ClassNotFoundException jdbc driver postgresql [duplicate] - postgresql

This question already has an answer here:
ClassNotFoundException with PostgreSQL and JDBC
(1 answer)
Closed 5 years ago.
so I am writing a programm that accesses a database but whenever i can the method Class.forName("org.postgresql.Driver); the ClassNotFoundException is thrown.
I have looked at every solution to this problem I could find, but nothing worked.
I hope you can help me with this.
Code:
public static void editDatabase(String[] values){
Connection connect = null;
Statement statement = null;
ResultSet result = null;
try {
Class.forName("org.postgresql.Driver");
connect = DriverManager.getConnection(values[0],values[1],values[2]);
statement = connect.createStatement();
result = statement.executeQuery("select * from Kunde");
} catch (SQLException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}

This problem means that your project does not load 'org.postgresql.Driver' at init.
If you are using IntelliJ, you must add org.postgresql.Driver using 'Project Structure', it's located at your top right window.
If you're not using IDE, I do recommend you to use one.
You could also use Maven and add 'org.postgresql.Driver' as a requirement for your project.
Bye.

Related

Connectjboss 4 with Firebird 3 via Jaybird 2.214-jdk1.6 [duplicate]

As soon as my code gets to my while(rs.next()) loop it produces the ResultSet is closed exception. What causes this exception and how can I correct for it?
EDIT: I notice in my code that I am nesting while(rs.next()) loop with another (rs2.next()), both result sets coming from the same DB, is this an issue?
Sounds like you executed another statement in the same connection before traversing the result set from the first statement. If you're nesting the processing of two result sets from the same database, you're doing something wrong. The combination of those sets should be done on the database side.
This could be caused by a number of reasons, including the driver you are using.
a) Some drivers do not allow nested statements. Depending if your driver supports JDBC 3.0 you should check the third parameter when creating the Statement object. For instance, I had the same problem with the JayBird driver to Firebird, but the code worked fine with the postgres driver. Then I added the third parameter to the createStatement method call and set it to ResultSet.HOLD_CURSORS_OVER_COMMIT, and the code started working fine for Firebird too.
static void testNestedRS() throws SQLException {
Connection con =null;
try {
// GET A CONNECTION
con = ConexionDesdeArchivo.obtenerConexion("examen-dest");
String sql1 = "select * from reportes_clasificacion";
Statement st1 = con.createStatement(
ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_READ_ONLY,
ResultSet.HOLD_CURSORS_OVER_COMMIT);
ResultSet rs1 = null;
try {
// EXECUTE THE FIRST QRY
rs1 = st1.executeQuery(sql1);
while (rs1.next()) {
// THIS LINE WILL BE PRINTED JUST ONCE ON
// SOME DRIVERS UNLESS YOU CREATE THE STATEMENT
// WITH 3 PARAMETERS USING
// ResultSet.HOLD_CURSORS_OVER_COMMIT
System.out.println("ST1 Row #: " + rs1.getRow());
String sql2 = "select * from reportes";
Statement st2 = con.createStatement(
ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_READ_ONLY);
// EXECUTE THE SECOND QRY. THIS CLOSES THE FIRST
// ResultSet ON SOME DRIVERS WITHOUT USING
// ResultSet.HOLD_CURSORS_OVER_COMMIT
st2.executeQuery(sql2);
st2.close();
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
rs1.close();
st1.close();
}
} catch (SQLException e) {
} finally {
con.close();
}
}
b) There could be a bug in your code. Remember that you cannot reuse the Statement object, once you re-execute a query on the same statement object, all the opened resultsets associated with the statement are closed. Make sure you are not closing the statement.
Also, you can only have one result set open from each statement. So if you are iterating through two result sets at the same time, make sure they are executed on different statements. Opening a second result set on one statement will implicitly close the first.
http://java.sun.com/javase/6/docs/api/java/sql/Statement.html
The exception states that your result is closed. You should examine your code and look for all location where you issue a ResultSet.close() call. Also look for Statement.close() and Connection.close(). For sure, one of them gets called before rs.next() is called.
You may have closed either the Connection or Statement that made the ResultSet, which would lead to the ResultSet being closed as well.
Proper jdbc call should look something like:
try {
Connection conn;
Statement stmt;
ResultSet rs;
try {
conn = DriverManager.getConnection(myUrl,"","");
stmt = conn.createStatement();
rs = stmt.executeQuery(myQuery);
while ( rs.next() ) {
// process results
}
} catch (SqlException e) {
System.err.println("Got an exception! ");
System.err.println(e.getMessage());
} finally {
// you should release your resources here
if (rs != null) {
rs.close();
}
if (stmt != null) {
stmt.close();
}
if (conn != null) {
conn.close();
}
}
} catch (SqlException e) {
System.err.println("Got an exception! ");
System.err.println(e.getMessage());
}
you can close connection (or statement) only after you get result from result set. Safest way is to do it in finally block. However close() could also throe SqlException, hence the other try-catch block.
I got same error everything was correct only i was using same statement interface object to execute and update the database.
After separating i.e. using different objects of statement interface for updating and executing query i resolved this error. i.e. do get rid from this do not use same statement object for both updating and executing the query.
Check whether you have declared the method where this code is executing as static. If it is static there may be some other thread resetting the ResultSet.
make sure you have closed all your statments and resultsets before running rs.next. Finaly guarantees this
public boolean flowExists( Integer idStatusPrevious, Integer idStatus, Connection connection ) {
LogUtil.logRequestMethod();
PreparedStatement ps = null;
ResultSet rs = null;
try {
ps = connection.prepareStatement( Constants.SCRIPT_SELECT_FIND_FLOW_STATUS_BY_STATUS );
ps.setInt( 1, idStatusPrevious );
ps.setInt( 2, idStatus );
rs = ps.executeQuery();
Long count = 0L;
if ( rs != null ) {
while ( rs.next() ) {
count = rs.getLong( 1 );
break;
}
}
LogUtil.logSuccessMethod();
return count > 0L;
} catch ( Exception e ) {
String errorMsg = String
.format( Constants.ERROR_FINALIZED_METHOD, ( e.getMessage() != null ? e.getMessage() : "" ) );
LogUtil.logError( errorMsg, e );
throw new FatalException( errorMsg );
} finally {
rs.close();
ps.close();
}
A ResultSetClosedException could be thrown for two reasons.
1.) You have opened another connection to the database without closing all other connections.
2.) Your ResultSet may be returning no values. So when you try to access data from the ResultSet java will throw a ResultSetClosedException.
It happens also when using a ResultSet without being in a #Transactional method.
ScrollableResults results = getScrollableResults("select e from MyEntity e");
while (results.next()) {
...
}
results.close();
if MyEntity has eager relationships with other entities. the second time results.next() is invoked the ResultSet is closed exception is raised.
so if you use ScrollableResults on entities with eager relationships make sure your method is run transactionally.
"result set is closed" happened to me when using tag <collection> in MyBatis nested (one-to-many) xml <select> statement
A Spring solution could be to have a (Java) Spring #Service layer, where class/methods calling MyBatis select-collection statements are annotated with
#Transactional(propagation = Propagation.REQUIRED)
annotations being:
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
this solution does not require to set the following datasource properties (i.e., in JBoss EAP standalone*.xml):
<xa-datasource-property name="downgradeHoldCursorsUnderXa">**true**\</xa-datasource-property>
<xa-datasource-property name="resultSetHoldability">**1**</xa-datasource-property>

Multiple exception catch block java 8 eclipse

I'm getting an unhandled message exception for IOException. As you can see in the pasted code I've handled the IOException. The JDK for both eclipse & the project is Java 8 update 121 so I know catching multiple exceptions is supported. What am I doing wrong?
try (InputStream inputStream = BatchMessageProperties.class.getClassLoader().
getResourceAsStream(propertiesFileName)) {
load(inputStream);
//need to make sure all properties are present & not null.
validate(this);
} catch (IOException | InvalidBatchMessagePropertiesFileException ex) {
logger.error(ex.getLocalizedMessage());
ex.printStackTrace();
throw ex;
}
You do rethrow ex inside your catch block, which may be an IOException, right?

