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Why is my Springboot application not starting up?

I bootstrapped the springboot application with JHipster but I have not been able to get it start up . It says build success but won't start up on a server . There is an embedded tomcat server added to the POM.XML , what could be wrong ?
Caused by: java.lang.IllegalArgumentException: Unable to resolve Configuration with the provided Issuer of "http://localhost:9080/auth/realms/jhipster"
at org.springframework.security.oauth2.client.registration.ClientRegistrations.getBuilder(ClientRegistrations.java:221)
at org.springframework.security.oauth2.client.registration.ClientRegistrations.fromIssuerLocation(ClientRegistrations.java:145)
at org.springframework.boot.autoconfigure.security.oauth2.client.OAuth2ClientPropertiesRegistrationAdapter.getBuilderFromIssuerIfPossible(OAuth2ClientPropertiesRegistrationAdapter.java:83)
at org.springframework.boot.autoconfigure.security.oauth2.client.OAuth2ClientPropertiesRegistrationAdapter.getClientRegistration(OAuth2ClientPropertiesRegistrationAdapter.java:59)
at org.springframework.boot.autoconfigure.security.oauth2.client.OAuth2ClientPropertiesRegistrationAdapter.lambda$getClientRegistrations$0(OAuth2ClientPropertiesRegistrationAdapter.java:53)
at java.base/java.util.HashMap.forEach(HashMap.java:1425)
at org.springframework.boot.autoconfigure.security.oauth2.client.OAuth2ClientPropertiesRegistrationAdapter.getClientRegistrations(OAuth2ClientPropertiesRegistrationAdapter.java:52)
at org.springframework.boot.autoconfigure.security.oauth2.client.servlet.OAuth2ClientRegistrationRepositoryConfiguration.clientRegistrationRepository(OAuth2ClientRegistrationRepositoryConfiguration.java:49)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
... 118 common frames omitted
Caused by: org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://localhost:9080/auth/realms/jhipster/.well-known/openid-configuration": Connection refused: connect; nested exception is java.net.ConnectException: Connection refused: connect
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:785)
at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:670)
at org.springframework.security.oauth2.client.registration.ClientRegistrations.lambda$oidc$0(ClientRegistrations.java:156)
at org.springframework.security.oauth2.client.registration.ClientRegistrations.getBuilder(ClientRegistrations.java:209)
... 130 common frames omitted
Caused by: java.net.ConnectException: Connection refused: connect
at java.base/sun.nio.ch.Net.connect0(Native Method)
at java.base/sun.nio.ch.Net.connect(Net.java:574)
at java.base/sun.nio.ch.Net.connect(Net.java:563)
at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:588)
at java.base/java.net.Socket.connect(Socket.java:648)
at java.base/java.net.Socket.connect(Socket.java:597)
at java.base/sun.net.NetworkClient.doConnect(NetworkClient.java:182)
at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:474)
at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:569)
at java.base/sun.net.www.http.HttpClient.<init>(HttpClient.java:242)
at java.base/sun.net.www.http.HttpClient.New(HttpClient.java:341)
at java.base/sun.net.www.http.HttpClient.New(HttpClient.java:362)
at java.base/sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1261)
at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1194)
at java.base/sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1082)
at java.base/sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:1016)
at org.springframework.http.client.SimpleBufferingClientHttpRequest.executeInternal(SimpleBufferingClientHttpRequest.java:76)
at org.springframework.http.client.AbstractBufferingClientHttpRequest.executeInternal(AbstractBufferingClientHttpRequest.java:48)
at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:66)
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:776)
... 133 common frames omitted

Ensure that keycloak is started before running the springboot app because jhispter provides ready to use keycloak config. The app tries to reach keycloak at localhost:9080.
If you have docker and docker-compose installed you can use the provided docker-compose configuration and start keycloak via docker-compose -f src/main/docker/keycloak.yml up
If you want to start it manually you need to make sure to setup the jhipster realm in your keycloak instance.

