Closing resultsets in loop
I have code that creates dynamic SQL statements in a loop to search for a value in a table. The Where clause is changed in each iteration of the loop until the value is found or the loop finishes. The code looks something like this:
(Sorry for the crappy formatting of the code. I tried indenting lines, but when I previewed it, it aligned everything. Damn )
/* NOTE: variables were changed to fit in this page better */
for( int i = 9; i >=0;i--) {
SelectSQL = new StringBuffer("SELECT col FROM tab WHERE ");
for( int j = 0; j <= i;j++) {
SelectSQL.append( "col" + j + "ID = " + Val[j]);
if( j != i ) { SelectSQL.append(","); }
stmt = con.createStatement(ResultSet.TYPE_FORWARD_ONLY,
ResultSet.CONCUR_READ_ONLY );
rs = stmt.executeQuery(SelectSQL.toString());
if( rs.next() ) {
ValID = rs.getLong(1);
/* TODO: Should I be closing these in loops? */
rs.close();
stmt.close();
if( ValID > 0 ) { break; }
My question is: Do I need to close the resultset(rs) and statement(stmt) at the bottom of the loop? That does not seem very efficient to me, but I am not sure. Any advice would be greatly appriciated. Thanks for your time.
declare the statement out of the loop and close it on the
end (also out of the loop) so you reuse the statement each time,
if the ResultSet is empty it closes, also if you loop through it it closes itself, when it is empty, but i recommend to close it each time you use it anyway (in the loop)
don't forget, only select statements return a resultset .. others (delete, update) don't
Similar Messages
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Please Help ! Exception in closing resultset,statement.
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finally {
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what the conditions exceptions may arise in closing resultset/statements.
when does the garbage collector free such resources and what are the implications of not catching exception while closing - can this cause database handle leaks.
Please help!I don't know what exceptions might occur, but since the close() method can throw SQLException, your program has to catch it. Maybe if you close twice, the second time will throw an exception? Anyway, it doesn't really matter, you still have to write a try-catch around it. What you do there is up to you -- you could ignore it (which is what I do) or you could end the program with a message.
When does the garbage collector free those resources? The garbage collector only frees memory. Nothing else. And the garbage collector will free a ResultSet object only when there are no references to it anywhere in your program. That doesn't mean just in code that you wrote, but anywhere in code that's running in your program. For example, the Statement object that produced the ResultSet might hold a reference to it. However, the API documentation for ResultSet does say that when the garbage collector does free a ResultSet object, it will automatically close it.
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Can we execute a query in resultset while loop
can we execute a query in resultset while loop
for ex:
rs=st.executeQuery("SQL");
while(rs.next())
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Vivek Nath
National Instruments
Applications Engineer
Machine Vision -
I'm getting desperate for a solution to this problem (as is the rest of the development team!).
Basically we've been trying to create a system that automatically assigns values (frequencies) to objects (nodes) based on a rule set. Each node contains a varying number of sub-objects (radios) and each radio needs one frequency. The database has been set up and has test data for our Solution class to go through. However, we've run into an odd problem where our ResultSets are suddenly closing.
The classes work like this:
Database Broker (handles connection to DB, as well as executeQuery and executeUpdate statements.)
Entry Broker (Holds all SQL statements for data retrieval in various methods. Each method contains an SQL statement to access data, and code to format that data into something useable by the main class.
Solution/Main class (Contains methods to use the data from the Entry Broker to test valid solutions. Certain rules apply to assigning frequencies to radios and this class ensures that the data applies to these rules before it writes the data back to the DB (via the EntryBroker).
The problem we continually run into is that whilst the ResultSets work fine in the Entry Broker, they are closed when they return to the Main class.
Here's the catch: It seems in most cases that only the FIRST ResultSet returned in each method is closed, the remaining ResultSets work fine. We worked around this problem by creating a 'dummy' ResultSet, which obtained data from the database which was never used (the project name). We put this in its own try catch bracket so it would not interrupt the project.
It worked fine for a few classes, but for others (notably the following one) it was ineffective. We've searched and searched but we cannot find anyone with a similar complaint (except a few people who have commented about ODBC version problems). Our ODBC version is 3.520.7713.0
Here's an example method from the Solution class (The entire class is over 1000 lines):
// Method to test Harmonic resonance for nodes within 10m
private boolean resonanceGlobal (boolean tstResonanceG, double txFreq, double rxFreq, int distance) {
System.out.println("Beginning global harmonic resonance check");
try {
// Getting Nodes
rsNode2 = eBroker.getNodes(projectNo);
// node loop
while (rsNode2.next()) {
System.out.println("602 Test Marker GHarm 1");
// get next node, store in nodeTemp
nodeTemp = rsNode2.getInt(1);
// System out to show which nodes will pass if statement
System.out.println(node + " compare to " + nodeTemp);
// avoid testing the same node against itself
if (nodeTemp != node) {
// distance check (only neccesary within 10m)
System.out.println("Test Marker Before Distance check");
distance = getDistance(node, nodeTemp, distance);
System.out.println("Test Marker After Distance check");
// distance check if statement
if (distance <= 10) {
System.out.println("618 Test Marker GHarm 2");
// get the radios of the node, foreign node
rsRadiosTemp = eBroker.getRadios(node);
rsDummy = eBroker.getDummy(projectNo);
rsRadios2 = eBroker.getRadios(nodeTemp);
// This dummy ResultSet normally fails so that
// the other ResultSets perform normally
try {
rsDummy.next();
} // end try
catch (java.sql.SQLException dummyException) {
System.out.println("dummyException " + dummyException);
} // end catch
// radio loop
while (rsRadiosTemp.next()) { // error occurs here
System.out.println("627 Test Marker GHarm 3");
// loop for foreign node radios
while (rsRadios2.next()) {
System.out.println("631 Test Marker GHarm 4");
// get next radio
radioTemp = rsRadios2.getInt(1);
// get the TX and RX of the radio
genericTX = getTX(radioTemp);
radioTempCon = getConnection(radioTemp);
genericRX = getTX(radioTempCon);
// calculate bounds for harmonics test
txLo = ((txFreq * 2) - genericTX) - 4; // 4Mhz below TX harmonics check
txHi = ((txFreq * 2) - genericTX) + 4; // 4Mhz above TX harmonics check
rxHi = ((rxFreq * 2) - genericRX) + 4; // 4Mhz above RX harmonics check
rxLo = ((rxFreq * 2) - genericRX) - 4; // 4Mhz below RX harmonics check
// checks TX and RX of foreign radio against TX, RX of current radio for separation
if ((txLo > genericTX && txHi < genericTX) || (rxLo > genericRX && rxHi < genericRX)) {
tstResonanceG = false;
break;
} //end if
else {
tstResonanceG = true;
} // end else
} //end foreign radio loop
// breaking out of loops for return
if (tstResonanceG == false)
break;
} // end radio loop
rsRadios2.close();
rsRadiosTemp.close();
} // end sameradio check
} // end distance check
}// end node loop
rsNode2.close();
} // end try
// Catch statement to stop from crashing in the
// event of an error during SQL statements.
