1、Action控制器

如果要使用校验，则需要继承ActionSupport类，覆写validate()方法，如果是实现Action接口，则无法覆写此方法。直接在之前的控制器基础上进行改造，修改后如下：

public class LoginAction extends ActionSupport {
	
	private static final long serialVersionUID = 1L;

	private String username;
	
	private String password;
	
	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;
	}

	@Override
	public String execute() throws Exception {
		if(username.equals("admin") && password.equals("ycz123456")) {
			HttpSession session = ServletActionContext.getRequest().getSession();
			session.setAttribute("currentUser", username);
			return SUCCESS;
		}
		return ERROR;
	}

	
	/**
	 * 此方法用于校验，会在execute()方法执行前先执行
	 */
	@Override
	public void validate() {
		if(StringUtils.isEmpty(username)) {
			addFieldError("username", "用户名不能为空！");
			return;
		}
		if(StringUtils.isEmpty(password)) {
			addFieldError("password", "密码不能为空！");
			return;
		}
		if(username.length() < 5) {
			addFieldError("username", "用户名不得少于5位！");
			return;
		}
		if(password.length() < 5) {
			addFieldError("password", "密码长度不得低于5位！");
			return;
		}
		if(!username.equals("admin") || !password.equals("ycz123456")) {
			addFieldError("msg", "用户名或密码错误！");
			return;
		}
	}
	
}

2、jsp页面

之前的login.jsp和success.jsp也需要进行改造。修改后的login.jsp如下：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%@ taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录页</title>
</head>
<body>
    <form action="login.action" method="post">
       <div>
           <label>用户名：</label>
           <input type="text"  name="username"  value="${username }"/>
           <font color="red">
                <s:fielderror fieldName="username" />
           </font>
       </div>
       <div>
          <label>密码：</label>
          <input type="password" name="password"  value="${password }"/>
          <font color="red">
                <s:fielderror fieldName="password" />
           </font>
           <font color="red">
                <s:fielderror fieldName="msg" />
           </font>
       </div>
       <div>
           <input  type="submit" value="登录" />
       </div>
    </form>
</body>
</html>

修改后的success.jsp如下：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%@ taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>主页面</title>
</head>
<%
    
%>
<body>
   <h1>当前用户：【${sessionScope.currentUser}】</h1>
</body>
</html>

3、struts.xml配置

                 <!-- 登录action -->
                 <action name="login" class="com.ycz.struts01.action.LoginAction">
                     <result name="success">/success.jsp</result>
                     <result name="error">/login.jsp</result>
                     <result name="input">/login.jsp</result>
                 </action>