我正在尝试使用JavaMailSender在我的spring MVC Web应用程序和Tomcat 7中发送注册确认电子邮件，但它总是返回NullPointerException。任何人都可以帮我找出为什么我得到空指针？以下是我的配置设置：
的web.xml
<!-- jndi mail session -->
<resource-ref>
<description>
Resource reference to a factory for javax.mail.Session
instances that may be used for sending electronic mail
messages, preconfigured to connect to the appropriate
SMTP server.
</description>
<res-ref-name>mail/Session</res-ref-name>
<res-type>javax.mail.Session</res-type>
<res-auth>Container</res-auth>
</resource-ref>
应用servlet.xml中
<!-- Mail Sender bean definition -->
<bean id="smtpSession" class="org.springframework.jndi.JndiObjectFactoryBean">
<property name="jndiName" value="java:comp/env/mail/session"/>
</bean>
<bean id="mailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">
<property name="session" ref="smtpSession"/>
<!--
<property name="host" value="smtp.gmail.com" />
<property name="port" value="465" />
<property name="username" value="abc@gmail.com" />
<property name="password" value="test123" />
<property name="protocol" value="smtp" />
<property name="defaultEncoding" value="UTF-8"/>
<property name="javaMailProperties">
<props>
<prop key="mail.smtp.auth">true</prop>
<prop key="mail.smtp.connectiontimeout">5000</prop>
<prop key="mail.smtp.sendpartial">true</prop>
<prop key="mail.smtp.userset">true</prop>
<prop key="mail.mime.charset">UTF-8</prop>
<prop key="mail.smtp.isSecure">true</prop>
<prop key="mail.smtp.requiresAuthentication">true</prop>
<prop key="mail.smtp.auth">true</prop>
<prop key="mail.smtp.port">465</prop>
<prop key="mail.smtp.socketFactory.class">javax.net.ssl.SSLSocketFactory</prop>
<prop key="mail.smtp.socketFactory.fallback">false</prop>
<prop key="mail.smtp.starttls.enable">true</prop>
<prop key="mail.debug">true</prop>
</props>
</property>
-->
</bean>
<bean id="simpleMailMessage" class="org.springframework.mail.SimpleMailMessage">
<property name="from" value="abc@hotmail.com"/>
</bean>
context.xml（在tomcat conf文件夹中）
<Context path="/MVC" docBase="MVC" debug="5" crossContext="false">
<Resource name="mail/session"
auth="Container"
type="javax.mail.Session"
username="abc@gmail.com"
password="test23"
mail.debug="true"
mail.user="abc@gmail.com"
mail.password="test123"
mail.transport.protocol="smtp"
mail.smtp.host="smtp.gmail.com"
mail.smtp.auth="true"
mail.smtp.port="25"
mail.smtp.starttls.enable="true"
/>
SendMail.java
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.mail.MailException;
import org.springframework.mail.MailParseException;
import org.springframework.mail.MailSender;
import org.springframework.mail.SimpleMailMessage;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.mail.javamail.MimeMessageHelper;
import org.springframework.mail.javamail.MimeMessagePreparator;
import org.springframework.stereotype.Service;
import com.wbkit.mvc.domain.User;
@Service
public class SendMail
{
@Autowired
private JavaMailSender mailSender;
@Autowired
private SimpleMailMessage simpleMailMessage;
public void confirmRegistrationMail(User user)
{
MimeMessage message = mailSender.createMimeMessage();
try
{
MimeMessageHelper helper = new MimeMessageHelper(message, true);
helper.setFrom(simpleMailMessage.getFrom());
helper.setTo(user.getEmail());
helper.setSubject("MVC Registration");
helper.setText("Hello " + user.getFirstName() + " "
+ user.getLastName() + ", \n" +
" Your MVC Account Registration was successful. Your user ID is "
+ user.getEmail() + " and your password is "
+ user.getUserPass() + ".\n" +
"You can now access the mobile applicatoin or the web application "
+ " your user name (email) and password.");
}
catch (MessagingException e)
{
throw new MailParseException(e);
}
mailSender.send(message);
}
public void requireApprovalMail(final User user)
{
}
}
堆栈追踪：
4-Sep-2012 7:47:16 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [MVC] in context with path [/MVC] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException
at com.wbkit.mvc.util.SendMail.confirmRegistrationMail(SendMail.java:79)
at com.wbkit.mvc.web.main.RegisterController.save(RegisterController.java:276)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:436)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:424)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1812)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
com.wbkit.mvc.util.SendMail.confirmRegistrationMail（SendMail.java:79）中的java.lang.NullPointerException指向
MimeMessage message = mailSender.createMimeMessage();
。我删除了一些已注释的代码。
感谢您的建议和帮助。
答案 0 :(得分：1)
我遇到了同样的错误。它来自于将JavaMailSender bean作为自动装配字段的类的手动实例化。在OP发布的代码中，这将是SendMail服务类。
This question揭示了这种现象：手动创建的对象的自动连接字段没有收到任何对JavaMailSender bean的实际引用，因为Spring无法知道它应该做什么。之后非常明显。
希望这有助于某人。
答案 1 :(得分：0)
除了您的例外细节之外，您似乎已经包含了所有内容。
此外，看起来你只是在编造属性名称。配置中的许多属性都不是有效的JavaMail属性。另请参阅此common mistakes列表。
答案 2 :(得分：0)
从@Autowired中删除SimpleMailMessage，并在confirmRegistrationMail()方法内创建其对象：
public void confirmRegistrationMail(User user) {
SimpleMailMessage simpleMailMessage = new SimpleMailMessage();
}
这可能是因为建议使用@Autowire作为界面。例如JavaMailSender
答案 3 :(得分：-1)
在您完成自动装配的助手类上编写@Service注释。然后在您使用该类的类中使用@autowire注释。