Develop Reference

Connect to Athena using JDBC in a maven project

I'm trying to connect to the Amazon Athena, using jdbc in a maven project, but an exception is being raised. I think that the class is not being found. In Athena's guide it says:
Set the JDBC property, aws_credentials_provider_class, equal to the class name, and include itin your classpath. (1)
Since I'm using eclipse, I thought that the class would be already in the classpath, but apparently not. I tested the code in a simple java project (not maven) and it worked.
AmazonCredentialsProvider.java:
package athena;
import com.amazonaws.auth.AWSCredentials;
public class AmazonCredentials implements AWSCredentials {
#Override public String getAWSAccessKeyId() { return "..."; }
#Override public String getAWSSecretKey() { return "..."; }
}
AmazonCredentialsProvider.java:
package athena;
import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.AWSCredentialsProvider;
public class AmazonCredentialsProvider implements AWSCredentialsProvider {
#Override public AWSCredentials getCredentials() { return new AmazonCredentials(); }
#Override public void refresh() {}
}
The code snippet of the connection :
Class.forName("com.amazonaws.athena.jdbc.AthenaDriver");
Properties properties = new Properties();
properties.setProperty("user", user);
properties.setProperty("password", password);
properties.setProperty("aws_credentials_provider_class", "athena.AmazonCredentialsProvider");
Connection connection = DriverManager.getConnection("jdbc:awsathena://athena." + region + ".amazonaws.com:443", properties);
The exception:
java.sql.SQLException: Failed to load AWS credentials provider class:
athena.AmazonCredentialsProvider at
com.amazonaws.athena.jdbc.AthenaDriverPropertiesFactory.lambda$parseProperties$2(AthenaDriverPropertiesFactory.java:52)
at
com.amazonaws.athena.jdbc.AthenaDriverPropertiesFactory.setClientConfigProperty(AthenaDriverPropertiesFactory.java:159)
at
com.amazonaws.athena.jdbc.AthenaDriverPropertiesFactory.parseProperties(AthenaDriverPropertiesFactory.java:40)
at
com.amazonaws.athena.jdbc.AthenaDriver.connect(AthenaDriver.java:110)
at java.sql.DriverManager.getConnection(Unknown Source) at
java.sql.DriverManager.getConnection(Unknown Source) at
athena.Athena.(Athena.java:94) at
services.GraphService.verify(GraphService.java:194) at
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at
java.lang.reflect.Method.invoke(Unknown Source) at
org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory.lambda$static$0(ResourceMethodInvocationHandlerFactory.java:76)
at
org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:148)
at
org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:191)
at
org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$VoidOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:183)
at
org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:103)
at
org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:493)
at
org.glassfish.jersey.server.model.ResourceMethodInvoker.lambda$apply$0(ResourceMethodInvoker.java:405)
at
org.glassfish.jersey.server.ServerRuntime$AsyncResponder$2$1.run(ServerRuntime.java:843)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:272) at
org.glassfish.jersey.internal.Errors$1.call(Errors.java:268) at
org.glassfish.jersey.internal.Errors.process(Errors.java:316) at
org.glassfish.jersey.internal.Errors.process(Errors.java:298) at
org.glassfish.jersey.internal.Errors.process(Errors.java:268) at
org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:289)
at
org.glassfish.jersey.server.ServerRuntime$AsyncResponder$2.run(ServerRuntime.java:838)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown
Source) at java.util.concurrent.FutureTask.run(Unknown Source) at
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at
java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at
java.lang.Thread.run(Unknown Source) Caused by:
java.lang.ClassNotFoundException: athena.AmazonCredentialsProvider at
java.net.URLClassLoader.findClass(Unknown Source) at
java.lang.ClassLoader.loadClass(Unknown Source) at
java.lang.ClassLoader.loadClass(Unknown Source) at
java.lang.Class.forName0(Native Method) at
java.lang.Class.forName(Unknown Source) at
com.amazonaws.athena.jdbc.AthenaDriverPropertiesFactory.lambda$parseProperties$2(AthenaDriverPropertiesFactory.java:44)
... 31 more
Does anyone know how to solve it?

