使用和/或在条件中时出现 NullPointerException
一个非常简单的示例，说明如何使用 createCriteria 方法在 Grails 应用程序中获取数据：
def c = SomeClassOfMine.createCriteria()
def projects = c.list(max: limit, offset: start) {
eq("userId", userId)
if (owner != null && owner.size() > 0) {
ilike("ownerName", owner + "%")
}
if (someParameter && someParameter.size() > 0) {
or {
ne("validated", 1)
ne("validated2", 1)
}
}
order("name", "asc")
}
在具有 或 { 的行上，我收到 NullPointerException，但没有消息。我尝试了各种组合，并密切关注各个地方给出的示例，却发现如果我尝试使用 和 也会遇到同样的问题。我知道还有其他方法来获取数据，但我非常想使用这种方法。我无法弄清楚自己可能出了什么问题，所以...在 或 / 和 上的此类代码块中可能导致 NullPointerException 的原因是什么？
如果我知道与此案例相关的内容，我会提供更多信息。
编辑：在代码示例中添加了 if 子句（检查所有者）。
我进行了更多调查，发现问题出在 if (owner != null &&owner.size() > 0) { 中，更具体地说，变量名称 所有者。当我将名称更改为其他名称时，问题就消失了。如果有人能解释为什么会发生这种情况，那就非常有趣了。
A very simplified example of how I use createCriteria method for getting data in my Grails application:
def c = SomeClassOfMine.createCriteria()
def projects = c.list(max: limit, offset: start) {
eq("userId", userId)
if (owner != null && owner.size() > 0) {
ilike("ownerName", owner + "%")
}
if (someParameter && someParameter.size() > 0) {
or {
ne("validated", 1)
ne("validated2", 1)
}
}
order("name", "asc")
}
On the line having or { I get NullPointerException without message. I have tried various combinations and followed closely the examples given in various places only to find that I get the same problem if I try to use and too. I know that there are other ways to get the data, but I would very much like to use this approach. I failed to figure out what might be wrong by myself so... What might cause NullPointerException in such code block on or / and?
I would provide more information if I would know what is relevant in this case.
EDIT: Added an if clause (where owner is checked) to code example.
I have investigated more and find out that the problem is in if (owner != null && owner.size() > 0) { and to be more specific, the variable name owner. When I change the name to anything else the problem is gone. It would be very interesting if someone could explain why this is happening.
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问题是“owner”是 Groovy 中的保留字。 Groovy Closures 对此进行了描述。
您可以尝试在“owner”周围放置单引号，以便您的代码行显示为：
这可能有效。最好的选择是使用新的变量名称以避免任何混淆。
The issue is "owner" is a reserved word in Groovy. This is described in Groovy Closures.
You can try placing single quotes around 'owner' so that your line of code would read:
That may work. Your best option is to use a new variable name to avoid any confusion.