接下来学习一下Struts2简单的类型转换，Struts2基于ognl.jar实现了简单类型的数据转换。比如jsp页面中的form值与字段值的转换，下面写一个例子。
1、创建一个jsp页面，编写一个form表单模拟登录，有一个用户名username和密码password，在加入一个登录按钮。如图：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@ taglib prefix="s" uri="/struts-tags" %> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>"> <title>My JSP 'index.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <s:form name="login" method="post" action="login" namespace="/"> <s:textfield label="username" name="username"></s:textfield> <s:textfield label="password" name="password"></s:textfield> <s:submit value="sgin in"></s:submit> </s:form> </body> </html>
jsp代码中使用了struts2的标签库，标签库的.tld文件在struts2-core-2.3.24.1.jar/META-INF路径下。
2、创建LoginAction，为了可以将jsp中表单的自动转换提取到变量中，需要在action文件里建立两个字段，并提供get/set方法用于接收：
public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } private String username; private String password;
其超类ActionSupport提供了验证功能，需要重写超类的validate()方法，对表单中的数据进行校验，并调用addFieldError()方法记录错误信息，当验证失败，会返回INPUT作为Result，所以需要在struts2.xml中配置返回值为input的result节点，LoginAction类具体代码如下：
package cn.net.bysoft.lesson2; import com.opensymphony.xwork2.ActionSupport; public class LoginAction extends ActionSupport { /** * */ private static final long serialVersionUID = -549393995867033046L; @Override public String execute() throws Exception { // TODO Auto-generated method stub if ("admin".equals(getUsername()) && "password".equals(getPassword())) { return SUCCESS; } else { addFieldError("username", "Sorry,wrong username or password,please login again"); return INPUT; } } @Override public void validate() { // TODO Auto-generated method stub if (getUsername().length() == 0) { addFieldError("username", "username is required"); } if (getPassword().length() == 0) { addFieldError("password", "password is required"); } } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } private String username; private String password; }
3、配置struts2.xml的内容：
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN" "http://struts.apache.org/dtds/struts-2.3.dtd">
<struts>
<package name="struts2_3_24_1" extends="struts-default">
<action name="helloWorld" class="cn.net.bysoft.lesson1.HelloWorldAction">
<result>lesson1/hello.jsp</result>
</action>
<action name="login" class="cn.net.bysoft.lesson2.LoginAction">
<result name="success">lesson2/success.jsp</result>
<result name="input">lesson2/login.jsp</result>
</action>
</package>
</struts>
4、最后当登录成功时，跳转到success.jsp页面。若login.jsp表单中输入的数据格式有误，则进行提示，如图所示，当用户名或密码为空时，提示：
当用户名密码错误时提示（这里默认用户名为admin，密码为password为正确的信息）：
当用户名和密码正确时，跳转到success.jsp：
success.jsp的代码如下：
<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%> <%@ taglib prefix="s" uri="/struts-tags" %> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>"> <title>My JSP 'success.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> username: <s:property value="username"/><br> password: <s:property value="password"/><br> </body> </html>