Are you using the latest version of the JDBC driver?
If yes, try to follow these instructions:
https://docs.aws.amazon.com/redshift/latest/mgmt/configure-jdbc-connection-with-maven.html

Check if webpage exists using Java

I'm using Java to check the response of a url I pass in. This is the current code I'm using. However, I keep getting a connection refused error. I'm testing with the basic Google home page so that I know the rough draft of my code works.
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import javax.net.ssl.HttpsURLConnection;
public class connectTest {
public static void main(String[] args)
{
boolean test = pageExists();
}
public static boolean pageExists(){
int returnCode= 0;
try {
HttpURLConnection.setFollowRedirects(false);
String httpsURL = "https://www.google.com/";
URL testUrl = new URL(httpsURL);
HttpsURLConnection con =
(HttpsURLConnection)testUrl.openConnection();
returnCode= con.getResponseCode();
System.out.println(returnCode);
} catch (Exception e) {
e.printStackTrace();
}
if (returnCode== HttpURLConnection.HTTP_OK){
return true;
}
else if (returnCode== HttpURLConnection.HTTP_BAD_REQUEST || returnCode==
HttpURLConnection.HTTP_NOT_FOUND ){
return false;
}
else
{
System.out.println("The return code was not 200,400 or 404");
return false;
}
}
}
This is the error I get when I run the following:
java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.security.ssl.SSLSocketImpl.connect(Unknown Source)
at sun.security.ssl.BaseSSLSocketImpl.connect(Unknown Source)
at sun.net.NetworkClient.doConnect(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.protocol.https.HttpsClient.<init>(Unknown Source)
at sun.net.www.protocol.https.HttpsClient.New(Unknown Source)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at java.net.HttpURLConnection.getResponseCode(Unknown Source)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getResponseCode(Unknown Source)

Unable to connect to sql server using java 8

I'm trying to connect to my sql server 21014 using java 8. But i'm getting error.
import java.sql.*;
import java.io.*;
import java.net.*;
import java.util.Scanner;
public class DBConnec
{
public static void main(String a[])
{
try
{
String url = "jdbc:jtds:sqlserver//localhost:1433/dictionary";
Class.forName("net.sourceforge.jtds.jdbc.Driver");
Connection conn = DriverManager.getConnection(url);
System.out.println("connection created");
Statement st=conn.createStatement();
String sql="select * from data where word LIKE 'hi'";
ResultSet rs=st.executeQuery(sql);
if (rs.next())
{
System.out.println(rs.getString(0));
}
if(st!=null)
st.close();
if(conn!=null)
conn.close();
}
catch(SQLException sqle)
{
sqle.printStackTrace();
}
catch(ClassNotFoundException e)
{
e.printStackTrace();
}
}
}
Exception i'm getting is:
java.sql.SQLException: The syntax of the connection URL 'jdbc:jtds:sqlserver//localhost:1433/dictionary' is invalid.
at net.sourceforge.jtds.jdbc.Driver.setupConnectProperties(Driver.java:241)
at net.sourceforge.jtds.jdbc.Driver.connect(Driver.java:181)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at DBConnec.main(DBConnec.java:15)
I'm running my code using this command:
java -cp .;"C:\Program Files\Java\jdk1.8.0_66\jre\lib\ext\jtds-1.3.0.jar" DBConnec
I've also tried url without writing "sqlserver". But it gives same exception.
Please help.. Thank you..
I've corrected my syntax but now i'm getting exception like this:
java.sql.SQLException: Network error IOException: Connection refused: connect
at net.sourceforge.jtds.jdbc.JtdsConnection.(JtdsConnection.java:434)
at net.sourceforge.jtds.jdbc.Driver.connect(Driver.java:183)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at DBConnec.main(DBConnec.java:15)
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)

Try this:
String url = "jdbc:jtds:sqlserver://localhost:1433/dictionary";
You missed the colon after sqlserver.
You should not be adding JDBC driver JARs to the jre/lib/ext directory. Learn how to use CLASSPATH properly.