catch (java.sql.SQLException resonanceGlobalException) {
// Prints out the error message produced
System.out.println(resonanceGlobalException);
} // end catch
// returns result
return tstResonanceG;
} //end checkHarmonicResonanceGlobal()
My apologies if it is a little hard to read, but the indenting is accurate. The Entry Broker methods which this method uses are here:
public ResultSet getNodes (int projectNo) {
// creating SQL statement
sqlStatement = "SELECT nodeNo from tblNode WHERE projectNo = " + projectNo;
System.out.println(sqlStatement);
// executing SQL statement
rsNodes = db.runQuery(sqlStatement);
// returns ResultSet
return rsNodes;
} // end getNodes
// Method to get the distance between any two nodes
public int getDistance (int projectNo, int node, int tempNode) {
ResultSet rsX1; // Used for obtaining the X-coord of node 1
ResultSet rsX2; // Used for obtaining the X-coord of node 2
ResultSet rsY1; // Used for obtaining the Y-coord of node 1
ResultSet rsY2; // Used for obtaining the Y-coord of node 2
double distance = 0; // Used in Global checks
int dist = 0; // Used in Global checks
int x1 = 0; // Used in calculating distance
int x2 = 0; // Used in calculating distance
int y1 = 0; // Used in calculating distance
int y2 = 0; // Used in calculating distance
int xDist = 0; // Used in calculating distance
int yDist = 0; // Used in calculating distance
int distint = 0; // Used to store converted values
try {
// get the X and Y co-ordinates of both nodes
sqlStatement = "SELECT xCoord FROM tblNode WHERE nodeNo = " + node + " AND projectNo = " + projectNo;
rsX1 = db.runQuery(sqlStatement);
rsX1.next();
x1 = rsX1.getInt(1);
sqlStatement = "SELECT yCoord FROM tblNode WHERE nodeNo = " + node + " AND projectNo = " + projectNo;
rsY1 = db.runQuery(sqlStatement);
rsY1.next();
y1 = rsY1.getInt(1);
sqlStatement = "SELECT xCoord FROM tblNode WHERE nodeNo = " + tempNode + " AND projectNo = " + projectNo;
rsX2 = db.runQuery(sqlStatement);
rsX2.next();
x2 = rsX2.getInt(1);
sqlStatement = "SELECT yCoord FROM tblNode WHERE nodeNo = " + tempNode + " AND projectNo = " + projectNo;
rsY2 = db.runQuery(sqlStatement);
rsY2.next();
y2 = rsY2.getInt(1);
} // end try
catch (java.sql.SQLException getDistanceException) {
System.out.println(getDistanceException);
// calculating distance
yDist = y2 - y1;
xDist = x2 - x1;
// perform pythagoras theorem for distance
dist = (xDist * xDist) + (yDist * yDist);
distance = java.lang.Math.sqrt(dist);
Double roundFreqTemp = new Double(freqTemp);
distint = roundFreqTemp.intValue() ;
return distint;
} // end get distance method
// Method to get all the radios in a node
public ResultSet getRadios(int node) {
ResultSet rsRadios; // Used for obtaining radios in a node
// creating sql Statement
sqlStatement = "SELECT * FROM tblRadio WHERE nodeNo =" + node;
System.out.println(sqlStatement);
// executing sql Statement
rsRadios = db.runQuery(sqlStatement);
System.out.println("EB Test Marker 1: Line 261");
// returning radio no
return rsRadios;
}//end getRadio
public double getTX(int radioTemp){
double txTemp = 0; // Used for storing TX of a radio
int freqNoTemp = 0; // Used for storing the frequency ID
rsDummy = getDummy(projectNo);
// creating SQL statement
sqlStatement ="Select frequencyNo from tblRadio where radioNo = " + radioTemp;
System.out.println(sqlStatement);
// executing SQL statement
rsTX = db.runQuery(sqlStatement);
try {
System.out.println("Test Marker EB1: 317");
try {
rsDummy.next();
} // end try
catch (java.sql.SQLException dummyException) {
System.out.println("dummyException" + dummyException);
} // end catch
System.out.println("Test MarkerEB2: 330");
// moving to first position in rs
rsTX.next();
System.out.println("Test MarkerEB3: 334");
// obtaining data from rs
freqNoTemp = rsTX.getInt(1);
System.out.println("Test MarkerEB4: 337");
rsTX.close();
} // end try
catch (java.sql.SQLException rsTXException) {
System.out.println("rsTXExeption: " + rsTXException);
} // emd catch
System.out.println("Frequency No is: " + freqNoTemp);
rsDummy = getDummy(projectNo);
sqlStatement = "Select frequency from tblFreq where frequencyNo = " + freqNoTemp;
System.out.println(sqlStatement);
rsRX = db.runQuery(sqlStatement);
try {
try {
System.out.println("Test MarkerEB6: 361");
rsDummy.next();
} // end try
catch (java.sql.SQLException dummyException) {
System.out.println("dummyException" + dummyException);
} // end catch
System.out.println("Test MarkerEB5: 373");
rsRX.next();
System.out.println("Test MarkerEB7: 376");
txTemp = rsRX.getDouble(1);
System.out.println("Test MarkerEB8: 379");
rsRX.close();
} // end try
catch (java.sql.SQLException rxException) {
System.out.println("rxException " + rxException);
} // end catch
System.out.println("393 Before return");
return txTemp;
} //end getTX
public int getConnection(int radio) {
int nodeCon = 0; // Used to return the connected node no
ResultSet rsConnection; // Used for obtaining the foreign radio
// creating SQL statement
sqlStatement = "SELECT radioNo FROM tblRadio where recRadio = " + radio;
System.out.println(sqlStatement);
// executing SQL statement
rsConnection = db.runQuery(sqlStatement);
try {
// moving to first position in rs
rsConnection.next();
// obtaining data from rs
nodeCon = rsConnection.getInt(1);
} // end try
catch (java.sql.SQLException getConnectionException) {
System.out.println("getConnectionException : " + getConnectionException);
} // end catch
// returns node no.
