFactory.getLogger("my-exception"); 15 16 @Override 17 public String intercept(ActionInvocation ai) throws Exception { 18 String result = null; 19 try { 20 logger.debug("ExceptionInterceptor.intercept() is called!"); 21 result = ai.invoke(); 22 } catch (MyException e) { 23 // 捕获自定义异常 24 myexLogger.error(ai.toString(), e); 25 // 转换成友好异常,并放入stack中 26 ai.getStack().push( 27 new ExceptionHolder(new Exception("业务繁忙,让我喘口气先!"))); 28 result = "error"; 29 } catch (Exception e) { 30 // 其它异常 31 logger.error(ai.toString(), e); 32 // 转换成友好异常,并放入stack中 33 ai.getStack().push( 34 new ExceptionHolder(new Exception("系统太累了,需要休息一下!"))); 35 result = "error"; 36 } 37 return result; 38 } 39 40 }
这样,用户看到的信息就变了(当然,实际应用中,下面这个页面,建议请艺术大师美化一下)
当然,也可以改变拦截器的返回string,比如业务错误,返回"biz-error",定位到业务错误的专用展示页面,常规错误返回"sys-error",返回 另一个专用错误处理页面(对应的struts.xml的全局错误配置也要相应修改)
小结:
经过以上处理,常见的异常(错误),比如:404/500、action路径不对、运行异常、业务异常等,即分门别类记录了详细日志(便于日后分析),也转换成了友好信息提示给用户,同时还保证了系统健壮性。最后,对于程序员更重要的是,不用手动写try/catch之类的代码了,干活更轻松 (妈妈,再也不担心我的异常了)