/jedispool-factory-tomcat

A simple project showing how to use a Jedis Pool from a Resource Factory

Primary LanguageJava

JedisPool Factory for Tomcat

This project shows how to create a Resource Factory for a Web Application and configure the JedisPool from there.

The implementation is based on the following documentation:

In this demonstration for simplicity I put everything in the Web application, for production environment the resource configuration should be externalized, for this you need to put the com.kanibl.sample.JedisPoolFactory class to Tomcat itself.

Configuration

Open the src/main/webapp/META-INF/context.xml file and adapt the configuration to your environment

    <Resource name="jedis/JedisPoolFactory" auth="Container"
              type="redis.clients.jedis.JedisPool"
              factory="com.kanibl.sample.JedisPoolFactory"
              singleton="true"
              url="redis://localhost:6379"
              minIdle="1"
              maxIdle="5
              maxTotal="11"
              maxWaitMillis="1000"

    />

For this example the choice is to use a simple URI to define the connection, with the format redis://[:password@]host[:port][/db-number][?option=value]

Build the application

 mvn clean package

This generate a WAR file that you can drop in your Tomcat.

Run the application

  1. You are a Redis instance running
  2. Download & decompress Tomcat 8 or later
  3. Start tomcat ./bin/startup.sh
  4. Copy /target/sample-web-app.war to Tomcat /webapps directory to deploy the application
  5. Access the application using: http://localhost:8080/hello or http://localhost:8080/goodbye

You will see that the 2 servlets are using the same JedisPool instance.

Configuration & Code

src/main/webapp/META-INF/context.xml**

This file contains the resource configuration and its JNDI name: jedis/JedisPoolFactory

This is used in the application using a resource reference in the web.xml

    <Resource name="jedis/JedisPoolFactory" auth="Container"
              type="redis.clients.jedis.JedisPool"
              factory="com.kanibl.sample.JedisPoolFactory"
              singleton="true"
              url="redis://localhost:6379"
              minIdle="1"
              maxIdle="5
              maxTotal="11"
              maxWaitMillis="1000"

    />

src/main/webapp/WEB-INF/web.xml

This define the name and type type to use.

The application will refer to the JNDI name java:comp/env/jedis/JedisPoolFactory.

The root context for environment is java:comp/env, then the name of the resource.

    <resource-env-ref>
        <description>
            Object factory for Jedis Pool.
        </description>
        <resource-env-ref-name>
            jedis/JedisPoolFactory
        </resource-env-ref-name>
        <resource-env-ref-type>
            redis.clients.jedis.JedisPool
        </resource-env-ref-type>
    </resource-env-ref>

com.kanibl.sample.JedisPoolFactory

This class instantiates the JedisPool.

The configuration is received from the XML configuration, each parameters are read to create:

  • the PoolConfig
  • the JedisPool itself

Note: this approach will only create a new Pool and will not manage it (closing for example)

com.kanibl.sample.HelloServlet

In the Init of the servlet we get a reference to the pool and use it in the various methods.

        try {
            Context initCtx =  new InitialContext();
            jedisPool = (JedisPool) initCtx .lookup("java:comp/env/jedis/JedisPoolFactory");
        } catch (NamingException e) {
            e.printStackTrace();
        }

It is also possible to do a lookup by name using the root name, look in the com.kanibl.sample.GoodbyeServlet Servlet code.