在java.sql实例中使用SQL IN子句的最佳变通方法是什么?由于SQL注入攻击安全问题,不支持多值的PreparedStatement:一个?占位符表示一个值,而不是一个值列表。
考虑下面的SQL语句:
SELECT my_column FROM my_table where search_column IN (?)
使用preparedStatement。setString(1, "'A', 'B', 'C'");本质上是一种无用的尝试,试图解决使用原因?首先。
有什么可行的解决办法?
在PreparedStatement中生成查询字符串,使其具有与列表中项目数量相匹配的多个?。这里有一个例子:
public void myQuery(List<String> items, int other) {
...
String q4in = generateQsForIn(items.size());
String sql = "select * from stuff where foo in ( " + q4in + " ) and bar = ?";
PreparedStatement ps = connection.prepareStatement(sql);
int i = 1;
for (String item : items) {
ps.setString(i++, item);
}
ps.setInt(i++, other);
ResultSet rs = ps.executeQuery();
...
}
private String generateQsForIn(int numQs) {
String items = "";
for (int i = 0; i < numQs; i++) {
if (i != 0) items += ", ";
items += "?";
}
return items;
}
在PreparedStatement中生成查询字符串,使其具有与列表中项目数量相匹配的多个?。这里有一个例子:
public void myQuery(List<String> items, int other) {
...
String q4in = generateQsForIn(items.size());
String sql = "select * from stuff where foo in ( " + q4in + " ) and bar = ?";
PreparedStatement ps = connection.prepareStatement(sql);
int i = 1;
for (String item : items) {
ps.setString(i++, item);
}
ps.setInt(i++, other);
ResultSet rs = ps.executeQuery();
...
}
private String generateQsForIn(int numQs) {
String items = "";
for (int i = 0; i < numQs; i++) {
if (i != 0) items += ", ";
items += "?";
}
return items;
}
您可以使用集合。nCopies生成一个占位符集合,并使用String.join将它们连接起来:
List<String> params = getParams();
String placeHolders = String.join(",", Collections.nCopies(params.size(), "?"));
String sql = "select * from your_table where some_column in (" + placeHolders + ")";
try ( Connection connection = getConnection();
PreparedStatement ps = connection.prepareStatement(sql)) {
int i = 1;
for (String param : params) {
ps.setString(i++, param);
}
/*
* Execute query/do stuff
*/
}