Spring Mail 教程帮助，接收空指针异常

Question

我正在遵循 Spring Mail 教程中的 Spring Mail 文档步骤 27.1 - 27.2.2。我的目标是将电子邮件功能添加到已经创建的 Spring-MVC 项目中。在创建新的 SimpleMailMessage 对象时，我遇到了java.lang.NullPointerException（更多详细信息在下面的完整堆栈跟踪中）。

SimpleOrderManager

我尽量靠近教程

public class SimpleOrderManager implements OrderManager {
    private MailSender mailSender;
    private SimpleMailMessage templateMessage;


    public void setMailSender(MailSender mailSender) {
        this.mailSender = mailSender;
    }

    public void setTemplateMessage(SimpleMailMessage templateMessage) {
        this.templateMessage = templateMessage;
    }

    public void placeOrder(User user) {
        SimpleMailMessage msg = new SimpleMailMessage(this.templateMessage);
        msg.setTo(user.getEmail());
        msg.setText("Dear you");
        try{
            this.mailSender.send(msg);
        }
        catch (MailException ex) {
            System.err.println(ex.getMessage());
        }
    }

我发现了一个尚未解决的related case。

我向 Maven 添加了 Javax Mail 依赖项。

另外，我创建了一个applicationContext-mail.xml 配置文件，我确保web.xml 文件引用了该文件

applicationContext-mail.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="mailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">
        <property name="host" value="mail.location.company.edu"/>
    </bean>

    <!-- this is a template message that we can pre-load with default state -->
    <bean id="templateMessage" class="org.springframework.mail.SimpleMailMessage">
        <property name="from" value="myEmail@mail.org"/>
        <property name="subject" value="Your order"/>
    </bean>

    <bean id="reminderManager" class="edu.company.peerreview.mvc.utility.SimpleOrderManager">
        <property name="mailSender" ref="mailSender"/>
        <property name="templateMessage" ref="templateMessage"/>
    </bean>
</beans>

堆栈跟踪

SEVERE: Servlet.service() for servlet [peerReview] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException
    at edu.example.department.peerreview.mvc.utility.SimpleOrderManager.placeOrder(SimpleOrderManager.java:61)
    at edu.example.department.peerreview.mvc.HomeController.home(HomeController.java:25)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:212)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:629)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:590)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:900)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:827)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:874)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:779)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:312)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:116)
    at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:324)
    at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:324)
    at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:101)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:324)
    at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:324)
    at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:324)
    at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:324)
    at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:150)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:324)
    at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:182)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:324)
    at edu.example.department.peerreview.security.RequestParameterAuthenticationFilter.doFilter(RequestParameterAuthenticationFilter.java:58)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:324)
    at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:324)
    at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:324)
    at org.springframework.security.web.session.ConcurrentSessionFilter.doFilter(ConcurrentSessionFilter.java:125)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:324)
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:174)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:196)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:722)

错误来自Assert语句

SimpleMailMessage的Spring源码

public SimpleMailMessage(SimpleMailMessage original) {
    Assert.notNull(original, "The 'original' message argument cannot be null");
    this.from = original.getFrom();
    this.replyTo = original.getReplyTo();
    if (original.getTo() != null) {
        this.to = copy(original.getTo());
    }
    if (original.getCc() != null) {
        this.cc = copy(original.getCc());
    }
    if (original.getBcc() != null) {
        this.bcc = copy(original.getBcc());
    }
    this.sentDate = original.getSentDate();
    this.subject = original.getSubject();
    this.text = original.getText();
}

据我所知，我已完成教程中的所有说明。在simpleOrderManager中，我尝试在创建新实例时使用空构造函数SimpleMailMessage msg = new SimpleMailMessage() but that gives me a null pointer expection error when executingthis.mailSender.send(msg);`

编辑：从 Home 控制器添加 home 操作

@RequestMapping(value = "/", method = RequestMethod.GET)
public String home(Model model) {
    // Redirect to the user's dashboard

    SimpleOrderManager qaFollowUp = new SimpleOrderManager();
    User user = userDAO.findById(485);
    qaFollowUp.placeOrder(user);

    return "redirect:/users/" + getAuthenticatedUser().getId() + "/dashboard/" + UserHelper.getURLName(getAuthenticatedUser());
}

Answer 1

你必须让 Spring 注入 SimpleOrderManager bean。如果您使用 new 创建它，Spring 将不会意识到它（它不是应用程序上下文的一部分）并且不会自动装配它的依赖项（您的 templateMessage案例）。