Servers : Apache Web-Server Vs Apache Tomcat

Apache web-server (also known as Apache Hyper Text Transfer Protocol server) and Apache Tomcat both are SERVERS( servers are software that works on network or on internet) and are both developed by APACHE.

Apache is a server designed to serve HTTP, or we can also call it as a web-server, which serves the requests from browsers for web-pages. But an Apache server is not limited to this only. It can effectively serve the HTTP requests for the static contents but can be also configured to handle requests for dynamic contents generated through a wide range of languages and technologies like PHP, J2EE or whatever.

Next comes is Apache Tomcat, which itself is a server and compliments Apache web-server. It is also developed by Apache and usually CONFUSES us with the Apache web-server developed by Apache itself. Although they are both servers that are meant for use in the Internet, but they have separate and distinct roles to play.

Apache Tomcat is a server specifically meant to run applications that were written in Java and JSP (Java Server Pages). It is open source software just like Apache web-server created by Apache, and is free to use. It's primary purpose is to implement the Java Servlet API and execute Java servlets for dynamic websites. Tomcat can also be used as a regular HTTP web-server that serves static pages, but that is not its primary purpose.

If we are putting up a Apache web-server and we want to have Java or JSP support, then we should go for offering that Apache Tomcat has as both are made by Apache. And, hence reduces the chances of encountering problem while configuring them to work together.

In short we can say "Apache Tomcat server is a SPECIALIZED web server called a "servlet container." And it features a BASIC web server CUSTOMIZED to execute Java servlets and JSP pages. BUT at the same time it can also be configured to serve other technologies as well."

Now, as the individuality of Apache web-server and Apache Tomcat is quite clear to us, we can say that "Apache web-server is usually configured to use the Tomcat server as a back-end handler for servlets and JSPs".

Spring : Configuring failover in Spring

WebClients can be configured in Spring to handle the failover in case any of the webservice connection fails to respond due to network or server failure or due to any other reason. In order to handle such issues Apache CXF provides Sequential and Random strategies, which are supported and implementers can develop more sophisticated failover features by retrieving alternate addresses.

The above could be achieved by doing the following configurations in spring-servlet.xml (Spring Web Context Configuration file) or whatever else you call it.

Spring-servlet.xml( failover configurations only)

____________________________________________________________________________

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xmlns:p="http://www.springframework.org/schema/p"

xmlns:context="http://www.springframework.org/schema/context"

xmlns:cache="http://www.springframework.org/schema/cache"

xmlns:cxf="http://cxf.apache.org/core"

xmlns:util="http://www.springframework.org/schema/util"

xsi:schemaLocation="http://cxf.apache.org/core http://cxf.apache.org/schemas/core.xsd

http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans.xsd

http://www.springframework.org/schema/context

http://www.springframework.org/schema/context/spring-context-3.0.xsd

http://www.springframework.org/schema/cache

http://www.springframework.org/schema/cache/spring-cache.xsd

http://www.springframework.org/schema/util

http://www.springframework.org/schema/util/spring-util-2.0.xsd

"

>

<!-- begin: Fail over configurations -->

<util:list id="alternateSerAddresses" list-class="java.util.concurrent.CopyOnWriteArrayList">

    <value>http://hostname:port/servie-location-1</value>

    <value>http://hostname:port/servie-location-2</value>

    <value>http://hostname:port/servie-location-3</value>

</util:list>

<bean id="serviceClientFactory" class="org.apache.cxf.jaxws.JaxWsProxyFactoryBean">

   <property name="serviceClass" value="com.soaptopupsuite.EndPointInterface"/>

   <property name="address" value="http://hostname:port/service-default-loc"/>

   <property name="username" value="service-username"/>

   <property name="password" value="service-password"/>

   <property name="features">

    <util:list>

      <bean class="org.apache.cxf.clustering.FailoverFeature">

             <property name="strategy">

                  <bean class="org.apache.cxf.clustering.SequentialStrategy">

                <property name="alternateAddresses" ref="alternateSerAddresses"/>

             </bean>

             </property>

         </bean>

     </util:list>

</property>

</bean>

<bean id="serviceClient" class="com.soaptopupsuite.EndPointInterface" factory-   bean="serviceClientFactory" factory-method="create"/>

<bean id="servicePort" class="com.swaraj.client.WsClient">

   <property name="port" ref="serviceClient" />

</bean>

<!-- end: Fail over configurations -->

</beans>

Here, the client factory does not itself defines the address attribute. It uses that alternateSerAddresses list exclusively throughout all the invocations and primary address exists as default location. SequentialStrategy will use one endpoint after another providing nice round robin implementation (RandomStrategy is available as well, where an end point is picked up randomly). Also in this configuration we will get failover – if any endpoint fails, all endpoints starting from the default one will be examined (except the one that has just failed).

Reference Java Code (Spring 3.1) :

package com.swaraj.client;

@Service

public class WsClient {

/* list of instance variable*/

// web service location

private EndPointInterface port;

// setter injection for EndPointInterface

   public void setPort(EndPointInterface port) {

       this.port = port;

   }

// Invoking web service method on EndPointInterface port.

   public String webSerMethodCall(){

       return port.testCall();

   }

}