CentOS/RedHat make port 8080 visible

I am a happy DigitalOcean customer primarily because of the low cost, the SSD drives, the friendly stuff and the flexibility by which you can reshape your purchased resources into droplets within the 4 DataCenters (2 in NY and 2 in Amsterdam) supported.

Until the need for a UK DataCenter arises which leads me to RackSpace.

On both private cloud hosting providers I am making a web service available that needs to be accessible @ port 8080. The CentOS flavour assembled in DigitalOcean has everything permitted by default in its iptables settings but the one assembled in RackSpace does not.

When I issue the iptables command I get:


[dimitrisli@lon1 ~]# iptables -L -n --line-numbers
Chain INPUT (policy ACCEPT)
num target prot opt source destination
1 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
2 ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0
3 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
4 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:22
5 REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited

Chain FORWARD (policy ACCEPT)
num target prot opt source destination
1 REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited

Chain OUTPUT (policy ACCEPT)
num target prot opt source destination

And just by adding permission for port 8080 will put it by default under the last reject input policy so the correct command should be putting the permission at the current spot of the reject input policy:


[dimitrisli@lon1 ~]# iptables -I INPUT 5 -m state --state NEW -m tcp -p tcp --dport 8080 -j ACCEPT -m comment --comment "Jetty Server port"

[dimitrisli@lon1 ~]# service iptables save

that eventually does the trick.

Advertisements

Scala, Stripes simple example

Here’s the sample Stripes application using Scala.

The skeletal implementation of Stripes ActionBean for the purposes of our project holding the context:

package com.dimitrisli.scalastripeswebapp.controller

import net.sourceforge.stripes.action.{ActionBeanContext, ActionBean}
import reflect.BeanProperty


class BaseActionBean extends ActionBean {

  @BeanProperty var context: ActionBeanContext = _

}

The calculator represented as a Stripe action bean:

package com.dimitrisli.scalastripeswebapp.controller

import net.sourceforge.stripes.action._
import net.sourceforge.stripes.validation.{SimpleError, ValidationErrors, ValidationMethod, Validate}
import reflect.BeanProperty


class CalculatorActionBean extends BaseActionBean {

  @BeanProperty @Validate(required=true) var numberOne: Double = _
  @BeanProperty @Validate(required=true) var numberTwo: Double = _
  @BeanProperty var result: Double = _

  @DefaultHandler
  def addition: Resolution = {
    result = getNumberOne + getNumberTwo
    new ForwardResolution("/index.jsp");
  }

  def division: Resolution = {
    result = getNumberOne / getNumberTwo
    new ForwardResolution("/index.jsp");
  }

  @ValidationMethod(on=Array("division"))
  def avoidDevideByZero(errors: ValidationErrors): Unit =
    if (getNumberTwo == 0)
      errors.add("numberTwo", new SimpleError("Dividing by zero is not allowed."))
}

Our view represented by a JSP will be excluded due to formatting issues in WordPress (look below for the Github repository).

The web.xml setting up the Stripe’s dispatcher servlet, filter and all the necessary mappings will also not be presented due to the same xml formatting issues (look below for the Github repository).

This project’s code can be found in this Github repository

Maven, Spring MVC, Eclipse example

Here’s a quick tutorial on how to make Maven, Spring MVC, log4j co-exist happily.

First off we need to create a Maven Project in Eclipse. Our POM is straight forward and looks like this:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.dimitrisli.springMVC</groupId>
  <artifactId>mavenSpringMVC</artifactId>
  <version>1.0</version>
  <packaging>war</packaging>
  <dependencies>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>3.1.0.RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
    	<groupId>log4j</groupId>
    	<artifactId>log4j</artifactId>
    	<version>1.2.16</version>
    </dependency>
  </dependencies>
  	<build>
		<finalName>MavenSpringMVC</finalName>
		<plugins>
			<plugin>
				<artifactId>maven-compiler-plugin</artifactId>
				<configuration>
					<source>1.6</source>
					<target>1.6</target>
				</configuration>
			</plugin>
		</plugins>
	</build>
  	<properties>
  		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  	</properties>
</project>

Note how the spring-webmvc dependency is enough to bring all the other main Spring dependencies along due to the dependency hierarchy that Maven is taking care of gracefully and silently behind the scenes.

Since we are building a webapp we would need the webapp/WEB-INF structure which we host in /src/main/.

The web.xml would look like this:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.dimitrisli.springMVC</groupId>
  <artifactId>mavenSpringMVC</artifactId>
  <version>1.0</version>
  <packaging>war</packaging>
  <dependencies>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>3.1.0.RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <dependency>
    	<groupId>log4j</groupId>
    	<artifactId>log4j</artifactId>
    	<version>1.2.16</version>
    </dependency>
  </dependencies>
  	<build>
		<finalName>MavenSpringMVC</finalName>
		<plugins>
			<plugin>
				<artifactId>maven-compiler-plugin</artifactId>
				<configuration>
					<source>1.6</source>
					<target>1.6</target>
				</configuration>
			</plugin>
		</plugins>
	</build>
  	<properties>
  		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  	</properties>
</project>

A few things to notice:

  • We define as the sole servlet of our application Spring’s DispatcherServlet that delegates requests to controllers accordingly.
  • We define Spring’s ContextLoaderListener  as a listener in the web.xml to initialize Spring on webapp startup.
  • The defined context-param needs to have to have as name: <servletNameWeGaveToTheServletDispatcher>-servlet.xml otherwise it will throw an error during runtime load-up.

The view of the response is built up internally using Spring’s InternalResourceViewResolver that is dynamically add a prefix and suffix:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.1.xsd">

	<context:component-scan base-package="com.dimitrisli.springmvc" />

	<bean
		class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<property name="prefix">
			<value>/WEB-INF/jspview/</value>
		</property>
		<property name="suffix">
			<value>.jsp</value>
		</property>
	</bean>

</beans>

Finally the Controller looks like this:

package com.dimitrisli.springmvc;

import org.apache.log4j.Logger;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@RequestMapping("/something.do")
@Controller
public class MyController {

	private static final Logger logger = Logger.getLogger(MyController.class);
	@RequestMapping(method = RequestMethod.GET)
	public String method(ModelMap modelMap){
		modelMap.addAttribute("msg","Hello world");
		return "test";
	}
}

The Spring annotations @Controller and @RequestMapping are defining the fact that the POJO is a Controller and where the request should be forwarded to respectively.

After we mvn package the war file should be ready for deployment waiting for us in Maven’s target dir. Making use of Eclipse’s WTP we can deploy the application inside the familiar place of Eclipse. To do so all we need is the Servers view where we need to create a new Tomcat server pointing to our Maven war file.

After starting-up the application pointing a browser session to the http://localhost:8080/mavenSpringMVC/something.do should go through the controller and give us back the hello world output.

The source code can be found in this Github repository.

How to deploy war to remote tomcat using the SCP Ant task

Useful properties, mainly the details of the remote login plus the location of the tomcat webapps folder to deploy the war:

remoteusername=my_username
remotehost=remote_box_name
remotepassword=my_pass
remotedir=/home/dliapis/apache-tomcat-5.5.28/webapps

and the actual scp ant task:

<target name="deployremote" depends="build" description="Deploy to the remote linux box">
    	<scp trust="yes" file="${name}.war" todir="${remoteusername}@${remotehost}:${remotedir}" password="${remotepassword}"/>
    </target>