在Java中使用Struts2进行表单验证的方法

要在Java中使用Struts2进行表单验证，可以按照以下步骤进行操作：

1. 在Struts2配置文件(struts.xml)中配置验证器：

<action name="login" class="com.example.LoginAction">
    <result name="input">/login.jsp</result>
    <result>/success.jsp</result>
    <interceptor-ref name="defaultStack">
        <param name="validation.excludeMethods">execute</param>
    </interceptor-ref>
    <interceptor-ref name="validation">
        <param name="excludeMethods">input</param>
    </interceptor-ref>
    <interceptor-ref name="workflow">
        <param name="excludeMethods">input</param>
    </interceptor-ref>
</action>

2. 在Action类中添加表单字段和对应的验证规则：

public class LoginAction extends ActionSupport {
    
    private String username;
    private String password;
    
    public void setUsername(String username) {
        this.username = username;
    }
    
    public String getUsername() {
        return username;
    }
    
    public void setPassword(String password) {
        this.password = password;
    }
    
    public String getPassword() {
        return password;
    }
    
    @Override
    public void validate() {
        if (username == null || username.trim().equals("")) {
            addFieldError("username", "Username is required");
        }
        if (password == null || password.trim().equals("")) {
            addFieldError("password", "Password is required");
        }
    }
    
    public String execute() {
        // Login logic
        return SUCCESS;
    }
}

3. 在JSP页面中添加表单和错误提示信息：

"login" method="post">
    "username" label="Username" />
    "password" label="Password" />
    "Login" />


"username" />
"password" />