Why Does My Java Application Throw a MySQLSyntaxError Exception When Inserting Data?

JDBC Reporting MySQLSyntaxError Exception with Valid Statement

In a Java application connecting to a MySQL database, an exception was encountered while attempting to insert new rows into a table. The MySQLSyntaxError Exception was thrown, despite the fact that the INSERT statement executed successfully when using MySQL Workbench.

The provided code is:

<code class="java">public static boolean aggiungiElem(String nome, GrafoGenerico g){
    //...
    PreparedStatement sInserim=conn.prepareStatement(sqlCommandInserim);
    sInserim.setString(1, utente);
    sInserim.setString(2, nome);
    //sInserim.setObject(3,g);
    System.out.println(sInserim.toString());
    sInserim.executeUpdate(sqlCommandInserim);
    sInserim.close();
    return true;
    //...
}</code>

The stack trace of the exception revealed the following:

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '? , ? , DEFAULT , NULL )' at line 1

Cause

The error suggests that there is a syntax issue in the INSERT statement. However, upon checking, the statement appears to be valid.

Resolution

The issue lies in the line:

<code class="java">sInserim.executeUpdate(sqlCommandInserim);</code>

This line attempts to execute the raw SQL string as opposed to executing the PreparedStatement with the set values. The proper method to execute the PreparedStatement is:

<code class="java">sInserim.executeUpdate();</code>

Additional Considerations

Apart from this specific issue, it is important to note that resource leaks can occur if PreparedStatements are not closed properly. To prevent this, it is recommended to use the finally block to close the PreparedStatement along with other resources such as Connection, Statement, and ResultSet.

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