<h:form>
    <h:outputLabel for="username" value="用户名:" />
    <h:inputText id="username" value="#{userBean.username}" required="true">
        <f:ajax event="blur" render="usernameMessage" />
    </h:inputText>
    <h:message id="usernameMessage" for="username" style="color:red" />
    
    <h:commandButton value="提交" action="#{userBean.submit}">
        <f:ajax execute="@form" render="@form" />
    </h:commandButton>
</h:form>

@FacesValidator("emailValidator")
public class EmailValidator implements Validator {
    @Override
    public void validate(FacesContext context, UIComponent component, Object value) throws ValidatorException {
        String email = (String) value;
        if (!email.matches("^[A-Za-z0-9+_.-]+@(.+)$")) {
            throw new ValidatorException(new FacesMessage("无效的邮箱格式"));
        }
    }
}

<h:inputText id="email" value="#{userBean.email}">
    <f:validator validatorId="emailValidator" />
    <f:ajax event="blur" render="emailMessage" />
</h:inputText>
<h:message id="emailMessage" for="email" style="color:red" />

public class UserBean {
    @NotNull(message="用户名不能为空")
    @Size(min=3, max=20, message="用户名长度必须在3-20个字符之间")
    private String username;
    
    // getter和setter
}

<h:inputText id="username" value="#{userBean.username}">
    <f:ajax event="blur" render="usernameMessage" />
</h:inputText>
<h:message id="usernameMessage" for="username" style="color:red" />

<h:inputText id="password" value="#{userBean.password}" />
<h:inputText id="confirmPassword" value="#{userBean.confirmPassword}">
    <f:validator validatorId="passwordMatchValidator" />
    <f:ajax event="blur" render="confirmPasswordMessage" />
    <f:attribute name="passwordComponent" value="#{password}" />
</h:inputText>
<h:message id="confirmPasswordMessage" for="confirmPassword" />

@FacesValidator("passwordMatchValidator")
public class PasswordMatchValidator implements Validator {
    @Override
    public void validate(FacesContext context, UIComponent component, Object value) {
        UIInput passwordInput = (UIInput) component.getAttributes().get("passwordComponent");
        String password = (String) passwordInput.getValue();
        String confirmPassword = (String) value;
        
        if (!password.equals(confirmPassword)) {
            throw new ValidatorException(new FacesMessage("两次输入的密码不匹配"));
        }
    }
}