Hibernate 类转换异常 [英] Hibernate Class Cast Exception
问题描述
当我尝试将结果集强制转换为映射类时,我遇到了一个带有休眠的类强制转换异常......我能够看到返回的结果集中的数据......但是它作为一个对象返回[] 并且我能够将对象 [] 设置为列表...我是否正确地进行了休眠映射?我从查询中得到了正确的数据,但它没有正确映射...
I am getting a class cast exception with hibernate when trying to cast the result set to the mapping class... I am able to see the data in the result set that is returned...however it comes back as an Object [] and I am able to set the Object [] to the a List...Am I doing my hibernate mappings correctly? I get the correct data back from the query but its not mapping correctly...
映射
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class">com.ibm.db2.jcc.DB2Driver</property>
<property name="hibernate.connection.url">jdbc:db2://****</property>
<property name="hibernate.connection.username">*****</property>
<property name="hibernate.connection.password">*****</property>
<property name="hibernate.connection.pool_size">1</property>
<property name="show_sql">true</property>
<property name="hbm2ddl.auto">NONE</property>
<property name="dialect">org.hibernate.dialect.DB2Dialect</property>
<property name="hibernate.cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
<property name="hibernate.current_session_context_class">thread</property>
<mapping package="db2"/>
<mapping class="db2.EQP_UT"/>
<mapping class="db2.EQP_COMP_PRIMARY"/>
</session-factory>
</hibernate-configuration>
映射类
@Entity
@Table(name = "EQP_UT")
public class EQP_UT implements Serializable {
@Id
private String INITIAL;
@Id
private String NUMBER;
private Integer AXL_CNT;
private String EQP_TYP_CD;
private String EIN;
private Integer TRUK_CNT;
@OneToOne
@JoinTable(name = "EQP_COMP_PRIMARY",
joinColumns = {@JoinColumn(name = "INITIAL"), @JoinColumn(name = "NUMBER")},
inverseJoinColumns = {
@JoinColumn(name = "INITIAL"), @JoinColumn(name="NUMBER")
}
)
public EQP_COMP_PRIMARY eqp_comp;
public EQP_UT(){
this.INITIAL = "";
this.NUMBER = " ";
int a = this.retrieve();
System.out.println("This is the data is here..." + a);
}
public String getNumber()
{
return NUMBER;
}
public void setNumber(String num)
{
this.NUMBER = num;
}
public String getInitial()
{
return INITIAL;
}
public void setInitial(String init)
{
this.INITIAL = init;
}
public int retrieve()
{
Session session = null;
Transaction transaction = null;
try{
session = HibernateUtil.getDB2SessionFactory().getCurrentSession();
transaction = session.beginTransaction();
String init = "AARE";
String number = String.format("%010d", 9350);
Integer num = Integer.parseInt(number);
String queryString = "SELECT A.INITIAL, A.NUMBER, " +
"A.TRUK_CNT, A.EQP_TYP_CD, A.AXL_CNT, " +
"B.TRUK_AXL_CNT, A.EIN FROM EQP_UT AS A " +
"LEFT JOIN A.eqp_comp AS B " +
"WHERE A.INITIAL||A.NUMBER IN (:carList) AND A.INITIAL IN (:initList) AND A.NUMBER IN (:numberList) " +
"AND B.TRUK_AXL_CNT > 0";
Query query = session.createQuery(queryString);
query.setParameterList("carList", Globals.returnCarList());
query.setParameterList("initList", Globals.returnCarListCarInits());
query.setParameterList("numberList", Globals.returnCarListCarNumbers());
@SuppressWarnings("unchecked")
List obj = query.list();
System.err.println("CLASS NAME IS " + obj.get(0).getClass().getClass().getName());
Globals.eqpList = obj; //Globals.eqpList is List<EQP_UT>
session.getTransaction().commit();
return 10;
}
catch(HibernateException ex)
{
ex.printStackTrace();
transaction.rollback();
}
catch(Exception ex)
{
System.err.println(ex.getMessage());
}
return -1;
}
}
加入班级
@Entity
@Table(name = "EQP_COMP_PRIMARY")
public class EQP_COMP_PRIMARY implements Serializable{
private Integer TRUK_AXL_CNT;
@Id
private String INITIAL;
@Id
private String NUMBER;
}
主要
//tons more code...
for(int i = 0; i < Globals.eqpList.size(); i++)
{
EQP_UT e = Globals.eqpList.get(i); //class cast exception - and Globals.eqpList is List<EQP_UT>
}
//tons more code...
推荐答案
对于测试,我建议您在产生类强制转换异常的语句周围放置一个 try-catch 子句,在 catch 块中设置一个断点并查看哪个将第 i 个元素归类.
For tests I recommend you to put a try-catch clause around the statement which is producing the class cast exception, set a breakpoint in the catch block and look which class the i-th element really is.
针对您的问题:
您正在使用 HQL SELECT
语句.带有该语句的查询返回一个列表,但该列表的元素不一定是 EQP_TU 的实例;它们也可以是一个对象数组.
You are using the HQL SELECT
statement. The query with this statement returns a list, but the elements of the list are not necessarily instances of EQP_TU; they also can be an array of object.
适合您的解决方案:
使用FROM
语句代替SELECT
语句.在您的代码中:
Use the FROM
statement instead of the SELECT
statement. In your code:
String queryString = "FROM EQP_UT AS A " +
"LEFT JOIN A.eqp_comp AS B " +
"WHERE A.INITIAL||A.NUMBER IN (:carList) AND A.INITIAL IN (:initList) AND A.NUMBER IN (:numberList) " +
"AND B.TRUK_AXL_CNT > 0";
然后您可以确保获得一个包含您在 FROM 之后提到的类的实例的列表(代码中的 EQP_UT).
Then you can be sure to get a list with instances of the class you mentioned after FROM (EQP_UT in your code).
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