Add Compiler

beehive-jdbc-mapper/src/main/java/com/moparisthebest/classgen/Compiler.java

@@ -0,0 +1,175 @@
+package com.moparisthebest.classgen;
+
+
+import javax.tools.*;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * This let's you take compile and then run Java source code at runtime, this class only allows you to compile 1 class
+ * at a time.
+ * <p>
+ * This is not thread safe, though it could be extended and made thread safe, or locked around.
+ *
+ * @author moparisthebest
+ * @see MultiCompiler for compiling multiple classes at once
+ * <p>
+ * The original idea was taken from:
+ * http://mindprod.com/jgloss/javacompiler.html#SAMPLECODE
+ */
+public class Compiler {
+
+	private final JavaCompiler compiler;
+	private final MemoryJavaFileManager mjfm;
+	//private final ClassLoader classLoader;
+	private final List<JavaFileObject> singleton = Arrays.asList(new JavaFileObject[1]);
+
+	public Compiler() {
+		this(false);
+	}
+
+	protected Compiler(final boolean multi) {
+		compiler = ToolProvider.getSystemJavaCompiler();
+		if (compiler == null)
+			throw new RuntimeException("tools.jar needs to be on classpath to compile code at runtime");
+		final JavaFileManager fileManager = compiler.getStandardFileManager(null, null, null);
+		mjfm = multi ? new MultiMemoryJavaFileManager(fileManager) : new SingleMemoryJavaFileManager(fileManager);
+		//classLoader = new MemoryClassLoader(mjfm);
+	}
+
+	protected ClassLoader compile(final Iterable<? extends JavaFileObject> source) {
+		//final MemoryJavaFileManager mjfm = new MemoryJavaFileManager(compiler.getStandardFileManager(null, null, null));
+		final JavaCompiler.CompilationTask task = compiler.getTask(null, mjfm, null, null, null, source);
+		return task.call() ?
+				new MemoryClassLoader(mjfm)
+				//classLoader
+				: null;
+	}
+
+	protected ClassLoader compile(final JavaFileObject... source) {
+		return compile(Arrays.asList(source));
+	}
+
+	public ClassLoader compile(final JavaFileObject source) {
+		singleton.set(0, source);
+		return compile(singleton);
+	}
+
+	protected <T> T compile(final String className, final Iterable<? extends JavaFileObject> source) {
+		// compile item
+		final ClassLoader cl = compile(source);
+		if (cl == null)
+			throw new RuntimeException("Error compiling class, aborting...");
+		return instantiate(cl, className);
+	}
+
+	protected <T> T compile(final String className, final JavaFileObject... source) {
+		return compile(className, Arrays.asList(source));
+	}
+
+	public <T> T compile(final String className, final JavaFileObject source) {
+		singleton.set(0, source);
+		return compile(className, singleton);
+	}
+
+	public <T> T compile(final String className, final CharSequence code) {
+		return compile(className, new StringJavaFileObject(className, code));
+	}
+
+	public <T> T instantiate(final ClassLoader cl, final String className) {
+		try {
+			// Load class and create an instance.
+			final Class<?> calcClass = cl.loadClass(className);
+			@SuppressWarnings("unchecked")            final T ret = (T) calcClass.newInstance();
+			return ret;
+		} catch (Exception e) {
+			throw new RuntimeException("Error finding or instantiating class, exiting...", e);
+		}
+	}
+
+}
+
+class MemoryJavaFileObject extends ForwardingJavaFileObject<JavaFileObject> {
+
+	final ByteArrayOutputStream baos = new ByteArrayOutputStream();
+
+	MemoryJavaFileObject(JavaFileObject fileObject) {
+		super(fileObject);
+	}
+
+	@Override
+	public OutputStream openOutputStream() throws IOException {
+		return baos;
+	}
+}
+
+interface MemoryJavaFileManager extends JavaFileManager {
+	MemoryJavaFileObject getMemoryJavaFileObject(final String name);
+}
+
+class SingleMemoryJavaFileManager extends ForwardingJavaFileManager<JavaFileManager> implements MemoryJavaFileManager {
+
+	private MemoryJavaFileObject classes = null;
+
+	SingleMemoryJavaFileManager(JavaFileManager fileManager) {
+		super(fileManager);
+	}
+
+	@Override
+	public MemoryJavaFileObject getMemoryJavaFileObject(final String name) {
+		final MemoryJavaFileObject ret = classes;
+		classes = null;
+		return ret;
+	}
+
+	@Override
+	public JavaFileObject getJavaFileForOutput(Location location, String className, JavaFileObject.Kind kind, FileObject sibling) throws IOException {
+		final MemoryJavaFileObject jfo = new MemoryJavaFileObject(super.getJavaFileForOutput(location, className, kind, sibling));
+		//System.out.printf("MemoryJavaFileManager.getJavaFileForOutput(%s, %s, %s, %s): %s\n", location, className, kind, sibling, jfo);
+		classes = jfo;
+		return jfo;
+	}
+}
+
+class MultiMemoryJavaFileManager extends ForwardingJavaFileManager<JavaFileManager> implements MemoryJavaFileManager {
+
+	private Map<String, MemoryJavaFileObject> classes = new HashMap<String, MemoryJavaFileObject>();
+
+	MultiMemoryJavaFileManager(JavaFileManager fileManager) {
+		super(fileManager);
+	}
+
+	@Override
+	public MemoryJavaFileObject getMemoryJavaFileObject(final String name) {
+		return classes.remove(name);
+	}
+
+	@Override
+	public JavaFileObject getJavaFileForOutput(Location location, String className, JavaFileObject.Kind kind, FileObject sibling) throws IOException {
+		final MemoryJavaFileObject jfo = new MemoryJavaFileObject(super.getJavaFileForOutput(location, className, kind, sibling));
+		//System.out.printf("MemoryJavaFileManager.getJavaFileForOutput(%s, %s, %s, %s): %s\n", location, className, kind, sibling, jfo);
+		classes.put(className, jfo);
+		return jfo;
+	}
+}
+
+class MemoryClassLoader extends ClassLoader {
+	final MemoryJavaFileManager jfm;
+
+	MemoryClassLoader(MemoryJavaFileManager jfm) {
+		this.jfm = jfm;
+	}
+
+	public Class findClass(String name) throws ClassNotFoundException {
+		final MemoryJavaFileObject jfo = jfm.getMemoryJavaFileObject(name);
+		if (jfo == null)
+			throw new ClassNotFoundException("Class '" + name + "' cannot be found in the MemoryJavaFileManager");
+		final byte[] b = jfo.baos.toByteArray();
+		return defineClass(name, b, 0, b.length);
+	}
+}

