Question

我正在使用速度1.7与spring 3.1框架发送电子邮件。 velocity用于电子邮件模板。

以下是配置

<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>
        </props>
    </property>
</bean>

以下是我的代码

 @Component
 public class EmailUtils {

    @Autowired
    private static VelocityEngine velocityEngine;

    public static void sendMail(String subject, Map data, String template,
            String toName, String toAddress) {


        HtmlEmail email = new HtmlEmail();

        try {
            email.setHostName(hostName);
            email.setSmtpPort(smtpPort);
            email.setSubject(subject);

            System.out.println(template +" template");
            System.out.println(data +" data ");
            System.out.println(velocityEngine +" velocityEngine ");

            String message = VelocityEngineUtils.mergeTemplateIntoString(
                    velocityEngine, template, data);

            System.out.println(message +" message message ");

            email.setMsg(message);
            email.addTo(toAddress, toName);
            email.setFrom(fromAddress, fromName);
            email.send();
        } catch (EmailException e) {
            // TODO Auto-generated catch block

            e.printStackTrace();
        }
    }
}

当我运行应用程序时，我得到以下错误。

java.lang.NullPointerException
at org.springframework.ui.velocity.VelocityEngineUtils.mergeTemplate(VelocityEngineUtils.java:58)

因速度引擎为空。

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd
    http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd">

<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>
        </props>
    </property>
</bean>

请帮帮我。我还需要做其他任何配置吗？

Answer 1

使用时遇到了同样的问题。我可以通过以下方式解决它：

@Configuration
public class ApplicationConfiguration {

    @Bean
    public VelocityEngine getVelocityEngine() throws VelocityException, IOException{
        VelocityEngineFactory factory = new VelocityEngineFactory();
        Properties props = new Properties();
        props.put("resource.loader", "class");
        props.put("class.resource.loader.class", "org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");
        factory.setVelocityProperties(props);
        return factory.createVelocityEngine();      
    }
}

但相反 - 因为我在视图中使用了速度模板，并且已经声明了VelocityConfigurer，所以我在我的VelocityConfigurer声明中使用了Autowired，并在其上调用了getVelocityEngine（）。

我确实发现，如果将它自动连接到@Service-s或@ Component-s并且您已在共享的applicationContext.xml文件中声明，那么xml声明也必须位于该共享的applicationContext.xml中而不是xxx-servlet.xml配置。

我认为这是因为applicationContext.xml在应用程序中的所有servlet之间共享，因此必须在xxx-servlet.xml文件之前完全处理它。

或者，您可以启用spring bean工厂调试，看看它是否有任何实例化问题：

log4j.category.org.springframework.beans.factory=DEBUG

Answer 2

我认为您不能将@Autowired与静态字段一起使用。您可以使用非静态setter解决此问题：

@Autowired
public void setVelocityEngine(VelocityEngine ve) {
  EmailUtils.velocityEngine = ve;
}

或以其他方式，但我强烈建议将EmailUtils转换为非静态bean。 Spring更好地处理非静态组件（不需要丑陋的黑客），可以交换实现，你的代码将坚持DI philosphy。

Answer 3

这是我的尝试，我通过ClassPathXmlApplicationContext手动初始化“velocityEngine”bean：

Spring application-context.xml

<bean id="velocityEngine" class="org.springframework.ui.velocity.VelocityEngineFactoryBean">
  <property name="velocityProperties">
    <value>
      resource.loader=class
      class.resource.loader.class=org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader
    </value>
  </property>
</bean>

这是我的template_text.vm，将它放在类路径中，与application-context.xml相同。

Dear $userName,

You have made the following request on $userTime.

#if( $isFileMissing )
Missing file(s) found in home directory:
#foreach( $missingFile in $missingFiles )
- $missingFile
#end
#end

Best regards,

这是Java代码：

public static void main(String[] args) throws Exception {
    String[] springConfig = {"application-context.xml"};
    org.springframework.context.ApplicationContext context = new org.springframework.context.support.ClassPathXmlApplicationContext(springConfig);

    java.util.Map<String, Object> model = new java.util.HashMap<String, Object>();
    model.put("userName", "John Low");
    model.put("userTime", "2015-10-28 23:59:59");
    model.put("isFileMissing", true);
    model.put("missingFiles", new String[] {"line 1", "line 2", "line 3"});
    String text = org.springframework.ui.velocity.VelocityEngineUtils.mergeTemplateIntoString((VelocityEngine)context.getBean("velocityEngine"), "/template_text.vm", "UTF-8", model);
    System.out.println(text);
}

输出：

Dear John Low,

You have made the following request on 2015-10-28 23:59:59.

Missing file(s) found in home directory:
- file 1
- file AAA
- line 3

Best regards,

Answer 4

将项目升级到Java 11 + Spring Boot 2.1.8时遇到相同的问题。我可以通过以下方式解决它：

@Configuration
public class AppConfig {
    @Bean
    public VelocityEngine velocityEngine() throws Exception {
        Properties properties = new Properties();
        properties.setProperty("input.encoding", "UTF-8");
        properties.setProperty("output.encoding", "UTF-8");
        properties.setProperty("resource.loader", "class");
        properties.setProperty("class.resource.loader.class", "org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");
        VelocityEngine velocityEngine = new VelocityEngine(properties);
        return velocityEngine;
    }
}

如何在Spring中使用速度1.7

4 个答案: