Java: Insert multiple rows into MySQL with PreparedStatement

I want to insert multiple rows into a MySQL table at once using Java. The number of rows is dynamic. In the past I was doing…

for (String element : array) {
    myStatement.setString(1, element[0]);
    myStatement.setString(2, element[1]);

    myStatement.executeUpdate();
}

I’d like to optimize this to use the MySQL-supported syntax:

INSERT INTO table (col1, col2) VALUES ('val1', 'val2'), ('val1', 'val2')[, ...]

but with a PreparedStatement I don’t know of any way to do this since I don’t know beforehand how many elements array will contain. If it’s not possible with a PreparedStatement, how else can I do it (and still escape the values in the array)?

Answer

You can create a batch by PreparedStatement#addBatch() and execute it by PreparedStatement#executeBatch().

Here’s a kickoff example:

public void save(List<Entity> entities) throws SQLException {
    try (
        Connection connection = database.getConnection();
        PreparedStatement statement = connection.prepareStatement(SQL_INSERT);
    ) {
        int i = 0;

        for (Entity entity : entities) {
            statement.setString(1, entity.getSomeProperty());
            // ...

            statement.addBatch();
            i++;

            if (i % 1000 == 0 || i == entities.size()) {
                statement.executeBatch(); // Execute every 1000 items.
            }
        }
    }
}

It’s executed every 1000 items because some JDBC drivers and/or DBs may have a limitation on batch length.

See also:

• JDBC tutorial – Using PreparedStatement
• JDBC tutorial – Using Statement Objects for Batch Updates