通过前面几篇博客,不知道大家有没有发现这个问题,虽然现在可以灵活控制跳转了,但是Action的数量还是比较多,如何既能保证跳转灵活,还能减少Action的数量?这就是我们这篇博客所说的DispatchAction,如其名,可以理解为“分发式Action”,使用它可以避免为每个Action创建一个类。
我们先来看一下实例。
DispatchAction继承的是Action,它的特点就是把以前的多个Action合并为一个,当多个Action关联较大时,可以像这样放在一起,减少Action类的同时,也降低了维护的难度。
package com.tgb.drp.web.actions; 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.tgb.drp.manager.UserManager; import com.tgb.drp.model.User; import com.tgb.drp.web.forms.UserActionForm; public class UserAction extends DispatchAction { @Override protected ActionForward unspecified(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception { //调用业务逻辑操作 List userList = UserManager.getInstance().findAllUserList(); request.setAttribute("userlist", userList); return mapping.findForward("list_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("del_success"); } /** * 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(); BeanUtils.copyProperties(user, uaf); user.setCreateDate(new Date()); //调用业务逻辑操作 UserManager.getInstance().addUser(user); return mapping.findForward("add_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); //调用业务逻辑操作 UserManager.getInstance().modifyUser(user); return mapping.findForward("modify_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"); } }
UserActionForm
封装表单中的数据,需要注意的是,不用为每个表单 建立一个ActionForm,多个表单可以使用一个进行封装。
package com.tgb.drp.web.forms; import java.util.Date; import org.apache.struts.action.ActionForm; /** * 用户管理ActionForm * */ public class UserActionForm extends ActionForm { //用户代码 private String userId; //用户名称 private String userName; //密码 private String password; //联系电话 private String contactTel; //email private String email; //创建日期 private Date createDate; //接收界面中的选中标记的集合 private String[] selectFlag; public String getContactTel() { return contactTel; } public void setContactTel(String contactTel) { this.contactTel = contactTel; } public Date getCreateDate() { return createDate; } public void setCreateDate(Date createDate) { this.createDate = createDate; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getUserId() { return userId; } public void setUserId(String userId) { this.userId = userId; } public String getUserName() { return userName; } public void setUserName(String userName) { this.userName = userName; } public String[] getSelectFlag() { return selectFlag; } public void setSelectFlag(String[] selectFlag) { this.selectFlag = selectFlag; } }
配置Action和ActionForm,区别于以前的是需要添加parameter属性。
<form-beans> <form-bean name="userForm" type="com.tgb.drp.web.forms.UserActionForm"/> </form-beans> <action-mappings> <action path="/user/user_maint" type="com.tgb.drp.web.actions.UserAction" name="userForm" scope="request" parameter="command" > <forward name="list_success" path="/user/user_list.jsp"/> <forward name="del_success" path="/user/user_maint.do" redirect="true"/> <forward name="add_success" path="/user/user_maint.do" redirect="true"/> <forward name="modify_success" path="/user/user_maint.do" redirect="true"/> <forward name="find_success" path="/user/user_modify.jsp"/> </action> <action path="/user/show_add" forward="/user/user_input.jsp" ></action> </action-mappings>
<body> <a href="user/user_maint.do" title="请点击访问用户管理系统">用户管理系统</a> </body>
如上所示,它是根据command属性的值确定的。
把断点主要设置在DispatchAction中,可以看到,执行流程如下:
在DispatchAction的execute函数中,有如下代码:
// Prevent recursive calls if ("execute".equals(name) || "perform".equals(name)){ String message = messages.getMessage("dispatch.recursive", mapping.getPath()); log.error(message); throw new ServletException(message); }所以在给parameter设置值时,不能为execute或perform。
在DispatchAction的dispatchMethod中,有如下代码:
if (name == null) { return this.unspecified(mapping, form, request, response); }
总而言之,DispatchAction的出现减少了Action的数量,将多个Action融合到一起,虽然有显而易见的好处,但是同样会有问题,这样的耦合性的提高,必然伴随着扩展性的降低,所以用还是不用,还要根据具体情况而定。
更多相关博客,请至《层层递进Struts1(八)之总结》