问题描述
- hibernate多对一提示空指针的问题
-
创建了product和factory两个实体类，字段什么的和数据库的都是一样的，配置文件如下：product.hbm.xml：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">factory.hbm.xml：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">操作查询：
try {
Session session = Hibernateutils.getSession();
session.beginTransaction();
Product product = (Product)session.get(Product.class, new Integer(1));
if(product == null)
{
System.out.println("111");
}
else {
System.out.println(product.getName());
session.getTransaction().commit();
}
} catch (Exception e) {
// TODO 自动生成的 catch 块
System.out.println("错误");
e.printStackTrace();
}
之后控制台就输出:log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
Hibernate: select product0_.id as id0_0_, product0_.name as name0_0_, product0_.price as price0_0_, product0_.factoryid as factoryid0_0_ from product product0_ where product0_.id=?
111
解决方案
http://cjh820425.iteye.com/blog/229063
解决方案二：
你这不是空指针吧？你这是没有查出来数据啊