Struts2学习笔记（八）：声明式异常详解

来源：互联网发布：淘宝店铺管理方案编辑：程序博客网时间：2024/06/10 06:40

本节主要讲解Struts2中的声明式异常管理，介绍如何配置声明式异常，如何访问异常相关的属性，并介绍全局声明式异常。

先看一个应用场景。

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body><form action="userAction" method="post">姓名：<input name="userName" type="text"/><br/><br/>年龄：<input name="userAge" type="text"/><br/><br/>性别：<input name="userGender" type="text"/><br/><br/><input value="submit" type="submit"/><br/><br/></form></body></html>

这是一个登陆界面，其中的年龄属性应该填写数字，但这里并未做显示限制，因此后台在获取该参数时就要加上try catch

try {age = Integer.valueOf(((String[])parameters.get("userAge"))[0]);} catch (NumberFormatException e) {e.printStackTrace();}

为了处理友好，这里应该返回一个result值，然后在action中定义相应的映射进行转发。

除了上述的方法外，Struts2还提供了另一种解决方案——声明式异常处理。

声明式异常处理的配置如下所示：

<action name="userAction" class="com.jiajia.actions.UserAction" method="login">            <exception-mapping result="error"             exception="java.lang.NumberFormatException"/>            <result name="success">/success.jsp</result>            <result name="error">/error.jsp</result>        </action>

声明式异常处理采用<exception-mapping>标签定义对异常的拦截操作，exception属性定义拦截的异常类型，result属性定义转发到的页面。

注意：若exception属性为空，则表示拦截所有类型的异常

做了上述的配置以后，Action类中就无需进行try catch操作了。异常发生时，Struts2会向对象栈中push一个com.opensymphony.xwork2.interceptor.ExceptionHolde对象

其中包含了exceptionStack和exception两个属性，携带了异常的相关信息，如下图所示

Struts ValueStack Debug

Value Stack Contents

ObjectProperty NameProperty Valuecom.opensymphony.xwork2.interceptor.ExceptionHolderexceptionStackjava.lang.NumberFormatException: For input string: "hu" at java.lang.NumberFormatException.forInputString(Unknown Source) at java.lang.Integer.parseInt(Unknown Source) at java.lang.Integer.valueOf(Unknown Source) at com.jiajia.actions.UserAction.login(UserAction.java:33) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at ognl.OgnlRuntime.invokeMethod(OgnlRuntime.java:891) at ognl.OgnlRuntime.callAppropriateMethod(OgnlRuntime.java:1293) at ognl.ObjectMethodAccessor.callMethod(ObjectMethodAccessor.java:68) at com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethodWithDebugInfo(XWorkMethodAccessor.java:117) at com.opensymphony.xwork2.ognl.accessor.XWorkMethodAccessor.callMethod(XWorkMethodAccessor.java:108) at ognl.OgnlRuntime.callMethod(OgnlRuntime.java:1369) at ognl.ASTMethod.getValueBody(ASTMethod.java:90) at ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:212) at ognl.SimpleNode.getValue(SimpleNode.java:258) at ognl.Ognl.getValue(Ognl.java:494) at ognl.Ognl.getValue(Ognl.java:458) at com.opensymphony.xwork2.ognl.OgnlUtil$2.execute(OgnlUtil.java:309) at com.opensymphony.xwork2.ognl.OgnlUtil.compileAndExecute(OgnlUtil.java:340) at com.opensymphony.xwork2.ognl.OgnlUtil.getValue(OgnlUtil.java:307) at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:423) at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:287) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:250) at org.apache.struts2.interceptor.DeprecationInterceptor.intercept(DeprecationInterceptor.java:41) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:167) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265) at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:76) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:229) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:229) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:191) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:73) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at org.apache.struts2.interceptor.DateTextFieldInterceptor.intercept(DateTextFieldInterceptor.java:125) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:91) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:253) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171) at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:139) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:193) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:189) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:244) at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54) at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:564) at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:81) at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Unknown Source)exceptionjava.lang.NumberFormatException: For input string: "hu"com.jiajia.actions.UserActionparametersThere is no read method for parametersuserUser [userName=jiajia, userAge=0, userGender=null]com.opensymphony.xwork2.DefaultTextProvidertextsnull可以用<s:property>标签访问这些属性

错误为：<s:property value="exception"/><br/><br/>错误消息为：<s:property value="exception.message"/>

除了在action标签内部配置声明式异常以外，还可以定义全局声明式异常

<!-- global-results必须写在global-exception-mappings的前面因为global-exception-mappings要引用global-results中的结果 --><global-results><result name="error2">/error2.jsp</result></global-results><global-exception-mappings><exception-mapping result="error2" exception=""></exception-mapping></global-exception-mappings>

这里需要做几点说明：

（1）若一个异常既可以被action内部拦截，也可以被全局声明式异常拦截，action内部的拦截优先处理

（2）全局声明式异常中的result属性会优先到抛出异常的action中去寻找相应的result，若找不到才会到全局结果中寻找

完整的示例代码在这里：http://download.csdn.net/detail/jiajia333666/9056203

1 0