POSTGRESQL: Batch entry 0 SELECT

Hi I have the following method which calls a stored function in postgresql. The call works when I use a standard executequery() method but does not work when I start using batchs. Any help will be appreciated.
public void addstuff3() throws Exception {
Statement statement = null;
ResultSet resultSet = null;
Connection conn = null;
try {
// this will load the MySQL driver, each DB has its own driver
Class.forName("org.postgresql.Driver");
// setup the connection with the DB.
conn = DriverManager
.getConnection("jdbc:postgresql://localhost/newmydb?"
+ "user=new_user&password=password");
// statements allow to issue SQL queries to the database
statement = conn.createStatement();
conn.setAutoCommit(false);
statement.addBatch("SELECT ADDSTUFF('comp1', 'mdel1','power','PROPERTY','STRING','ON', '1396983600000', 'testing');");
statement.addBatch("SELECT ADDSTUFF('comp2', 'mdel2','power','PROPERTY','STRING','ON', '1396983600000', 'testing');");
conn.commit();
statement.executeBatch();
} catch (ClassNotFoundException | SQLException e) {
throw e;
} finally {
conn.close();
// resultSet.close();
statement.close();
}
This is the Error I get:
Batch entry 0 SELECT ADDSTUFF('comp1', 'mdel1','power','PROPERTY','STRING','ON', '1396983600000', 'testing') was aborted. Call getNextException to see the cause.
at org.postgresql.jdbc2.AbstractJdbc2Statement$BatchResultHandler.handleError(AbstractJdbc2Sta tement.java:2743)
at org.postgresql.core.v3.QueryExecutorImpl$1.handleError(QueryExecutorImpl.java:461)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1928)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:405)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeBatch(AbstractJdbc2Statement.java:2892)
at jdbc.testing.MySQLAccess.addIndicators3(MySQLAccess.java:125)
at jdbc.testing.JDBCTesting.main(JDBCTesting.java:21)
Any help? I am using jdbc and postgresql.
ok thanks to #Dave I found that
e.getNextException()
Prints:
A result was returned when none was expected
I should not return a value
Works!

MongoDB and Play! Framework Inconsistent Behaviour

I have some code in a test as follows:
#Test
public void testRetrieveMongoDBFailUnkownHost()
{
//Set up test port and host on DSMongo
MyMongo mongoTest = new MyMongo();
mongoTest.setHost("failure");
mongoTest.setPort("0");
//attempt to make the connection
try
{
mongoTest.attemptMongoConnection();
assertTrue(false);
}
catch (Exception e)
{
assertEquals("Incorrect error message received: " + e.getMessage(),"Error (3013) : Unknown database host.", e.getMessage());
}
}
And the attempt MongoConnection() method runs the new Mongo(host, port) method which should fail with an unknown host exception. It isn't failing on my machine (no matter what string I put in instead of failure) but it is failing on my colleagues machine. So the test fails on my machine and passes on his (i.e. he gets the exception). Any ideas cause I am stumped!
Thanks
Paul
EDIT: The code in the attempt Connection Method is
*/
public static void attemptMongoConnection() throws MYException
{
try {
singleMongo = new Mongo(getHost(), getPort());
Logger.debug("Retrieved Mongo database from " + host);
} catch (UnknownHostException e) {
Logger.error("Unknown Host Exception", e);
throw new MYException(MYMessage.MY_UNKNOWN_HOST);
} catch (MongoException e) {
Logger.error("Mongo error", e);
throw new MYException(MYMessage.DS_MONGO_ERROR);
}
}
where singleMOngo is a Mongo variable and the getHost and getPort are the ones we have set (.e. failure and 0).
I have found this was a problem with the DNS somewhere. When I ran it at home (from where I originally made the post) it failed and seems to hav been resolving the name of "failure" so when I instead entered something like "localhost_123" it works perfectly.
I have come into the office this morning and it works with "failure" again. Doing some further digging it seems therefore that my router or something at home is resolving "failure" to an address it is aware of which is not present on the network here in the office.
Thanks for all those who looked at this. Very bizarre.

