Struts 1.x中的DispatchAction用法

引用

在采用标准的Action时每个单独的操作都要写一个Action的类，这样会使我们的Action类膨胀起来，为了解决这个问题，可以使用Struts给我们提供的DispatchAction。

DispatchAction的用法：

1.首先我们要先建一个Action类，并继承Struts的DispatchAction

package com.yx.zzg.action;

import java.util.Date;
import java.util.List;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.beanutils.BeanUtils;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.actions.DispatchAction;

import com.yx.zzg.form.UserActionForm;
import com.yx.zzg.manager.UserManager;
import com.yx.zzg.model.User;

/**
 * 用户CRUD
 * 
 * @author Administrator
 * 
 */
public class UserAction extends DispatchAction {

	/**
	 * 覆写Struts的unspecified方法，当传递的参数值不存在时，会执行到此方法
	 */
	@Override
	protected ActionForward unspecified(ActionMapping mapping, ActionForm form,
			HttpServletRequest request, HttpServletResponse response)
			throws Exception {

		System.out.println("-----------UserAction.unspecified()-----------");

		// 调用业务逻辑操作
		List userList = UserManager.getInstance().findAllUserList();
		request.setAttribute("userlist", userList);

		return mapping.findForward("list_success");

		// ActionForward af = new ActionForward();
		// af.setPath("/user/usermaint.do?command=list");
		// af.setRedirect(true);
		// return af;
	}

	/**
	 * 用户添加
	 * 
	 * @param mapping
	 * @param form
	 * @param request
	 * @param response
	 * @return
	 * @throws Exception
	 */
	public ActionForward add(ActionMapping mapping, ActionForm form,
			HttpServletRequest request, HttpServletResponse response)
			throws Exception {

		// 获取从页面表单中提交过来的值
		UserActionForm uaf = (UserActionForm) form;

		User user = new User();
		//此方法是用来属性的拷贝（常用）
		//用法BeanUtils.copyProperties(目标对象, 源对象);
		BeanUtils.copyProperties(user, uaf);
		user.setCreateDate(new Date());

		// 调用业务逻辑操作
		UserManager.getInstance().addUser(user);

		return mapping.findForward("success");
	}

	/**
	 * 用户删除
	 * 
	 * @param mapping
	 * @param form
	 * @param request
	 * @param response
	 * @return
	 * @throws Exception
	 */
	public ActionForward del(ActionMapping mapping, ActionForm form,
			HttpServletRequest request, HttpServletResponse response)
			throws Exception {
		// 获取从页面表单中提交过来的值
		UserActionForm uaf = (UserActionForm) form;

		// 取得需要删除的userId的集合
		String[] userIdList = uaf.getSelectFlag();

		// 调用业务逻辑操作
		UserManager.getInstance().deleteUsers(userIdList);
		return mapping.findForward("success");
	}

	/**
	 * 根据ID查询用户
	 * 
	 * @param mapping
	 * @param form
	 * @param request
	 * @param response
	 * @return
	 * @throws Exception
	 */
	public ActionForward find(ActionMapping mapping, ActionForm form,
			HttpServletRequest request, HttpServletResponse response)
			throws Exception {
		// 获取从页面表单中提交过来的值
		UserActionForm uaf = (UserActionForm) form;

		String userId = uaf.getUserId();

		// 调用业务逻辑操作
		User user = UserManager.getInstance().findUserById(userId);

		// 将user对象从Action传递到JSP页面
		request.setAttribute("user", user);

		return mapping.findForward("find_success");
	}

	/**
	 * 修改用户
	 * 
	 * @param mapping
	 * @param form
	 * @param request
	 * @param response
	 * @return
	 * @throws Exception
	 */
	public ActionForward modify(ActionMapping mapping, ActionForm form,
			HttpServletRequest request, HttpServletResponse response)
			throws Exception {
		// 获取从页面表单中提交过来的值
		UserActionForm uaf = (UserActionForm) form;

		User user = new User();
		BeanUtils.copyProperties(user, uaf);
		user.setCreateDate(new Date());

		// 调用业务逻辑操作
		UserManager.getInstance().modifyUser(user);

		return mapping.findForward("success");
	}
}

2.配置struts-config.xml文件

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE struts-config PUBLIC
          "-//Apache Software Foundation//DTD Struts Configuration 1.3//EN"
          "http://struts.apache.org/dtds/struts-config_1_3.dtd">
<struts-config>
	<!-- 定义ActionForm -->
	<form-beans>
		<form-bean name="userForm" type="com.yx.zzg.form.UserActionForm"></form-bean>
	</form-beans>

	<!-- 定于一个全局的转向 -->
	<global-forwards>
		<forward name="success" path="/user/usermaint.do" redirect="true" />
	</global-forwards>

	<!-- 定义Action -->
	<action-mappings>
		<!-- parameter定义参数名称为command，参数名称的值跟的是方法名称 -->
		<action path="/user/usermaint" type="com.yx.zzg.action.UserAction"
			name="userForm" scope="request" parameter="command">
			<forward name="find_success" path="/user/user_modify.jsp" />
			<forward name="list_success" path="/user/user_list.jsp" />
		</action>
	</action-mappings>
</struts-config>

注意：使用DispatchAction必须注意以下几个方面

引用

1.如果在Action中覆写execute方法，必须显示的用super调用父类的execute方法，否则DispatchAction就会失效。

2.在配置Action时parameter的属性值不能为execute或perform，否则会抛出异常，参见struts源码。

3.如果我们在访问一个parameter为null或不存在的parameter时，就会抛出异常，我们可以在Action里覆写struts的unspecified方法，并在这个方法里做处理。