The url format for JTDS is:
jdbc:jtds:<server_type>://<server>[:<port>][/<database>][;<property>=<value>[;...]]
So your url should be like:
String url = "jdbc:jtds:sqlserver://localhost:1433/dictionary";
^^^____missing colon

RMI with different PCs

I am learning RMI and I made a basic program that uses codebase.
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;
public class Server implements sInterface,s2int {
public void go()
{
System.out.println("GO");
}
public void doIt()
{
}
public static void main(String[] args)
{
if(System.getSecurityManager()==null)
{
System.setSecurityManager(new SecurityManager());
}
try
{
System.setProperty("java.rmi.server.hostname","helios");
String s = "SERVER";
Registry r = LocateRegistry.getRegistry();
sInterface stub = (sInterface) UnicastRemoteObject.exportObject(new Server(),0);
r.rebind(s,stub);
}catch(Exception x){x.printStackTrace();}
}
}
Client:
public class Client {
public static void main(String[] args)
{
if(System.getSecurityManager()==null)
{
System.setSecurityManager(new SecurityManager());
}
try{
String name = "SERVER";
Registry r = LocateRegistry.getRegistry(args[0]);
sInterface inf = (sInterface)r.lookup(name);
inf.go();
}catch(Exception x)
{
x.printStackTrace();
}
}
}
Client does not have 's2int' interface and that is downloaded from the codebase.
The commands used to start the server and the client modules are as follows:
java -Djava.rmi.server.codebase=http://helios/~owner/rmi.jar
-Djava.security.policy=server.policy Server
java -Djava.security.policy=client.policy
-Djava.rmi.server.codebase=http://helios/~owner/
-Djava.rmi.server.hostname=helios Client localhost
Now,this works when both the server and client are on the same PC, but when I tried running it on a different PC on the same network, I got a
java.rmi.ConnectException: Connection refused to host: localhost; nested exception is:
java.net.ConnectException: Connection refused: connect
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(Unknown Source)
at sun.rmi.transport.tcp.TCPChannel.createConnection(Unknown Source)
at sun.rmi.transport.tcp.TCPChannel.newConnection(Unknown Source)
at sun.rmi.server.UnicastRef.newCall(Unknown Source)
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
at Client.main(Client.java:20)
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at
sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(Unknown S
ource) at
sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(Unknown S
ource)
... 6 more
I am not very knowledgeable when it comes to networking. Can anyone explain why it's not working?

Your client is looking up the wrong Registry. It needs to lookup the Registry at the server host, not its own localhost.

Connect MySql (CPanel) remotely via JAVA

=================Code===================
package com.name.file;
import java.sql.*;
public class JDBC {
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://162.219.26.220:3306/waseianc_db";
// Database credentials
static final String USER = "waseianc_vinit";
static final String PASS = "pass";
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
try {
// STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
// STEP 3: Open a connection
System.out.println("Connecting to database...");
conn = DriverManager.getConnection(DB_URL, USER, PASS);
// STEP 4: Execute a query
System.out.println("Creating statement...");
stmt = conn.createStatement();
String sql;
sql = "SELECT id, first, last, age FROM Employees";
ResultSet rs = stmt.executeQuery(sql);
// STEP 5: Extract data from result set
while (rs.next()) {
// Retrieve by column name
int id = rs.getInt("id");
int age = rs.getInt("age");
String first = rs.getString("first");
String last = rs.getString("last");
// Display values
System.out.print("ID: " + id);
System.out.print(", Age: " + age);
System.out.print(", First: " + first);
System.out.println(", Last: " + last);
}
// STEP 6: Clean-up environment
rs.close();
stmt.close();
conn.close();
} catch (SQLException se) {
// Handle errors for JDBC
se.printStackTrace();
} catch (Exception e) {
// Handle errors for Class.forName
e.printStackTrace();
}
======================Errors========================
Connecting to database...
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
Last packet sent to the server was 2 ms ago.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2104)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:729)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:302)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:283)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at com.name.file.JDBC.main(JDBC.java:24)
Caused by: java.net.ConnectException: Connection timed out: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:276)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2027)
... 12 more
=============================== Cpanel Remote Access ====================
=========================== Cpanel MySQL DataBase =========================

Yes, Please contact your hosting provider and ask them to enable mysql port 3306 in firewall and try to login again.