Top Most JAMon plugin for Grails: Part 2 of 4

In part 1 we discussed four tasks needed to create a JAMon plugin. The first task was completed simply by adding jamon.jar to our plugin's lib folder. To review, the steps are:

1. Add jamon.jar to the application classpath
2. Use JAMon's datasource proxy to monitor SQL
   
3. Implement the JAMonServletFilter to monitor page hits
   
4. Leverage Spring AOP via Spring's JamonPerformanceMonitorInterceptor class to monitor services
5. Add a Spring filter to monitor Grails controllers.

As I mentioned previously, our plugin project has a file named: JamonGrailsPlugin.groovy. This is where we'll implement steps 2-5.

JamonGrailsPlugin.groovy comes with a series of closures pre-defined. To change the datasource we add code to the doWithSpring closure. This closure allows you to update your Spring configuration.

We need to change the driverClassName to "com.jamonapi.proxy.JAMonDriver" and alter the url by adding "jamon:" after "jdbc:" and appending a parameter named "jamonrealdriver".

First lets add an import:

import javax.sql.DataSource

Then code the closure:

def doWithSpring = {
   def config = application.config
   def orgUrl = config.dataSource.url
   def driverClassName = config.dataSource.driverClassName
   
   String appendUrl = (orgUrl.contains('?')? '&': '?') + 'jamonrealdriver=' + driverClassName
   if (orgUrl.contains("oracle:")) appendUrl = 'jamonrealdriver=' + driverClassName
   def url = orgUrl.replace("jdbc:","jdbc:jamon:") + appendUrl

   config.dataSource.url = url
   config.dataSource.driverClassName = "com.jamonapi.proxy.JAMonDriver"
}

Step 3 is "implement the JAMonServletFilter to monitor page hits."

The doWithWebDescriptor closure will allow us to add our filter to the application. We need to append to both the <filter> and <filter-mapping> sections. Note that this is typical Grails builder code. The 'filter-mapping' node needs to be in quotes due to the hyphen in it's name:

def doWithWebDescriptor = { webXml ->
   def filters = webXml.filter
   filters + {
      filter {
         'filter-name'("jAMonServletFilter")
         'filter-class'("com.jamonapi.http.JAMonServletFilter")
      }
   }

   def filterMappings = webXml.'filter-mapping'
      filterMappings + {
         'filter-mapping' {
            'filter-name'("jAMonServletFilter")
            'url-pattern'("/*")
          }
      }
   }

} 

In part 3 we'll move on to step #4.