本文介绍了在数据库中搜索时发生NullPointerException的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有以下实体Customer:
@Entity
@Table(name = "customer")
@NamedQueries({
@NamedQuery(name = "**Customer.findByEmail**", query = "SELECT c FROM Customer c WHERE c.email = :email"),
(...)
以及以下会话外观方法:
And the following session facade method:
public List<Customer> GetPorEmail(String match){
List customers = em.createNamedQuery("Customer.findByEmail").setParameter("email", match).getResultList();
return customers;
}
当我调用该方法时，结果始终为java.lang.NullPointerException.
When I call the method, the result is always java.lang.NullPointerException.
我确定我的数据库中有匹配match的电子邮件.
I am certain that there are emails matching the match in my DB.
这是怎么引起的，我该如何解决?
How is this caused and how can I solve it?
推荐答案
我认为您的EntityManager为null.请检查您是否正确注入了EntityManager引用，并且引用不为null.
I think your EntityManager is null. Please check whether you are injecting EntityManager reference properly and its not null.
此致
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