Spring邮件发送2

前言：上一篇博文讲解了邮件发送的基础用法(数据是写死的)，然而在实际开发中，大多数情况下邮件内容都是根据业务来动态生成的。所以在此篇博文中，我们将讲解邮件发送携带数据的几种方案。

一、解析自定义占位符

　　实现方法：通过解析自定义占位符，将传递到邮件中的数据，转换成html内容，进行发送。

1）占位符替换函数

/**
 * Replaces place holder ("${}") string in template with values in Map
 * 
 * @param template
 * @param models
 * @return
 */
public static String replacePlaceHolder(String template, Map<String, String> models) {

    if (template.indexOf("${") == -1) {
        return template;
    }
    
    while (true) {
    
        int start = template.indexOf("${");
        int end = template.indexOf("}", start);
        
        if (start != -1 && end != -1) {
            
            String key = template.substring(start + 2, end);
            
            if (models.containsKey(key)) {
                template = template.substring(0, start) + models.get(key) + template.substring(end + 1);
            }
            
        } else {
            break;
        }
        
    }
    
    return template;
    
}

2) 邮件发送Test-Case

// 1. Resolve html template to real text
String htmlTemplate = "<html lang='zh-cn'><head></head><body><h1>发送带模板数据的Email</h1><p>你好，${username}。本次您的验证码为${code}，请妥善保管</p></body></html>";
        
Map<String, String> models = new HashMap<String, String>();
models.put("username", "XXX");
models.put("code", "4551");
        
String text = StringUtils.replacePlaceHolder(htmlTemplate, models);
        
// 2. send email
boolean result = mailHandler.sendText("收件人邮箱", "发送带模板数据的Email", text);
Assert.assertEquals(true, result);

二、使用Velocity模板

　　实现方法：借用VelocityEngineUtils合并Velocity模板和数据，得到要发送的Email，进行发送。

1) 引入依赖jar包

<!-- velocity -->
<dependency>
    <groupId>org.apache.velocity</groupId>
    <artifactId>velocity</artifactId>
    <version>1.7</version>
</dependency>

2) 配置Velocity模板引擎

<!-- Define velocity engine -->
<bean id="velocityEngine" class="org.springframework.ui.velocity.VelocityEngineFactoryBean">
    <property name="configLocation" value="classpath:velocity.properties" />
</bean>

velocity.properties:

input.encoding=UTF-8
output.encoding=UTF-8
resource.loader=class
class.resource.loader.class=org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader

3) 发送邮件实现函数

// Get email content by velocity merge models
String content = VelocityEngineUtils.mergeTemplateIntoString(velocityEngine, template, encoding, models);


// Send email
MimeMessage mimeMessage = mailSender.createMimeMessage();
MimeMessageHelper helper = new MimeMessageHelper(mimeMessage, true, encoding);
helper.setFrom(form);           // set sender
helper.setTo(to);               // set recipients
helper.setSubject(subject);
helper.setText(content, true);  // Indicate the text included is HTML
mailSender.send(mimeMessage);

三、使用FreeMarker模板

　　实现方法：借用FreeMarkerTemplateUtils合并FreeMarker模板和数据，得到要发送的Email，进行发送。

1) 引入依赖jar包

<dependency>
　　<groupId>org.freemarker</groupId>
　　<artifactId>freemarker</artifactId>
　　<version>2.3.23</version>
</dependency>

2）配置FreeMarker

<!-- Define freemarker configuration -->
<bean id="freeMarkerConfiguration" class="org.springframework.ui.freemarker.FreeMarkerConfigurationFactoryBean">
　　<property name="templateLoaderPath" value="classpath:template/freemarker" />
　　<property name="defaultEncoding" value="utf-8" />
　　<property name="freemarkerSettings">
   　　<props>
       　　<prop key="template_update_delay">10</prop>
       　　<prop key="locale">zh_CN</prop>
　　　　　　<prop key="number_format">#.##</prop>
　　　　</props>
　　</property>
</bean>

3) 发送邮件实现函数

// Get email content by freeMarker template
Template realTemplate = freeMarkerConfigurer.getTemplate(template);
String content = FreeMarkerTemplateUtils.processTemplateIntoString(realTemplate, models);

// Send email
MimeMessage mimeMessage = mailSender.createMimeMessage();
MimeMessageHelper helper = new MimeMessageHelper(mimeMessage, true, encoding);
helper.setFrom(form);           // set sender
helper.setTo(to);               // set recipients
helper.setSubject(subject);
helper.setText(content, true);  // Indicate the text included is HTML
mailSender.send(mimeMessage);