未能懒散地初始化角色集合 [英] failed to lazily initialize a collection of role

问题描述

  public class Indicator implements Serializable {
 ... 
 
 @OneToMany（mappedBy =indicator，fetch = FetchType.LAZY）
 private List< IndicatorAlternateLabel> indicatorAlternateLabels; 
 
公共列表< IndicatorAlternateLabel> getIndicatorAlternateLabels（）{
 return indicatorAlternateLabels; 
} 
 
 public void setIndicatorAlternateLabels（List< IndicatorAlternateLabel> indicatorAlternateLabels）{
 this.indicatorAlternateLabels = indicatorAlternateLabels; 
} 
 ... 
} 
 
 public class IndicatorAlternateLabel实现Serializable {
 ... 
 @ManyToOne（cascade = CascadeType.REFRESH ，fetch = FetchType.EAGER）
 @JoinColumn（name =IndicatorID）
 @XmlTransient 
 private指标指标; 
 ... 
} 
  

当我像这样使用它们时：

  public MetricTypeDetail getMetricTypeDetail（Integer metricTypeId）{
 Criteria crit = sessionFactory.getCurrentSession（）。createCriteria（Indicator.class， sub）
 .add（Restrictions.eq（number，metricTypeId））
 .setResultTransformer（Criteria.DISTINCT_ROOT_ENTITY）.setCacheable（true）; 
 crit.setMaxResults（1）; 
指标指标=（指标）crit.uniqueResult（）; 
 MetricTypeDetail metricTypeDetail = new MetricTypeDetail（indicator）; 
列表< IndicatorAlternateLabel> indicatorAlternateLabels = null; 
 indicatorAlternateLabels = indicator.getIndicatorAlternateLabels（）; 
 metricTypeDetail.setIndicatorAlternateLabels（indicatorAlternateLabels）; 
返回metricTypeDetail; 
} 
  

这段代码返回一个异常：
未能延迟初始化一个集合角色：com.porism.service.domain.Indicator.indicatorAlternateLabels，没有会话或会话已关闭

任何想法？我对Hibernate非常陌生

当您获取一个通常包含一个延迟加载的集合的对象时，就会发生延迟异常，并且尝试访问该集合。

您可以通过访问事务内的懒惰集合来避免此问题。

• 。


• 使用 Hibernate.initialize（obj）;
获取集合

• 另一项交易


• 使用 获取配置文件 选择延迟/非延迟获取运行时


• 将fetch设置为非懒惰（通常不会推荐）

此外，我建议您查看 相关的 链接到你的权利，这个问题已经被多次回答。另请参阅 Hibernate延迟加载应用程序设计。

Hi I have two classes like this:

public class Indicator implements Serializable {
...

    @OneToMany(mappedBy = "indicator",fetch=FetchType.LAZY)
    private List<IndicatorAlternateLabel>  indicatorAlternateLabels;

    public List<IndicatorAlternateLabel> getIndicatorAlternateLabels() {
        return indicatorAlternateLabels;
    }

        public void setIndicatorAlternateLabels(List<IndicatorAlternateLabel> indicatorAlternateLabels) {
            this.indicatorAlternateLabels = indicatorAlternateLabels;
        }
...
    }

public class IndicatorAlternateLabel implements Serializable {
...
 @ManyToOne(cascade = CascadeType.REFRESH, fetch = FetchType.EAGER)
    @JoinColumn(name = "IndicatorID")
    @XmlTransient
    private Indicator indicator;
...
}

When I use them like this:

 public MetricTypeDetail getMetricTypeDetail(Integer metricTypeId) {
        Criteria crit = sessionFactory.getCurrentSession().createCriteria(Indicator.class, "sub")
                    .add(Restrictions.eq("number", metricTypeId))
                    .setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY).setCacheable(true);
        crit.setMaxResults(1);
        Indicator indicator=(Indicator) crit.uniqueResult();
        MetricTypeDetail metricTypeDetail=new MetricTypeDetail(indicator);
        List<IndicatorAlternateLabel> indicatorAlternateLabels = null;
        indicatorAlternateLabels=indicator.getIndicatorAlternateLabels();
        metricTypeDetail.setIndicatorAlternateLabels(indicatorAlternateLabels);
        return metricTypeDetail;
    }

This code returns an exception: failed to lazily initialize a collection of role: com.porism.service.domain.Indicator.indicatorAlternateLabels, no session or session was closed

Any idea? I'm very new to Hibernate

解决方案

Lazy exceptions occur when you fetch an object typically containing a collection which is lazily loaded, and try to access that collection.

You can avoid this problem by

• accessing the lazy collection within a transaction.
• Initalizing the collection using Hibernate.initialize(obj);
• Fetch the collection in another transaction
• Use Fetch profiles to select lazy/non-lazy fetching runtime
• Set fetch to non-lazy (which is generally not recommended)

Further I would recommend looking at the related links to your right where this question has been answered many times before. Also see Hibernate lazy-load application design.

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