Struts-第一个Struts应用

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摘自：《精通struts.基于MVC的.Java.Web设计与开发》---电子出版社--2004年8月第1版

应用首页：

输入test，单击提交后显示：

保持输入框为空再次提交：

最后输入Monster,显示页面如下：

1.配置web.xml,加入Struts框架：

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns="http://java.sun.com/xml/ns/j2ee"         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee         http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"         version="2.4">  <display-name>HelloApp Struts Application</display-name>  <!-- The Usual Welcome File List -->  <welcome-file-list>    <welcome-file>hello.jsp</welcome-file>  </welcome-file-list>    <!-- Standard Action Servlet Configuration -->  <servlet>     <servlet-name>action</servlet-name>     <servlet-class>     org.apache.struts.action.ActionServlet     </servlet-class>     <init-param>         <param-name>config</param-name>         <param-value>/WEB-INF/struts-config.xml</param-value>     </init-param>     <load-on-startup>2</load-on-startup>  </servlet>    <!-- Standard Action Servlet Mapping -->  <servlet-mapping>      <servlet-name>action</servlet-name>      <url-pattern>*.do</url-pattern>  </servlet-mapping></web-app>

2.编写视图页面hello.jsp：

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean" %><%@ taglib uri="http://struts.apache.org/tags-html" prefix="html" %><%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic" %><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html:html xhtml="true"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title><bean:message key="hello.jsp.title" /></title></head><body bgcolor="white">   <h2><bean:message key="hello.jsp.page.heading" /></h2>   <html:errors />   <logic:present name="presonbean" scope="request">      <h2>         <bean:message key="hello.jsp.page.hello" />         <bean:write name="presonbean" property="userName" />!      </h2>   </logic:present>      <html:form action="/HelloWorld.do" focus="userName">      <bean:message key="hello.jsp.prompt.person" />      <html:text property="userName" size="16" maxlength="16" /><br/>      <html:submit property="submit" value="提交" />      <html:reset />   </html:form><br />      <html:img page="/struts-power.gif" alt="Powered by Struts" /></body></html:html>

<bean:message>：用于输出本地化的文本内容，它的Key属性指定properties资源文件的消息key。
<bean:write>：用于输出JavaBean的属性值。本例中，它用于输出personbean对象的userName属性。
<html:form>：用于创建HTML表单，它能够把HTML表单的字段和ActionFrom Bean的属性关联起来。
<html:text>：该标签是<html:form>的子标签，用于创建HTML表单的文本框。它和ActionFrom Bean的属性相关联。
<html:errors>：用于显示Struts 框架中其他组件产生的错误消息。它通过把request范围内的ActionErrors对象包含的错误消息显示出来。
<logic:presont>：用于判断JavaBean在特定的范围内是否存在，只有当JavaBean存在时，才会执行标签主体中的内容。

3.编写HelloForm.java

package hello;import javax.servlet.http.HttpServletRequest;import org.apache.struts.action.ActionErrors;import org.apache.struts.action.ActionForm;import org.apache.struts.action.ActionMapping;import org.apache.struts.action.ActionMessage;public class HelloForm extends ActionForm {/** * Version ID */private static final long serialVersionUID = 1L;private String userName="null";public String getUserName() {return userName;}public void setUserName(String userName) {this.userName = userName;}/** * Reset all properties to their default values. */public void reset(ActionMapping Mapping, HttpServletRequest request) {this.userName = null;}/** * Validate the properties posted in this request. If validation errors are * found, return an <code>ActionErrors</code> object containing the errors. * If no validation errors occur, return <code>null</code> or an empty * <code>ActionErrors</code> object. */public ActionErrors validate(ActionMapping mapping, HttpServletRequest request) {ActionErrors errors = new ActionErrors();if((userName==null)|(userName.length()<1))errors.add("username", new ActionMessage("hello.no.username.error"));return errors;}}

当用户提交HTML表单后，Struts框架将自动把表单数据组装到ActionForm Bean中，接下来Struts框架会自动调用ActionForm Bean的Validate()方法进行表单验证。如果validate()方法返回的ActionErrors对象为null，或者不包含任何ActionMessage对象，就表示没有错误，数据验证通过。如果ActionErrors中包含ActionMessage对象，就表示发生了验证错误，Struts框架会把ActionErrors对象保存到request范围内，然后把请求转发到恰当的视图，视图组件通过<html:errors>标签显示。

4.编写PresonBean.java：

package hello;public class PersonBean {private String userName = null;public String getUserName() {return userName;}public void setUserName(String userName) {this.userName = userName;}/** * This is a stub method that would be used for the Model to save * the information submitted to persistent store. In this sample * application it is not */public void saveToPersistentStore() {/** * This is a stub method that might be used to save the person's * name to persistent store(i.e. database)if this were a real application. *  * The actual business operations that would exist within a Model * component would depend upon the requirements of application. */}}

