JDBC PreparedStatement.setString（）在SQLite中不能正常工作吗？

Question

I'm using Xerials SQLite JDBC driver and want to do the simplest thing you can imagine:

I have created the following table:

CREATE TABLE IF NOT EXISTS households (hostname_id_pk INTEGER PRIMARY KEY, hostname TEXT UNIQUE, vm TEXT);

Now, as I want a parametrized insertion statment I use PreparedStatment as follows:

public static void main(String[] args) throws ClassNotFoundException {
    Class.forName("org.sqlite.JDBC");
    Connection con = null;
    PreparedStatement updateHouseholdStmt = null;

    try {
        con = DriverManager.getConnection(DB_IDENTIFIER);           

        String getHouseholdString = "SELECT hostname_id_pk FROM households WHERE hostname = ?";
        String updateHouseholdString = "INSERT INTO households (hostname, vm) values(?, 'VM1')";

        getHouseholdStmt = con.prepareStatement(getHouseholdString);
        getHouseholdStmt.setString(1, "test1");

        updateHouseholdStmt = con.prepareStatement(updateHouseholdString);
        getHouseholdStmt.setString(1, "test1");

        ResultSet hhRS = getHouseholdStmt.executeQuery();
        int hhId = -1;

        if(hhRS.next()){
            hhId = hhRS.getInt(1);
            System.out.println(hhId);
        } else {
            System.out.println(updateHouseholdStmt.executeUpdate());
        }

    } catch (SQLException e) {
        System.err.println(e.getMessage());
    } finally {
        try {
            if (con != null) {
                con.close();
            }
            if (getHouseholdStmt != null){
                getHouseholdStmt.close();
            }
            if (updateHouseholdStmt != null) {
                updateHouseholdStmt.close();
            }
        } catch (SQLException e) {
            System.err.println(e);
        }
    }

}

In this case, the only thing I can find in the DB is a new entry with (1, , VM1) meaning that the entry is created, but the string parameter is missing for some reason.

When I'm replacing the "?" in the updateHousholdStatement() with a sample value and remove the .setString(...) method line everything works fine.

What the heck am I missing?! I already checked this a thousand times this morning.

Thx in advance.

Answer 1

Please correct the following lines:

updateHouseholdStmt = con.prepareStatement(updateHouseholdString);
getHouseholdStmt.setString(1, "test1");

to

updateHouseholdStmt = con.prepareStatement(updateHouseholdString);
updateHouseholdStmt.setString(1, "test1");

Answer 2

When updating, you're setting and executing the wrong variable:

getHouseholdStmt = con.prepareStatement(getHouseholdString);
getHouseholdStmt.setString(1, "test1");

updateHouseholdStmt = con.prepareStatement(updateHouseholdString);
getHouseholdStmt.setString(1, "test1"); //updating the select query
ResultSet hhRS = getHouseholdStmt.executeQuery(); //you're executing the select query again!

It should be:

getHouseholdStmt = con.prepareStatement(getHouseholdString);
getHouseholdStmt.setString(1, "test1");

updateHouseholdStmt = con.prepareStatement(updateHouseholdString);
updateHouseholdStmt .setString(1, "test1"); //update stmt 
ResultSet hhRS = updateHouseholdStmt .executeQuery(); //update stmt

Answer 3

First, getHouseholdStmt Statement isn't declared as a PreparedStatement. Second, you need to executeUpdate() your PreparedStatement for updateHouseholdStmt(updateHouseholdStatement.executeUpdate();)