10.struts2_声明式异常的处理

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1.异常处理：exception-mapping元素

struts.xml中配置 exception-mapping标签，可以捕捉在Action中出现的异常，

exception：需要捕捉的异常名称

result：出现异常后，跳转到哪个result

<struts><!-- 修改当前 Struts 应用的主题 --><constant name="struts.ui.theme" value="simple"></constant>    <package name="default" namespace="/" extends="struts-default"><action name="product-save" class="com.atguigu.struts.valuestack.Product"method="save"><exception-mapping result="input" exception="ArithmeticException"></exception-mapping><result name="input">/input.jsp</result><result>/details.jsp</result></action><action name="emp-*"class="com.atguigu.struts.valuestack.app.Employee"method="{1}"><result name="{1}">/emp-{1}.jsp</result></action>    </package></struts>

Struts2框架的ExceptionMappingInterceptor拦截器会将Exception放入值栈。

 @Override    public String intercept(ActionInvocation invocation) throws Exception {        String result;        try {            result = invocation.invoke();        } catch (Exception e) {            if (isLogEnabled()) {                handleLogging(e);            }            List<ExceptionMappingConfig> exceptionMappings = invocation.getProxy().getConfig().getExceptionMappings();            ExceptionMappingConfig mappingConfig = this.findMappingFromExceptions(exceptionMappings, e);            if (mappingConfig != null && mappingConfig.getResult()!=null) {                Map parameterMap = mappingConfig.getParams();                // create a mutable HashMap since some interceptors will remove parameters, and parameterMap is immutable                invocation.getInvocationContext().setParameters(new HashMap<String, Object>(parameterMap));                result = mappingConfig.getResult();                publishException(invocation, new ExceptionHolder(e));            } else {                throw e;            }        }        return result;    }

源码中的publishException

  protected void publishException(ActionInvocation invocation, ExceptionHolder exceptionHolder) {        invocation.getStack().push(exceptionHolder);    }

对应页面可以打印出错误信息 input.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><%@ taglib prefix="s" uri="/struts-tags"%><!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><s:debug></s:debug><s:property value="exceptionStack"/><br>异常对象：<s:property value="exception.message"/><br><br><br><form action="product-save.action" method="post">ProductName: <input type="text" name="productName"/><br><br>ProductDesc: <input type="text" name="productDesc"/><br><br>ProductPrice: <input type="text" name="productPrice" /><br><br><input type="submit" value="Submit"/><br><br></form></body></html>

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