return nodeCon;
And finally, the dummy rs:
// Dummy method to fix resultSet closed error
public ResultSet getDummy (int projectNo) {
sqlStatement = "Select projectName from tblProject where projectNo = " + projectNo;
System.out.println(sqlStatement);
rsDummy = db.runQuery(sqlStatement);
return rsDummy;
Here is some sample output that we have:
----jGRASP exec: java MainGui
slider value constructor: 50
116: if(singleton==null) {
120: singleton=new Resolvotron
Connection to D/Base establised
Select projectName from tblProject where projectNo = 3
Init OK. Beginning solve process
main OK: beginning frequency assign process
SELECT nodeNo from tblNode WHERE projectNo = 3
267: Node number = 2
SELECT * FROM tblRadio WHERE nodeNo =2
EB Test Marker 1: Line 261
Test Marker 1: Line 289
298: Radio number = 4
Test Marker 5: Line 308
Test Marker 3: Line 313
SELECT frequency from tblFreq WHERE projectNo = 3
125.5
Beginning test process
Test Marker 4: Line 386
Beginning check 257072
Test Marker 6: Line 774
70 Mhz Margin = false
Beginning local 10Mhz separation check
SELECT * FROM tblRadio WHERE nodeNo =2
EB Test Marker 1: Line 261
Getting TX of radio: 4
Select projectName from tblProject where projectNo = 3
Select frequencyNo from tblRadio where radioNo = 4
Test Marker EB1: 317
dummyExceptionjava.sql.SQLException: ResultSet is closed
Test MarkerEB2: 330
Test MarkerEB3: 334
Test MarkerEB4: 337
Frequency No is: 2
Select projectName from tblProject where projectNo = 3
Select frequency from tblFreq where frequencyNo = 2
Test MarkerEB6: 361
dummyExceptionjava.sql.SQLException: ResultSet is closed
Test MarkerEB5: 373
Test MarkerEB7: 376
Test MarkerEB8: 379
393 Before return
432: getting connection
SELECT radioNo FROM tblRadio where recRadio = 4
438: getting TX of radio: 6
Select projectName from tblProject where projectNo = 3
Select frequencyNo from tblRadio where radioNo = 6
Test Marker EB1: 317
dummyExceptionjava.sql.SQLException: ResultSet is closed
Test MarkerEB2: 330
Test MarkerEB3: 334
Test MarkerEB4: 337
Frequency No is: 2
Select projectName from tblProject where projectNo = 3
Select frequency from tblFreq where frequencyNo = 2
Test MarkerEB6: 361
dummyExceptionjava.sql.SQLException: ResultSet is closed
Test MarkerEB5: 373
Test MarkerEB7: 376
Test MarkerEB8: 379
393 Before return
java.sql.SQLException: ResultSet is closed
10 Mhz Local = true
Beginning 10 Mhz separation check
SELECT nodeNo from tblNode WHERE projectNo = 3
Node number is 2
10 Mhz Global = false
Beginning local harmonic resonance check
SELECT * FROM tblRadio WHERE nodeNo =2
EB Test Marker 1: Line 261
Select projectName from tblProject where projectNo = 3
Select frequencyNo from tblRadio where radioNo = 4
Test Marker EB1: 317
dummyExceptionjava.sql.SQLException: ResultSet is closed
Test MarkerEB2: 330
Test MarkerEB3: 334
Test MarkerEB4: 337
Frequency No is: 2
Select projectName from tblProject where projectNo = 3
Select frequency from tblFreq where frequencyNo = 2
Test MarkerEB6: 361
dummyExceptionjava.sql.SQLException: ResultSet is closed
Test MarkerEB5: 373
Test MarkerEB7: 376
Test MarkerEB8: 379
393 Before return
SELECT radioNo FROM tblRadio where recRadio = 4
Select projectName from tblProject where projectNo = 3
Select frequencyNo from tblRadio where radioNo = 6
Test Marker EB1: 317
dummyExceptionjava.sql.SQLException: ResultSet is closed
Test MarkerEB2: 330
Test MarkerEB3: 334
Test MarkerEB4: 337
Frequency No is: 2
Select projectName from tblProject where projectNo = 3
Select frequency from tblFreq where frequencyNo = 2
Test MarkerEB6: 361
I'll leave it at that, since the program goes into an endless loop. The dummy Exceptions are our dummy resultsets crashing so the rest can survive. The other stuff is from different methods. You should be able to locate the logic of the program by following the System.outs
Test Markers with EB refer to the Entry Broker.
Any help would be appreciated since we cannot find any other way of running this class successfully.
SteveOk problem solved...
Basically I was calling one ResultSet after another. Thanks to the Database Broker's structure, this was killing the first ResultSet. I fixed up the loops so that ResultSets were only ever called just before they were needed, and it fixed the problem. The only other errors were simple logic faults which I drummed out in short order. Thanks for the help everyone! -
Too many connections - even after closing ResultSets and PreparedStatements
I'm getting a "Too many connections" error with MySQL when I run my Java program.
2007-08-06 15:07:26,650 main/CLIRuntime [FATAL]: Too many connections
com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: Too many connections
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:921)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2870)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:812)
at com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:3269)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1182)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2670)I researched on this and found out that I wasn't closing the ResultSet and the PreparedStatement.
The JDBC connection is closed by a central program that handles connections (custom connection pooling).
I added the code to close all ResultSets and PreparedStatements, and re-started MySQL as per the instructions here
but still get "Too many connections" error.
A few other things come to mind, as to what I may be doing wrong, so I have a few questions:
1) A few PreparedStatements are created in one method, and they are used in a 2nd method and closed in the 2nd method
does this cause "Too many connections" error?
2) I have 2 different ResultSets, in nested while loops where the outer loop iterates over the first ResultSet and
the inner loop iterates over the second ResultSet.
I have a try-finally block that wraps the inner while loop, and I'm closing the second ResultSet and PreparedStement
in the inner while loop.
I also have a try-finally block that wraps the outer while loop, and I'm closing the first ResulSet and PreparedStatement
in the outer while loop as soon as the inner while loop completes.
So, in the above case the outer while loop's ResultSet and PreparedStatements remain open until the inner while loop completes.
Does the above cause "Too many connections" error?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The following is relevant sections of my code ( it is partially pseudo-code ) that shows the above 2 cases:
init( Connection jdbcConnection ){
String firstSQLStatement = "....";
PreparedStatement ps1 = jdbcConnection.prepareStatement( firstSQLStatement );
String secondSQLStatement = "....";
PreparedStatement ps2 = jdbcConnection.prepareStatement( secondSQLStatement );
String thirdSQLStatement = "....";
PreparedStatement ps3 = null;
ResultSet rsA = null;
try{
ps3 = jdbcConnection.prepareStatement( thirdSQLStatement );
rsA = ps3.executeQuery();
if( rsA.next() ){
rsA.getString( 1 );
}finally{
if( rsA != null )
rsA.close();
if( ps3 != null )
ps3.close();
//Notice, how ps1 and ps2 are created here but not used immediately, but only ps3 is
//used immediately.
//ps1 and ps2 are used in another method.
run( Connection jdbcConnection ){
ResultSet rs1 = ps1.executeQuery();
try{
while(rs1.next()){
String s = rs1.getString();
ps2.setString(1, s);
ResultSet rs2 = ps2.executeQuery();
try{
while(rs2.next()){
String s2 = rs2.getString();
}finally{
if( rs2 != null )
rs2.close();
if( ps2 != null )
ps2.close();
}catch( Exception e ){
e.printStackTrace();
}finally{
if( rs1 != null )
rs1.close();
if( ps1 != null )
ps1.close();
//Notice in the above case rs1 and ps1 are closed only after the inner
//while loop completes.
}I appreciate any help.Thanks for your reply.
I will look at the central connection pooling mechanism ( which was written by someone else) , but that is being used by many other Java programs others have written.
They are not getting this error.
An addendum to my previous note, I followed the instructions here.
http://dev.mysql.com/doc/refman/5.0/en/too-many-connections.html
There's probably something else in my code that is not closing the connection.
But I just wanted to rule out the fact that opening a PreparedStatement in one method and closing it in another is not a problem.
Or, if nested ResultSet loops don't cause the problem.
I've read in a few threads taht "Too many connections" can occur for unclosed RS and PS , and not just JDBC connections. -
Not closing ResultSet, but not getting ORA-01000
I have an application that is generating the familiar ORA-01000 error.
Whilst investigating the problem, I wrote a small test program. In the test program I tried to get the ORA-01000, but I don't get it (has anyone ever complained about not getting ORA-01000 before?!)
connection = DriverManager.getConnection("<connection string>");
String sql = "SELECT c1 FROM pdtab2 WHERE Id>=? AND Id<=?";
PreparedStatement ps = connection.prepareStatement(sql);
for (int i = 1; i <= 30000; ++i)
ps.setInt(1, i-1);
ps.setInt(2, i+1);
if (i % 100 == 0)
System.out.println("i=" +i);
System.out.println("getCurrentOpenCursors(connection)="
+getCurrentOpenCursors(connection));
try
rs = ps.executeQuery();
while (rs.next())
result = rs.getInt(1);
catch (SQLException e2)
e2.printStackTrace();
finally
// Do nothing! Do not close the result set
}getCurrentOpenCursors does:
select count(*) AS COUNT from v$open_cursor where user_name like 'me'
I have reduced OPEN_CURSORS down from 300 to 100, but getCurrentOpenCursors always returns less that what it is set to. Suggesting that OPEN_CUSRORS is not a limit, but rather a pool size?
The result set returns more than one record, I never close the result set, yet I do not get an ORA-01000 error. I have tried auto-commit true and false on the connection. Is the prepared statement closing its previous result set on each new iteration of the loop, hence stopping me getting a problem?
I am using Oracle version 10.2.0.1, the corresponding ojdbc14.jar, and Java 1.4.
Thanks,
PaulHere is a program that does that for you.
To fix the program, un-comment the line 24 of the code and run again.
C:\> type TestCursors.java
import java.lang.* ;
import java.util.* ;
import java.sql.* ;
import oracle.jdbc.* ;
public class TestCursors
public static void main(String[] args) throws SQLException, ClassNotFoundException
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection connection = DriverManager.getConnection("jdbc:oracle:oci:@localhost:1521:ORCL");
ResultSet rs ;
PreparedStatement ps ;
for (int i = 1; i <= 30000; ++i)
String sql = "SELECT 20 FROM scott.emp WHERE deptno = ?";
ps = connection.prepareStatement(sql);
ps.setInt(1, 10);
try
rs = ps.executeQuery();
rs.close() ;
//ps.close() ;
catch (SQLException e2)
System.out.println("The value if i is " + i) ;
throw e2 ;
C:\> javac TestCursors.java
C:\> java TestCursors
The value if i is 301
Exception in thread "main" java.sql.SQLException: ORA-01000: maximum open cursors exceeded
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:111)
at oracle.jdbc.driver.T2CConnection.checkError(T2CConnection.java:671)
at oracle.jdbc.driver.T2CConnection.checkError(T2CConnection.java:597)
at oracle.jdbc.driver.T2CPreparedStatement.executeForDescribe(T2CPreparedStatement.java:570)
at oracle.jdbc.driver.OracleStatement.executeMaybeDescribe(OracleStatement.java:1030)
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1123)
at oracle.jdbc.driver.OraclePreparedStatement.executeInternal(OraclePreparedStatement.java:3284)
at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:3328)
at TestCursors.main(TestCursors.java:22)
C:\> -
Unclear about closing ResultSets
Please provide clarification: The JavaDoc for ResultSets says that you don't have to explicitly close ResultSet objects since the RS will be closed when its defining Statement is closed or when the RS is garbage collected.
The Oracle JDBC Developer's Guide and Reference states (in the section titled "Closing the Result Set and Statement Objects"):
"You must explicitly close the ResultSet and Statement objects after you finish using them. This applies to all
ResultSet and Statement objects you create when using the Oracle JDBC drivers. The drivers do not have
finalizer methods; cleanup routines are performed by the close() method of the ResultSet and Statement
classes. If you do not explicitly close your ResultSet and Statement objects, serious memory leaks could
occur. You could also run out of cursors in the database."
So, does the Oracle driver operate differently than the JDBC standard in this regard?The JavaDoc for ResultSets says that you don't have to explicitly close ResultSet objects since the RS will be closed when its defining Statement is closed or when the RS is garbage collected.In Oracle JDBC, if you close the statement, then the result set is also closed, unless you obtained the result set as an OUT parameter from a stored procedure or function that returns a REF CURSOR.
However, it is definitely not prudent to wait until the result set is garbage collected, since you have no explicit control over that! Depending on your database setup, you'll typically be able to open a couple dozen statements before you start running out of database cursors.
This is even more important if you are using SQLJ: there statements are automatically managed for you, so you'll never have to worry about closing them. However, if you do not close result sets (called iterators in SQLJ), the associated statement will be kept around and stays open (again, it might be garbage collected or it might not - no guarantees). -
Getting java.lang.NullpointerException while closing resultset aft using it
Hi,
I kindly request to share your ideas reg. my problem.
I am opening a database connection using connection pool and i am using two or more resultsets and statement objects.I am closing these objects at the end of their usage.But i am getting java.lang.NullpointerException when i close them(if i don't close them it works fine). what might be the reason. Had i did any thing wrong in the code.
please view the code
public String storeNewConnection(String CIRCLE,String DIVISION,String SUB_DIVISION,String SECTION,String CONSUMER_NAME,String FATHER_NAME,String STREET_NAME,String DOOR_NO,String TOWN_CITY,String LAND_MARK,String PINCODE,String STDCODE,String PHONE_NO,String EMAIL,String NEIGHBOUR_SCNO,String DOCUMENT_CODE,String LT_APR_NO,String year1,String month1,String day1,String PCBNO,String CONSUMER_STATUS,String SOCIAL_GROUP,String CATEGORY_SUPPLY,String LOCATION_PREMISES,String PURPOSE_OF_SUPPLY,String DURATION,String LOAD_TYPE,String CONNECTED_LOAD,String CONTRACTED_LOAD,String APPLICATION_FEE,String DEVELOPMENT_CHARGES,String SECURITY_DEPOSIT,String ADDL_SECURITY_DESPOSIT,String DEPOSITED_THRU,String DD_CHEQUE_DETAILS,String year2,String month2,String day2,String REMARKS,String POLE_NO)
int count=0;
Statement st=null;
ResultSet rs=null,rs1=null,rs2=null,rs3=null;
PreparedStatement pst=null;
