Compile java file at runtime

Question

I'm trying to compile a java file at runtime. If I run my code in Eclipse there is no problem, I can compile the external java file and instantiate the object of that class.

The problem occur when I generate the jar of my application (using the spring boot plugin). If I run my application using java -jar the runtime compilation task fails with the error: error: package 'com.myLib' does not exist

I've extracted the jar and I can find com.myLib in BOOT-INF/lib/mylib.jar

I think that it is just a problem of setting the right class path before compile at runtime my external java file

This is my external java file to be compiled at runtime:

  package com.mypackage;
  import com.myLib.myclass;

  public class filter implements MyInterface {

  @Override
  public void print(myclass obj) {
    System.out.println(obj);
  }
}

This is the code used to compile at runtime:

 final JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
 final StandardJavaFileManager fileManager = compiler.getStandardFileManager(errorListener, Locale.ENGLISH,
        Charset.defaultCharset());

  StringBuilder sb = new StringBuilder();
  for (URL url : ((URLClassLoader) Thread.currentThread().getContextClassLoader()).getURLs()) {
    sb.append(url.getPath()).append(File.pathSeparator);
  }
  final classPath = sb.toString();
  final List<String> optionList = new ArrayList<>();
  optionList.addAll(Arrays.asList("-classpath", classPath));
  optionList.add("-Xlint:unchecked");
  optionList.add("-Xlint:none");
  optionList.addAll(Arrays.asList("-d", "outputFolder"));
  final JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager, errorListener, optionList, null,
        files);
  task.call();

EDIT

I think that the problem is how the jar of my application is created. If I use the 'com.github.johnrengelman.shadow' plugin there is no problem. But if I use spring-boot and I generate the jar using bootJar task, I have a runtime exception during the execution of my application. If I extract both jars I see that spring-boot put the jars (of the libraries) into the jar of my application, instead 'shadow' put the .class (of the libraries) into the jar of my application.

I've created 2 gradle projects:

• https://github.com/fabry00/test-compile
• https://github.com/fabry00/test-compile-boot (with spring boot)

Both run in Eclpise without problem. The first one runs also in command line (./gradlew shadowJar) the second one does not run in command line (./gradlew bootJar and then run it 'java -jar')

The logic of the project is to read external xmls (filters directory) and create java classes at runtime mixing the content of the xmls and the content of the file skeleton/skeleton.java

Once you run the application, you can see the generated .java and .class files in the compiled folder