Getting spring boot jar files through gradle - spring

Question

The spring framework wants users to use dependency tools to download the framework, so I am trying to use gradle. I got this sample from their website http://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/#howto
buildscript {
repositories {
jcenter()
maven { url "http://repo.spring.io/snapshot" }
maven { url "http://repo.spring.io/milestone" }
}
dependencies {
classpath("org.springframework.boot:spring-boot-gradle-plugin:1.3.0.BUILD-SNAPSHOT")
}
}
apply plugin: 'java'
apply plugin: 'spring-boot'
jar {
baseName = 'root'
version = '0.0.1-SNAPSHOT'
}
repositories {
jcenter()
maven { url "http://repo.spring.io/snapshot" }
maven { url "http://repo.spring.io/milestone" }
}
dependencies {
compile("org.springframework.boot:spring-boot-starter-web")
testCompile("org.springframework.boot:spring-boot-starter-test")
}
I saved this to a file called build.gradle. Then in the CMD I went to the directory where the build.gralde file is located and type:
gradle build
It seemed to run fine but towards the building it's not working, here is the last logs I got from the command prompt:
:compileJava UP-TO-DATE
:processResources UP-TO-DATE
:classes UP-TO-DATE
:findMainClass
:jar
:bootRepackage FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':bootRepackage'.
Unable to find main class
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug
option to get more log output.
BUILD FAILED
Total time: 9.664 secs
I don't understand this "> Unable to find main class". I only want to get all the jar files and put them inside WEB-INF/lib of my eclipse projects. I am extremely new at gradle. What should I do?

Answer 1

It's not really clear to me, acoording to your comments, what are you trying to achieve, if you don't have a project sources, but for some reason wants to download dependent libraries. Gradle doesn't work this way, all the libraries are dowloded on demand, that means, they are dowloaded then you, for example, try to build your source files.
The exception you get, means, that gradle spring boot plugin's task bootRepackage Didn't find a main class in your project. This main class is mandatory for this task, since the task creates a standalone executable jar.
Sure, it is possble to dowload deps by custom task, like:
task getDeps(type: Copy) {
from sourceSets.main.runtimeClasspath
into 'runtime/'
}
But it seems, that you don't properly understand, how does it work. You should try to read gradle user guide first and let gradle to build your project for you, but not just combine some libs.