Can we use Map for accessing data from database.

[Rupa Katkar]

Hi to all,
I want to access database using map. My database is in Oracle 10g.
can we access.

[Sagar Rohankar]

NO, you can't access database using Map, you need JDBC.
And if you want to store database row data into the Map, then you have to do something like this:

Map<Long, String[]> idDataMap;
// read data from db
if(rs.next())
{
      Long id = rs.getLong(1);
      String data[];
      data[0] = rs.getString(2);
      idDataMap.put(id, data);
}

Please note, I haven't initialize the object.

[Sagar Rohankar]

And this shouldn't be asked in Servlet section, its related to JDBC and MUST be asked in JDBC section.

[Rupa Katkar]

Sagar Rohankar wrote:And this shouldn't be asked in Servlet section, its related to JDBC and MUST be asked in JDBC section.

Pl. tell me, how should i transfer my query to JDBC section..

[Bear Bibeault]

Already done.

[Rupa Katkar]

Sagar Rohankar wrote:NO, you can't access database using Map, you need JDBC.
And if you want to store database row data into the Map, then you have to do something like this:

Map<Long, String[]> idDataMap;
// read data from db
if(rs.next())
{
      Long id = rs.getLong(1);
      String data[];
      data[0] = rs.getString(2);
      idDataMap.put(id, data);
}

Please note, I haven't initialize the object.

Hi..
I am using map for retrieving database contents..
Now i am able to save my contents in map, but i am not getting how to get it back
for displaying purpose / for further processing

My code is like this

             
HashMap hm = new HashMap(); 
....
..


               if(hm.isEmpty())  {
                  PreparedStatement st = conn.prepareStatement("SELECT * FROM TBL_B60");
                  ResultSet rs = st.executeQuery();   
              
                  while(rs.next()){
                    Batch_B60 b = new Batch_B60 (rs.getInt("BATCH_NO"),rs.getInt("RECEIPT_AMOUNT"));
                    hm.put(new Integer(b.b60_batch), b);    
                  }
                  rs.close(); 
              }

Now here after i want to retrieve the data which i saved in this map.
how should i do this?
please tell me...

[Jonathon Stride]

sample code from my project ^

Iterator i=hashmap.keySet().iterator();
	
	int k=0;
	while(i.hasNext())
	{	k++;
		Integer j=(Integer)i.next();
		System.out.println(j);
			
		//(String)hashmap.get(j) value in the hashmap
		
		System.out.println(hashmap.get((int)j));
	}
 

[Sagar Rohankar]

Rupa Katkar wrote:Now here after i want to retrieve the data which i saved in this map.

Where do you want to display this data, Don't make us guessing !

Still, I guess its JSP :

// This is will access the 'Batch_B60 b' object
${map.key}

[Rupa Katkar]

Jonathon Stride wrote:sample code from my project ^

Iterator i=hashmap.keySet().iterator();
	
	int k=0;
	while(i.hasNext())
	{	k++;
		Integer j=(Integer)i.next();
		System.out.println(j);
			
		//(String)hashmap.get(j) value in the hashmap
		
		System.out.println(hashmap.get((int)j));
	}
 

Actually the database with which i am dealing is very large.
so i think to retrieve its contents Map is suitable..
& here in Jonathon's code i am able to access only BATCH_NO from table.
remaining fields i am unable to access..
How should i access to fields.

[Rupa Katkar]

Sagar Rohankar wrote:

Rupa Katkar wrote:Now here after i want to retrieve the data which i saved in this map.

Where do you want to display this data, Don't make us guessing !

Still, I guess its JSP :

// This is will access the 'Batch_B60 b' object
${map.key}

Hi Sagar,

I want to retrieve the table contents first, then i am going to process on that data.
& after processing the results i have display on jsp page.
But first i should able to retrieve the whole data from my database. my table contains thousands of records.
Please you suggest me should i go for Map or should i use something else.

Finally after processing data i am going to display it on jsp page only.

thanks for your support.

[Sagar Rohankar]

First, I correct your original code:

int batchNo;
double receiptAmt;
while(rs.next())
{  
        batchNo  = rs.getInt("BATCH_NO");
        receiptAmt = s.getInt("RECEIPT_AMOUNT");
        Batch_B60 b = new Batch_B60(batchNo, receiptAmt);  
        // I hope this is what you want <batch no : receipt amount> as a key:value pair
        hm.put(batchNo, receiptAmt);      
} 

Rupa Katkar wrote:& here in Jonathon's code i am able to access only BATCH_NO from table.
remaining fields i am unable to access..
How should i access to fields.

To access both the key and value:

Iterator i=hashmap.keySet().iterator();  
int k;
while(i.hasNext())  
{
       k = i.next();  
       System.out.println("KEY : " + k " :: VALUE : " + hashmap.get(k));  
}

But first i should able to retrieve the whole data from my database. my table contains thousands of records.
Please you suggest me should i go for Map or should i use something else.

Its depends upon, what you want to do with the data. Map's are used to associate the bunch of data with the unique identifier.

[Rupa Katkar]

Sagar Rohankar wrote:First, I correct your original code:

int batchNo;
double receiptAmt;
while(rs.next())
{  
        batchNo  = rs.getInt("BATCH_NO");
        receiptAmt = s.getInt("RECEIPT_AMOUNT");
        Batch_B60 b = new Batch_B60(batchNo, receiptAmt);  
        // I hope this is what you want <batch no : receipt amount> as a key:value pair
        hm.put(batchNo, receiptAmt);      
} 

Rupa Katkar wrote:& here in Jonathon's code i am able to access only BATCH_NO from table.
remaining fields i am unable to access..
How should i access to fields.

To access both the key and value:

Iterator i=hashmap.keySet().iterator();  
int k;
while(i.hasNext())  
{
       k = i.next();  
       System.out.println("KEY : " + k " :: VALUE : " + hashmap.get(k));  
}

But first i should able to retrieve the whole data from my database. my table contains thousands of records.
Please you suggest me should i go for Map or should i use something else.

Its depends upon, what you want to do with the data. Map's are used to associate the bunch of data with the unique identifier.

Sagar, your code is working in my project, thanks for that..
One thing i want to ask is

        Batch_B60 b = new Batch_B60(batchNo, receiptAmt);  

in this code, we are not using this "b" object anywhere, how should we use it..

[Sagar Rohankar]

Rupa Katkar wrote:

        Batch_B60 b = new Batch_B60(batchNo, receiptAmt);  

in this code, we are not using this "b" object anywhere, how should we use it..

I think you want to use "bean", that's why I kept that code as it is. But if your need is fulfilled without using the bean instance "b", then you can delete that line.