java - TimerService 抛出 NullPointerException

Question

我正在尝试编写一个服务，该服务将从远程源收集数据并将其保存到数据库中。但是，它会在服务器启动时引发 NullPointerException。我关注了Oracle's tutorial

这是日志:

java.lang.NullPointerException
    at org.eclipse.persistence.platform.server.ServerPlatformUtils.createServerPlatform(ServerPlatformUtils.java:99)
    at org.eclipse.persistence.sessions.factories.SessionManager.init(SessionManager.java:77)
    at org.eclipse.persistence.sessions.factories.SessionManager.<clinit>(SessionManager.java:71)
    at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.addSessionToGlobalSessionManager(EntityManagerSetupImpl.java:907)
    at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.initSession(EntityManagerSetupImpl.java:2671)
    at org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:675)
    at org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.getAbstractSession(EntityManagerFactoryDelegate.java:205)
    at org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.createEntityManagerImpl(EntityManagerFactoryDelegate.java:305)
    at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManagerImpl(EntityManagerFactoryImpl.java:337)
    at org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:318)
    at com.sun.enterprise.container.common.impl.EntityManagerWrapper._getDelegate(EntityManagerWrapper.java:197)
    at com.sun.enterprise.container.common.impl.EntityManagerWrapper.createNamedQuery(EntityManagerWrapper.java:521)
    at org.glassfish.ejb.persistent.timer.TimerBean.findTimersByOwnerAndState(TimerBean.java:209)
    at org.glassfish.ejb.persistent.timer.TimerBean.findActiveTimersOwnedByThisServer(TimerBean.java:523)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.glassfish.ejb.security.application.EJBSecurityManager.runMethod(EJBSecurityManager.java:1081)
    at org.glassfish.ejb.security.application.EJBSecurityManager.invoke(EJBSecurityManager.java:1153)
    at com.sun.ejb.containers.BaseContainer.invokeBeanMethod(BaseContainer.java:4786)
    at com.sun.ejb.EjbInvocation.invokeBeanMethod(EjbInvocation.java:656)
    at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:822)
    at com.sun.ejb.EjbInvocation.proceed(EjbInvocation.java:608)
    at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.doCall(SystemInterceptorProxy.java:163)
    at com.sun.ejb.containers.interceptors.SystemInterceptorProxy.aroundInvoke(SystemInterceptorProxy.java:140)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at com.sun.ejb.containers.interceptors.AroundInvokeInterceptor.intercept(InterceptorManager.java:883)
    at com.sun.ejb.containers.interceptors.AroundInvokeChainImpl.invokeNext(InterceptorManager.java:822)
    at com.sun.ejb.containers.interceptors.InterceptorManager.intercept(InterceptorManager.java:369)
    at com.sun.ejb.containers.BaseContainer.__intercept(BaseContainer.java:4758)
    at com.sun.ejb.containers.BaseContainer.intercept(BaseContainer.java:4746)
    at com.sun.ejb.containers.EJBLocalObjectInvocationHandler.invoke(EJBLocalObjectInvocationHandler.java:212)
    at com.sun.ejb.containers.EJBLocalObjectInvocationHandlerDelegate.invoke(EJBLocalObjectInvocationHandlerDelegate.java:88)
    at com.sun.proxy.$Proxy166.findActiveTimersOwnedByThisServer(Unknown Source)
    at org.glassfish.ejb.persistent.timer.PersistentEJBTimerService.restoreEJBTimers(PersistentEJBTimerService.java:369)
    at org.glassfish.ejb.persistent.timer.PersistentEJBTimerService.resetEJBTimers(PersistentEJBTimerService.java:1400)
    at com.sun.ejb.containers.EJBTimerService.initEJBTimerService(EJBTimerService.java:236)
    at com.sun.ejb.containers.EJBTimerService.getEJBTimerService(EJBTimerService.java:205)
    at com.sun.ejb.containers.EJBTimerService.getEJBTimerService(EJBTimerService.java:187)
    at com.sun.ejb.containers.BaseContainer.<init>(BaseContainer.java:825)
    at com.sun.ejb.containers.AbstractSingletonContainer.<init>(AbstractSingletonContainer.java:127)
    at com.sun.ejb.containers.CMCSingletonContainer.<init>(CMCSingletonContainer.java:76)
    at com.sun.ejb.containers.SingletonContainerFactory.createContainer(SingletonContainerFactory.java:68)
    at org.glassfish.ejb.startup.EjbApplication.loadContainers(EjbApplication.java:221)
    at org.glassfish.ejb.startup.EjbDeployer.load(EjbDeployer.java:291)
    at org.glassfish.ejb.startup.EjbDeployer.load(EjbDeployer.java:99)

