Handling errors

Άρθρο
08/01/2024

When using the Microsoft JDBC Driver for SQL Server, all database error conditions are returned to your Java application as exceptions using the SQLServerException class. The following methods of the SQLServerException class are inherited from java.sql.SQLException and java.lang.Throwable; and they can be used to return specific information about the SQL Server error that has occurred:

getSQLState() returns the standard X/Open or SQL99 state code of the exception.
getErrorCode() returns the specific database error number.
getMessage() returns the full text of the exception. The error message text describes the problem, and frequently includes placeholders for information, such as object names, that are inserted in the error message when it's displayed.
getSQLServerError() returns the SQLServerError object containing detailed info about the exception as received from SQL Server. This method returns null if no server error has occurred.

The following methods of the SQLServerError class can be used to obtain more details about the error generated from the server.

SQLServerError.getErrorMessage() returns the error message as received from the server.
SQLServerError.getErrorNumber() returns a number that identifies the type of the error.
SQLServerError.getErrorState() returns a numeric error code from SQL Server that represents an error, warning or "no data found" message.
SQLServerError.getErrorSeverity() returns the severity level of the error received.
SQLServerError.getServerName() returns the name of the computer that is running an instance of SQL Server that generated the error.
SQLServerError.getProcedureName() returns the name of the stored procedure or remote procedure call (RPC) that generated the error.
SQLServerError.getLineNumber() returns the line number within the Transact-SQL command batch or stored procedure that generated the error.

In the next example, an open connection to the SQL Server AdventureWorks2022 sample database is passed in to the function and a malformed SQL statement is constructed that doesn't have a FROM clause. Then, the statement is run and a SQL exception is processed.

public static void executeSQLException(Connection con) {
    try (Statement stmt = con.createStatement();) {
        String SQL = "SELECT TOP 10 * Person.Contact";
        ResultSet rs = stmt.executeQuery(SQL);

        while (rs.next()) {
            System.out.println(rs.getString("FirstName") + " " + rs.getString("LastName"));
        }
    }
    catch (SQLException se) {
        do {
            System.out.println("SQL STATE: " + se.getSQLState());
            System.out.println("ERROR CODE: " + se.getErrorCode());
            System.out.println("MESSAGE: " + se.getMessage());
            System.out.println();
        }
        while (se != null);
    }
}

Using the ServerMessageHandler

Starting from release 12.8.0, the driver has an added ServerMessageHandler allowing a greater amount of control over error feedback and logging. In order to use the ServerMessageHandler, one needs to implement the ISQLServerMessageHandler interface. Features of the ServerMessageHandler include:

Message feedback

Allows you to receive feedback from long-running queries (such as progress messages). E.g., RAISERROR ('Progress message...', 0, 1) WITH NOWAIT.

Universal error logging

Allows your message handler to handle logging for all errors.

Universal error handling

Allows you to place error handling logic is just the ServerMessageHandler, as opposed to repeating the same error handling throughout your application.

Remapping of error message severity

Allows you to recognize, and change the severity of, specific error messages:

SQLServerError.toSQLServerInfoMessage() returns a ISQLServerMessage, created by downgrading an error message to an info message.
SQLServerError.toSQLServerInfoMessage(int newErrorSeverity) returns a ISQLServerMessage, created by downgrading an error message to an info message, with a new error severity.
SQLServerError.toSQLServerInfoMessage(int newErrorSeverity, int newErrorNumber) returns a ISQLServerMessage, created by downgrading an error message to an info message, with a new error severity and error number.
SQLServerInfoMessage.toSQLServerError() returns a ISQLServerMessage, created by upgrading an info message to an error message.
SQLServerInfoMessage.toSQLServerError(int newErrorSeverity) returns a ISQLServerMessage, created by upgrading an info message to an error message, with a new error severity.
SQLServerInfoMessage.toSQLServerError(int newErrorSeverity, int newErrorNumber) returns a ISQLServerMessage, created by upgrading an info message to an error message, with a new error severity and error number.

SQLExceptionChaining

Also with release 12.8.0, SQLExceptions can be chained together, so the final exception message automatically contains all exceptions that may have otherwise been lost. This feature is enabled by default.

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