Com.mysql.jdbc.JDBC4Connection suspected memory leak in java

Question

We have a java application where we are using Bonecp pooling library. Below is how we setup the pooling.
[code]
try {
   // setup the connection pool
   BoneCPConfig config = new BoneCPConfig();
  config.setJdbcUrl("jdbc:mysql://**.**.**.**:3306/test1");  config.setUsername("******");
  config.setPassword("*******");  config.setMinConnectionsPerPartition(5);
  config.setMaxConnectionsPerPartition(40);
  config.setPartitionCount(1);
  connectionPool = new BoneCP(config); // setup the connection pool 
   catch (SQLException e) {
  e.printStackTrace(System.out);
[/code]
Then for insert and update queries we do this and below we make sure closed the statement.
[code]
Statement stmt1 = null;
stmt1 = dbconn.createStatement();
String insertQuery3 =........
count = stmt9.executeUpdate(insertQuery3);
try{
   if ( stmt1!= null ){  stmt1.close();
   else{
   System.out.println("No stm1 exist");
}catch(SQLException ex){   System.out.println("SQLException has been caught for stmt1");
ex.printStackTrace(System.out);
For select we do this 
Statement stmt2 = null;
stmt2 = dbconn.createStatement();
String selectQuery2= .........
ResultSet rs2 = stmt2.executeQuery(selectQuery2);
if(rs2.next())
try{
   if ( rs2!= null ){  rs2.close();
   }   else{
   System.out.println("No rs2 exist");
   if ( stmt2!= null ){  stmt2.close();
   }   else{
   System.out.println("No stm2 exist");
}catch(SQLException ex){   System.out.println("SQLException has been caught for stmt2");
ex.printStackTrace(System.out);
[/code]
Thus we have ensured that every resultset and statement is closed immediately after its use. The problem now when we took few sample from MAT is show increasing memory usage as below.
Sample 1
[code]
21 instances of "com.mysql.jdbc.JDBC4Connection", loaded by "sun.misc.Launcher$ExtClassLoader @ 0xf000a4f0" occupy 11,793,200 (76.19%) bytes.
Biggest instances:
com.mysql.jdbc.JDBC4Connection @ 0xf016d728 - 958,096 (6.19%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0094478 - 875,568 (5.66%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0201ba0 - 816,048 (5.27%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf04ab3f0 - 754,016 (4.87%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf006ee40 - 727,024 (4.70%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0076a90 - 663,872 (4.29%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf04ad490 - 618,200 (3.99%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf00b7bd0 - 616,608 (3.98%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0467bc0 - 612,544 (3.96%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf015fcf0 - 598,400 (3.87%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf021c830 - 584,992 (3.78%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0097818 - 561,224 (3.63%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf01a27c0 - 531,816 (3.44%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf00bea28 - 531,416 (3.43%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf01c2d80 - 522,184 (3.37%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf04693e0 - 482,992 (3.12%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf012b158 - 453,256 (2.93%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf147f438 - 424,656 (2.74%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf15ff7d0 - 187,008 (1.21%) bytes.
Keywords
com.mysql.jdbc.JDBC4Connection
sun.misc.Launcher$ExtClassLoader @ 0xf000a4f0
file:///C:/Documents%20and%20Settings/ss/Local%20Settings/Temp/report2060944296830228239/pages/18.html# Reference Pattern
Class Name
Shallow Heap
Retained Heap
Percentage
class java.lang.Thread @ 0xf0003840
40
208
0.00%
[/code]
Sample 2
[code]
21 instances of "com.mysql.jdbc.JDBC4Connection", loaded by "sun.misc.Launcher$ExtClassLoader @ 0xf000a4f0" occupy 13,827,392 (78.27%) bytes.
Biggest instances:
com.mysql.jdbc.JDBC4Connection @ 0xf016d728 - 1,093,888 (6.19%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0094478 - 957,888 (5.42%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0201ba0 - 916,672 (5.19%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf04ab3f0 - 878,392 (4.97%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf006ee40 - 841,136 (4.76%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf015fcf0 - 758,336 (4.29%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf04ad490 - 747,240 (4.23%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0076a90 - 735,712 (4.16%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf00b7bd0 - 700,912 (3.97%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0467bc0 - 681,336 (3.86%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf00bea28 - 668,080 (3.78%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf021c830 - 658,816 (3.73%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0097818 - 638,208 (3.61%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf01a27c0 - 605,376 (3.43%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf01c2d80 - 582,104 (3.29%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf04693e0 - 558,344 (3.16%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf147f438 - 523,952 (2.97%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf012b158 - 508,232 (2.88%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf1603618 - 276,944 (1.57%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf15ff7d0 - 275,288 (1.56%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf148fd70 - 220,536 (1.25%) bytes.
Keywords
com.mysql.jdbc.JDBC4Connection
sun.misc.Launcher$ExtClassLoader @ 0xf000a4f0
file:///C:/Documents%20and%20Settings/ss/Local%20Settings/Temp/report8548522855535006676/pages/18.html# Reference Pattern
Class Name
Shallow Heap
Retained Heap
Percentage
class java.lang.Thread @ 0xf0003840
40
208
0.00%
[/code]
Sample 3
[code]
21 instances of "com.mysql.jdbc.JDBC4Connection", loaded by "sun.misc.Launcher$ExtClassLoader @ 0xf000a4f0" occupy 17,339,632 (80.79%) bytes.
Biggest instances:
com.mysql.jdbc.JDBC4Connection @ 0xf016d728 - 1,228,048 (5.72%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0094478 - 1,144,056 (5.33%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0201ba0 - 1,126,120 (5.25%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf04ab3f0 - 1,074,552 (5.01%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf006ee40 - 993,912 (4.63%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0076a90 - 931,512 (4.34%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf015fcf0 - 930,952 (4.34%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf04ad490 - 918,176 (4.28%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf00bea28 - 874,512 (4.07%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0467bc0 - 846,368 (3.94%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf00b7bd0 - 838,448 (3.91%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf021c830 - 799,184 (3.72%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf0097818 - 791,256 (3.69%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf01a27c0 - 763,264 (3.56%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf01c2d80 - 745,088 (3.47%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf012b158 - 710,704 (3.31%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf04693e0 - 704,072 (3.28%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf147f438 - 680,400 (3.17%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf1603618 - 458,472 (2.14%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf148fd70 - 390,984 (1.82%) bytes.
com.mysql.jdbc.JDBC4Connection @ 0xf15ff7d0 - 389,552 (1.82%) bytes.
Keywords
com.mysql.jdbc.JDBC4Connection
sun.misc.Launcher$ExtClassLoader @ 0xf000a4f0
file:///C:/Documents%20and%20Settings/ss/Local%20Settings/Temp/report3656754586920669017/pages/18.html# Reference Pattern
Class Name
Shallow Heap
Retained Heap
Percentage
class java.lang.Thread @ 0xf0003840
40
208
0.00%
[/code]