beehive-jdbc-mapper/src/main/java/com/moparisthebest/classgen/MultiCompiler.java

@@ -0,0 +1,35 @@
+package com.moparisthebest.classgen;
+
+import javax.tools.JavaFileObject;
+
+/**
+ * This lets you compile multiple source files at once
+ */
+public class MultiCompiler extends Compiler {
+
+	public static Compiler instance = new MultiCompiler();
+
+	public MultiCompiler() {
+		super(true);
+	}
+
+	@Override
+	public ClassLoader compile(final Iterable<? extends JavaFileObject> source) {
+		return super.compile(source);
+	}
+
+	@Override
+	public ClassLoader compile(final JavaFileObject... source) {
+		return super.compile(source);
+	}
+
+	@Override
+	public <T> T compile(final String className, final JavaFileObject... source) {
+		return super.compile(className, source);
+	}
+
+	@Override
+	public <T> T compile(final String className, final Iterable<? extends JavaFileObject> source) {
+		return super.compile(className, source);
+	}
+}

beehive-jdbc-mapper/src/main/java/com/moparisthebest/classgen/StringJavaFileObject.java

@@ -0,0 +1,22 @@
+package com.moparisthebest.classgen;
+
+import javax.tools.SimpleJavaFileObject;
+import java.net.URI;
+
+/**
+ * For sending java source as strings to a Compiler
+ * @see Compiler
+ */
+public class StringJavaFileObject extends SimpleJavaFileObject {
+	private final CharSequence code;
+
+	public StringJavaFileObject(final String name, final CharSequence code) {
+		super(URI.create("string:///" + name.replace('.', '/') + Kind.SOURCE.extension), Kind.SOURCE);
+		this.code = code;
+	}
+
+	@Override
+	public CharSequence getCharContent(boolean ignoreEncodingErrors) {
+		return code;
+	}
+}

beehive-jdbc-mapper/src/test/java/com/moparisthebest/classgentest/Calculator.java

@@ -0,0 +1,10 @@
+package com.moparisthebest.classgentest;
+
+/**
+ * Created by mopar on 5/15/17.
+ */
+public interface Calculator {
+	public double calc(double a, double b);
+
+	public java.util.Date whenGenerated();
+}

beehive-jdbc-mapper/src/test/java/com/moparisthebest/classgentest/CalculatorCompiler.java

