JOpenID是一个开源的Java客户端库，用于实现OpenID认证。它提供了一些方便的方法来处理OpenID认证流程，并提供了一些辅助方法来解析和验证OpenID身份。

使用JOpenID可以方便地集成OpenID登录功能到Java应用程序中。以下是一个使用JOpenID的示例代码：

import org.openid4java.consumer.ConsumerManager;  
import org.openid4java.consumer.VerificationResult;  
import org.openid4java.discovery.DiscoveryInformation;  
import org.openid4java.discovery.Identifier;  
import org.openid4java.message.AuthRequest;  
import org.openid4java.message.ParameterList;  
import org.openid4java.message.ax.FetchRequest;  
import org.openid4java.message.ax.FetchResponse;  
import org.openid4java.message.ax.AxMessage;  
import javax.servlet.http.HttpServletRequest;  
import javax.servlet.http.HttpServletResponse;  
import java.util.List;  
public class OpenIdClient {  
    private ConsumerManager manager;  
    public OpenIdClient() {  
        manager = new ConsumerManager();  
    }  
    public String getAuthenticationUrl(String openId, String returnToUrl, String realm) {  
        try {  
            List discoveries = manager.discover(openId);  
            DiscoveryInformation discovered = manager.associate(discoveries);  
            org.openid4java.message.AuthRequest authReq = manager.authenticate(discovered, returnToUrl, realm);  
            FetchRequest fetch = FetchRequest.createFetchRequest();  
            fetch.addAttribute("email", "http://axschema.org/contact/email", true);  
            fetch.addAttribute("fullname", "http://axschema.org/namePerson", true);  
            authReq.addExtension(fetch);  
            return authReq.getDestinationUrl(true);  
        } catch (Exception e) {  
            e.printStackTrace();  
            return null;  
        }  
    }  
    public Identifier verifyResponse(HttpServletRequest request, String returnToUrl) {  
        try {  
            ParameterList response = new ParameterList(request.getParameterMap());  
            DiscoveryInformation discovered = (DiscoveryInformation) request.getSession().getAttribute("openid-disc");  
            StringBuffer receivingURL = request.getRequestURL();  
            String queryString = request.getQueryString();  
            if (queryString != null && queryString.length() > 0) {  
                receivingURL.append("?").append(request.getQueryString());  
            }  
            VerificationResult verification = manager.verify(returnToUrl, response, discovered);  
            Identifier verified = verification.getVerifiedId();  
            if (verified != null) {  
                AuthRequest authReq = (AuthRequest) request.getSession().getAttribute("openid-auth");  
                if (authReq != null) {  
                    FetchResponse fetchResp = (FetchResponse) verification.getAuthResponse().getExtension(AxMessage.OPENID_NS_AX);  
                    if (fetchResp != null) {  
                        List emails = fetchResp.getAttributeValues("email");  
                        String email = (String) emails.get(0);  
                        List fullnames = fetchResp.getAttributeValues("fullname");  
                        String fullname = (String) fullnames.get(0);  
                        // 将获取到的用户邮箱和姓名保存下来  
                        request.getSession().setAttribute("openid-email", email);  
                        request.getSession().setAttribute("openid-fullname", fullname);  
                        return verified;  
                    }  
                }  
            }  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
        return null;  
    }  
}  

上述代码是一个简单的OpenID客户端实现，提供了两个主要方法：

• getAuthenticationUrl()方法用于生成OpenID认证的URL并返回给前端，该URL会重定向到OpenID认证提供方进行认证。
• verifyResponse()方法用于验证OpenID返回的响应并获取用户信息，包括用户的邮箱和姓名。

以上只是一个简单的示例，可根据具体需求进行进一步定制和拓展。要使用JOpenID，需要在项目中引入相应的依赖，如下所示：

<dependencies>  
    <dependency>  
        <groupId>org.openid4java</groupId>  
        <artifactId>openid4java</artifactId>  
        <version>0.9.8</version>  
    </dependency>  
    <!-- 其他依赖... -->  
</dependencies>  

请注意，JOpenID目前已经不再活跃维护，因此建议在选择OpenID客户端库时考虑其他更为活跃和稳定的解决方案。