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@UniqueConstraint annotation in Java
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@Entity
@Table(uniqueConstraints={@UniqueConstraint(columnNames = {"id_1" , "id_2"})})
public class class_name {
@Id
@GeneratedValue
public Long id;
@NotNull
public Long id_1;
@NotNull
public Long id_2;
}
Hope it helped.
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In Eclipse, what can cause Package Explorer “red-x” error-icon when all Java sources compile without
I'm using Eclipse for Java development. All my sources compile fine and the resulting application compiles fine. However, I keep getting an "red-x" error notification in the Package Explorer.
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Add a new item to a dictionary in Python [duplicate]
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default_data['item3'] = 3
Easy as py.
Another possible solution:
default_data.update({'item3': 3})
which is nice if you want to insert multiple items at once.
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How to append text to an existing file in Java?
...he file does not already exist. It also does not append a newline automatically (which you often want when appending to a text file). Steve Chambers's answer covers how you could do this with Files class.
However, if you will be writing to the same file many times, the above has to open and close t...
Exception messages in English?
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This issue can be partially worked around. The Framework exception code loads the error messages from its resources, based on the current thread locale. In the case of some exceptions, this happens at the time the Message property is accessed.
For...
Calculate the median of a billion numbers
...bably too late if this had been an interview, but never mind:
Machine 1 shall be called the "control machine", and for the sake of argument either it starts with all the data, and sends it in equal parcels to the other 99 machines, or else the data starts evenly distributed between the machines, an...
How can I get a web site's favicon?
Simple enough question: I've create a small app that is basically just a favourites that sits in my system tray so that I can open often-used sites/folders/files from the same place. Getting the default icons from my system for known file types isn't terribly complicated, but I don't know how to get...
Center Oversized Image in Div
...mething like this. This should center any huge element in the middle vertically and horizontally with respect to its parent no matter both of their sizes.
.parent {
position: relative;
overflow: hidden;
//optionally set height and width, it will depend on the rest of the styling used
}
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fstream默认不支持中文路径和输出整数带逗号的解决办法 - C/C++ - 清泛网 -...
... i << "/n"; //输出带逗号
outfile.close();
setlocale( LC_ALL, "C" ); //恢复全局locale，如果不恢复，可能导致cout无法输出中文
}
创建文件成功，在程序的“测试”文件下出现个test.txt文件。需要注意的是最后需要调用setlocale( ...
MySQL和MongoDB设计实例进行对比 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...查询：
db.getCollection("mobiles").find({
"params": {
$all: [
{$elemMatch: {"name": "待机时间", "value": {$gt: 100}}},
{$elemMatch: {"name": "外观设计", "value": "直板"}}
]
}
});
注：查询中用到的$all，$elemMatch等高...