Checking for a null int value from a Java ResultSet

Question

In Java I m trying to test for a null value  from a ResultSet  where the column is being cast to a primitive int type    int iVal  ResultSet rs   magicallyAppearingStmt executeQuery query   if  rs next        if  rs getObject  ID PARENT      null  amp  amp   rs wasNull          iVal   rs getInt  ID PARENT            From the code fragment above  is there a better way to do this  and I assume that the second wasNull   test is redundant   Educate us  and Thanks

User · Answer

For convenience  you can create a wrapper class around ResultSet that returns null values when ResultSet ordinarily would not   public final class ResultSetWrapper        private final ResultSet rs       public ResultSetWrapper ResultSet rs            this rs   rs             public ResultSet getResultSet             return rs             public Boolean getBoolean String label  throws SQLException           final boolean b   rs getBoolean label           if  rs wasNull                  return null                    return b             public Byte getByte String label  throws SQLException           final byte b   rs getByte label           if  rs wasNull                  return null                    return b

User · Answer

AFAIK you can simply use  iVal   rs getInt  ID PARENT    if  rs wasNull           do somthing interesting to handle this situation     even if it is NULL

User · Answer

The default for ResultSet getInt when the field value is NULL is to return 0  which is also the default value for your iVal declaration  In which case your test is completely redundant   If you actually want to do something different if the field value is NULL  I suggest   int iVal   0  ResultSet rs   magicallyAppearingStmt executeQuery query   if  rs next          iVal   rs getInt  ID PARENT        if  rs wasNull                 handle NULL field value            Edited as  martin comments below  the OP code as written would not compile because iVal is not initialised

User · Answer

With java 8 you can do this   Long nVal   Optional ofNullable resultSet getBigDecimal  col name                         map BigDecimal  longValue  orElse null      In that case you ensure that the nVal will be null  and not zero  if the SQL value is NULL

User · Answer

Just check if the field is null or not using ResultSet getObject    Substitute -1 with whatever null-case value you want   int foo   resultSet getObject  foo      null   resultSet getInt  foo     -1    Or  if you can guarantee that you use the right DB column type so that ResultSet getObject   really returns an Integer  and thus not Long  Short or Byte   then you can also just typecast it to an Integer   Integer foo    Integer  resultSet getObject  foo

User · Answer

You can call this method using the resultSet and the column name having Number type  It will either return the Integer value  or null  There will be no zeros returned for empty value in the database  private Integer getIntWithNullCheck ResultSet rset  String columnName        try           Integer value   rset getInt columnName           return rset wasNull     null   value        catch  Exception e            return null

User · Answer

Another nice way of checking  if you have control the SQL  is to add a default value in the query itself for your int column  Then just check for that value   e g for an Oracle database  use NVL  SELECT NVL ID PARENT  -999  FROM TABLE NAME    then check  if  rs getInt  ID PARENT      -999        Of course this also is under the assumption that there is a value that wouldn t normally be found in the column

User · Answer

I think  it is redundant  rs getObject  ID PARENT   should return an Integer object or null  if the column value actually was NULL  So it should even be possible to do something like   if  rs next        Integer idParent    Integer  rs getObject  ID PARENT      if  idParent    null        iVal   idParent     works for Java 1 5      else          handle this case

User · Answer

Just an update with Java Generics   You could create an utility method to retrieve an optional value of any Java type from a given ResultSet  previously casted   Unfortunately  getObject columnName  Class  does not return null  but the default value for given Java type  so 2 calls are required   public  lt T gt  T getOptionalValue final ResultSet rs  final String columnName  final Class lt T gt  clazz  throws SQLException       final T value   rs getObject columnName  clazz       return rs wasNull     null   value      In this example  your code could look like below   final Integer columnValue   getOptionalValue rs  Integer class   if  columnValue    null          null handling   else         use int value of columnValue with autoboxing     Happy to get feedback

User · Answer

Another solution   public class DaoTools       static public Integer getInteger ResultSet rs  String strColName  throws SQLException           int nValue   rs getInt strColName           return rs wasNull     null   nValue

[java] Checking for a null int value from a Java ResultSet

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