我的代码:

package db;

import sun.net.www.protocol.http.HttpURLConnection;

import javax.annotation.Resource;
import javax.ejb.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.logging.Level;
import java.util.logging.Logger;

@Singleton
@Startup
public class DataCollector{

    @Resource
    TimerService timerService;

    private DBController db = new DBController();

    private static final Logger logger = Logger.getLogger("db.DataCollector");

    @Schedule(second = "*/4")
    public void collectData(Timer timer){
        String URL = "...";
        try{
            java.net.URL url = new URL(URL);

            HttpURLConnection connection = (HttpURLConnection) url.openConnection();

            InputStream is = connection.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(is));
            String line;
            String [] columns;

            while((line = reader.readLine()) != null){
                if(line.contains("Err")) {
                    logger.log(Level.WARNING, "[SENSORS]: {s}", line);
                    continue;
                }
                columns = parseData(line);
                if(columns.length != 10) {
                    logger.log(Level.WARNING, "[SENSORS]: BAD DATA");
                    continue;
                }

                db.insertToProcessingCollection(columns);
            }
        } catch (IOException e) {
            logger.log(Level.SEVERE, e.getLocalizedMessage());
        }
    }

    private String [] parseData(String data){
        return data.split("\t");
    }
}

编辑:

DBController.java:

public class DBController {
    private MongoDatabase db;

    DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.ENGLISH);
    private static final Logger logger = Logger.getLogger("db.DBController");

    public DBController(){
        MongoClient client = new MongoClient();
        db = client.getDatabase("master");
    }

    public boolean insertToProcessingCollection(String [] data){
        MongoCollection<Document> collection = db.getCollection("newData");

        try {
            Document doc = new Document()...

            collection.insertOne(doc);

            return true;
        } catch (ParseException e) {
            logger.log(Level.SEVERE, e.getMessage());
            return false;
        }
    }

    public void pushDataToHistoryCollection(){
        try {
            MongoCollection<Document> historyCollection = db.getCollection("oldData");
            MongoCollection<Document> processingCollection = db.getCollection("newData");

            processingCollection.find().forEach((Block<Document>) historyCollection::insertOne);

            processingCollection.deleteMany(new Document());
        } catch (Exception e) {
            logger.log(Level.SEVERE, e.getMessage());
        }
    }

    public JSONArray getNewData(){
        try {
            MongoCollection<Document> collection = db.getCollection("newData");

            FindIterable<Document> newData = collection.find();

            JSONArray result = convertToJSON(newData);

            pushDataToHistoryCollection();

            return result;
        } catch (Exception e) {
            logger.severe(e.getMessage());
            return null;
        }
    }

    public JSONArray convertToJSON(FindIterable<Document> data){
        JSONArray result = new JSONArray();

        data.forEach((Block<Document>) document -> {
            JSONObject object = new JSONObject(document.toJson());
            object.put("dateTime", dateFormat.format(document.get("dateTime")));
            result.put(object);
        });

        return result;
    }

    public void removeOldData(){
        MongoCollection<Document> collection = db.getCollection("oldData");
        collection.deleteMany(new Document());
    }
}

Answer 1

经过一番挖掘，我发现您的应用程序所发生的情况已经在其他几个问题上得到了报告。

即使您没有直接使用 EclipseLink，Glassfish 也在 hood 下使用它。建立数据库连接。

Glassfish 的 JIRA 上存在报告的问题之一，修复已在 EclipseLink's 2.6.2 release 上完成。 :

• https://java.net/jira/browse/GLASSFISH-21468

此外，我发现 Payara(基于 Glassfish)也有同样的问题:

• https://github.com/payara/Payara/issues/509

此外，正如 @vempo 所说，报告的问题也与另外两个 SO 问题有关:

• java.lang.NullPointerException at org.eclipse.persistence.platform.server.ServerPlatformUtils.createServerPlatform(ServerPlatformUtils.java)
• NullPointer in log during first connection to database

作为解决方案，您可以尝试将新(稳定)版本的 EclipseLink ( 2.6.2 ) 绑定(bind)到您的项目并部署它，如 @Tiny 建议的 here 。 GlassFish 提供的 EclipseLink 版本将替换为您的应用程序中包含的版本。