Handling the null value from a resultset in JAVA

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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).

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 <code>NULL</code>.
* 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 <code>wasNull</code> to see if the value read was
* SQL <code>NULL</code>.
*
* @return <code>true</code> if the last column value read was SQL
*         <code>NULL</code> and <code>false</code> otherwise
* @exception SQLException if a database access error occurs or this method is 
*            called on a closed result set
*/

How to handle Null values while working with JDBC?, How to handle Null values while working with JDBC? Avoid using getXXX( ) methods that return primitive data types. Use wrapper classes for primitive data types, and use the ResultSet object's wasNull( ) method to test whether the wrapper class variable that received the value returned by the getXXX( ) method should be I am converting the resultset to JSON using the following approach and trying to figure out how to handle null value based on the scenario described below:. When I run the following SQL query (which is used in the code below) in Oracle SQL developer :

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= "";
}

java.sql.ResultSet.wasNull java code examples, Best Java code snippets using java.sql.ResultSet. Checking for a null int value from a Java ResultSet. int iVal wasNull()) { // handle NULL field value } }. Retrieves the value of the designated column in the current row of this ResultSet object as a String in the Java programming language. Parameters: columnLabel the label for the column specified with the SQL AS clause. It says the returned value is null, but I'm not sure if this means "null" or null.

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.

How to handle null database fields with Java, There are two ways to detect whether a null value is read. 1) Use the wasNull() method provided by the ResultSet class. 2) Use the getObject() method instead of the getInt() method to retrieve the value of the job-id column. By using the getObject() method, we are able to get null values if there any appears. A ResultSet object maintains a cursor pointing to its current row of data - Unless your calling method has no guarantee the passed Resultset is generated by executing a statement via a specific query, then handling the Null Pointer using;

I was able to do this:

String a;
if(rs.getString("column") != null)
{
    a = "Hello world!";
}
else
{
    a = "Bye world!";
}

how to check for null string in resultset [Solved] (JDBC and , hoping you could help me with a question I had in Java. So I'm using a Result Set to get a result. However, one of my strings has a null value. Retrieving the Value of a Column Using the Column Name: 20.6.7. Selecting all rows from a table and creates a result set: 20.6.8. If you Do Not Know the Name, Position, and Type of Each Column, how to get value from ResultSet: 20.6.9. Determine If a Fetched Value Is NULL: 20.6.10. Get int value from ResultSet: 20.6.11. Get the Number of Rows in

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.

How to check if ResultSet is empty in JDBC - Java , Hence, when a Java programmer needs to determine if ResultSet is DBTest { public static void main(String args[]) { Connection con = null;  retrieving null values from ResultSet. When I call ResultSet.getInt() the method will return 0 if the column value is either 0 or null, which is extremely inconvenient, because in many (maybe most) cases, one needs to distinguish between 0 and null.

Retrieving and Modifying Values from Result Sets (The Java , 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  jdbc resultset example, jdbc resultset, jdbc resultset types, resultset, resultset in jdbc, resultset java example, resultset, jdbc resultset statement, jdbc resultset getdata, JDBC ResultSet Example, In this This tutorial you will learn how to use java.sql.ResultSet interface in an application, and how update a database table using ResultSet.

Determine If a Fetched Value Is NULL : Query ResultSet « Database , This JDBC Java tutorial describes how to use JDBC API to create, insert into, update, String dbName) throws SQLException { Statement stmt = null; String query ResultSet Interface; Retrieving Column Values from Rows; Cursors; Updating To allow for correct error handling, you should always disable auto-​commit  The insert row is a special row associated with an updatable result set. It is essentially a buffer where a new row can be constructed by calling the updater methods prior to inserting the row into the result set. For example, this method calls the method ResultSet.updateString to update the insert row's COF_NAME column to Kona.

Handling the null value from a resultset in JAVA, To determine whether the actual value is a NULL, wasNull() must be called. import java.sql.Connection; import java.sql.DriverManager; import java.sql.​ResultSet  So, to handle SQL NULL values in Java, there are three tactics you can use − Avoid using getXXX( ) methods that return primitive data types. Use wrapper classes for primitive data types, and use the ResultSet object's wasNull( ) method to test whether the wrapper class variable that received the value returned by the getXXX( ) method should be set to null.

Comments
  • If the column is null, the ResultSet should return null. Are you sure the ResultSet is not null?
  • normally, you can call the wasNull() method. I don't see why an NPE would be thrown here.
  • while(rs.next()){ rs.getX(); }
  • I'm decidedly curious as to why this was downvoted.
  • thank you d-live very much....that solves my problem....chris guided me that it couldn't be a NPE (so i checked again and it was not)...Peter suggested me a suggestion similar to yours but i couldn't understand him previously. But i do now :-)Thanks to all of the guys for helping me...I'm really overwhelemed that the guys here were so quick in replying...i could solve the problem in just a few minutes.
  • Glad that it solves your problem! Please accept an answer you find appropriate!
  • Why wasn't this answer picked for 5 years @javaNOob?
  • @CaioIglesias Because this seems to be his only question and he left after his problem was solved... What, obviously is not the right way to do so....
  • This is a better answer than the above "rs.wasNull()" which is not applicable for every case.
  • yes perfectly...I think you understand what i am trying to say. Since rs.getString(col) returns the null when column is infact database null, an exception is thrown instantly. I want to check that when the column is database null(i.e. getString() returns null), output[i] is assigned N/A(but for me empty string "" is also acceptable)
  • For rs.getString() you can use the null comparison, but when you have database columns that don't allow null (e.g. rs.getInt()), then you have to use rs.wasNull().
  • works well, but does not work for rs.getInt() as it returns a primitive (0 by default). rs.wasNull should be used