Question

我有一个像这样的主要方法

public static void main(String[] args) {
        String dbHosts = args[0];
        String[] dbHostsArr = dbHosts .split(",");
            for(String dbHost: dbHostsArr ){
                try {
                    Thread t = new Thread(new UpdateDataForDb(dbHost));
                    t.start();
                } catch (Exception e) {
                    e.printStackTrace();
                } 
            }
        }

在我的run方法中，我连接到db并运行一些hibernate查询来更新不同表中的数据。 main方法和run方法都在同一个Java文件中返回。当我运行此文件时，我收到以下异常

java.lang.NullPointerException at org.hibernate.engine.jdbc.internal.JdbcServicesImpl.configure（JdbcServicesImpl.java:119）在 org.hibernate.service.internal.StandardServiceRegistryImpl.configureService（StandardServiceRegistryImpl.java:75）在 org.hibernate.service.internal.AbstractServiceRegistryImpl.initializeService（AbstractServiceRegistryImpl.java:159）在 org.hibernate.service.internal.AbstractServiceRegistryImpl.getService（AbstractServiceRegistryImpl.java:131）在 org.hibernate.cfg.SettingsFactory.buildSettings（SettingsFactory.java:77）在 org.hibernate.cfg.Configuration.buildSettingsInternal（Configuration.java:2283）在 org.hibernate.cfg.Configuration.buildSettings（Configuration.java:2279）在 org.hibernate.cfg.Configuration.buildSessionFactory（Configuration.java:1748）在 org.hibernate.cfg.Configuration.buildSessionFactory（Configuration.java:1788）在 com.myfw.runtime.Application.getSessionFactory（Application.java:15）在 com.myfw.runtime.ServiceExecutionContext.setup（ServiceExecutionContext.java:114）在 com.myorg.customer.CustomerUtils.getServiceExecutionContextForCustomer（CustomerUtils.java:633）在 com.myorg.utils.UpdateDataForDb.updateDataMethod（UpdateDataForDb.java:747）在com.myorg.utils.UpdateDataForDb.run（UpdateDataForDb.java:736）at java.lang.Thread.run（Unknown Source）初始SessionFactory创建 failed.java.lang.NullPointerException线程“Thread-1”中的异常 java.lang.ExceptionInInitializerError at com.myfw.runtime.Application.getSessionFactory（Application.java:21）在 com.myfw.runtime.ServiceExecutionContext.setup（ServiceExecutionContext.java:114）在 com.myorg.customer.CustomerUtils.getServiceExecutionContextForCustomer（CustomerUtils.java:633）在 com.myorg.utils.UpdateDataForDb.updateDataMethod（UpdateData.java:747）在com.myorg.utils.UpdateDataForDb.run（UpdateData.java:736）at java.lang.Thread.run（未知来源）

只有当我使用线程运行方法时才出现此问题，如果我不使用线程并逐个调用多个dbs的updatedata方法，那么一切似乎都能正常工作。

我的代码中使用的所有方法如下：

public void run() {
        updateDataMethod(dbHost);
        return;
    }

/ * *将db名称作为输入并在db中更新表的方法 * /

private void updateDataMethod(String dbHost) {
        ServiceExecutionContext ctx = null;
            try {
                ctx = CustomerUtils.getServiceExecutionContextForCustomer(dbHost);
                System.out.println("ctx for "+dbHost);
                if(ctx != null){
                    // different methods to insert data into tables
                  ctx.tearDownNormal();
                }
            }
            catch(Exception e){
                e.printStackTrace();
                if(ctx != null)
                  ctx.tearDownException();
           }

}

/ ** *创建与db的连接 * /

public static ServiceExecutionContext getServiceExecutionContextForCustomer(String dbHost) {
        CustomerInfoThreadLocal.setDBHost(dbHost);
        ServiceExecutionContext ctx = null;
        try {
            ctx = new ServiceExecutionContext(null);
            ctx.setTransactionMode(ServiceExecutionContext.READWRITE);
            ctx.setup();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
         return ctx;
    }

public void setup() throws Exception
    {
        try
        {
            System.out.println("Hibernate session setup started");
            if (session == null)
                session = Application.getInstance().getSessionFactory().openSession();
            tx = session.beginTransaction();
            if (this.transactionMode == ServiceExecutionContext.READWRITE)
                session.setFlushMode(FlushMode.AUTO);
            else
                if (this.transactionMode == ServiceExecutionContext.READWRITECOMMITAFTER)
                    session.setFlushMode(FlushMode.COMMIT);
                else
                    session.setFlushMode(FlushMode.MANUAL);
            System.out.println("Hibernate session setup done");
        } catch (Exception e)
        {
            throw e;
        }
    }

从hibernate.cfg.xml获取sessionfactory如下

public SessionFactory getSessionFactory() throws Exception
    {
        if (sessionFactory == null)
        {
            try {
                // Create the SessionFactory from hibernate.cfg.xml
                sessionFactory =  new Configuration().configure().buildSessionFactory();
            }
            catch (Throwable ex) {
                ex.printStackTrace();
                throw new ExceptionInInitializerError(ex);
            }           
        }
        return sessionFactory;
    }

Answer 1

同步getSessionFactory()，因为它会抛出ExceptionInInitializerError，这在处理多线程时是一个常见问题。

public synchronized SessionFactory getSessionFactory() throws Exception
{
    if (sessionFactory == null)
    {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            sessionFactory =  new Configuration().configure().buildSessionFactory();
        }
        catch (Throwable ex) {
            ex.printStackTrace();
            throw new ExceptionInInitializerError(ex);
        }           
    }
    return sessionFactory;
}

通过线程

1 个答案: