Why are connections not getting closed? - java

I have a code where I am connecting to db using a resultset and then after getting the necessary values closing the connection in finally block.
But for some reason the query is still running and the connection pool is not release.
Can someone help here.
try {
rsU = dbAccess.query(FasoCommon.sqlUpdatable, params, true);
if (rsU.next()) {
updatable = rsU.getString("UpdatableFields");
logger.info("UpdatableFields:: "+updatable);
}
}
finally {
close(rsU, null, null);
}
private void close(ResultSet rs, Statement stmt, Connection conn) {
if (rs != null) {
try {
rs.close();
rs=null;
//logger().info("ResultSet Closed : " + rs);
} catch (SQLException e) {
//logger().error("The result set cannot be closed.", e);
}
}
if (stmt != null) {
try {
stmt.close();
stmt=null;
//logger().info("Statement Closed : " + stmt);
} catch (SQLException e) {
//logger().error("The statement cannot be closed.", e);
}
}
if (conn != null) {
try {
conn.close();
conn=null;
//logger().info("Data Source Connection Closed : " + conn);
} catch (SQLException e) {
}
}
}


In finally block, Connection object is being passed as null and even Statement object is also being passed as null.
finally {
close(rsU, null, null);
}
Check them and pass these object references, if you have access to them and
non-null references, pass to that close() method and check.


there was an set object which was keeping the refence to the connection even after closing the connection.Fixing that part resolved the issue.

Related

SQL query in Java does not work, no error is appearing but the data isn't appearung in DB

I try to insert a row to the database, but it doesn't appear in the table after running:
This is the main class:
public class Tester {
public static void main(String[] args) {
CouponsDbDao coupDbDao = new CouponsDbDao();
Coupon coupon = new Coupon(1, 0, Category.Food, null, null, null, null, 25, 0, null);
coupDbDao.addCoupon(coupon);
}
}
And this is the method:
public class CouponsDbDao {
public void addCoupon(Coupon coupon) {
try {
Connection connection = JdbcUtils.getConnection();
String sqlStatement = "insert into coupons (COMPANY_ID,CATEGORY_ID,TITLE,DESCRIPTION,START_DATE,END_DATE,AMOUNT,PRICE,IMAGE) values(?,?,?,?,?,?,?,?,?)";
PreparedStatement statement = connection.prepareStatement(sqlStatement);
statement.setInt(1, coupon.getCompanyId());
statement.setObject(2, coupon.getCategory());
statement.setString(3, coupon.getTitle());
statement.setString(4, coupon.getDescription());
statement.setDate(5, coupon.getStartDate());
statement.setDate(6, coupon.getEndDate());
statement.setInt(7, coupon.getAmount());
statement.setDouble(8, coupon.getPrice());
statement.setString(9, coupon.getImage());
} catch (Exception e) {
e.printStackTrace();
}
}

You need to execute the statement after setting values. Additionally, you need to close the connection created, the preparedstatement etc in a finally block.
public class CouponsDbDao {
Connection connection = null;
PreparedStatement statement = null;
public void addCoupon(Coupon coupon) {
try {
connection= JdbcUtils.getConnection();
String sqlStatement = "insert into coupons (COMPANY_ID,CATEGORY_ID,TITLE,DESCRIPTION,START_DATE,END_DATE,AMOUNT,PRICE,IMAGE) values(?,?,?,?,?,?,?,?,?)";
statement = connection.prepareStatement(sqlStatement);
statement.setInt(1, coupon.getCompanyId());
statement.setObject(2, coupon.getCategory());
statement.setString(3, coupon.getTitle());
statement.setString(4, coupon.getDescription());
statement.setDate(5, coupon.getStartDate());
statement.setDate(6, coupon.getEndDate());
statement.setInt(7, coupon.getAmount());
statement.setDouble(8, coupon.getPrice());
statement.setString(9, coupon.getImage());
statement.executeUpdate();
} catch (Exception e) {
e.printStackTrace();
}
finally{
if (statement != null) {
try {
statement.close();
} catch (SQLException e) { /* print here */}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) { /* print here */}
}
}
}

As told by others you need to call executeUpdate to really perform the query:
Executes the SQL statement in this PreparedStatement object, which must be an SQL Data Manipulation Language (DML) statement, such as INSERT, UPDATE or DELETE
I suggest you also to use the try with resources:
The try-with-resources statement is a try statement that declares one or more resources. A resource is an object that must be closed after the program is finished with it. The try-with-resources statement ensures that each resource is closed at the end of the statement. Any object that implements java.lang.AutoCloseable, which includes all objects which implement java.io.Closeable, can be used as a resource.
This has been introduced in java 7 and let you eliminate the finally boiler plate code as follow:
// ORIGINAL CODE
Connection connection = ...
try {
connection = JdbcUtils.getConnection();
...
statement.executeUpdate();
} catch (Exception e) {
e.printStackTrace();
} finally {
if (statement != null) {
try {
statement.close();
} catch (SQLException e) { /* print here */}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) { /* print here */}
}
}
becomes:
// USING try with resources
try (Connection connection = JdbcUtils.getConnection()) {
...
statement.executeUpdate();
} catch (Exception e) {
e.printStackTrace();
} // NO need of the finally block because connection is AutoCloseable

You need to execute update for statement, like:
statement.executeUpdate();

Fortify: fails to release a database resource

I am trying to see the vulnerability of my code with fortify. The report said that I have an issue which said "the function sometimes fails to release a database resource allocated by". Here is the code and in which line the issue pointed. I've tried to close the connection in the finally block but it not solve the issue. How to fix this?
private AnotherService anotherService;
private void create() {
Connection conn = null;
try {
conn = getCon(); // With fortify, there's an issue which said "the function sometimes fails to release a database resource allocated by", and it refers to this line
conn.setAutoCommit(false);
anotherService.myFunction(conn);
// the conn.commit() is inside anotherService, because I have to make one connection
// rest of code
} catch (Exception e) {
e.printStackTrace;
if (null != conn) {
conn.rollback();
}
} finally {
if (null != conn) {
conn.close();
}
}
}
private static Connection getCon() {
Connection connection = null;
try {
Class.forName("org.postgresql.Driver");
connection = DriverManager.getConnection(
"jdbc:postgresql://localhost:5432/dbname",
"username",
"password");
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return connection;
}
Addition:
If I use try-with-resource (like this try (Connection conn = getCon()), to automatically close things, how I could call conn.rollback() in the catch block if any exception occured? Since the conn variable declared inside the try-with-resources.

Well, I solve my problem, the close method should call inside try-catch in the finally block, as mentioned in this link.
In case the link broken, here is the code that I use to solve my problem:
Statement stmt = null;
ResultSet rs = null;
Connection conn = getConnection();
try {
stmt = conn.createStatement();
rs = stmt.executeQuery(sqlQuery);
processResults(rs);
} catch (SQLException e) {
// Forward to handler
} finally {
try {
if (rs != null) {rs.close();}
} catch (SQLException e) {
// Forward to handler
} finally {
try {
if (stmt != null) {stmt.close();}
} catch (SQLException e) {
// Forward to handler
} finally {
try {
if (conn != null) {conn.close();}
} catch (SQLException e) {
// Forward to handler
}
}
}
}

STS/Eclipse showing Potential resource leak, why?

I have a service method which connects to MySQL and get data in ResultSet and in finally closed it's PreparedStatement, but STS showing a warning at return statement as
Potential resource leak: 'resultSet' may not be closed at this
location
Method:
public boolean checkData() {
Connection dbConnection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
boolean status = false;
try {
dbConnection = icrud.getConnection();
preparedStatement = dbConnection.prepareStatement("query on table");
resultSet = preparedStatement.executeQuery();
if (resultSet.next()) {
status = resultSet.getBoolean("STATUS");
}
return status; //Potential resource leak warning shows here.
} catch (Exception e) {
LOGGER.error("Exception Occurred:: " , e);
} finally {
try {
if (preparedStatement != null) {
preparedStatement.close();
preparedStatement = null;
}
} catch (SQLException e) {
LOGGER.error("Exception Occured while Closing statement" , e);
}
try {
if (dbConnection != null) {
dbConnection.close();
dbConnection = null;
}
} catch (SQLException e) {
LOGGER.error("Exception Occured while closing connection" , e);
}
}
return status;
}
As per Doc,
When a Statement object is closed, its current ResultSet object, if
one exists, is also closed.
So I am closing Statement in finally though its showing warning. I have checked by closing result set in finally still warning doesn't go off.
Is it false positive? or Am I doing something wrong?

You are returning "status" without closing your connections. The "finally" clause isn't executed when you get to the return statement.

SonarLint is still showing blocker errors even though we have handled the statement, Connection closes in finally block

SonarLint is showing below errors:
'Use try-with-resources or close this "Statement" in a "finally" clause.'
'Use try-with-resources or close this "Connection" in a "finally" clause.'
blocker errors even though we have closed the Statement stmt, Connection con in finally block.
Please find the sample code.
public String getProductNumber() throws BusinessDelegateException {
String productNo = null;
Connection con = null;
Statement stmt = null;
ResultSet rs = null;
String query = //some query
try {
DataSource ds = getDataSource();
con = ds.getConnection();
stmt = con.createStatement();
rs = stmt.executeQuery(query);
productNo =.......
....................
}catch (Exception e) {
String errorMsg = "Error occured in getProductNumber()";
throw new BusinessDelegateException(errorMsg, e);
}finally{
try {
if(rs != null)
rs.close();
if (stmt != null)
stmt.close();
if (con != null)
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
return productNo;
}
We were able to fix the issue by modifying the finally block in below manner. But still it seems like repetition of catch blocks. Any other way we can fix this?
finally{
try {
if(rs != null)
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
try {
if (stmt != null)
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
try {
if (con != null)
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}

Without try-with-resources you can only improve the code by using methods for re-usability, call main method:
closeResources(rs, stmt, con);
Which will call each for each resource a different method for example Statement:
public void closeResource(Statement stmt) {
if (stmt != null) {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
BTW, you better use logger instead of e.printStackTrace()
For complete solution, you can check extensive example which add resources in array and close them in a loop:
for (Closeable resource : resources) {
try {
resource.close();

Use Try-with-resources. This is the best option.

Statement Leakage in JDBC

Statement Leakage in JDBC:
pstmt =
StatementLeakage : An open JDBC Statement is not closed on all paths. This can cause a transaction or Statement resources to remain active indefinitely, slowing or preventing access to the database by other requests.: for (object created at line = TunnelDBHandler:139, type = java.sql.PreparedStatement), object used at prepareStatement() # TunnelDBHandler:139
dbManager
.getConnection()
.prepareStatement(
"update TUNNEL_STORE set IS_TUNNEL_OPEN=? where TUNNEL_ID=?");

Add a finally block and call close() on all of your ResultSet(s), Statement(s) and Connection(s). As a very rough example,
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
// ...
// get a statement for stmt
// get a resultset from the stmt
// ...
while (rs.next()) {
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException e) {
}
}
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
}
}
}

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