You have to check 9080 port
Is it use by another process
You can do it by this command : netstat -aon
Then kill process by processor: taskkill -f /pid process_id

Can not connect to amazon RDS from spring boot container app

I want to dockerization all our Spring Boot services, but stack on the issue with connection to the Amazon RDS Aurora MySQL.
The issue is with the communication to the Amazon RDS instance.
The weird thing is that if I run the service.jar file using the java command java -jar service.jar everything works as expected.
Stack trace of the error:
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_292]
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_292]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_292]
at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_292]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:340) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
at com.mysql.cj.protocol.a.NativeAuthenticationProvider.connect(NativeAuthenticationProvider.java:167) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
at com.mysql.cj.protocol.a.NativeProtocol.connect(NativeProtocol.java:1348) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
at com.mysql.cj.NativeSession.connect(NativeSession.java:157) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:956) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:826) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
... 165 common frames omitted
Caused by: javax.net.ssl.SSLHandshakeException: No appropriate protocol (protocol is disabled or cipher suites are inappropriate)
at sun.security.ssl.HandshakeContext.<init>(HandshakeContext.java:171) ~[na:1.8.0_292]
at sun.security.ssl.ClientHandshakeContext.<init>(ClientHandshakeContext.java:98) ~[na:1.8.0_292]
at sun.security.ssl.TransportContext.kickstart(TransportContext.java:220) ~[na:1.8.0_292]
at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:428) ~[na:1.8.0_292]
at com.mysql.cj.protocol.ExportControlled.performTlsHandshake(ExportControlled.java:317) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
at com.mysql.cj.protocol.StandardSocketFactory.performTlsHandshake(StandardSocketFactory.java:188) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
at com.mysql.cj.protocol.a.NativeSocketConnection.performTlsHandshake(NativeSocketConnection.java:97) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
at com.mysql.cj.protocol.a.NativeProtocol.negotiateSSLConnection(NativeProtocol.java:331) ~[mysql-connector-java-8.0.22.jar!/:8.0.22]
... 170 common frames omitted
My docker file looks like this:
FROM openjdk:8
ARG app_name
ENV version /
ENV build /
COPY ./target/${app_name}.jar ./app.jar
CMD ["java", "-Dserver.port=80","-Dproject.version=${version}", "-Dbuild.number=${build}", "-jar", "./app.jar"]
The application properties have next data:
# Hibernate ddl auto (create, create-drop, update)
spring.jpa.hibernate.ddl-auto=validate
spring.jpa.properties.hibernate.show-sql=true
spring.jpa.properties.hibernate.use-sql-comments=true
spring.jpa.properties.hibernate.format-sql=true
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQLDialect
#MySQL DIALECT
spring.datasource.driverClassName=com.mysql.cj.jdbc.Driver
spring.datasource.tomcat.test-on-borrow=true
spring.datasource.tomcat.validation-query=SELECT 1
spring.datasource.url=jdbc:mysql://aws_rds:3306/service_db?serverTimeZone=UTC&useSSL=false
spring.datasource.username=#database.username#
spring.datasource.password=#database.password#
spring.datasource.initialization-mode=always
spring.datasource.hikari.maximum-pool-size=5
# Flyway
spring.flyway.locations=classpath:db/migration
spring.flyway.check-location=true
spring.flyway.validate-on-migrate=false
spring.flyway.out-of-order=true
spring.flyway.table=schema_version
What I miss in the docker?

Most likely openjdk:8 base Docker image that you used doesn't support TLS version required by AWS Aurora. You have to review which TLS version is allowed by your AWS Aurora and then make sure that Java installed in your Docker image supports it. You can take a look at this answer or this answer.
Please note that recently, in April 2021, Java™ SE Development Kit 8, Update 291 (JDK 8u291) changed allowed TLS versions:
➜ Disable TLS 1.0 and 1.1
TLS 1.0 and 1.1 are versions of the TLS protocol that are no longer considered secure and have been superseded by more secure and modern versions (TLS 1.2 and 1.3).
These versions have now been disabled by default. If you encounter issues, you can, at your own risk, re-enable the versions by removing "TLSv1" and/or "TLSv1.1" from the jdk.tls.disabledAlgorithms security property in the java.security configuration file.

Not Recommended for production
you can disable ssl check by adding --ssl=0 command to your mysql docker-compose.yml e.g
version: '3.3'
services:
mysql:
image: mysql:5.7
command: --ssl=0
volumes:
- ./data:/var/lib/mysql
restart: always
environment:
MYSQL_ROOT_PASSWORD: yourPassword
ports:
- "3306:3306"

Handle database down in Spring Boot

I would like to test on my system if the database is down with Spring Boot. I have written a rest call for testing. When the database is up, it return "test" which is correct result. But the database is down, it return nothing.
The Goal is to make it to return "test" even the database is down. Below is the error
2020-04-27 17:27:00.003 ERROR 9536 [] --- [pool-1-thread-1] o.s.s.s.TaskUtils$LoggingErrorHandler : Unexpected error occurred in scheduled task.
org.springframework.transaction.CannotCreateTransactionException: Could not open JPA EntityManager for transaction; nested exception is org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection
at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:450)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:378)
at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:137)
at org.springframework.session.jdbc.JdbcOperationsSessionRepository.cleanUpExpiredSessions(JdbcOperationsSessionRepository.java:589)
at org.springframework.session.jdbc.config.annotation.web.http.JdbcHttpSessionConfiguration.lambda$configureTasks$0(JdbcHttpSessionConfiguration.java:194)
at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54)
at org.springframework.scheduling.concurrent.ReschedulingRunnable.run(ReschedulingRunnable.java:93)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused by: org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection
at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:48)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:111)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:97)
at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.acquireConnectionIfNeeded(LogicalConnectionManagedImpl.java:109)
at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.getPhysicalConnection(LogicalConnectionManagedImpl.java:136)
at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.getConnectionForTransactionManagement(LogicalConnectionManagedImpl.java:254)
at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.begin(LogicalConnectionManagedImpl.java:262)
at org.hibernate.resource.transaction.backend.jdbc.internal.JdbcResourceLocalTransactionCoordinatorImpl$TransactionDriverControlImpl.begin(JdbcResourceLocalTransactionCoordinatorImpl.java:214)
at org.hibernate.engine.transaction.internal.TransactionImpl.begin(TransactionImpl.java:56)
at org.springframework.orm.jpa.vendor.HibernateJpaDialect.beginTransaction(HibernateJpaDialect.java:162)
at org.springframework.orm.jpa.JpaTransactionManager.doBegin(JpaTransactionManager.java:400)
... 13 common frames omitted
Caused by: java.sql.SQLTransientConnectionException: HikariCP - Connection is not available, request timed out after 60000ms.
at com.zaxxer.hikari.pool.HikariPool.createTimeoutException(HikariPool.java:669)
at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:183)
at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:148)
at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:128)
at org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection(DatasourceConnectionProviderImpl.java:122)
at org.hibernate.internal.NonContextualJdbcConnectionAccess.obtainConnection(NonContextualJdbcConnectionAccess.java:35)
at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.acquireConnectionIfNeeded(LogicalConnectionManagedImpl.java:106)
... 20 common frames omitted
Caused by: org.postgresql.util.PSQLException: Connection to X:X:X:X:xxxx refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:280)
at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)
at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:195)
at org.postgresql.Driver.makeConnection(Driver.java:454)
at org.postgresql.Driver.connect(Driver.java:256)
at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:117)
at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:123)
at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:365)
at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:194)
at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:460)
at com.zaxxer.hikari.pool.HikariPool.access$100(HikariPool.java:71)
at com.zaxxer.hikari.pool.HikariPool$PoolEntryCreator.call(HikariPool.java:699)
at com.zaxxer.hikari.pool.HikariPool$PoolEntryCreator.call(HikariPool.java:685)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
... 3 common frames omitted
Caused by: java.net.ConnectException: Connection refused (Connection refused)
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 org.postgresql.core.PGStream.<init>(PGStream.java:70)
at org.postgresql.core.v3.ConnectionFactoryImpl.tryConnect(ConnectionFactoryImpl.java:91)
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:192)
... 16 common frames omitted
And the test controller is in below
#RestController
public class TestController {
#GetMapping(value = "/test")
public String test() {
System.out.println("test");
return "Test";
}
}
the application.properties is like below
spring.datasource.hikari.maximumPoolSize=10
spring.datasource.hikari.idleTimeout=50000
spring.datasource.hikari.maxLifetime=2000000
spring.datasource.hikari.connectionTimeout=60000
spring.datasource.continue-on-error=true
spring.datasource.initialization-mode=never
spring.datasource.hikari.pool-name=KlmsHikariCP
spring.datasource.hikari.connection-test-query=SELECT 1
spring.datasource.hikari.initialization-fail-timeout= -1
spring.datasource.hikari.isolate-internal-queries=true
spring.datasource.hikari.allow-pool-suspension=true
spring.datasource.test-while-idle=true
spring.datasource.test-on-borrow=true
spring.datasource.test-on-return=false
spring.datasource.validation-interval=40000
spring.datasource.validation-query=SELECT 1 FROM DUAL
spring.datasource.time-between-eviction-runs-millis=5000
spring.datasource.min-evictable-idle-time-millis=5000
spring.datasource.remove-abandoned=true
spring.datasource.remove-abandoned-timeout=3
spring.datasource.log-abandoned=true
spring.datasource.log-validation-errors=true
################### Hibernate Configuration ##########################
spring.jpa.hibernate.ddl-auto=none
spring.jpa.show-sql=false
spring.jpa.properties.hibernate.temp.use_jdbc_metadata_defaults=true
spring.jpa.database-platform=org.hibernate.dialect.PostgreSQLDialect