@@ -0,0 +1,126 @@
+package com.moparisthebest.classgentest;
+
+import com.moparisthebest.classgen.Compiler;
+import com.moparisthebest.classgen.MultiCompiler;
+import com.moparisthebest.classgen.StringJavaFileObject;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * This is a sample program that shows how to generate java source code, compile, and run it, all at runtime and
+ * without ever touching the filesystem.  It can be used for much more complicated (and usefull) things, perhaps
+ * like creating Pojo instances from ResultSets. :)
+ * <p>
+ * You need tools.jar on your classpath, and this class in the same package as well:
+ * public interface Calculator {
+ * public double calc(double a, double b);
+ * public java.util.Date whenGenerated();
+ * }
+ * <p>
+ * The original idea was taken from:
+ * http://mindprod.com/jgloss/javacompiler.html#SAMPLECODE
+ *
+ * @author moparisthebest
+ */
+public class CalculatorCompiler {
+
+	@Test
+	public void testSingle() throws InterruptedException {
+		final Compiler compiler = new Compiler();
+		final Calculator mult1 = genCalc(compiler, "Multiply", "a * b");
+		final Calculator hyp = genCalc(compiler, "Hypotenuse", "Math.sqrt( a*a + b*b )");
+		final Calculator mult2 = genCalc(compiler, "Multiply", "a * b * 2");
+		final Calculator mult3 = genCalc(compiler, "Multiply", "a * b * 3");
+		final Calculator mult4 = genCalc(compiler, "Multiply", "a * b * 4");
+		assertEquals(12.0, mult1.calc(3.0, 4.0), 0.01);
+		assertEquals(5.0, hyp.calc(3.0, 4.0), 0.01);
+		assertEquals(24.0, mult2.calc(3.0, 4.0), 0.01);
+		assertEquals(48.0, mult3.calc(4.0, 4.0), 0.01);
+		assertEquals(48.0, mult4.calc(3.0, 4.0), 0.01);
+	}
+
+	@Test
+	public void testMulti() throws InterruptedException {
+		final MultiCompiler compiler = new MultiCompiler();
+		final Calculator mult1 = genCalc(compiler, "Multiply", "a * Var.var", "Var", "4.0");
+		final Calculator hyp = genCalc(compiler, "Hypotenuse", "Math.sqrt( a*a + Var.var*Var.var )", "Var", "4.0");
+		final Calculator mult2 = genCalc(compiler, "Multiply2", "a * Var.var * 2", "Var", "4.0");
+		final Calculator mult3 = genCalc(compiler, "Multiply3", "a * Var.var * 3", "Var", "4.0");
+		final Calculator mult4 = genCalc(compiler, "Multiply", "a * Var.var * 4", "Var", "4.0");
+		assertEquals(mult1.calc(3.0, 4.0), 12.0, 0.01);
+		assertEquals(hyp.calc(3.0, 4.0), 5.0, 0.01);
+		assertEquals(mult2.calc(3.0, 4.0), 24.0, 0.01);
+		assertEquals(mult3.calc(4.0, 4.0), 48.0, 0.01);
+		assertEquals(48.0, mult4.calc(3.0, 4.0), 0.01);
+	}
+
+	private static String writeCalculator(String className, String expression) {
+		String packageName = null;
+		final int lastIndex = className.lastIndexOf(".");
+		if (lastIndex != -1) {
+			packageName = className.substring(0, lastIndex);
+			className = className.substring(lastIndex + 1);
+		}
+
+		return (packageName == null ? "" : "package " + packageName + ";\n") +
+				"import java.util.Date;\n" +
+				"public final class " + className + " implements " + Calculator.class.getName() + " {\n" +
+				"  public double calc(double a, double b) {\n" +
+				"    return " + expression + ";\n" +
+				"  }\n" +
+				"  public Date whenGenerated() {\n" +
+				"    return new Date(" + System.currentTimeMillis() + "L);\n" +
+				"  }\n" +
+				"}\n";
+	}
+
+	private static StringJavaFileObject writeCalculatorOb(String className, String expression) {
+		return new StringJavaFileObject(className, writeCalculator(className, expression));
+	}
+
+	private static StringJavaFileObject writeVar(String className, String expression) {
+		String packageName = null;
+		final int lastIndex = className.lastIndexOf(".");
+		if (lastIndex != -1) {
+			packageName = className.substring(0, lastIndex);
+			className = className.substring(lastIndex + 1);
+		}
+
+		return new StringJavaFileObject(className, (packageName == null ? "" : "package " + packageName + ";\n") +
+				"public final class " + className + " {\n" +
+				"  public static final double var = " + expression + ";\n" +
+				"}\n");
+	}
+
+	public static Calculator genCalc(final Compiler compiler, final String className, final String expression) {
+		// compose text of Java program on the fly.
+		final String calc = writeCalculator(className, expression);
+		/*
+		System.out.println("calc:");
+		System.out.println(calc);
+		*/
+		return compiler.compile(className, calc);
+	}
+
+	public static Calculator genCalc(final MultiCompiler compiler, final String className, final String expression, final String varClass, final String varExpression) {
+		// compose text of Java program on the fly.
+		final StringJavaFileObject calc = writeCalculatorOb(className, expression);
+		final StringJavaFileObject var = writeVar(varClass, varExpression);
+		/*
+		System.out.println("calc:");
+		System.out.println(calc.getCharContent(true));
+		System.out.println("var:");
+		System.out.println(var.getCharContent(true));
+		*/
+		return compiler.compile(className, calc, var);
+	}
+
+	public static double runCalc(final String className, final String expression, final double a, final double b) {
+		final Calculator calc = genCalc(new Compiler(), className, expression);
+		double ret = calc.calc(a, b);
+		System.out.printf("%s.calc( %f, %f ) is : %f\n", className, a, b, ret);
+		System.out.printf("%s generated on: %s\n", className, calc.whenGenerated());
+		return ret;
+	}
+}

pom.xml

@@ -241,8 +241,8 @@
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.1</version>
                 <configuration>
-                    <source>1.5</source>
-                    <target>1.5</target>
+                    <source>1.6</source>
+                    <target>1.6</target>
                     <debug>true</debug>
                     <!--compilerArgument>-Xlint:unchecked</compilerArgument-->
                 </configuration>