Struts2输入结果：它是如何工作的？(Struts2 INPUT result: how does it work? How are conversion / validation errors handled?)

 主要问题 
 
 工作流程应该是这样的：如果输入的字符串不是数字，首先应该通过一个异常拦截器，并且当通过param拦截器时，在转换为int类型时，它不能使用Integer.parseInt来完成Integer.parseInt并会发生异常; 不应该将那个异常（即NumberFormatException ）推入值栈？ 为什么它不显示NumberFormatException并显示结果，即使结果不应被打印？ 
 
 侧面问题 
 
 每当我在表单中添加一个字母时，它就会变成零...？ 为什么这样 ？ 
 
 的index.jsp 
 
<%@ taglib uri="/struts-tags" prefix="s"%>
<s:form action="divide">
    <s:textfield name="number1" label="number1"/>
    <s:textfield name="number2" label="number2"/>
    <s:submit value="divide"/>
</s:form>
 
 divide.java 
 
package actions;

public class divide {
    int number1,number2,result;
    public String execute() throws Exception
    {
        result=number1/number2;
        return "success";
    }
    public int getNumber1() {
        return number1;
    }
    public void setNumber1(int number1) {
        this.number1 = number1;
    }
    public int getNumber2() {
        return number2;
    }
    public void setNumber2(int number2) {
        this.number2 = number2;
    }
    public int getResult() {
        return result;
    }


}
 
 result.jsp中 
 
<%@taglib uri="/struts-tags" prefix="s" %>
<b>
    the result of division is
    <s:property value="result"/>
</b>
<jsp:include page="index.jsp"></jsp:include>
 
 处理程序jsp 
 
<%@taglib uri="/struts-tags" prefix="s"%>
<b>
    following exception occured during the processing
    <s:property value="exception"/>
</b>
<jsp:include page="index.jsp"/>
 
 在struts.xml 
 
<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE struts PUBLIC 
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">
    <struts>
        <package name="yo" extends="struts-default">
            <action name="divide" class="actions.divide">
                <exception-mapping result="error" exception="Exception"/>
                <result name="success">/result.jsp</result>
                <result name="error">/handler.jsp</result>
            </action>
        </package>
    </struts>

Main Question 
 
The work flow should be like this: if an String is entered other than a number, first it should pass through a exception interceptor, and when passing through param interceptor, while converting to int type, it wont be able to do it using Integer.parseInt and an exception would occur; shouldn't that exception (that is NumberFormatException) be pushed into Value Stack ? Why does it not show NumberFormatException and show the result even though result should not be printed instead ?
 
Side Question 
 
Whenever I add an alphabet in the form, it changed to zero...? Why so ?
 
index.jsp
 
<%@ taglib uri="/struts-tags" prefix="s"%>
<s:form action="divide">
    <s:textfield name="number1" label="number1"/>
    <s:textfield name="number2" label="number2"/>
    <s:submit value="divide"/>
</s:form>
 
divide.java
 
package actions;

public class divide {
    int number1,number2,result;
    public String execute() throws Exception
    {
        result=number1/number2;
        return "success";
    }
    public int getNumber1() {
        return number1;
    }
    public void setNumber1(int number1) {
        this.number1 = number1;
    }
    public int getNumber2() {
        return number2;
    }
    public void setNumber2(int number2) {
        this.number2 = number2;
    }
    public int getResult() {
        return result;
    }


}
 
result.jsp
 
<%@taglib uri="/struts-tags" prefix="s" %>
<b>
    the result of division is
    <s:property value="result"/>
</b>
<jsp:include page="index.jsp"></jsp:include>
 
handler jsp
 
<%@taglib uri="/struts-tags" prefix="s"%>
<b>
    following exception occured during the processing
    <s:property value="exception"/>
</b>
<jsp:include page="index.jsp"/>
 
struts.xml
 
<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE struts PUBLIC 
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">
    <struts>
        <package name="yo" extends="struts-default">
            <action name="divide" class="actions.divide">
                <exception-mapping result="error" exception="Exception"/>
                <result name="success">/result.jsp</result>
                <result name="error">/handler.jsp</result>
            </action>
        </package>
    </struts>

原文：https://stackoverflow.com/questions/23448616