Do you mean during the startup of Spring or while the application is running?
Your RestController currently does not access the DB so I fail to see how the DB connection could result in errors and if the DB is down the controller should return "Test".
If you mean during startup you can try:
spring.datasource.continue-on-error=true

Check that the hostname and port are correct and that the postmaster
is accepting TCP/IP connections.
Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.

Cause of error if Caused by: org.postgresql.util.PSQLException: Connection to X:X:X:X:xxxx refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
Please make sure the database host and port in your application.properties file are mentioned and are correct and also the database instance is up and running in mentioned host.

Spring: Cannot connect to a JMX Server using RMI from behind a firewall

My Spring application is running on a machine that is behind a NAT firewall (pfSense). The machine's internal IP is a.b.c.d, and the NAT IP is w.x.y.z
The Spring configuration's serviceUrl is set to my internal IP (a.b.c.d) on port 1100, and when I start the application, I provide the following switches:
-Dcom.sun.management.jmxremote -Djava.rmi.server.hostname=w.x.y.z -Dcom.sun.management.jmxremote.port=1099 -Dcom.sun.management.jmxremote.local.only=false -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false
As shown above, I set -Djava.rmi.server.hostname=w.x.y.z in order to make it possible to connect to the application through the NAT. I have also opened up the relevant ports on the machine's firewall, and set up a port forward from w.x.y.z:1100 to a.b.c.d:1100
When I then try to connect to the app from outside the network using jconsole on w.x.y.z:1100, I get a java.io.IOException: jmxrmi
java.io.IOException: jmxrmi
at sun.tools.jconsole.ProxyClient.checkSslConfig(ProxyClient.java:236)
at sun.tools.jconsole.ProxyClient.<init>(ProxyClient.java:127)
at sun.tools.jconsole.ProxyClient.getProxyClient(ProxyClient.java:483)
at sun.tools.jconsole.JConsole$3.run(JConsole.java:524)
Caused by: java.rmi.NotBoundException: jmxrmi
at sun.rmi.registry.RegistryImpl.lookup(RegistryImpl.java:136)
at sun.rmi.registry.RegistryImpl_Skel.dispatch(Unknown Source)
at sun.rmi.server.UnicastServerRef.oldDispatch(UnicastServerRef.java:409)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:267)
at sun.rmi.transport.Transport$1.run(Transport.java:177)
at sun.rmi.transport.Transport$1.run(Transport.java:174)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:173)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:556)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:811)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:670)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:275)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:252)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:378)
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
at sun.tools.jconsole.ProxyClient.checkSslConfig(ProxyClient.java:234)
If I try to connect using jconsole on w.x.y.z:1099, I get a java.rmi.ConnectException (Connection refused). How can I expose my JMX MBeans outside my NATted firewall?
java.rmi.ConnectException: Connection refused to host: w.x.y.z; nested exception is:
java.net.ConnectException: Operation 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:2373)
at javax.management.remote.rmi.RMIConnector.connect(RMIConnector.java:297)
at sun.tools.jconsole.ProxyClient.tryConnect(ProxyClient.java:355)
at sun.tools.jconsole.ProxyClient.connect(ProxyClient.java:313)
at sun.tools.jconsole.VMPanel$2.run(VMPanel.java:292)
Caused by: java.net.ConnectException: Operation timed out
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:579)
at java.net.Socket.connect(Socket.java:528)
at java.net.Socket.<init>(Socket.java:425)
at java.net.Socket.<init>(Socket.java:208)
at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:40)
at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:147)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:613)
... 9 more
Interestingly enough, I can connect to both ports (1099 and 1100) on w.x.y.z using telnet.
The relevant portion of my Spring configuration is:
<bean id="registry" class="org.springframework.remoting.rmi.RmiRegistryFactoryBean">
<property name="port" value="1100" />
</bean>
<bean id="serverConnector" class="org.springframework.jmx.support.ConnectorServerFactoryBean" depends-on="registry">
<property name="server" ref="mbeanServer" />
<property name="objectName" value="connector:name=rmi" />
<property name="serviceUrl" value="service:jmx:rmi://a.b.c.d:1100/jndi/rmi://a.b.c.d:1100/server" />
<property name="environment">
<props>
<prop key="jmx.remote.jndi.rebind">true</prop>
</props>
</property>
</bean>
<bean id="mbeanServer" class="org.springframework.jmx.support.MBeanServerFactoryBean">
<!-- indicate to first look for a server -->
<property name="locateExistingServerIfPossible" value="true"/>
</bean>
Note: I am not using any servlet containers.
EDIT: The first answer provided me with the basis for the solution to my specific problem, which can be seen in the second answer.

