问题
When using raw JDBC, you can parameterize a PreparedStatement
like so:
PreparedStatement statement = connection.prepareStatement(someSQLString);
String someString = getSomeString();
Integer int = getSomeInteger();
statement.setString(1, someString);
statement.setLong(2, 5L);
statement.setInt(3, int);
...
Here, if someString
is null
, that's fine - strings are nullable. But if getSomeInteger()
returns null
, we have a problem.
PreparedStatement#setInt(int,int)
sets a primitive int
as the value, and therefore cannot be null
.
However, it's perfectly plausible that I might want the value of the 3rd column above to be null
for this particular record. After all, every RDBMS I've ever worked with allows numeric (INT, LONG, etc.) fields to be NULLABLE...
So what's the workaround?
回答1:
Don't use any of those and use setObject instead, let the JDBC driver to manage the null
values instead of you.
回答2:
You can use the setNull(int parameterIndex, int sqlType) method of the PreparedStatement
class.
Here's an example of how to use it:
String query =
"insert into nullable_table(id,string_column, int_column) values(?, ?, ?)";
// create PrepareStatement object
PreparedStatement pstmt = connection.prepareStatement(query);
pstmt.setString(1, id);
pstmt.setNull(2, java.sql.Types.VARCHAR);
pstmt.setNull(3, java.sql.Types.INTEGER);
Example taken from here.
回答3:
You need to use setNull() method. Based on parameter is null
or not check you need to either call setNull()
(or) setInt()
.
来源:https://stackoverflow.com/questions/17657057/workaround-for-null-primitives-in-jdbc-preparedstatement