findAll()不返回正确的对象类型 [英] findAll() Not Returning Correct Object Type
问题描述
这个简单的查询按预期工作。我得到一个ItemTags列表,并可以完成ItemTag应该做的所有美妙事情:
def theTags1 = ItemTag.findAll (from ItemTag b)
例如:
println(theTags1 [0] .tag.tag)
朝圣者进步
但是,只要向条件中添加另一个表,而不是获取ItemTag列表,我只需获取一个通用对象列表。
例如以下
def theTags2 = ItemTag.findAll(from ItemTag b,Tag a其中b.tag = a)
theTags2.each {
theClass = it.getClass();
nameOfClass = theClass.getName();
println(nameOfClass)
}
返回
[Ljava.lang.Object;
[Ljava.lang.Object;
[Ljava.lang.Object;
我根本无法使用结果对象。例如:
println(theTags2 [0] .tag.tag)
给我这个错误:
异常评估属性'标签'为java.util.ArrayList,原因:groovy.lang.MissingPropertyException:没有这样的属性:类的标签:java.lang.String
和
def exTag2 =(ItemTag)theTags2 [0]
code>
给我这个错误:
不能将类'[Ljava.lang.Object; @ 2d81f'与类'[Ljava.lang.Object;'转换为类'org.maflt.flashlit.pojo.ItemTag''
获取可用对象需要做些什么?感谢!
在Hibernate中,
lockquote
$ b $查询是一个交叉连接。此查询的结果是一个Object数组列表,其中第一个项目是ItemTag实例,第二个项目是一个Tag实例。
您必须使用例如
(ItemTag)theTags2 [0] [0]
访问第一个ItemTag实例。
ItemTag objects contain an Item object and a Tag object. (These are Java domain objects.)
This simple query works as expected. I get back a list ItemTags and can do all the wonderful things that ItemTags are supposed to do:
def theTags1 = ItemTag.findAll("from ItemTag b")
For example:
println(theTags1[0].tag.tag)
gives me this as expected:
Pilgrim's Progress
However, as soon as I add another table to the criteria, instead of getting a list of ItemTags, I just get a list of generic objects.
e.g the following
def theTags2 = ItemTag.findAll("from ItemTag b, Tag a where b.tag= a")
theTags2.each {
theClass = it.getClass();
nameOfClass = theClass.getName();
println(nameOfClass)
}
returns
[Ljava.lang.Object;
[Ljava.lang.Object;
[Ljava.lang.Object;
And I can't use the resulting objects at all. For example:
println(theTags2[0].tag.tag)
gives me this error:
Exception evaluating property 'tag' for java.util.ArrayList, Reason: groovy.lang.MissingPropertyException: No such property: tag for class: java.lang.String
and
def exTag2 = (ItemTag) theTags2[0]
gives me this error:
Cannot cast object '[Ljava.lang.Object;@2d81f' with class '[Ljava.lang.Object;' to class 'org.maflt.flashlit.pojo.ItemTag'
What do I need to do to get usable objects? Thanks!
In Hibernate, the
"from ItemTag b, Tag a where b.tag= a"
query is a cross-join. The result of this query is a list of Object arrays where the first item is an ItemTag instance and the second is a Tag instance.
You have to use e.g.
(ItemTag) theTags2[0][0]
to access the first ItemTag instance.
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