LookupDispatchAction使用示例

当表单中出现两个或以上的同名按钮时，可以通过LookupDispatchAction查询properties文件实现定位到不同方法的操作。
本文以简单的加减乘除为例：
一、编写properties文件

add=加
sub=减
mutiply=乘
div=除

二、编写jsp页面

<%@ page language="java" pageEncoding="UTF-8"%>
<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean"%>
<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%>

<html>
    <head>
        <title>JSP for CalcForm form</title>
    </head>
    <body>
        <html:form action="/calc">
            操作数1 : <html:text property="num01"/><html:errors property="num01"/><br/>
            操作数2 : <html:text property="num02"/><html:errors property="num02"/><br/>
            <html:submit property="meo">
                <bean:message key="add"/>
            </html:submit>
            <html:submit property="meo">
                <bean:message key="sub"/>
            </html:submit>
            <html:submit property="meo">
                <bean:message key="mutiply"/>
            </html:submit>
            <html:submit property="meo">
                <bean:message key="div"/>
            </html:submit>
        </html:form>

        <br>结果:${result}
    </body>
</html>

查看客户端源代码可得

<html>
    <head>
        <title>JSP for CalcForm form</title>
    </head>
    <body>
        <form name="calcForm" method="post" action="/lookup/calc.do">
            操作数1 : <input type="text" name="num01" value="5"><br/>
            操作数2 : <input type="text" name="num02" value="7"><br/>
            <input type="submit" name="meo" value="加">
            <input type="submit" name="meo" value="减">
            <input type="submit" name="meo" value="乘">
            <input type="submit" name="meo" value="除">
        </form>

        <br>结果:12.0    </body>
</html>

可见<html:submit property="meo">中的property="meo"被转换为submit按钮的name="meo"而<bean:message key="add"/>
的作用是通过该key值去properties文件中获得value值作为submit按钮的value属性的值。

三、编写CalcAction类
加减乘除这四种逻辑都在CalcAction类中定义，该类继承自LookupDispatchAction，而且必须重写getKeyMethodMap()方法。
假设按下<input type="submit" name="meo" value="加">,LookupDispatchAction会根据value值(加),在属性文件中找到对应的key值，然后根据该Key值与getKeyMethodMap()得知要执行CalcAction类中的add()。

public class CalcAction extends LookupDispatchAction {

    public ActionForward add(ActionMapping mapping, ActionForm form,
            HttpServletRequest request, HttpServletResponse response) {
        CalcForm calcForm = (CalcForm) form;
        double result = Double.parseDouble(calcForm.getNum01())
                + Double.parseDouble(calcForm.getNum02());
        request.setAttribute("result", result);
        return mapping.findForward("bi");
    }

    public ActionForward sub(ActionMapping mapping, ActionForm form,
            HttpServletRequest request, HttpServletResponse response) {
        CalcForm calcForm = (CalcForm) form;
        double result = Double.parseDouble(calcForm.getNum01())
                - Double.parseDouble(calcForm.getNum02());
        request.setAttribute("result", result);
        return mapping.findForward("bi");
    }

    public ActionForward mutiply(ActionMapping mapping, ActionForm form,
            HttpServletRequest request, HttpServletResponse response) {
        CalcForm calcForm = (CalcForm) form;
        double result = Double.parseDouble(calcForm.getNum01())
                * Double.parseDouble(calcForm.getNum02());
        request.setAttribute("result", result);
        return mapping.findForward("bi");
    }

    public ActionForward div(ActionMapping mapping, ActionForm form,
            HttpServletRequest request, HttpServletResponse response) {
        CalcForm calcForm = (CalcForm) form;
        double result = Double.parseDouble(calcForm.getNum01())
                / Double.parseDouble(calcForm.getNum02());
        request.setAttribute("result", result);
        return mapping.findForward("bi");
    }

    @Override
    protected Map getKeyMethodMap() {
        //map中的key与资源文件中的key相同，value为方法名
        Map map = new HashMap();
        map.put("add", "add");
        map.put("sub", "sub");
        map.put("mutiply", "mutiply");
        map.put("div", "div");
        return map;
    }
}

四、配置stuts-config.xml

<action-mappings>
        <action attribute="calcForm"
                     input="/calc.jsp"
                     name="calcForm"
                     parameter="meo" //该值为页面中按钮的名字
                     path="/calc"
                     scope="request"
                     type="com.fskjb.struts.action.CalcAction">
            <forward name="bi" path="/calc.jsp" />
        </action>
</action-mappings>