OSGI & Apache Commons-DBCP Classloading Issue

I inherited some code that is using the Apache commons-dbcp Connection pools in an OSGi bundle. This code works fine with Eclipse/Equinox OSGi version 3.4.3 (R34x_v20081215), commons-dbcp 1.2.2 and the postgres jdbc3 8.3.603 bundles from springsource.org.
I wanted to modernize, maybe this was my first mistake!
When I use the new version of Felix or Equinox OSGI Cores with the new postgresql JDBC3 or JDBC4 bundles along with the latest version of commons-dbcp (1.4.1), I am getting a classloading issue. I have done numerous searches and found that the commons-dbcp code should have a fix DBCP-214, but it still seems to fail.
I have tried to put the org.postgresql on the commons-dbcp MANIFEST.MF import-package line, but that did not work either.
I wrote a simple test in an activator that first does a basic class.forName() and DriverManager.getConnection(), this works fine, but when I add in BasicDataSource() and setup the connection with BasicDataSource.getConnection(), I get the ClassNotFoundException. See the code example below.
Thanks in Advance for any help, suggestions, ...
Sau!
// This one fails with an exception
public void dsTest() {
BasicDataSource bds = new BasicDataSource();
ClassLoader cl;
try {
logger.debug("ContextClassLoader: {}",
Thread.currentThread().getContextClassLoader().toString());
cl = this.getClass().getClassLoader();
logger.debug("ClassLoader: {}", cl);
if (bds.getDriverClassLoader() != null) {
logger.debug(bds.getDriverClassLoader().toString());
}
// The failure is the same with and with the setDriverClassLoader() line
bds.setDriverClassLoader(cl);
bds.setDriverClassName("org.postgresql.Driver");
bds.setUrl("jdbc:postgresql://127.0.0.1/dbname");
bds.setUsername("user");
bds.setPassword("pword");
Class.forName("org.postgresql.Driver").newInstance();
conn = bds.getConnection();
Statement st = conn.createStatement();
ResultSet rs = st.executeQuery("SELECT COUNT(*) FROM table");
conn.close();
logger.debug("Closed DataSource Test");
} catch (Exception ex) {
ex.printStackTrace();
logger.debug("Exception: {} ", ex.getMessage());
}
}
// This one works
public void managerTest() {
ClassLoader cl;
try {
cl = this.getClass().getClassLoader();
logger.debug("ClassLoader: {}", cl);
Class.forName("org.postgresql.Driver").newInstance();
String url = "jdbc:postgresql://127.0.0.1/dbname";
conn = DriverManager.getConnection(url, "user", "pword");
Statement st = conn.createStatement();
ResultSet rs = st.executeQuery("SELECT COUNT(*) FROM table");
conn.close();
logger.debug("Closed Manger Test");
} catch (Exception ex) {
ex.printStackTrace();
logger.debug("Exception: {} ", ex.getMessage());
}
}
this is due to the fact that the commons-dbcp bundle cannot look at the actual driver class, because of the osgi class loader. The solution to this is to attach a fragment to the commons-dbcp class with Dynamic Import *. The actual headers that you need in your MANIFEST are the following:
Fragment-Host: org.apache.commons.dbcp
DynamicImport-Package: *
After this, the code you mentioned worked. Hope this doesnt come too late.