String result="",query="",sysDate="",sysDate2="";
String reg_no = "";
try
st=con.createStatement();
//Check dates with sys date
String date1 =null;
String date2 =null;
if(! (year1.equals("") || month1.equals("") || day1.equals("")) )
date1=day1+"-"+month1+"-"+year1;
rs2=st.executeQuery("select round(to_date('"+date1+"','dd-Mon-yyyy')-to_date(sysdate,'dd-Mon-yy')) from dual");
rs2.next();
if(rs2.getInt(1) != 0)
return "false";
if(! (year2.equals("") || month2.equals("") || day2.equals("")) )
date2=day2+"-"+month2+"-"+year2;
rs3=st.executeQuery("select round(to_date('"+date2+"','dd-Mon-yyyy')-to_date(sysdate,'dd-Mon-yy')) from dual");
rs3.next();
if(rs3.getInt(1) != 0)
return "false";
rs1=st.executeQuery("select to_char(sysdate,'yyyyMONdd'),to_char(sysdate,'dd-Mon-yyyy') from dual");
rs1.next();
sysDate=rs1.getString(1);
sysDate2=rs1.getString(2);
rs=st.executeQuery("select max(SERIAL_NO) from NEW_CONNECTIONS where to_char(sysdate,'yyyy') = to_char(REG_DATE,'yyyy') and to_char(sysdate,'mm') = to_char(REG_DATE,'mm') and SUB_DIVISION_CODE = "+SUB_DIVISION+" and DIVISION_CODE = "+DIVISION+" and CIRCLE_CODE = "+CIRCLE+" ");
if(rs.next())
count = rs.getInt(1);
count++;
else
count=1;
query="insert into NEW_CONNECTIONS ( "+
" REG_NO,SERIAL_NO,REG_DATE,CIRCLE_CODE,DIVISION_CODE,SUB_DIVISION_CODE,SECTION_CODE, "+
" CONSUMER_NAME,FATHER_NAME,STREET_NAME,DOOR_NO,TOWN_CITY,LAND_MARK,PINCODE, "+
" STDCODE,PHONE_NO,EMAIL,NEIGHBOUR_SCNO,DOCUMENT_CODE,LT_APR_NO,LT_APR_DATE, "+
" PCBNO,CONSUMER_STATUS,SOCIAL_GROUP,CATEGORY_SUPPLY,LOCATION_PREMISES,PURPOSE_OF_SUPPLY,"+
" DURATION,LOAD_TYPE,CONNECTED_LOAD,CONTRACTED_LOAD,APPLICATION_FEE,DEVELOPMENT_CHARGES, "+
" SECURITY_DEPOSIT,ADDL_SECURITY_DEPOSIT,DEPOSITED_THRU,DD_CHEQUE_DETAILS,DD_CHEQUE_DATE,REMARKS,APPLICATION_STATUS,POLE_NO) "+
" values(?,?,'"+sysDate2+"',?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)";
pst = con.prepareStatement(query);
String cnt ="";
if(count <= 9)
cnt="0000";
else if(count <= 99)
cnt="000";
else if(count <= 999)
cnt="00";
else if(count <= 9999)
cnt="0";
cnt+=Integer.toString(count);
reg_no = CIRCLE+DIVISION+SUB_DIVISION+SECTION+"N"+cnt+sysDate;
int serial_no =count;
int pin = 0;
if(!PINCODE.equals(""))
pin =Integer.parseInt(PINCODE);
int std = 0;
if(!STDCODE.equals(""))
std = Integer.parseInt(STDCODE);
int status = Integer.parseInt(CONSUMER_STATUS);
int social_group = Integer.parseInt(SOCIAL_GROUP);
int supply = Integer.parseInt(CATEGORY_SUPPLY);
int location = Integer.parseInt(LOCATION_PREMISES);
int purpose = Integer.parseInt(PURPOSE_OF_SUPPLY);
int duration = Integer.parseInt(DURATION);
int laod_type = Integer.parseInt(LOAD_TYPE);
float conn_load = Float.parseFloat(CONNECTED_LOAD);
int cont_load = 0;
if(!CONTRACTED_LOAD.equals(""))
cont_load =Integer.parseInt(CONTRACTED_LOAD);
int app_fee = Integer.parseInt(APPLICATION_FEE);
int dev_chg = Integer.parseInt(DEVELOPMENT_CHARGES);
int sec_dep = Integer.parseInt(SECURITY_DEPOSIT);
int addl_sec_dep = 0;
if(!ADDL_SECURITY_DESPOSIT.equals(""))
addl_sec_dep =Integer.parseInt(ADDL_SECURITY_DESPOSIT);
int dep_thru = Integer.parseInt(DEPOSITED_THRU);
pst.setString(1,reg_no);
pst.setInt(2,serial_no);
pst.setString(3,CIRCLE);
pst.setString(4,DIVISION);
pst.setString(5,SUB_DIVISION);
pst.setString(6,SECTION);
pst.setString(7,CONSUMER_NAME);
pst.setString(8,FATHER_NAME);
pst.setString(9,STREET_NAME);
pst.setString(10,DOOR_NO);
pst.setString(11,TOWN_CITY);
pst.setString(12,LAND_MARK);
pst.setInt(13,pin);
pst.setInt(14,std);
pst.setString(15,PHONE_NO);
pst.setString(16,EMAIL);
pst.setString(17,NEIGHBOUR_SCNO);
pst.setString(18,DOCUMENT_CODE);
pst.setString(19,LT_APR_NO);
pst.setString(20,date1);
pst.setString(21,PCBNO);
pst.setInt(22,status);
pst.setInt(23,social_group);
pst.setInt(24,supply );
pst.setInt(25,location);
pst.setInt(26,purpose);
pst.setInt(27,duration);
pst.setInt(28,laod_type);
pst.setFloat(29,conn_load );
pst.setInt(30,cont_load);
pst.setInt(31,app_fee);
pst.setInt(32,dev_chg);
pst.setInt(33,sec_dep);
pst.setInt(34,addl_sec_dep);
pst.setInt(35,dep_thru );
pst.setString(36,DD_CHEQUE_DETAILS);
pst.setString(37,date2);
pst.setString(38,REMARKS);
pst.setInt(39,1);
pst.setString(40,POLE_NO);
pst.executeUpdate();
result=reg_no;
rs.close();
rs=null;
rs1.close();
rs1=null;
rs2.close();
rs2=null;
rs3.close();
rs3=null;
st.close();
st=null;
pst.close();
pst=null;
catch(Exception e)
e.printStackTrace();
result="false";
return result;
finally
if (rs != null)
try
rs.close();
catch (SQLException e)
rs = null;
if (rs1 != null)
try
rs1.close();
catch (SQLException e)
rs1 = null;
if (rs2 != null)
try
rs2.close();
catch (SQLException e)
rs2 = null;
if (rs3 != null)
try
rs3.close();
catch (SQLException e)
rs3 = null;
if (st != null)
try
st.close();
catch (SQLException e)
st = null;
if (pst != null)
try
pst.close();
catch (SQLException e)
pst = null;
return result;
Also plz help me to improve the code if necessary so that it will work fine for multiple users
thaks & regards
Prasanth.CThanks a lot.
