Handling the null value from a resultset in JAVA

Question

I currently have a resultset returned and in one of the columns the string value may be null  i mean no values at all   I have a condition to implement like following      rs   st executeQuery selectSQL        output   rs getString  column      Since the column may be null in the database  the rs getString    will throw a NullPointerException   when column is null   If column is null  I want output to be an empty string like output       I can t check if rs getString  column     null either  How can I tackle this situation   My real problem      try        rs   st executeQuery sql          int i   0        while rs next                 output i    rs getString column                            column field in the database contains multiple results  but sometimes                may be null             i              catch SQLException e         e printStackTrace         other than tracing the exception i want to fill the array too    return output    Now if one of the column values contains no value i e  null i want output i  defined as N A  All this problem stems from the fact that the column field is NULL allowed in the database  And sorry guys for telling you that its a NPE while in fact its SQLException    noob here

User · Answer

The description of the getString   method says the following    the column value  if the value is SQL NULL  the value returned is null   That means your problem is not that the String value is null  rather some other object is  perhaps your ResultSet or maybe you closed the connection or something like this  Provide the stack trace  that would help

User · Answer

output   rs getString  column      if data is null  output  would be null  so there is no chance of NPE unless  rs  is  null   if output    null     if you fetched null value then initialize output with blank string   output

User · Answer

I was able to do this    String a  if rs getString  column      null        a    Hello world      else       a    Bye world

User · Answer

To treat validation when a field is null in the database  you could add the following condition   String name    oRs getString   name column       Null  oRs getString   name column          with this you can validate when a field is null and do not mark an exception

User · Answer

The code should be like given below  String selectSQL    SELECT IFNULL tbl column        AS column FROM MySQL table AS tbl   Statement st        Result set rs   st executeQuery selectSQL

User · Answer

The String being null is a very good chance  but when you see values in your table  yet a null is printed by the ResultSet  it might mean that the connection was closed before the value of ResultSet was used   Class forName  org sqlite JDBC    con   DriverManager getConnection  jdbc sqlite My db db    String sql     select   from cust where cust id      cus         pst   con prepareStatement sql   rs   pst executeQuery    con close    System out println rs getString 1      Would print null even if there are values   Class forName  org sqlite JDBC    con   DriverManager getConnection  jdbc sqlite My db db    String sql     select   from cust where cust id      cus         pst   con prepareStatement sql   rs   pst executeQuery    System out println rs getString 1    con close      Wouldn t print null if there are values in the table

User · Answer

Since the column may be null in the   database  the rs getString   will   throw a NullPointerException     No   rs getString will not throw NullPointer if the column is present in the selected result set  SELECT query columns  For a particular record if value for the  comumn is null in db  you must do something like this -   String myValue   rs getString  myColumn    if  rs wasNull          myValue          set it to empty string as you desire      You may want to refer to wasNull   documentation -   From java sql ResultSet boolean wasNull   throws SQLException     Reports whether   the last column read had a value of SQL  lt code gt NULL lt  code gt     Note that you must first call one of the getter methods   on a column to try to read its value and then call   the method  lt code gt wasNull lt  code gt  to see if the value read was   SQL  lt code gt NULL lt  code gt        return  lt code gt true lt  code gt  if the last column value read was SQL            lt code gt NULL lt  code gt  and  lt code gt false lt  code gt  otherwise    exception SQLException if a database access error occurs or this method is               called on a closed result set

User · Answer

I came across with the same issue  But I believe   handling null in the sql is not a good option  such things should be handled in java program for better performance  secondly   rs getString  quot column quot      NULL is also not a good option as you are comparing string s reference not value  better to use  equals   method while checking null or isEmpty   method  Again  with this you can use null check  that is  fine

[java] Handling the null value from a resultset in JAVA

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