Initial commit of the Compiler class

Author: pborissow

src/javaxt/orm/Compiler.java

@@ -0,0 +1,272 @@
+package javaxt.orm;
+
+import java.io.*;
+import java.net.*;
+import java.util.*;
+import javax.tools.*;
+import java.nio.charset.Charset;
+
+import static javaxt.utils.Console.console;
+
+//******************************************************************************
+//**  Compiler
+//******************************************************************************
+/**
+ *   Used to compile ORM models into Java classes. The classes are ephemeral
+ *   meaning they are not saved anywhere on disk (no class files or jar files).
+ *   Instead the classes are stored in memory and are tied to the lifecycle of
+ *   the JVM.
+ *
+ ******************************************************************************/
+
+public class Compiler {
+
+    private Class[] classes;
+    private HashMap<String, SimpleJavaFileObject> outputFiles;
+    private URLClassLoader urlClassLoader;
+    private DiagnosticListener<JavaFileObject> listener = null;
+    private Locale locale = null;
+    private Charset charset = Charset.defaultCharset();
+
+
+  //**************************************************************************
+  //** Constructor
+  //**************************************************************************
+    public Compiler(Model[] models) throws Exception {
+
+        if (models==null || models.length==0){
+            classes = new Class[0];
+        }
+        else{
+
+            outputFiles = new HashMap<>();
+            urlClassLoader = getClassLoader();
+
+
+
+          //Convert models into an ArrayList
+            ArrayList<Model> arr = new ArrayList<>();
+            for (Model model : models){
+                arr.add(model);
+            }
+
+
+          //Compile classes
+            ArrayList<Class> classes = new ArrayList<>();
+            int numErrors = 0;
+            while (classes.size()<models.length){
+                try{
+                    Model model = arr.get(0);
+                    classes.add(compile(model));
+                    arr.remove(0);
+                }
+                catch(Exception e){
+                    numErrors++;
+
+                  //The following logic assumes that the compile error is due
+                  //to an ordering issue where one class depends on another
+                  //but the dependency hasn't been compiled yet. So we'll
+                  //shuffle the list of models and try again.
+
+                    if (arr.size()==1) throw e;
+                    String firstClass = getClassName(arr.get(0));
+                    while (true){
+                        Collections.shuffle(arr);
+                        String className = getClassName(arr.get(0));
+                        if (!className.equals(firstClass)) break;
+                    }
+                }
+
+
+              //Safety switch
+                if (numErrors>(models.length*models.length)){
+                    throw new Exception("Failed to compile " + getClassName(arr.get(0)));
+                }
+            }
+
+
+          //Convert the class list into an array. Sorts the classes to match
+          //the order of the input models.
+            this.classes = new Class[classes.size()];
+            for (int i=0; i<models.length; i++){
+                String className = getClassName(models[i]);
+                for (Class c : classes){
+                    String name = c.getPackageName() + "." + c.getSimpleName();
+                    if (name.equals(className)){
+                        this.classes[i] = c;
+                        break;
+                    }
+                }
+            }
+        }
+    }
+
+
+  //**************************************************************************
+  //** getClasses
+  //**************************************************************************
+  /** Returns classes generated by the compiler for each model
+   */
+    public Class[] getClasses(){
+        return classes;
+    }
+
+
+
+  //**************************************************************************
+  //** compile
+  //**************************************************************************
+  /** Used to compile a model and return a class
+   */
+    private Class compile(Model model) throws Exception {
+
+        JavaCompiler c = ToolProvider.getSystemJavaCompiler();
+        String className = getClassName(model);
+
+
+      //Create input file object
+        SimpleJavaFileObject src = new SimpleJavaFileObject(
+        URI.create("string:///" + model.getName() + ".java"),
+        JavaFileObject.Kind.SOURCE) {
+            public CharSequence getCharContent(boolean ignoreEncodingErrors) {
+                return model.getJavaCode();
+            }
+        };
+
+
+
+      //Create output file object
