使用问题？ 从 Java 更新时 MySQL 存储过程的通配符

Question

I have the following Java class that accepts 11 parameters and uses them to create a new record in a database. The stored procedure is tested and works in MySQL, but I can't get the Java class accessing it to work:

public void insert_saved_pub_set(int user_id, String presProfile, String procProfile, String dateLabel, String doc_id, String pubName, String lastLoaded, String publicV, String label, String description, String out_id)
                throws SQLException {                   

    String sql = "call insert_saved_pub_set(?,?,?,?,?,?,?,?,?,?,?);";

    PreparedStatement stmt = conn.prepareStatement(sql);

    stmt.setInt(1, user_id);        
    stmt.setInt(2, Integer.parseInt(presProfile));
    stmt.setInt(3, Integer.parseInt(procProfile));
    stmt.setString(4, dateLabel);
    stmt.setInt(5, Integer.parseInt(doc_id));
    stmt.setString(6, pubName);
    stmt.setInt(7, Integer.parseInt(lastLoaded));
    stmt.setInt(8, Integer.parseInt(publicV));
    stmt.setString(9, label);
    stmt.setString(10, description);
    stmt.setInt(11, Integer.parseInt(out_id));

    stmt.executeUpdate(sql);

}

The error I get when I attempt to test this is:

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 '?,?,?,?,?,?,?,?,?,?,?)' at line 1

I've tested the prepared statement from Java with hardcoded values and it works, but I've doing something stupid with the wildcards and I've stared at it too long.

** comment added post-fix below **

Just to close this off, the fixed code looks like this:

public void insert_saved_pub_set(int user_id, String presProfile, String procProfile, String dateLabel, String doc_id, String pubName, String lastLoaded, String publicV, String label, String description, String out_id)
            throws SQLException {               

        String sql = "call insert_saved_pub_set(?,?,?,?,?,?,?,?,?,?,?);";       

        CallableStatement cStmt = conn.prepareCall(sql);        

        cStmt.setInt(1, user_id);       
        cStmt.setInt(2, Integer.parseInt(presProfile));
        cStmt.setInt(3, Integer.parseInt(procProfile));
        cStmt.setString(4, dateLabel);
        cStmt.setInt(5, Integer.parseInt(doc_id));
        cStmt.setString(6, pubName);
        cStmt.setInt(7, Integer.parseInt(lastLoaded));
        cStmt.setInt(8, Integer.parseInt(publicV));
        cStmt.setString(9, label);
        cStmt.setString(10, description);   
        cStmt.setInt(11, Integer.parseInt(out_id)); 

        cStmt.executeUpdate();
        }       

    }

Answer 1

The executeUpdate(String) method is inherited from Statement and attempts to execute the given SQL statement as is -- without placeholder substitution.

The executeUpdate() method (no parameters), declared in PreparedStatement , will perform placeholder substitution. This works with PreparedStatements such as update statements.

In addition, you aren't running a straight SQL statement here. You are calling a stored procedure. Switch from PreparedStatement to CallableStatement .

CallableStatement cStmt = conn.prepareCall(sql);

The "set" methods work as before, but then you call execute() to execute the CallableStatement .

Answer 2

To call a stored procedure, you need a CallableStatement , not a PreparedStatement . Quoting CallableStatement Javadoc:

The interface used to execute SQL stored procedures.

This is a sample code to get you started:

CallableStatement cStmt = conn.prepareCall("{call insert_saved_pub_set(?,?,?,?,?,?,?,?,?,?,?)}");
cStmt.setInt(1, user_id);
// ... rest of code

boolean hadResults = cStmt.execute(); // executes the stored procedure
while (hadResults) {
    ResultSet rs = cStmt.getResultSet();

    // process result set
    ...

    hadResults = cStmt.getMoreResults();
}

I suggest you read MySQL documentation about the usage of stored procedure in Java code.