Develop Reference

I have error an mysql connection with tomcat server

My code:
import java.sql.Connection;
import java.sql.DriverManager;
public class sqlConnection {
private static String url = "jdbc:mysql://localhost:3306/hosapi";
private static String uname = "root";
private static String pword = "1016";
public static void main(String[] arg) {
Connection con = null;
try {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection(url, uname, pword);
System.out.println("connection created");
} catch (Exception e) {
System.out.println("error");
e.printStackTrace();
}
}
}
error
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet successfully received from the server was 322 milliseconds ago. The last packet sent successfully to the server was 297 milliseconds ago.
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:499)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:480)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:981)
at com.mysql.jdbc.ExportControlled.transformSocketToSSLSocket(ExportControlled.java:164)
at com.mysql.jdbc.MysqlIO.negotiateSSLConnection(MysqlIO.java:4801)
at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1643)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1215)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2255)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2286)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2085)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:795)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:44)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:499)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:480)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:400)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:327)
at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:681)
at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:229)
at com.project.Hospital.sqlConnection.main(sqlConnection.java:19)
Caused by: javax.net.ssl.SSLHandshakeException: No appropriate protocol (protocol is disabled or cipher suites are inappropriate)
at java.base/sun.security.ssl.HandshakeContext.<init>(HandshakeContext.java:172)
at java.base/sun.security.ssl.ClientHandshakeContext.<init>(ClientHandshakeContext.java:103)
at java.base/sun.security.ssl.TransportContext.kickstart(TransportContext.java:240)
at java.base/sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:448)
at java.base/sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:426)
at com.mysql.jdbc.ExportControlled.transformSocketToSSLSocket(ExportControlled.java:149)
... 19 more

Remote Connections Don't Work for JMX Started from main method

The code works when the server and client are on the same machine. When I run the server code on a different machine, I get the exception below.
[WARNING]
java.rmi.ConnectException: Connection refused to host: 127.0.1.1; nested exception is:
java.net.ConnectException: Operation timed out (Connection timed out)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:619)
at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:216)
at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:202)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:129)
at javax.management.remote.rmi.RMIServerImpl_Stub.newClient(Unknown Source)
at javax.management.remote.rmi.RMIConnector.getConnection(RMIConnector.java:2430)
at javax.management.remote.rmi.RMIConnector.connect(RMIConnector.java:308)
at javax.management.remote.JMXConnectorFactory.connect(JMXConnectorFactory.java:270)
at Client.main(Client.java:70)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:282)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.net.ConnectException: Operation timed out (Connection timed out)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at java.net.Socket.connect(Socket.java:538)
at java.net.Socket.<init>(Socket.java:434)
at java.net.Socket.<init>(Socket.java:211)
at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:40)
at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:148)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:613)
... 14 more
It's suspicious that the exception says 127.0.1.1 refused the connection when the client really used the JMXServiceURL below:
service:jmx:rmi:///jndi/rmi://10.10.173.196:8474/jmxrmi
If I start the application using the -Dcom.sun.management.jmxremote.* settings, the client doesn't not have an issue with remote connections.
Code is pasted below:
import javax.management.MBeanServer;
import javax.management.remote.JMXConnectorServer;
import javax.management.remote.JMXConnectorServerFactory;
import javax.management.remote.JMXServiceURL;
import java.lang.management.ManagementFactory;
import java.rmi.registry.LocateRegistry;
import java.util.*;
public class Server {
public static void main(String[] args) throws Exception {
if(args.length != 2) {
throw new IllegalArgumentException("Server <port> <path suffix>"
+ "\nservice:jmx:rmi://0.0.0.0:<port>/jndi/rmi://0.0.0.0:<port>/<pathsuffix>"
);
}
int port = Integer.parseInt(args[0]);
String pathSuffix = args[1];
LocateRegistry.createRegistry(port);
MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
JMXServiceURL url = new JMXServiceURL("service:jmx:rmi://0.0.0.0:"
+ port + "/jndi/rmi://0.0.0.0:" + port + "/" + pathSuffix);
Map<String, Object> envConf = new HashMap<>();
envConf.put("jmx.remote.x.password.file", "password.properties");
envConf.put("jmx.remote.x.access.file", "access.properties");
JMXConnectorServer cs = JMXConnectorServerFactory.newJMXConnectorServer(url, envConf, mbs);
cs.start();
while(true) {
Thread.sleep(1000);
}
}
}
I also used the JMXServiceURL on the server:
service:jmx:rmi:///jndi/rmi://0.0.0.0:<port>/jmxrmi

https://stackoverflow.com/a/11654322/1810962 mentions that /etc/hosts must be configured properly. On the machine that JMX works I have:
hostname -i
10.10.172.72 10.10.172.72
On the machine that doesn't work:
hostname -i
127.0.1.1