i replaced the code below
if (rs != null)
try
rs.close();
catch (SQLException e)
rs = null;
if (rs1 != null)
try
rs1.close();
catch (SQLException e)
rs1 = null;
if (rs2 != null)
try
rs2.close();
catch (SQLException e)
rs2 = null;
if (rs3 != null)
try
rs3.close();
catch (SQLException e)
rs3 = null;
if (st != null)
try
st.close();
catch (SQLException e)
st = null;
if (pst != null)
try
pst.close();
catch (SQLException e)
pst = null;
instead of blindly closing the resultsets and statements
now it works fine.
One more thing, is my code structurally correct, i mean the variables, try...catch blocks,results,statements,database connections and overall coding. whether it looks like professional code.
thaks & regards,
Prasanth.C -
Closing resultset and statements
Hi!
I just got told that I do not need to close my resultsets and statements in the code, it it enough that the connection are closed. Is this correct?
Eg:
public method myMethod() {
ResultSet rs = null;
Statement sqlStmt = null;
try {
query = "SELECT something";
rs = sqlStmt.executeQuery(query);
if (rs.next())
do something...
// close rs
if (rs != null) {
rs.close();
rs = null;
sqlStmt.close();
sqlStmt = null;
} // end try
catch (errors)...
finally {
if (con != null) { <-- Is this line enough to close everything and release connections?
try {
con.close();
catch (exception)...
} // end finallyNo, you have to explicitly close the resultset, statement, and connection in order to release resources allocated to each of them. Closing the connection will only relase the connection, not the resultset, and statement.
you could do all of it in the finally as follows:
finally {
try {
if (rs != null) {
rs.close();
if (stmt != null) {
stmt.close();
if (conn != null) {
conn.close();
} catch (Exception e) {}
also there is no need to set rs = null, stmt = null after the close() -
Help with resultset and looping thru a sql filed
Hi,
I have a SQL statement which connects two tables with accounting number, the table2 have multiple rows for one accounting number in table1.
So I did if else condition in accounting number in resultset as following:
List<AccRecord> retval = new ArrayList<AccRecord>();
while(rs.next())
//instance of account record
AcciRecord acct1 = new AccRecord();;
if(acc_No != accountNumber)
//then get all data from table1
acc1.setEmpId(rs.getInt("ACC_ID"));
acc1.setEmpId(rs.getString("Acc_Name"));//and other 20 fields like this
else if(acc_No == accountNumber) //this is where it breaks down if same acc number has more than one row in table2,we don't //want to get all other data again from table1
//also get all data associated with that accounting number from table2
Other other1 = new Other();
other1.setEmpId(rs.getInt("EMP_ID"));//these are datas from table2
other1.setjobCode(rs.getString("JOB_CD"));
other1.add(crew1);
retval.add(acc1);
}My question is how can I make logic right, in above code for the first account number it will go to else if condition (coz very first time acc number is never going to be different then previous accounting number,so it won't get my accounting data, the way I have compared it)
I want to code like for one accounting number it brings all accounting data and for that accounting number it also brings all employee data (which is in table2) which will more than one entires,
So..when accounting number is same as previous it shouldn't get all data again from table 1 ,it should go to only else if condition to get data from table 2 , it should go to my if block only when there is a new accounting number, in other words when there is next record in table1
Can anybody help me??
Please...
Thanks
Edited by: ASH_2007 on Mar 28, 2008 11:55 AMhi there,
thanks for ur feedback
but it is always going to contian accno .. so it will never go in your condition
May be I haven't explained it well
I need something which gets all data for every new account number in table 1
Now for that same account number, table2 have 3 rows including that account number 3 times (I am connecting this 2 tables with acc no, table 1 doesn't have duplicate acc no but table 2 does)So my resultset runs 3 times for the first record in table 1, because for that accno table 2 has 3 entries
This is because my sql is as follow,,which I have to,,I can't change due to requirements...
SELECT A.accNumber, A.Date, B.EMP_ID, B.JOB_CD
FROM Table A, Table B, (SELECT SSA.accNumber FROM Table SSA, Table SSB
WHERE SSB.EMP_ID = ? AND
SSA.accNumber = accNumber) C
WHERE A.accNumber = C.accNumber
AND A.accNumber = B.accNumber
//so if I do: like this in my resultset
while(rs.next())
Integer accNumber = rs.getINt(accNumber);
accno =accnumber;
if (accno != accNumber)
{ get all account data
else if(accno == accNumber)
{ get all other data
}but question is it will not satisfy my if condition , because for a new record ,in this case,in first record acc number will never match...
I appreciate your help and time
Please help me
THnaks
Edited by: ASH_2007 on Mar 28, 2008 1:54 PM -
Can we execute a query in resultset of while loop
can we execute a query in resultset while loop
for ex:
rs=st.executeQuery("SQL");
while(rs.next())
rs1=st.executequery("SQL1");
while(rs1.next())
}yup no problem..if it doesn work declare the second one as st1
-
How could I Fix this problem .. ResultSet closed
In my JSP page after 4or 5 refreshings i am getting an exeption either saying "Invalid state for getResultSet" of "ResultSet is closed". I'm not getting this if i refresh again. I've tried even by closing ResultSet, Statement and Connection objects at the end of page. Can u give me the solution
This is correct, unless the guy is lucky enough to be using a driver that adheres to JDBC 3. Try unloading the ResultSet object into a cache and then referencing that on subsequent calls to the page, (unless data staleness is an issue). You'd probably find it useful to browse some of the data transfer patterns to understand the deeper issues in what you're doing.
