无法调用方法，因为注入是 null

Question

我正在创建 web 应用程序，我正在使用 java ee 7，使用 mavenAA8359D845065 插件部署它。 我有 servlets、ejb、一些逻辑、jpa 集成等。我使用命令模式来处理请求。 我的主 servlet 获取参数并根据来自隐藏输入的命令作为参数将用户重定向到下一页。

我有实现登录逻辑的登录表单和类。 这些课程是下一个

编辑（我编辑了添加 bean 注入的代码。我还为每个命令创建了相应的限定符）

我的代码

登录Command.java

@SigninCommandQualifier
public class SigninCommand implements Command {

    @Inject
    private UserEJB userEJB;

    public String execute(HttpServletRequest request, HttpServletResponse response) throws IOException {
        String password = request.getParameter("password");
        String email = request.getParameter("email");
        User signinUser = new User(email, password);
        User foundUser = userEJB.findUser(signinUser);
        if (foundUser != null) {
            request.setAttribute("passedAuth", true);
            return PagesManager.getProperty("page.nameGeneration");
        } else {
            request.setAttribute("passedAuth", false);
            return PagesManager.getProperty("page.signin");
        }
    }
}

用户EJB.java

@Stateless
public class UserEJB implements UserEJBRemote{
    @Inject
    private EntityManager em;
    public List<User> findUsers() {
        TypedQuery<User> query = em.createNamedQuery(FIND_ALL, User.class);
        return query.getResultList();
    }

    public User findUser(@NotNull User user) {
        return em.find(User.class, user);
    }

    public
    @NotNull
    User createUser(@NotNull User user) {
        em.persist(user);
        return user;
    }

    public
    @NotNull
    User updateUser(@NotNull User user) {
        return em.merge(user);
    }

    public void deleteUser(@NotNull User user) {
        em.remove(em.merge(user));
    }
}

豆子.xml

<beans xmlns="http://xmlns.jcp.org/xml/ns/javaee"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/beans_1_1.xsd"
       version="1.1" bean-discovery-mode="all">
</beans>

ProjectServlet.java

public class ProjectServlet extends HttpServlet {

    @Inject
    @EmptyCommandQualifier
    private Command command;

    @Inject
    private ActionFactory actionFactory;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        processRequest(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        processRequest(request, response);
    }

    private void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
        String action = request.getParameter("command");
        try {
            command = actionFactory.defineCommand(action);
        } catch (IllegalArgumentException e) {
            request.setAttribute("msg", action + " " + MessageManager.getProperty("message.wrongaction"));
        }
        String page;
        try {
            page = command.execute(request, response);
        } catch (IOException e) {
            page = PagesManager.getProperty("page.error");
        }
        if (page != null) {
            if (page.equals("not redirecting")) {
                return;
            }
            RequestDispatcher dispatcher = getServletContext().getRequestDispatcher(page);
            dispatcher.forward(request, response);
        } else {
            page = PagesManager.getProperty("page.index");
            request.getSession().setAttribute("nullPage",
                    MessageManager.getProperty("message.nullpage"));
            response.sendRedirect(request.getContextPath() + page);
        }
    }
}

命令.java

public interface Command {
    String execute(HttpServletRequest request, HttpServletResponse response) throws IOException;
}

CommandEnum.java

public enum CommandEnum {

    EMPTY_COMMAND {
        {
            this.command = emptyCommand;
        }
    },
    NAME_GENERATION {
        {
            this.command = nameGenerationCommand;
        }
    },
    NAME_GENERATION_SETTINGS {
        {
            this.command = nameGenerationSettingsCommand;
        }
    },
    SIGNIN {
        {
            this.command = signinCommand;
        }
    };

    Command command;

    @Inject
    EmptyCommand emptyCommand;
    @Inject
    NameGenerationCommand nameGenerationCommand;
    @Inject
    NameGenerationSettingsCommand nameGenerationSettingsCommand;
    @Inject
    SigninCommand signinCommand;

    public Command getCommand() {
        return command;
    }
}

ActionFactory.java

public class ActionFactory {

    @Inject
    @EmptyCommandQualifier
    private Command command;

    @Inject
    private CommandEnum commandEnum;

    public Command defineCommand(String action) throws IllegalArgumentException {
        if (action == null || action.isEmpty()) {
            return command;
        }
        commandEnum = CommandEnum.valueOf(action.toUpperCase());
        command = commandEnum.getCommand();
        return command;
    }

    @Produces
    public static CommandEnum getEmptyCommandEnum()
    {
        return CommandEnum.EMPTY_COMMAND;
    }
}

问题

当我单击登录页面上的登录按钮时，我捕获下一个异常：

java.lang.NullPointerException: Cannot invoke "factory.ActionFactory.defineCommand(String)" because "this.actionFacto
ry" is null
        at servlet.ProjectServlet.processRequest(ProjectServlet.java:39)
        at servlet.ProjectServlet.doPost(ProjectServlet.java:33)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
        at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
        at java.base/java.lang.Thread.run(Thread.java:832)
        at org.apache.coyote.http11.AbstractHttp11Proces
sor.process(AbstractHttp11Processor.java:1041)
        at org.apache.coyote.AbstractProtocol$AbstractCo
nnectionHandler.process(AbstractProtocol.java:603)
        at org.apache.tomcat.util.net.JIoEndpoint$Socket
Processor.run(JIoEndpoint.java:310)
        at java.base/java.util.concurrent.ThreadPoolExec
utor.runWorker(ThreadPoolExecutor.java:1130)
        at java.base/java.util.concurrent.ThreadPoolExec
utor$Worker.run(ThreadPoolExecutor.java:630)
        at java.base/java.lang.Thread.run(Thread.java:83
2)

actionFactory 是 null 我不知道为什么。

我试过的

1. 向@Stateless添加SigninCommand注解
2. 将 bean.xml 文件添加到 WEB-INF 文件夹（在它被放置在 META-INF 之前）
3. 清除 IDEA 缓存
4. 将@Named注释附加到UserEJB class

但我仍然得到NPE。

请帮忙。

Answer 1

问题是，除了 CDI bean 使用 new 之外，tomcat 被用作容器，没有像 Weld-Standalone 这样的任何添加。 因此，@Ejb、@Standalone 等 Ejb 注释和 @Inject 等 CDI 注释在部署战争文件期间都没有任何影响。 合理的解决方案是从纯 servlet-container 切换到 microprofile-container，如 wildfly、kumuluzee...

Answer 2

这通常是由调用层次结构中某处的 new 实例化引起的。 确保您的SigninCommand class 的任何实例都没有被new实例化。 由于我们没有您的主要 servlet 代码，我很抱歉这只是一个猜测，因为我无法发表评论要求包含您的 servlet 代码。 干杯。