Hibernate的預測與收藏ArrayIndexOutOfBoundsException異常

Question

好傢伙我有這樣的代碼：

Criteria criteria = session.createCriteria(Department.class); 

ProjectionList properties = Projections.projectionList(); 
properties.add(Projections.property("id"), "id"); 
properties.add(Projections.property("name"), "name"); 
properties.add(Projections.property("children"), "children"); 

criteria.setProjection(properties); 
criteria.setFetchMode("children", FetchMode.JOIN); 
criteria.setResultTransformer(Transformers.aliasToBean(Department.class)); 

criteria.add(Restrictions.isNull("parent.id")); 
criteria.add(Restrictions.eq("active", true)); 

return criteria.list(); 

和實體類

public class Department extends Model { 

    @Size(max = 200) 
    private String name; 

    @Size(max = 10) 
    private String sg; 

    @Size(max = 1000) 
    private String description; 

    @ManyToOne 
    @JoinColumn(name = "id_parent") 
    private Department parent; 

    private boolean active; 

    @OneToMany(mappedBy = "parent") 
    private List<Department> children; 

...加上getter和setter ...

我執行標準並給我堆棧例外：

java.lang.ArrayIndexOutOfBoundsException: 2 
at org.hibernate.loader.criteria.CriteriaLoader.getResultRow(CriteriaLoader.java:166) 
at org.hibernate.loader.criteria.CriteriaLoader.getResultColumnOrRow(CriteriaLoader.java:146) 
at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:747) 
at org.hibernate.loader.Loader.processResultSet(Loader.java:949) 
at org.hibernate.loader.Loader.doQuery(Loader.java:917) 
at 

我在做什麼錯？

在此先感謝。

Answer 1

不知道你想用Projection查詢做什麼，很難說如何解決它。我認爲你的主要問題是你需要爲孩子創建一個別名，然後在你的投影中使用這個別名。在你的投影中，你還需要引用兒童的屬性。你可以這樣做：

Criteria criteria = session.createCriteria(Department.class); 

ProjectionList properties = Projections.projectionList(); 
properties.add(Projections.property("id"), "id"); 
properties.add(Projections.property("name"), "name"); 
properties.add(Projections.property("children.id"), "id"); 
properties.add(Projections.property("children.name"), "name"); 

criteria.setProjection(properties); 
criteria.createAlias("children", "children", JoinType.FULL_JOIN); 
criteria.setResultTransformer(Transformers.aliasToBean(Department.class)); 

criteria.add(Restrictions.isNull("parent.id")); 
criteria.add(Restrictions.eq("active", true)); 
return criteria.list(); 

這麼說，我覺得使用投影這裏是一個錯誤，不必要的，如果你的意圖是返回根部門的清單與他們的孩子系樹。爲此，您可以這樣做：

Criteria criteria = session.createCriteria(Department.class); 
criteria.createAlias("children", "children", JoinType.FULL_JOIN); 
criteria.add(Restrictions.isNull("parent.id")); 
criteria.add(Restrictions.eq("active", true)); 

retun criteria.list();