5.编写HelloAction.jsp：

package hello;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.apache.struts.action.Action;import org.apache.struts.action.ActionForm;import org.apache.struts.action.ActionForward;import org.apache.struts.action.ActionMapping;import org.apache.struts.action.ActionMessage;import org.apache.struts.action.ActionMessages;import org.apache.struts.util.MessageResources;public class HelloAction extends Action {/** * Process the specified HTTP request, and create the corresponding HTTP * response (or forward to another web component that will create it). * Return an <code>ActionForward</code> instance describing where and how * control should be forwarded, or <code>null</code> if the response has * already bean completed. */public ActionForward execute(ActionMapping mapping, ActionForm form,HttpServletRequest request, HttpServletResponse response)throws Exception {// These "messages" come from the ApplicationResource.properties fileMessageResources messages = getResources(request);/* * Validate the request parameters specified by the user * Note: Basic field validation done in HelloForm.java *       Business logic validation done in HelloAction.java */ActionMessages errors = new ActionMessages();String userName = (String)((HelloForm)form).getUserName();String badUserName = "Monster";if(userName.equalsIgnoreCase(badUserName)) {errors.add("username", new ActionMessage("hello.dont.talk.to.monster",badUserName));saveErrors(request, errors);return(new ActionForward(mapping.getInput()));}/* * Having received and validated the data submitted * from the View, we now update the model */PersonBean pb = new PersonBean();pb.setUserName(userName);pb.saveToPersistentStore();/* * If there was choice of View components that depended on the model * (or some other)status, we'd make the decision here as to which * to display. In this case,there is only one View component. *  *  We pass data to the View components by setting them as attributes *  in the page, request, session or servlet context. In this case, the *  most appropriate scoping is the "request" context since the data *  will not be neaded after the View is generated. *   *  Constants.PERSON_KEY provides a key accessible by both the *  Controller component(i.e. this class) and the View component *  (i.e the jsp file we forward to). */request.setAttribute(Constants.PERSON_KEY, pb);// Remove the Form Bean - don't need to carry values forwardrequest.removeAttribute(mapping.getAttribute());// Forward control to the specified success URIreturn (mapping.findForward("SayHello"));}}

在Action类中定义了getResources(HtttpServletRequest requets)方法，该方法返回当前默认的MessageResources对象，它封装了Resource Bundle中的文本内容，接下来Action类可以通过MessageResources对象访问properties资源文件的内容，例如,读取消息Key为"hello.jsp.title"对应的文本内容，可以调用MessageResources类的getMessage(String key)方法：

MessageResources messages = getResources(request);String title = messages.getMessage("hello.jsp.title");

6.创建存放常量的Constants.java文件:

package hello;public final class Constants {/** * The application scope attribute under which our user database * is stored */public static final String PERSON_KEY = "presonbean";}

7.配置struts-config.xml文件管理Action：

<?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"><!--    This is the Struts configuration file for the "Hello!" sample application  --> <struts-config>     <!--=============================From Bean Definitions  -->     <form-beans>         <form-bean name="HelloForm" type="hello.HelloForm" />     </form-beans>          <!-- ============================Action Mapping Definitions -->     <action-mappings>         <!-- Say Hello! -->         <action path="/HelloWorld" type="hello.HelloAction"             name="HelloForm" scope="request"             validate="true" input="/hello.jsp">             <forward name="SayHello" path="/hello.jsp" />         </action>     </action-mappings>          <!-- ===============Message Resources Definitions=========== -->     <message-resources parameter="hello.application" /> </struts-config>

8.创建资源文件application.properties：

# Application Resources for the "Hello" sample applicationhello.jsp.title=Hello - 第一个Struts程序hello.jsp.page.heading=Hello World!第一个Struts应用hello.jsp.prompt.person=请输入一个昵称来打个招呼hello:hello.jsp.page.hello=Hello# Validation and error messages for HelloForm.java and HelloAction.javahello.dont.talk.to.monster=不能向Monster说Hello！！！hello.no.username.error=请输入一个<i>用户名</i>！

为了解决中文编码问题，使用下列命令进行转码：

native2ascii -encoding UTF-8 source.properties dest.properties

9.本应用引入的Struts1.3的Jar包如下：

struts-core-1.3.10.jar
struts-taglib-1.3.10.jar
commons-beanutils-1.8.0.jar
commons-chain-1.2.jar
commons-digester-1.8.jar
commons-logging-1.0.4.jar

整个程序的结构图，如下：