org.hibernate.HibernateException:无法实例化默认tuplizer [org.hibernate.tuple.entity.PojoEntityTuplizer]

Question

我正在使用Hibernate框架开发Web应用程序.尝试运行webapp时出现此错误.

错误控制台:

Exception caught in Create Account Dataorg.hibernate.HibernateException: Unable to
instantiate default tuplizer [org.hibernate.tuple.entity.PojoEntityTuplizer]
java.lang.NullPointerException

我的映射文件(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">
<hibernate-mapping>
<class name="org.vgec.bean.CreateAccount" table="CreateAccount" >
        <id name="enrollment_number" type="java.lang.String">
            <column name="enrollment_number" length="20"/>
            <generator class="assigned" />
        </id>
       <property name="activation_code" type="java.lang.String">
        <column name="activation_code" length="50"/>
       </property>


</class>
</hibernate-mapping>

DataAccessObject文件代码:

public void addCreateAccount(CreateAccount act) throws Exception {

    Session session = null;

    try{
        //this step will read hibernate.cfg.xml
        SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
        session = sessionFactory.openSession();
        Transaction tx = session.beginTransaction();
        session.save(act);
        tx.commit();

    }catch(Exception e) {
        System.out.println("Exception caught in Create Account Data" + e);
    }finally{
        session.flush();
        session.close();
    }

}

在上面的代码抛出异常 - catch中的字符串显示在控制台的错误中.

这是我的bean或POJO文件:

package org.vgec.bean;

public class CreateAccount {

    private String enrollment_number;
    private String activation_code;

    public String getEnrollment_number() {
        return enrollment_number;
    }

    public void setEnrollment_number(String enrollment_number) {
        this.enrollment_number = enrollment_number;
    }

    public String getActivation_code() {
        return activation_code;
    }

    public void setActivation_code(String activation_code) {
        this.activation_code = activation_code;
    }

}

• 我检查了其他线程的解决方案.
• 我已经包含了javaassist.jar文件
• 所有的setter和getter都没有任何拼写错误.
• 我也有java.lang.NullPointerException.

这个错误的根本原因是什么？

Answer 1

您应该显式定义无参数构造函数。这是 Hibernate 对所有 POJO 的要求。

详细说明可以在这里找到：https ://stackoverflow.com/a/2971717/283426