Hibernate org.hibernate.LazyInitializationException：無法初始化

Question

我有兩節課：

Etudiant並支付

在數據庫中，表Etudiant具有表Pays的外鍵。

在我的代碼中，我有這樣的東西：

List<Etudiant> listEtudiants = (List<Etudiant>) etudiantService.getAll();

for(Etudiant etudiant : listEtudiants) {
    if(((JTextField)arg0.getSource()).getText().equals(etudiant.getNom())){
        System.out.println(etudiant.getPays().getNom());
    }
}

但是，當我運行這段代碼時，它失敗並出現以下異常：

org.hibernate.LazyInitializationException: could not initialize proxy - no Session

在行中：

System.out.println(etudiant.getPays().getNom());

映射學生：

<hibernate-mapping>
    <class name="tp.ihm.domain.Etudiant" table="etudiant" schema="public" optimistic-lock="version">

        <id name="numInsc" type="java.lang.Long">
            <column name="num_insc" />
            <generator class="assigned" />
        </id>
        <many-to-one name="pays" class="tp.ihm.domain.Pays" fetch="select">
            <column name="pays" not-null="true" />
        </many-to-one>

        <property name="nom" type="string">
            <column name="nom" length="50" not-null="true" />
        </property>

        <property name="prenom" type="string">
            <column name="prenom" length="50" not-null="true" />
        </property>

    </class>
</hibernate-mapping>

薪酬映射：

<hibernate-mapping>
    <class name="tp.ihm.domain.Pays" table="pays" schema="public" optimistic-lock="version">

        <id name="id" type="java.lang.Long">
            <column name="id" />
            <generator class="assigned" />
        </id>

        <property name="nom" type="string">
            <column name="nom" length="45" not-null="true" />
        </property>

        <set name="etudiants" table="etudiant" inverse="true" lazy="true" fetch="select">
            <key>
                <column name="pays" not-null="true" />
            </key>
            <one-to-many class="tp.ihm.domain.Etudiant" />
        </set>

    </class>
</hibernate-mapping>

我嘗試刪除Pays映射中的fetch屬性，然后將其值更改為渴望，但沒有任何效果。

有人可以幫我嗎？

編輯：

這是getAll方法的代碼：

public List getAll() throws EntityNotFoundException {

        // Get the current session
        Session s = getSession();
        List list = null;

        // If the BLL layer started a transaction
        // In this case it is the BLL layer that manages the session and transaction
        if (anActiveTransactionExist(s)) {
            list = s.createCriteria(Etudiant).list();
        } else {
            LOGGER.debug("DAO initialize its own transaction");
            Transaction tx = null;
            try {

                // Starts a transaction locally
                tx = s.beginTransaction();
                list = s.createCriteria(boClass).list();
                tx.commit();
            } catch (RuntimeException ex) {
                // Cancel the transaction if there is a problem
                handleDaoOpError(tx, ex);
            } finally {
                closeSession(s);
            }
        }
        if (list == null || list.size() == 0)
            throw new EntityNotFoundException();
        return list;
    }

Answer 1

您需要將Etudiant的映射從fetch=select更改為fetch=join

fetch-“join” = Disable the lazy loading, always load all the collections and entities.
fetch-“select” (default) = Lazy load all the collections and entities.

    <many-to-one name="pays" class="tp.ihm.domain.Pays" fetch="join">
        <column name="pays" not-null="true" />
    </many-to-one>