-
PreparedStatement ResultSet wrapper to auto close cursor
Hi !
Is it possible to create wrapper that will automatically close result set and prepared statements ?
I am sick of closing resultsets and preparedstatements in all my dao objects. Its all about neverending try catch and close code lines, it is all against the java garbage collector idea.
Do you have any workaround ? Or I need to use with those try catch and close.
Thanks !when u allocate object u dont need to call free nor destory when u dont need the object anymore.
on the other hand, you need to call .close() when u dont need the prepared statement anymore -
Implicit vs explicit close of resultsets and statements?
Hi friends.I am a newbie Java Developer..Okay Here goes
I have just made a LAN based Java application using Swing,JDBC with backend as MS-Access..The backend is on a shared network drive..
The application is distributed as jar files on the LAN PCs..
Everywhere I have connected to the database I have just closed the connection explicitly like this
con.close();
I do not close the associated resultset and statement explicitly
The specification says associated statements and resultsets close when you close
the connection,even if you don't explicitly close them
Also I am not using connection pool..its simple basic connection using DriverManager
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
String url = "jdbcdbcSN name";
String user = "";
String pw = "";
con = DriverManager.getConnection(url, user, pw);
Statement stmt = con.createStatement();
String select = "" ;
ResultSet rows = stmt.executeQuery(select);
On the net everyone says to explicitly close everything..but I did not know that
earlier..
If specification says everything closes on
closing connection why do ppl insist on closing everything explicitly..?
Or is this driver dependent..don't the drivers go through the specification..
My driver is the Sun JDBC ODBC bridge.....
I found this method DriverManager.setLogwriter()
It prints out a trace of all JDBC operations..
So I ran a sample program with this method included...
I redirected output to a log file..
In that program I just explicitly close the connection without closing the
statements and resultsets explicitly...
After running the program and seeing the log I saw that the statements
and resultsets are closed implicitly If I just close the connection explicitly..
I am putting the log file and the code..
Have a look at the end of the log file..
Code
import java.sql.;
import java.io.;
class gc4test
public static void main(String args[])
Connection con = null;
try
FileWriter fwTrace = new FileWriter("c:\\log.txt");
PrintWriter pwTrace= new PrintWriter(fwTrace);
DriverManager.setLogWriter(pwTrace);
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
String url = "jdbc:odbc:pravahcon";
String user = "admin";
String pw = "ash123";
con = DriverManager.getConnection(url, user, pw);
Statement stmt = con.createStatement();
Statement stmt1 = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
Statement stmt2 = con.createStatement();
Statement stmt3 = con.createStatement();
Statement stmt4 = con.createStatement();
Statement stmt5 = con.createStatement();
Statement stmt6 = con.createStatement();
Statement stmt7 = con.createStatement();
String select = "SELECT * FROM Users" ;
ResultSet rows = stmt.executeQuery(select);
ResultSet rows1 = stmt1.executeQuery(select);
while(rows.next())
con.close();
catch (ClassNotFoundException f)
System.out.println(f.getMessage());
System.exit(0);
catch (SQLException g)
System.out.println(g.getMessage());
System.exit(0);
catch (Exception e)
System.out.println(e.getMessage());
System.exit(0);
End of Log File
Setting statement option (SQLSetStmtAttr), hStmt=50275112, fOption=25
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
Fetching (SQLFetch), hStmt=50274224
End of result set (SQL_NO_DATA)
*Connection.close
8 Statement(s) to close
*Statement.close
Free statement (SQLFreeStmt), hStmt=50281544, fOption=1
deregistering Statement sun.jdbc.odbc.JdbcOdbcStatement@2e7263
*Statement.close
Free statement (SQLFreeStmt), hStmt=50277224, fOption=1
deregistering Statement sun.jdbc.odbc.JdbcOdbcStatement@1bf216a
*Statement.close
*ResultSet.close
*ResultSet has been closed
Free statement (SQLFreeStmt), hStmt=50274224, fOption=1
deregistering Statement sun.jdbc.odbc.JdbcOdbcStatement@156ee8e
*Statement.close
Free statement (SQLFreeStmt), hStmt=50280464, fOption=1
deregistering Statement sun.jdbc.odbc.JdbcOdbcStatement@c20e24
*Statement.close
Free statement (SQLFreeStmt), hStmt=50278304, fOption=1
deregistering Statement sun.jdbc.odbc.JdbcOdbcStatement@12ac982
*Statement.close
*ResultSet.close
*ResultSet has been closed
Free statement (SQLFreeStmt), hStmt=50275112, fOption=1
deregistering Statement sun.jdbc.odbc.JdbcOdbcStatement@e0e1c6
*Statement.close
Free statement (SQLFreeStmt), hStmt=50276144, fOption=1
deregistering Statement sun.jdbc.odbc.JdbcOdbcStatement@6ca1c
*Statement.close
Free statement (SQLFreeStmt), hStmt=50279384, fOption=1
deregistering Statement sun.jdbc.odbc.JdbcOdbcStatement@1389e4
Disconnecting (SQLDisconnect), hDbc=50271048
Closing connection (SQLFreeConnect), hDbc=50271048
Closing environment (SQLFreeEnv), hEnv=50270880
So like what these implicitly closed statements and resultsets are different from explicitly closed
resultsets and statements..?Please do not crosspost/doublepost the same question again. It is rude in terms of netiquette.
Stick to one topic: [http://forums.sun.com/thread.jspa?threadID=5393387&messageID=10745794#10745794].
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