Java Dynamic Loading

Put a note first, follow-up need to dig deeper.

 Packagetest;ImportJava.io.File;Importjava.io.IOException;Importjava.lang.reflect.InvocationTargetException;ImportJava.lang.reflect.Method;ImportJava.net.URL;ImportJava.net.URLClassLoader;Importjava.nio.charset.StandardCharsets;ImportJava.nio.file.Files;ImportJavax.tools.JavaCompiler;ImportJavax.tools.ToolProvider; Public classSimplerun { Public Static voidShowcompile () {//Prepare source somehow.String Source = "Package test; public class Test {static {System.out.println (\ "hello\"),} public Test () {System.out.println (\ "world\"), public void Hello () {System.out.println (\ "Fuck\");}} "; //Save source in. java file.File root =NewFile ("~/temp");//On Windows running on \ c \, this is//C:\java.File sourcefile =NewFile (Root, "Test/test.java");        Sourcefile.getparentfile (). Mkdirs (); Try{files.write (Sourcefile.topath (), Source.getbytes (Standardcharsets.utf_8)); //Compile source file.Javacompiler compiler =Toolprovider.getsystemjavacompiler (); intSuccess = Compiler.run (NULL,NULL,NULL, Sourcefile.getpath ()); if(Success = = 0) {                //Load and instantiate compiled class.URLClassLoader ClassLoader = urlclassloader.newinstance (Newurl[] {Root.touri (). Tourl ()}); Class<?>CLS; Try {                    //should print "Hello".CLS = Class.forName ("Test. Test ",true, ClassLoader); //should print "World".Object instance =cls.newinstance (); //should print "[email protected]".System.out.println (instance); Method m= Cls.getmethod ("Hello",NewClass<?>[] {});                    System.out.println (m); M.invoke (instance,Newobject[]{}); } Catch(ClassNotFoundException | instantiationexception |illegalaccessexception e)                {E.printstacktrace (); } Catch(nosuchmethodexception e) {e.printstacktrace (); } Catch(SecurityException e) {e.printstacktrace (); } Catch(IllegalArgumentException e) {e.printstacktrace (); } Catch(InvocationTargetException e) {e.printstacktrace (); }            } Else{System.out.println ("Compile Failed"); }        } Catch(IOException e) {e.printstacktrace (); }    }    Private Static DoubleCalculate (String expr) {string ClassName= "Calculator"; String MethodName= "Calculate"; String Source= "Package test; public class ' + ClassName + ' {public static double ' + MethodName + ' () {return ' +Expr+ "; } }"; //Set Work directoryFile root =NewFile ("~/temp"); //Set Work packageFile sourcefile =NewFile (Root, "Test/calculator.java");        Sourcefile.getparentfile (). Mkdirs (); Try{files.write (Sourcefile.topath (), Source.getbytes (Standardcharsets.utf_8)); //Compile source file.Javacompiler compiler =Toolprovider.getsystemjavacompiler (); intSuccess = Compiler.run (NULL,NULL,NULL, Sourcefile.getpath ()); if(Success = = 0) {                //Load and instantiate compiled class.URLClassLoader ClassLoader = urlclassloader.newinstance (Newurl[] {Root.touri (). Tourl ()}); Class<?>CLS; Try{CLS= Class.forName ("Test. Calculator ",true, ClassLoader); Object instance=cls.newinstance (); Method Method= Cls.getmethod (MethodName,NewClass<?>[] {}); Object value= Method.invoke (instance,Newobject[] {}); return(Double) value; } Catch(ClassNotFoundException |illegalaccessexception e)                {E.printstacktrace (); } Catch(nosuchmethodexception e) {e.printstacktrace (); } Catch(SecurityException e) {e.printstacktrace (); } Catch(IllegalArgumentException e) {e.printstacktrace (); } Catch(InvocationTargetException e) {e.printstacktrace (); } Catch(instantiationexception e) {e.printstacktrace (); }            } Else{System.out.println ("Compile Failed"); }        } Catch(IOException e) {e.printstacktrace (); }        return0.0; }     Public Static voidMain (string[] args) {simplerun.showcompile (); if(Args.length >= 1) {System.out.println (args[0] + "=" + simplerun.calculate (args[0])); }    }}

Reference:

Http://www.infoq.com/cn/articles/cf-java-byte-code

Java Dynamic Loading