小编tux*_*uxx的帖子

我从Java应用程序中收到此错误:

com.mchange.v2.c3p0.impl.NewPooledConnection - [c3p0] Another 
error has occurred [     
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: 
No operations allowed after connection closed. ] which will not be 
reported to listeners!

Java代码:

try {
    sessionFactory.beginTransaction();
    //...
    sessionFactory.commitTransaction();
} catch (Exception e) {
    sessionFactory.rollbackTransaction();
    throw new RuntimeException(e);
}

会议工厂:

try {
    sessionFactory.beginTransaction();
    ...
    sessionFactory.commitTransaction();
} catch (Exception e) {
    sessionFactory.rollbackTransaction();
    throw new RuntimeException(e);
}

public Transaction beginTransaction() throws HibernateException {
    try {
        return sessionFactory.getCurrentSession().beginTransaction();
    } catch (HibernateException hex) {
        LOG.error(String.format("Unable to start database transaction due to exception: %s.", …

我有一个包含100个字段的Base类和一个包含2个字段的Derived类.我希望通过调用Base类中的getter来在Derived类中访问所有100个字段,这就是为什么我使用继承而不是组合.在Derived中我想要一个构造函数来初始化Base的所有内容:

class Base {
  ... // 100 fields.
}

class Derived extends Base {
  ... // 2 more fields.
  Derived (Base base) {
    ... // Initialize here all 100 fields from base. Don't care about my 2 fields, can have default values.
  }
}

MySQL 数据库列：

PLANNING_DATE datetime

Java 领域：

private java.util.Date planningDate;

休眠映射：

<property name="planningDate" column="PLANNING_DATE" type="timestamp" not-null="true"/>

问题： PLANNING_DATE在 MySQL DB 中并不总是匹配planningDate字段。有时，它会得到 1 秒的偏移量。这是一个四舍五入的问题吗？