What is the best way to modify a project configuration from within a plugin?

Question

As I am trying to write a Grails Plugin, I stumbled upon two problems:

• how do I modify one of the configuration files like Config.groovy or

Answer 1

Here is an example of editing configuration files from scripts/_Install.groovy.
My plugin copies three files to the target directory.

• .hgignore is used for version control,
• DataSource.groovy replaces the default version, and
• SecurityConfig.groovy contains extra settings.

I prefer to edit the application's files as little as possible, especially because I expect to change the security setup a few years down the road. I also need to use properties from a jcc-server-config.properties file which is customized for each application server in our system.

Copying the files is easy.

println ('* copying .hgignore ')
ant.copy(file: "${pluginBasedir}/src/samples/.hgignore",
         todir: "${basedir}")
println ('* copying SecurityConfig.groovy')
ant.copy(file: "${pluginBasedir}/src/samples/SecurityConfig.groovy",
         todir: "${basedir}/grails-app/conf")
println ('* copying DataSource.groovy')
ant.copy(file: "${pluginBasedir}/src/samples/DataSource.groovy",
         todir: "${basedir}/grails-app/conf")

The hard part is getting Grails to pick up the new configuration file. To do this, I have to edit the application's grails-app/conf/Config.groovy. I will add two configuration files to be found on the classpath.

println ('* Adding configuration files to grails.config.locations');
// Add configuration files to grails.config.locations.
def newConfigFiles = ["classpath:jcc-server-config.properties", 
                      "classpath:SecurityConfig.groovy"]
// Get the application's Config.groovy file
def cfg = new File("${basedir}/grails-app/conf/Config.groovy");
def cfgText = cfg.text
def appendedText = new StringWriter()
appendedText.println ""
appendedText.println ("// Added by edu-sunyjcc-addons plugin");
// Slurp the configuration so we can look at grails.config.locations.
def config = new ConfigSlurper().parse(cfg.toURL());
// If it isn't defined, create it as a list.
if (config.grails.config.locations.getClass() == groovy.util.ConfigObject) {
    appendedText.println('grails.config.locations = []');
} else {
    // Don't add configuration files that are already on the list.
    newConfigFiles = newConfigFiles.grep {
      !config.grails.config.locations.contains(it)
    };
}
// Add each surviving location to the list.
newConfigFiles.each {
    // The name will have quotes around it...
    appendedText.println "grails.config.locations << \"$it\"";
}
// Write the new configuration code to the end of Config.groovy.
cfg.append(appendedText.toString());

The only problem is adding SecurityConfig.groovy to the classpath. I found that you can do that by creating the following event in the plugin's /scripts/Events.groovy.

eventCompileEnd = {
    ant.copy(todir:classesDirPath) {
      fileset(file:"${basedir}/grails-app/conf/SecurityConfig.groovy")
    }
}

Ed.

Answer 2

You might try changing the configuration within the MyNiftyPlugin.groovy file (assuming that your plugin is named my-nifty). I've found that I can change the configuration values within the doWithApplicationContext closure. Here's an example.

def doWithApplicationContext = { applicationContext ->  
  def config = application.config;
  config.edu.mycollege.server.name = 'http://localhost:8080'
  config.edu.mycollege.server.instance = 'pprd'
}

The values you enter here do show up in the grailsApplication.config variable at run time. If it works for you, it will be a neater solution, because it doesn't require changes to the client project.

I must qualify that with the fact that I wasn't able to get Spring Security to work by this technique. I believe that my plugin (which depends on Spring Security) was loaded after the security was initialized. I decided to add an extra file to the grails-app/conf directory.

HTH.

Answer 3

For modifying configuration files, you should use ConfigSlurper:

def configParser = new ConfigSlurper(grailsSettings.grailsEnv)
configParser.binding = [userHome: userHome]
def config = configParser.parse(new URL("file:./grails-app/conf/Config.groovy"))

If you need to get application name from script, try:

metadata.'app.name'