Hibernate删除fetch上的manyToMany关系行

Question

我正在使用Hibernate4和Spring，我正在尝试将Term类映射到Document类。术语可能出现在许多文档中，文档可能包含许多术语。我已经阅读了这篇文章，并尝试了一些修复，包括重写equals和hashCode方法。

在我的数据库中，术语和文档存储在由关系表调解的分隔表中。在这里的代码中，它被称为jtable。我正在使用hibernates多对多映射，但每次我尝试获取一个term对象时，它只是删除关系表中的行。

以下是hibernate的show sql发出的示例sql输出：

Hibernate：SELECT * FROM tags WHERE token='rose'

Hibernate：delete from jtable where tag_id=?

以下是相关课程和配置：

public class Term {

    public String getWord() {
        return word;
    }

    public void setWord(String word) {
        this.word = word;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public Set<Document> getDocuments() {
        return documents;
    }

    public void setDocuments(Set<Document> documents) {
        documents = documents;
    }


    @Override
    public boolean equals(Object obj) {
        if(obj.getClass() != getClass()){
            return false;
        }
        Term term = (Term) obj;
        if (hashCode() == term.hashCode()){
            return true;
        }
        return false;
    }
    @Override
    public int hashCode(){
        return word.hashCode();
   }
 private String word;
   private int id;
   private Set<Document> documents = new HashSet<Document>();
}

文档类：

public class Document implements Comparable<Document> {


    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public URL getUrl() {
        return url;
    }

    public void setUrl(URL url) {
        this.url = url;
    }

    public Integer getLength() {
        return length;
    }

    public void setLength(Integer length) {
        this.length = length;
    }


    public Double getRank() {
        return rank;
    }

    public void setRank(Double rank) {
        this.rank = rank;
    }

    @Override
    public boolean equals(Object obj) {
        if(obj.getClass() != getClass()){
            return false;
        }
        Document document = (Document) obj;
        if (hashCode() == document.hashCode()){
            return true;
        }
        return false;
    }

    @Override
    public int hashCode(){
        int hash = 1;
        hash *= 1 + (length == null ? 0 :length);
        hash *= 2 + (rank == null ? 0 :rank);
        hash *= 3 + (title == null ? 0 : title.hashCode());
        hash *= 4 + (url.hashCode());
        return hash;

    }

    @Override
    public int compareTo(Document document) {
        return rank.compareTo(document.getRank());
    }

    private int id;
    private Integer  length;
    private Double rank;
    private String title;
    private URL url;

}

Document.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="package.Document" table="documents">
        <id name="id" type="java.lang.Integer">
            <column name="document_id" />
            <generator class="native" />
        </id>
        <property name="title" type="java.lang.String">
            <column name="title" length="255" not-null="false" />
        </property>
        <property name="length">
            <column name="length" not-null="false"/>
        </property>
        <property name="rank" type="java.lang.Double">
            <column name="rank"  not-null="false" />
        </property>
        <property name="url" type="org.hibernate.type.UrlType">
            <column name="url" length="255" not-null="false" />
        </property>

    </class>
</hibernate-mapping>

Term.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="package.Term" table="tags">
        <id name="id" type="java.lang.Integer">
            <column name="tag_id" />
            <generator class="native" />
        </id>
        <property name="word" type="string">
            <column name="token" not-null="true" unique="true" />
        </property>
        <set name="documents" table="jtable"
             inverse="false" lazy="true" fetch="select" cascade="all" >
            <key>
                <column name="tag_id" not-null="true" />
            </key>
            <many-to-many entity-name="package.Document">
                <column name="document_id" not-null="true" />
            </many-to-many>
        </set>
    </class>
</hibernate-mapping>

相关的上下文配置部分：

  <bean id="dataSource"
          class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="${database.driver}"/>
        <property name="url" value="${database.url}"/>
        <property name="username" value="${database.user}"/>
        <property name="password" value="${database.password}"/>
    </bean>

    <bean id="sessionFactory"
          class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <property name="mappingResources">
            <list>
                <value>Document.hbm.xml</value>
                <value>Term.hbm.xml</value>
            </list>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">${hibernate.dialect}</prop>
                <prop key="hibernate.show_sql">${hibernate.show_sql}</prop>
                <prop key="format_sql">true</prop>
                <prop key="hibernate.hbm2ddl.auto">${hibernate.hbm2ddl.auto}</prop>
            </props>
        </property>
    </bean>

我一直在看这个错误，所以任何答案都会受到赞赏。