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package dynaclasstest;

import java.util.ArrayList;
import java.util.List;
import javax.tools.JavaCompiler;
import javax.tools.JavaFileManager;
import javax.tools.JavaFileObject;
import javax.tools.ToolProvider;

/**
 *
 * @author dhaval
 */
public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws Exception{
        String fullName = "DynaClass";

        StringBuilder src = new StringBuilder();
        src.append("public class DynaClass {\n");
        src.append("    public String toString() {\n");
        src.append("        return \"Hello, I am \" + ");
        src.append("this.getClass().getSimpleName();\n");
        src.append("    }\n");
        src.append("}\n");

        // We get an instance of JavaCompiler. Then
        // we create a file manager
        // (our custom implementation of it)
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        JavaFileManager fileManager = new ClassFileManager(compiler.getStandardFileManager(null, null, null));

        // Dynamic compiling requires specifying
        // a list of "files" to compile. In our case
        // this is a list containing one "file" which is in our case
        // our own implementation (see details below)
        List<JavaFileObject> jfiles = new ArrayList<JavaFileObject>();
        jfiles.add(new CharSequenceJavaFileObject(fullName, src));

        // We specify a task to the compiler. Compiler should use our file
        // manager and our list of "files".
        // Then we run the compilation with call()
        compiler.getTask(null, fileManager, null, null,
            null, jfiles).call();

        // Creating an instance of our compiled class and
        // running its toString() method
        Object instance = fileManager.getClassLoader(null)
            .loadClass(fullName).newInstance();
        System.out.println(instance);
    }
}