+        SimpleJavaFileObject cls = new SimpleJavaFileObject(
+        URI.create("runtime:///" + model.getName() + ".class"),
+        JavaFileObject.Kind.CLASS) {
+            private ByteArrayOutputStream out = new ByteArrayOutputStream();
+            public OutputStream openOutputStream() throws IOException {
+                //console.log("openOutputStream");
+                return out;
+            }
+            public InputStream openInputStream() throws IOException {
+                //console.log("openInputStream");
+                return new ByteArrayInputStream(out.toByteArray());
+            }
+        };
+        outputFiles.put(className, cls);
+
+
+
+      //Create in-memory file manager
+        StandardJavaFileManager fm = c.getStandardFileManager(listener, locale, charset);
+        JavaFileManager fileManager = new ForwardingJavaFileManager(fm) {
+            public JavaFileObject getJavaFileForOutput(
+                JavaFileManager.Location location, String className,
+                JavaFileObject.Kind kind, FileObject sibling) throws IOException {
+                return outputFiles.get(className);
+            }
+
+
+            public Iterable list(JavaFileManager.Location location,
+                String packageName, Set kinds, boolean recurse) throws IOException {
+
+                if (location==StandardLocation.CLASS_PATH){
+                    ArrayList<SimpleJavaFileObject> arr = new ArrayList<>();
+                    Iterator<String> it = outputFiles.keySet().iterator();
+                    while (it.hasNext()){
+                        String name = it.next();
+                        if (name.startsWith(packageName + ".")){
+                            if (!name.equals(className)){ //don't include the current file since it hasn't been compiled yet
+                                arr.add(outputFiles.get(name));
+                            }
+                        }
+                    }
+                    if (!arr.isEmpty()) return arr;
+                }
+
+                return super.list(location, packageName, kinds, recurse);
+            }
+
+
+
+            public String inferBinaryName(JavaFileManager.Location location, JavaFileObject file) {
+
+                if (location==StandardLocation.CLASS_PATH){
+                    Iterator<String> it = outputFiles.keySet().iterator();
+                    while (it.hasNext()){
+                        String name = it.next();
+                        SimpleJavaFileObject f = outputFiles.get(name);
+                        if (file==f) return name;
+                    }
+                }
+
+                return super.inferBinaryName(location, file);
+            }
+        };
+
+
+
+
+      //Compile class
+        JavaCompiler.CompilationTask task = c.getTask(
+            null,
+            fileManager,
+            listener,
+            Collections.emptySet(),
+            Collections.emptySet(),
+            Collections.singleton(src)
+        );
+
+        if (task.call()) {
+            return urlClassLoader.loadClass(className);
+        }
+        else{
+            throw new Exception("Failed to compile " + className);
+        }
+    }
+
+
+  //**************************************************************************
+  //** getClassLoader
+  //**************************************************************************
+  /** Returns a custom class loader used to find classes created by this class
+   */
+    private URLClassLoader getClassLoader(){
+        return new URLClassLoader(new URL[0]){
+            protected Class<?> findClass(final String name) throws ClassNotFoundException {
+
+
+                SimpleJavaFileObject f = outputFiles.get(name);
+                if (f!=null){
+                    try (InputStream is = f.openInputStream()) {
+
+
+                        ByteArrayOutputStream out = new ByteArrayOutputStream();
+
+                        int x;
+                        byte[] buffer = new byte[256];
+                        while ((x = is.read(buffer, 0, buffer.length)) != -1) {
+                            out.write(buffer, 0, x);
+                        }
+
+                        out.flush();
+                        byte[] classBytes = out.toByteArray();
+                        return defineClass(name, classBytes, 0, classBytes.length);
+
+                    }
+                    catch(Exception e){
+                        e.printStackTrace();
+                    }
+                }
+
+                return super.findClass(name);
+            }
+        };
+    }
+
+
+  //**************************************************************************
+  //** getClassName
+  //**************************************************************************
+    private String getClassName(Model model){
+        return model.getPackageName() + "." + model.getName();
+    }
+
+
+}