How to read a properties files and use the values in project Gradle script?

Another way... in build.gradle:

Add :

classpath 'org.flywaydb:flyway-gradle-plugin:3.1'

And this :

def props = new Properties()
file("src/main/resources/application.properties").withInputStream { props.load(it) }
apply plugin: 'flyway'
flyway {
    url = props.getProperty("spring.datasource.url")
    user = props.getProperty("spring.datasource.username")
    password = props.getProperty("spring.datasource.password")
    schemas = ['db_example']
}

If using the default gradle.properties file, you can access the properties directly from within your build.gradle file:

gradle.properties:

applicationName=Admin
projectName=Hello Cool

build.gradle:

task printProps {
    doFirst {
        println applicationName
        println projectName
    }
}

If you need to access a custom file, or access properties which include . in them (as it appears you need to do), you can do the following in your build.gradle file:

def props = new Properties()
file("build.properties").withInputStream { props.load(it) }

task printProps {
    doFirst {
        println props.getProperty("application.name")
        println props.getProperty("project.name")
    }
}

Take a look at this section of the Gradle documentation for more information.

Edit

If you'd like to dynamically set up some of these properties (as mentioned in a comment below), you can create a properties.gradle file (the name isn't important) and require it in your build.gradle script.

properties.gradle:

ext {
    subPath = "some/sub/directory"
    fullPath = "$projectDir/$subPath"
}

build.gradle

apply from: 'properties.gradle'

// prints the full expanded path
println fullPath

We can use a separate file (config.groovy in my case) to abstract out all the configuration.

In this example, we're using three environments viz.,

1. dev
2. test
3. prod

which has properties serverName, serverPort and resources. Here we're expecting that the third property resources may be same in multiple environments and so we've abstracted out that logic and overridden in the specific environment wherever necessary:

config.groovy

resources {
    serverName = 'localhost'
    serverPort = '8090'
}

environments {
    dev {
        serverName = 'http://localhost'   
        serverPort = '8080'
    }

    test {
        serverName = 'http://www.testserver.com'
        serverPort = '5211'
        resources {
            serverName = 'resources.testserver.com'
        }
    }

    prod {
        serverName = 'http://www.productionserver.com'
        serverPort = '80'
        resources {
            serverName = 'resources.productionserver.com'
            serverPort = '80'
        }
    }
}

Once the properties file is ready, we can use the following in build.gradle to load these settings:

build.gradle

loadProperties()

def loadProperties() {
    def environment = hasProperty('env') ? env : 'dev'
    println "Current Environment: " + environment

    def configFile = file('config.groovy')
    def config = new ConfigSlurper(environment).parse(configFile.toURL())
    project.ext.config = config
}

task printProperties {
    println "serverName:  $config.serverName"
    println "serverPort:  $config.serverPort"
    println "resources.serverName:  $config.resources.serverName"
    println "resources.serverPort:  $config.resources.serverPort"
}

---

Let's run these with different set of inputs:

1. gradle -q printProperties

   Current Environment: dev
   serverName:  http://localhost
   serverPort:  8080
   resources.serverName:  localhost
   resources.serverPort:  8090
   

2. gradle -q -Penv=dev printProperties

   Current Environment: dev
   serverName:  http://localhost
   serverPort:  8080
   resources.serverName:  localhost
   resources.serverPort:  8090
   

3. gradle -q -Penv=test printProperties

   Current Environment: test
   serverName:  http://www.testserver.com
   serverPort:  5211
   resources.serverName:  resources.testserver.com
   resources.serverPort:  8090
   

4. gradle -q -Penv=prod printProperties

   Current Environment: prod
   serverName:  http://www.productionserver.com
   serverPort:  80
   resources.serverName:  resources.productionserver.com
   resources.serverPort:  80