我使用的是Spring 4.1.0和休眠实体管理器4.1.9
另外，我使用的是Postgres 9.6
我有以下实体：

@Entity
@Table(name = "audit", schema = "public")
@SequenceGenerator(name = "AUDIT_SEQUENCE", sequenceName = "AUDIT_SEQUENCE", allocationSize = 1, initialValue = 1)
public class AuditTrail {

        @Id
        @Column(name = "auditid", unique = true)
        @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "AUDIT_SEQUENCE")
        private long auditId;

        @Column(name = "auditvalue")
        private String auditValue;

        ... getter setters ...
}

这给出了字符变化的列结构（255）。
我想将auditValue列的长度更新为10000。因此，我将实体更新为：

@Column(name = "auditvalue", length = 10000)
private String auditValue;

但列结构不会更新。
我的应用程序上下文. xml包含：

<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
    <property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>
<bean id="entityManagerFactory"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="packagesToScan" value="com.avaya.mediamanager.entity" />
    <property name="jpaVendorAdapter" ref="hbAdapterBean_pgsql"/>   
    <property name="jpaProperties">
        <props>
            <prop key="hibernate.show_sql">false</prop>
            <prop key="hibernate.format_sql">true</prop>
            <prop key="hibernate.hbm2ddl.auto">update</prop>
            <prop key="hibernate.id.new_generator_mappings">true</prop>
        </props>
    </property>     
</bean>
<bean id="hbAdapterBean_pgsql" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">  
    <property name="showSql" value="false"></property>  
    <property name="generateDdl" value="true"></property>  
    <property name="databasePlatform" value="org.hibernate.dialect.PostgreSQLDialect"></property>  
</bean>

如何从应用程序中更新列？