JDBC : Exception and Warning Handling

SQLException is Checked Exception it encounters an error when interacting with database , executing query on Databases etc. It throws instance of SQLException.

SQLException contains several kind information on a database access error or other errors which can help to determine the cause of error:

  • Description of Error : A string describing the error mesage. It can be retrieved by SQLException.getMessage().
  • SQLStateCode : These codes and their respective meanings have been standardized by ISO/ANSI and Open Group (XOPEN), although some codes have been reserved for database vendors to define for themselves. This String object consists of five alphanumeric characters. Retrieve this code by calling the method SQLException.getSQLState().
  • DatabaseMetaData: The DatabaseMetaData method getSQLStateType can be used to discover whether the driver returns the XOPEN type or the SQL:2003 type.
  • ErrorCode: This is an integer value identifying the error that caused the SQLException instance to be thrown. Its value and meaning are implementation-specific and might be the actual error code returned by the underlying data source. Retrieve the error by calling the method SQLException.getErrorCode().
  • Exception Chaining: If more than one error occurs, the exceptions are referenced through this chain. Retrieve these exceptions by calling the method SQLException.getNextException() on the exception that was thrown.
  • Cause: A SQLException instance might have a causal relationship, which consists of one or more Throwable objects that caused the SQLException instance to be thrown. To navigate this chain of causes, recursively call the method SQLException.getCause() until a null value is returned.

Constructors

  • SQLException() : Constructs a SQLException object.
  • SQLException(String reason) : Constructs a SQLException object with given reason.
  • SQLException(String reason, String SQLState) : Constructs a SQLException with given reason and SQLState.
  • SQLException(String reason, String SQLState, int vendorCode) : Constructs a SQLException with given reason ,SQLState and vendorCode.
  • SQLException(String reason, String SQLState, int vendorCode, Throwable cause) : Constructs a SQLException with given reason ,SQLState ,vendorCode and cause.
  • SQLException(String reason, Throwable cause) : Constructs a SQLException with given reason  and cause.
  • SQLException( Throwable cause) : Constructs a SQLException with given  cause.

SQLException Sub-classes

Our JDBC driver might throw a subclass of SQLException that corresponds to a common SQLState or a common error state that is not associated with a specific SQLState class value. This enables you to write more portable error-handling code. These exceptions are subclasses of one of the following classes:

  • BatchUpdateException
  • RowSetWarning
  • SerialException
  • SQLClientInfoException
  • SQLNonTransientException
  • SQLRecoverableException
  • SQLTransientException
  • SQLWarning
  • SynchFactoryException
  • SynchProviderException

SQLException Hierarchy

Lets focus on some most common happening SQLException:

BatchUpdateException

BatchUpdateException is thrown when an error occurs during a batch update operation. In addition to the information provided by SQLException, BatchUpdateException provides the update counts for all statements that were executed before the error occurred.

SQLClientInfoException

SQLClientInfoException is thrown when one or more client information properties could not be set on a Connection. In addition to the information provided by SQLException, SQLClientInfoException provides a list of client information properties that were not set.

SQLWarning

SQLWarning objects are a subclass of SQLException that deal with database access warnings. Warnings do not stop the execution of an application, as exceptions they simply alert the user that something did not happen as planned. For example, a warning might let you know that a privilege you attempted to revoke was not revoked. Or a warning might tell you that an error occurred during a requested disconnection.

A warning can be reported on a Connection object, a Statement object (including PreparedStatement and CallableStatement objects), or a ResultSet object. Each of these classes has a getWarnings method, which you must invoke in order to see the first warning reported on the calling object. If getWarnings returns a warning, you can call the SQLWarning method getNextWarning on it to get any additional warnings. Executing a statement automatically clears the warnings from a previous statement, so they do not build up. This means, however, that if you want to retrieve warnings reported on a statement, you must do so before you execute another statement.

Example of SQLWarning

The most common warning is a DataTruncation warning, a subclass of SQLWarning. All DataTruncation objects have a SQLState of 01004, indicating that there was a problem with reading or writing data. DataTruncation methods let you find out in which column or parameter data was truncated, whether the truncation was on a read or write operation, how many bytes should have been transferred, and how many bytes were actually transferred.

