如何在java程序里面发送html邮件

        </dependency>    

package com.xxx.tools;

import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeUtility;

public class HtmlEmail {

    private String smtpServer;

    private String username;

    private String password;

    public void sendMessage(String to, String subject, String messageText) throws MessagingException, java.io.UnsupportedEncodingException {
        java.util.Properties props = new java.util.Properties();
        props.setProperty("mail.smtp.auth", "true");//指定是否需要SMTP验证
        props.setProperty("mail.smtp.host", smtpServer);//指定SMTP服务器
        props.put("mail.transport.protocol", "smtp");
        Session mailSession = Session.getDefaultInstance(props);
        //mailSession.setDebug(true);//是否在控制台显示debug信息

        InternetAddress fromAddress = new InternetAddress(username);
        InternetAddress toAddress = new InternetAddress(to);

        MimeMessage emailMessage = new MimeMessage(mailSession);
        emailMessage.setFrom(fromAddress);
        emailMessage.addRecipient(javax.mail.Message.RecipientType.TO, toAddress);
        emailMessage.setSentDate(new java.util.Date());
        emailMessage.setSubject(MimeUtility.encodeText(subject, "utf-8", "B"));

        emailMessage.setContent(messageText, "text/html;charset=utf-8");

        
        Transport transport = mailSession.getTransport("smtp");
        transport.connect(smtpServer, username, password);
        transport.sendMessage(emailMessage, emailMessage.getAllRecipients());
        transport.close();
    }

    public String getSmtpServer() {
        return smtpServer;
    }

    public void setSmtpServer(String smtpServer) {
        this.smtpServer = smtpServer;
    }

    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;
    }
}

<bean id="htmlMail" class="com.xxx.tools.HtmlEmail">
        <property name="smtpServer" value="smtp.qq.com"/>
        <property name="username" value="1xxxx7@qq.com"></property>
        <property name="password" value="xxxxxxx"></property>
    </bean>

@Controller
@RequestMapping("/user")
public class UserRegController {

    @Resource
    private HtmlEmail email;

    @RequestMapping("/reg")
    public void sendMail(@RequestParam("username") String username, @RequestParam("userpass") String userpass, @RequestParam("email") String email_addr, HttpServletRequest request) {

        String valid_string = request.getSession(true).getId();

        String valid_url = " 点击此链接激活账号";

        try {
            email.sendMessage(email_addr, "用户激活", valid_url);
        } catch (MessagingException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }

    }