The initial port you define with com.sun.management.jmxremote.port is called a registry port and is only used to start negotiation and determine next port(s) to use for "real" communication. Java RMI mechanism uses dynamically allocated ports and in general is not compatible with firewalls.
What port is used by Java RMI connection?
That said, for JMX it is possible to work around it
a) Use system properties to lock both ports (requires Java 7)
com.sun.management.jmxremote.port
com.sun.management.jmxremote.rmi.port
b) Use custom code to request a specific port. See
JConsole over ssh local port forwarding
See also:
Why Java opens 3 ports when JMX is configured?
http://realjenius.com/2012/11/21/java7-jmx-tunneling-freedom/

Elaborating on the solution I identified using the links and pointers anttix gave me in his answer.
So, as mentioned in the answer above, using the system properties com.sun.management.jmxremote.port and com.sun.management.jmxremote.rmi.port is the basis for the solution.
I changed my Spring config to remove the registry and serverConnector beans, as this was not allowing me to register port 1099 (PermissionExceptions resulted in my being unable to bind to port 1099), and used the platform mbean server.
The Spring config I used was just this:
<bean id="mbeanServer" class="java.lang.management.ManagementFactory" factory-method="getPlatformMBeanServer"/>
Then, I started the application using the following switches:
-Dcom.sun.management.jmxremote -Djava.rmi.server.hostname=w.x.y.z -Dcom.sun.management.jmxremote.port=1099 -Dcom.sun.management.jmxremote.rmi.port=1099 -Dcom.sun.management.jmxremote.local.only=false -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false
Setting the java.rmi.server.hostname to the NAT VIP w.x.y.z is critical as we need to be able to execute remote operations on locally created remote objects from outwith the network.
Note: This solution will only work on Java 7u4 or higher.

Java JPA proxy issue

I am using JPA(EclipseLink impl) in my java application. The application works find when there is no proxy configured at system level but when I configure a proxy at system level, the application fails at
EntityManager entityManager = emf.createEntityManager();
and throws the following exception
Caused by: java.net.SocketException: Unknown proxy type : null
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:341)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:395)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2137)
at java.net.Socket.connect(Socket.java:579)
... 24 more
at java.net.Socket.connect(Socket.java:528)
Caused by: java.net.SocketException: Unknown proxy type : null
at java.net.Socket.<init>(Socket.java:425)
at java.net.Socket.<init>(Socket.java:241)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:395)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:253)
at java.net.Socket.connect(Socket.java:579)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:290)
... 25 more
at java.net.Socket.connect(Socket.java:528)
at java.net.Socket.<init>(Socket.java:425)
at java.net.Socket.<init>(Socket.java:241)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:253)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:290)
... 25 more
I suspect that it is trying to access mysql db at localhost via configured proxy and thus failing. But at the system level proxy configuration, I have configured the following IPs as ignored host
127.0.0.1 localhost
and using the following jdbc url
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/clharvester" />

When you are using a proxy you have to use the real IP address of the server machine to connect to the database.