利用Velocity结合Spring发email

在spring中发mail是一件容易的事，如果利用Velocity做mail的模板来发送就更得心应手了。

首先，还是简单描述sping中的配置，发mail需要一个mail的engin：

<bean id="mailEngine" class="com.aodragon.jdt.backend.service.impl.MailEngineImpl">

    <property name="mailSender">

      <ref local="mailSender"/>

    </property>

    <property name="velocityEngine">

      <ref local="velocityEngine"/>

    </property>

  </bean>

实现的类如下：

package com.aodragon.jdt.backend.service.impl;

import java.util.Map;

import javax.mail.MessagingException;

import javax.mail.internet.MimeMessage;

import org.apache.commons.logging.*;

import org.apache.velocity.app.VelocityEngine;

import org.apache.velocity.exception.VelocityException;

import org.springframework.core.io.ClassPathResource;

import org.springframework.mail.*;

import org.springframework.mail.javamail.*;

import org.springframework.ui.velocity.VelocityEngineUtils;

import com.aodragon.jdt.backend.service.MailEngine;

public class MailEngineImpl implements MailEngine {

    protected static final Log log = LogFactory.getLog(MailEngineImpl.class);

    private MailSender mailSender;

    private VelocityEngine velocityEngine;

    public void setMailSender(MailSender mailSender) {

        this.mailSender = mailSender;

    }

    public void setVelocityEngine(VelocityEngine velocityEngine) {

        this.velocityEngine = velocityEngine;

    }

    public void sendMessage(SimpleMailMessage msg, String templateName,

                            Map model) {

        String result = null;

        try {

            result =                VelocityEngineUtils.mergeTemplateIntoString(velocityEngine, templateName, model);

        } catch (VelocityException e) {

            e.printStackTrace();

        }

        msg.setText(result);

        send(msg);

    }

    public void sendMessage(SimpleMailMessage msg, String templateName, String encoding, Map model) {

        String result = null;

        try {

            result =                VelocityEngineUtils.mergeTemplateIntoString(velocityEngine, templateName, encoding,model);

        } catch (VelocityException e) {

            e.printStackTrace();

        }

        msg.setText(result);

        send(msg);

    }

    public void send(SimpleMailMessage msg) {

        try {

            mailSender.send(msg);

        } catch (MailException ex) {

            //log it and go on

            log.error(ex.getMessage());

        }

    }

    public void sendMessage(String[] emailAddresses,

                            ClassPathResource resource, String bodyText,

                            String subject, String attachmentName)

    throws MessagingException {

        MimeMessage message =

            ((JavaMailSenderImpl) mailSender).createMimeMessage();

        // use the true flag to indicate you need a multipart message

        MimeMessageHelper helper = new MimeMessageHelper(message, true);

        helper.setTo(emailAddresses);

        helper.setText(bodyText);

        helper.setSubject(subject);

        helper.addAttachment(attachmentName, resource);

        ((JavaMailSenderImpl) mailSender).send(message);

    }

}

这个engin实现了4个方法，在需要的时候调用，这里也需要两个对象：

private MailSender mailSender;

    private VelocityEngine velocityEngine;

所以在配置的时候需要注意有：

<bean id="mailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">

    <property name="host">

      <value>${email.host}</value>

    </property>

    <property name="username">

      <value>${email.username}</value>

    </property>

    <property name="password">

      <value>${email.password}</value>

    </property>

  </bean>

<bean id="velocityEngine" class="org.springframework.ui.velocity.VelocityEngineFactoryBean">

    <property name="velocityProperties">

      <props>

        <prop key="resource.loader">class</prop>

        <prop key="class.resource.loader.class">org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader</prop>

        <prop key="velocimacro.library"/>

      </props>

    </property>

  </bean>

这样配置是完成了，下面给一个在Action中发mail的调用示例

public ActionForward save(ActionMapping actionMapping,

                              ActionForm actionForm,

                              HttpServletRequest httpServletRequest,

                              HttpServletResponse httpServletRresponse) throws

        Exception {

        String toEmail = "…"

HashMap model = new HashMap();

        this.smm.setTo(toEmail);

        this.smm.setSubject("谢谢您的关注");

        model.put("content","………….. ");

        MessageResources resources = getResources(httpServletRequest);

        this.mailEngin.sendMessage(this.smm,resources.getMessage(_locale,"velocity.email.bookproduct"),model);

        return list(actionMapping, actionForm, httpServletRequest,

                    httpServletRresponse);

    } // end save

这里需要说明的就是调用sendMessage中的第2个参数为resources.getMessage(_locale,"velocity.email.bookproduct")，这里是为了适应多语言版本，调用对应的vm文件，velocity.email.bookproduct是保存在ApplicationResource.properties各个版本中的vm文件对应的路径。其中_locale = (Locale)request.getSession().getAttribute(Globals.LOCALE_KEY)。

这样，简单的Velocity结合Spring发送email就完成了，还可以添加一个TASK来管理邮件的队列，让系统定时发送队列中的邮件；在线管理mailSender中的各个参数等等。