Answer 1

Dear Masijade,
                      Actually I was confuse with where to put and not to put the try and catch. Below is how my skeleton of my codes will be looking like. I just put one sample query there. If you notice at the very end finally I already have even now dbconn.close(); which closes the pooling connection. The problem  I am worried now is that incase there is any exception how will it be rollbacked. Because if you notice now I lump all the queries under one big try and catch but with your suggestion I have to do try and catch for each query right?
[code]
BoneCP connectionPool = null;
  class ConnectionHandler implements Runnable {
    private Socket receivedSocketConn1;
    ConnectionHandler(Socket receivedSocketConn1) {
      this.receivedSocketConn1=receivedSocketConn1;
    Connection dbconn = null;
    public void run() { // etc
     BufferedWriter writeBuffer = null;
     BufferedReader readBuffer = null;
     String capturedMessage="";
     try{
        dbconn = connectionPool.getConnection();
        dbconn.setAutoCommit(false);
        while ((nextChar=readBuffer.read()) != -1){          
          capturedMessage += (char) nextChar;
          if (nextChar == '*')
           try{
                //all queries here.
                try{            
                    Statement stmt1 = null;
                    stmt1 = dbconn.createStatement();
                    try{
                      String updateCommand1 = //query
                      count = stmt1.executeUpdate(updateCommand1);
                    finally{
                      if( stmt1 != null ){
                       stmt1.close();
                    else{
                    System.out.println("stmt1 is null in finally close");
               catch(SQLException ex){
                 ex.printStackTrace(System.out);
               dbconn.commit
           catch (SQLException ex){
                ex.printStackTrace(System.out);
                try{  
              dbconn.rollback();
           catch (Exception rollback){  
              rollback.printStackTrace(System.out);
       catch (Exception e){
           e.printStackTrace(System.out);
           try{  
              dbconn.rollback();
           catch (Exception rollback){  
              rollback.printStackTrace(System.out);
       finally
     catch (SocketTimeoutException ex){
           ex.printStackTrace();
     catch (IOException ex){
           ex.printStackTrace();
     catch (Exception ex){
           ex.printStackTrace(System.out);
      finally{
        try{
         if ( dbconn != null ){
           dbconn.close();
         else{
          System.out.println("dbConn is null in finally close");
        catch(SQLException ex){
            ex.printStackTrace();
        try{
          if ( writeBuffer != null ){
            writeBuffer.close();
         else{
          System.out.println("w is null in finally close");
        catch(IOException ex){
            ex.printStackTrace(System.out);
[/code]