Java exception when adding to map

Question

Not sure what is wrong...it should work or maybe am missing something? the following is the code:

public class TestOracleMap implements java.io.Serializable{
static TreeMap<String, Integer> map;
static TreeMap<String, Integer> localMap = new TreeMap<String, Integer>();

public static void StoreMapInDB(TreeMap<String, Integer> map) throws
        IOException, FileNotFoundException{
    try {
  PreparedStatement insertMap = null;
  //String insertString = "INSERT INTO TESTMAP(ID, MPFIELD) VALUES (1, ?)";
  Connection con=null;
  con.setAutoCommit(false);
  Class.forName("oracle.jdbc.driver.OracleDriver");
  con=DriverManager.getConnection(
    "jdbc:oracle:thin:@oXXX",
    "XXX",
    "XXX");

  ByteArrayOutputStream bos = new ByteArrayOutputStream() ;
  ObjectOutputStream out = new ObjectOutputStream(bos);
  out = new ObjectOutputStream(bos) ;
  out.writeObject(map);
  out.close();

  byte[] buf = bos.toByteArray();
  PreparedStatement prepareStatement = con.prepareStatement("insert into  

  TESTMAP(ID,MAPFIELD)values(?,?)");
  prepareStatement.setLong(1, 1);
  prepareStatement.setBinaryStream(2, new ByteArrayInputStream(buf), buf.length);



 // insertMap.executeUpdate();
  con.commit();
    } catch(Exception e){e.printStackTrace();}
}

public static void main(String[] args)
{
    try{
    DateTime today = new DateTime();
    int x = 1;
    map.put("Hello!", x);
    StoreMapInDB(map);
    }catch(IOException ioe){
        System.err.print(ioe);
    }
}
}

the error is in the line in the main method that is:

map.put("Hello!", x);

it gives:

Exception in thread "main" java.lang.NullPointerException
at core.smd.classes.TestOracleMap.main(TestOracleMap.java:61)
 Java Result: 1

Did you init 'map' somewhere? I see only initialization of localMap... — Volker
– Volker, Commented Dec 7, 2011 at 10:11

Averroes · Accepted Answer · 2011-12-07 10:11:28Z

9

Seems like you never instantiate map. You declare it here

static TreeMap<String, Integer> map;

but when you use it here it is still null giving you the NullPointerException.

map.put("Hello!", x);

If you do this before

map = new TreeMap<String, Integer>();

it should run fine.

answered Dec 7, 2011 at 10:11

Averroes

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2 Comments

sys_debug Over a year ago

cool that doesn't return the null anymore...now the line where it says connection con = null; then I do con.setAutoCommit(false); the thing here is it is returning null but clearly because I set it null in the line before. if I dont, it says it is not initialized. anyway out?

Averroes Over a year ago

duffymo gives you the solution for the con problem :)

duffymo · Accepted Answer · 2011-12-07 10:25:02Z

3

Where did you initialize "map"? Looks null to me.

Change this line:

static TreeMap<String, Integer> map = new TreeMap<String, Integer>();

You declare this and set it to null, but I don't see where you use it.

PreparedStatement insertMap = null;

You've got more heartache ahead here:

Connection con=null;
  Class.forName("oracle.jdbc.driver.OracleDriver");
  con=DriverManager.getConnection(
    "jdbc:oracle:thin:@oXXX",
    "XXX",
    "XXX");
  con.setAutoCommit(false);

Move the autoCommit down until after you get the connection from the driver manager.

You're serializing the Map to INSERT it into the database? That's not normalized. A normalized schema would have a row per entry.

The more I read your code, the less sense it makes. Good luck.

edited Dec 7, 2011 at 10:25

answered Dec 7, 2011 at 10:11

duffymo

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3 Comments

sys_debug Over a year ago

I know the code is messy but the map after testing the table solution instead seemed better for this purpose. I am attempting this for the first time so yeh it might not look good. Thanks though :)

Ilan Over a year ago

maybe its being serialised as a caching mechanism or as a way to maintain state. See Fowler's Enterprise Patterns book about different reasons for doing that.

duffymo Over a year ago

Fair enough. Good point, Ilan. The OP just needs to realize that it's not normalized. The implication is that s/he won't be able to search on individual values in the Map. Storing and retrieving are "all or none" operations.

Romain · Accepted Answer · 2011-12-07 10:11:07Z

2

You never initialize map to anything, hence it is null. You'll need to assign a valid TreeMap<String, Integer> to it somewhere, like for instance on line 2 when you declare it, use:

static TreeMap<String, Integer> map = new TreeMap<String, Integer>();

answered Dec 7, 2011 at 10:11

Romain

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Comments

AndroidHustle · Accepted Answer · 2011-12-07 10:12:01Z

1

the variable map is never initialized, only declared in the constructor.

map = new TreeMap<String, Integer>();

answered Dec 7, 2011 at 10:12

AndroidHustle

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Comments

QinL · Accepted Answer · 2011-12-07 10:12:18Z

1

you only declare map,but not initialize it

static TreeMap<String, Integer> map=new HashMap<String,Integer>();

answered Dec 7, 2011 at 10:12

QinL

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user497849 · Accepted Answer · 2011-12-07 10:14:58Z

1

static TreeMap<String, Integer> map = new TreeMap<String, Integer>(); // <-- in your code, you're not constructing it
static TreeMap<String, Integer> localMap = new TreeMap<String, Integer>();

answered Dec 7, 2011 at 10:14

user497849

Comments

shree · Accepted Answer · 2011-12-07 10:59:10Z

1

You r initializing a variable Connection con = null; then u r setting con.setAutoCommit(false).. Without creating object for that how can u set auto commit for that?

answered Dec 7, 2011 at 10:59

shree

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Comments

Pratik · Accepted Answer · 2011-12-07 10:12:28Z

0

you did initialize map object as you initialized localMap object at declaration just check that

answered Dec 7, 2011 at 10:12

Pratik

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