Complete Example for Handling SQLException and Warning

In below example i have created one JDBC utilities class which will help to handle SQLException, SQLWarning chained Exception related to Connection, Statement and ResultSet etc. Here you will also see like how we can skip particular warning and exceptions.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class JDBCExceptionHandeling {

public static void main(String[] args) {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/facingissuesonitdb","root","root");
Statement stmt = conn.createStatement();
// Print JDBC Statement Warnings
JDBCUtilities.getWarningsFromStatement(stmt);
ResultSet rs = stmt.executeQuery("select * from employee");
// Print JDBC ResultSet Warnings
JDBCUtilities.getWarningsFromResultSet(rs);

while (rs.next()) {
System.out.println("ID :"+rs.getInt(1));
System.out.println("Name :"+rs.getString(2));
System.out.println("Job :"+rs.getString(3));
System.out.println("Salary :"+rs.getDouble(4));
System.out.println("*******************************");
	}
} catch (ClassNotFoundException ex) {
  System.err.println("SQL Driver is Not Found :"+ex.getMessage());
} catch (SQLException ex) {
  JDBCUtilities.printSQLException(ex);
 }
}
}

Utilities Class to Handle JDBC Exception and Warnings

import java.sql.BatchUpdateException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.SQLWarning;
import java.sql.Statement;

public class JDBCUtilities {
// Write method so that can handle SQL exception easily
public static void printSQLException(SQLException ex) {

for (Throwable e : ex) {
  if (e instanceof SQLException) {
     if (ignoreSQLException(((SQLException) e).getSQLState()) == false) {
	e.printStackTrace(System.err);
        System.err.println("SQLState: " + ((SQLException) e).getSQLState());
	System.err.println("Error Code: " + ((SQLException) e).getErrorCode());
	System.err.println("Message: " + e.getMessage());

Throwable t = ex.getCause();
	while (t != null) {
	  System.out.println("Cause: " + t);
	  t = t.getCause();
					}
				}
			}
		}
	}
// Some Exception we can ignore so that no any action required.
	public static boolean ignoreSQLException(String sqlState) {

	if (sqlState == null) {
	 System.out.println("The SQL state code is not defined!");
	 return false;
	}
// X0Y32: Jar file already exists in schema
	if (sqlState.equalsIgnoreCase("X0Y32"))
	return true;
// 42Y55: Table already exists in schema
	if (sqlState.equalsIgnoreCase("42Y55"))
	return true;

	return false;
	}
//Print Batch update Exception
	public static void printBatchUpdateException(BatchUpdateException b) {

	System.err.println("----BatchUpdateException----");
	System.err.println("SQLState:  " + b.getSQLState());
	System.err.println("Message:  " + b.getMessage());
	System.err.println("Vendor:  " + b.getErrorCode());
//BatchUpdateException contains array of update counts that is similar to //execute update
	System.err.print("Update counts:  ");
	int [] updateCounts = b.getUpdateCounts();

	for (int i = 0; i < updateCounts.length; i++) {
	        System.err.print(updateCounts[i] + "   ");
	    }
	}

// retrieve result set related warnings
	public static void getWarningsFromConnection(Connection conn) throws SQLException {
		JDBCUtilities.printWarnings(conn.getWarnings());
	}

// retrieve result set related warnings
	public static void getWarningsFromResultSet(ResultSet rs) throws SQLException {
		JDBCUtilities.printWarnings(rs.getWarnings());
	}

	// retrieve statement related warnings
	public static void getWarningsFromStatement(Statement stmt) throws SQLException {
		JDBCUtilities.printWarnings(stmt.getWarnings());
	}

	// This method is to print any warning from JDBC statement or result set
	public static void printWarnings(SQLWarning warning) throws SQLException {

	if (warning != null) {
	System.out.println("\n---Warning---\n");

	while (warning != null) {
	System.out.println("Message: " + warning.getMessage());
	System.out.println("SQLState: " + warning.getSQLState());
	System.out.print("Vendor error code: ");
	System.out.println(warning.getErrorCode());
	System.out.println("");
	warning = warning.getNextWarning();
			}
		}

	}
}

below is one SQlException output detail for one example where String value retrive with getInt()


ID :301
Name :Tester
Job :Rajesh
java.sql.SQLException: Bad format for number 'Jain' in column 4.
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1074)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:988)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:974)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:919)
    at com.mysql.jdbc.ResultSetImpl.getDoubleInternal(ResultSetImpl.java:2549)
    at com.mysql.jdbc.ResultSetImpl.getDoubleInternal(ResultSetImpl.java:2488)
    at com.mysql.jdbc.ResultSetImpl.getDouble(ResultSetImpl.java:2449)
    at JDBCExceptionHandeling.main(JDBCExceptionHandeling.java:24)
SQLState: S1009
Error Code: 0
Message: Bad format for number 'Jain' in column 4.

More on JDBC

Follow below links to know more on JDBC and solving JDBC issues :

JDBC Tutorial

JDBC Sample Code

JDBC Issues and Solutions

JDBC Interview Questions And Answers

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