本文介绍了在 IN 子句中带有参数列表的 PreparedStatement的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
如何在执行查询时为 JDBC 中的 PreparedStatement 中的 in 子句设置值.
How to set value for in clause in a preparedStatement in JDBC while executing a query.
示例:
connection.prepareStatement("Select * from test where field in (?)");
如果这个子句可以包含多个值,我该怎么做.有时我事先知道参数列表,有时我事先不知道.这个案子怎么处理?
If this in-clause can hold multiple values how can I do it. Sometimes I know the list of parameters beforehand or sometimes I don't know beforehand. How to handle this case?
推荐答案
我要做的是添加一个?"对于每个可能的值.
What I do is to add a "?" for each possible value.
var stmt = String.format("select * from test where field in (%s)",
values.stream()
.map(v -> "?")
.collect(Collectors.joining(", ")));
使用 StringBuilder
的替代方法(这是 10 多年前的原始答案)
Alternative using StringBuilder
(which was the original answer 10+ years ago)
List values = ...
StringBuilder builder = new StringBuilder();
for( int i = 0 ; i < values.size(); i++ ) {
builder.append("?,");
}
String placeHolders = builder.deleteCharAt( builder.length() -1 ).toString();
String stmt = "select * from test where field in ("+ placeHolders + ")";
PreparedStatement pstmt = ...
然后愉快地设置参数
int index = 1;
for( Object o : values ) {
pstmt.setObject( index++, o ); // or whatever it applies
}
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