MailConnectException when sending email with JavaMail

I am trying to send an email with JavaMail following this tutorial:
http://www.tutorialspoint.com/java/java_sending_email.htm
This is my code:
public void sendAccountActivationEmail()
{
String to = "myemail#gmail.com";
String from = "myemail#gmail.com";
String host = "localhost";
Properties properties = System.getProperties();
properties.setProperty("mail.smtp.host", host);
Session session = Session.getDefaultInstance(properties);
try{
MimeMessage message = new MimeMessage(session);
message.setFrom(new InternetAddress(from));
message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));
message.setSubject("Account activation");
message.setContent("<h1>This is actual message</h1>", "text/html" );
Transport.send(message);
System.out.println("Sent message successfully....");
}catch (MessagingException mex) {
mex.printStackTrace();
}
}
However when running this method I get the following exception:
com.sun.mail.util.MailConnectException: Couldn't connect to host, port: localhost, 25; timeout -1;
nested exception is:
java.net.ConnectException: Connection refused: connect
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:2100)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:699)
at javax.mail.Service.connect(Service.java:366)
at javax.mail.Service.connect(Service.java:246)
at javax.mail.Service.connect(Service.java:195)
at javax.mail.Transport.send0(Transport.java:254)
at javax.mail.Transport.send(Transport.java:124)
at com.myproject.managed.UserRegistrationController.sendAccountActivationEmail(UserRegistrationController.java:161)
...
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.TwoStacksPlainSocketImpl.socketConnect(Native Method)
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 com.sun.mail.util.SocketFetcher.createSocket(SocketFetcher.java:331)
at com.sun.mail.util.SocketFetcher.getSocket(SocketFetcher.java:238)
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:2066)
... 58 more
Any idea of what should I do?

Java exception java.net.SocketTimeoutException: connect timed out

I have the following code
public static void main(String[] args) {
Connection connection = Jsoup.connect("http://prospective.bryantschools.org/");
connection.timeout(5000);
Document doc;
try {
doc = Jsoup.connect("http://prospective.bryantschools.org/").get();
// get page title
String title = doc.title();
System.out.println("title : " + title);
// get all links
Elements links = doc.select("a[href]");
for (Element link : links) {
// get the value from href attribute
System.out.println("\nlink : " + link.attr("href"));
System.out.println("text : " + link.text());
}
} catch (IOException e) {
e.printStackTrace();
}
}
And I am getting the following errors
java.net.SocketTimeoutException: connect timed out
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at sun.net.NetworkClient.doConnect(NetworkClient.java:175)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:432)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:527)
at sun.net.www.http.HttpClient.<init>(HttpClient.java:211)
at sun.net.www.http.HttpClient.New(HttpClient.java:308)
at sun.net.www.http.HttpClient.New(HttpClient.java:326)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1168)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1104)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:998)
at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:932)
at org.jsoup.helper.HttpConnection$Response.execute(HttpConnection.java:512)
at org.jsoup.helper.HttpConnection$Response.execute(HttpConnection.java:493)
at org.jsoup.helper.HttpConnection.execute(HttpConnection.java:205)
at org.jsoup.helper.HttpConnection.get(HttpConnection.java:194)
at com.example.kaleb.testjsoup.HTMLParserExample1.main(HTMLParserExample1.java:25)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)
I've looked around and many people have mentioned that it might because the server's firewall is blocking my request. Is there is any other reason why I'd be getting these exceptions? Is there something I'm doing in my code that is casuing these exceptions?

Try Jsoup.connect(url).userAgent("Mozilla").get();. Our web server blocked it because it didn't have a user agent and blocks non-real-person-looking requests.

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.