Lib: 2015/12

import javax.tools.*;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.InvocationTargetException;
import java.net.URI;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Arrays;
/**
* Created by nanashi07 on 15/12/13.
*/
public class CompileOnFly {
public static void main(String args[]) throws IOException {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>();
StringWriter writer = new StringWriter();
PrintWriter out = new PrintWriter(writer);
out.println("package com.prhythm.output;");
out.println();
out.println("public class OutputImpl implements IOutput {");
out.println();
out.println(" public void printFor(String message) {");
out.println(" System.out.printf(\"Print from %s : %s%n\", getClass().getName(), message);");
out.println(" }");
out.println();
out.println("}");
out.close();
JavaFileObject file = new TextJavaObject("com.prhythm.output.OutputImpl", writer.toString());
Iterable<? extends JavaFileObject> compilationUnits = Arrays.asList(file);
JavaCompiler.CompilationTask task = compiler.getTask(null, null, diagnostics, null, null, compilationUnits);
boolean success = task.call();
for (Diagnostic diagnostic : diagnostics.getDiagnostics()) {
System.out.printf("Code: %s%n", diagnostic.getCode());
System.out.printf("Kind: %s%n", diagnostic.getKind());
System.out.printf("Position: %s%n", diagnostic.getPosition());
System.out.printf("StartPosition: %s%n", diagnostic.getStartPosition());
System.out.printf("EndPosition: %s%n", diagnostic.getEndPosition());
System.out.printf("Source: %s%n", diagnostic.getSource());
System.out.printf("Message: %s%n", diagnostic.getMessage(null));
}
if (success) {
try {
URLClassLoader classLoader = URLClassLoader.newInstance(new URL[]{new File("").toURI().toURL()});
Class<?> outClass = Class.forName("com.prhythm.output.OutputImpl", true, classLoader);
Object outInstance = outClass.newInstance();
outClass.getDeclaredMethod("printFor", new Class[]{String.class}).invoke(outInstance, "Bruce");
} catch (ClassNotFoundException e) {
System.err.println("Class not found: " + e);
} catch (NoSuchMethodException e) {
System.err.println("No such method: " + e);
} catch (IllegalAccessException e) {
System.err.println("Illegal access: " + e);
} catch (InvocationTargetException e) {
System.err.println("Invocation target: " + e);
} catch (InstantiationException e) {
System.err.println("Initialize instance: " + e);
}
}
}
}
class TextJavaObject extends SimpleJavaFileObject {
final String code;
TextJavaObject(String name, String code) {
super(URI.create("string:///" + name.replace('.', '/') + Kind.SOURCE.extension), Kind.SOURCE);
this.code = code;
}
@Override
public CharSequence getCharContent(boolean ignoreEncodingErrors) {
return code;
}
}

Project structure

+ ---- annotation- processor
| + ---- annotation- lib
|   + ---- build.gradle
|   + ---- src
|     + ---- main
|     | + ---- java
|     |   + ---- com
|     |     + ---- prhythm
|     |       + ---- annotations
|     |         + ---- PrintUsage.java
|     |         + ---- PrintUsageProcessor.java
|     | + ---- resources
|         + ---- META-INF
|           + ---- services
|             + ---- javax.annotation.processing.Processor
| + ---- foo
|   + ---- build.gradle
|   + ---- src
|     + ---- main
|       + ---- java
|         + ---- com
|           + ---- prhythm
|             + ---- foo
|               + ---- Bar.java
| + ---- build.gradle
| + ---- settings.gradle

PrintUsage.java

package com.prhythm.annotations;
 
/**
 * Print usage
 * Created by nanashi07 on 15/12/2.
 */
public @interface PrintUsage {
}

PrintUsageProcessor.java

package com.prhythm.annotations;
 
import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.Messager;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;
import javax.tools.Diagnostic;
import java.util.Set;
 
/**
 * Processor of {@link PrintUsage}
 * Created by nanashi07 on 15/12/2.
 */
@SupportedAnnotationTypes("com.prhythm.annotations.PrintUsage")
public class PrintUsageProcessor extends AbstractProcessor {
    @Override
    public boolean process(Set annotations, RoundEnvironment roundEnv) {
        Messager messager = processingEnv.getMessager();
        for (TypeElement typeElement : annotations) {
            for (Element element : roundEnv.getElementsAnnotatedWith(typeElement)) {
                String msg = String.format("Use %s on %s#%s", typeElement, element.getEnclosingElement(), element);
                messager.printMessage(Diagnostic.Kind.NOTE, msg);
            }
        }
        return true;
    }
}

javax.annotation.processing.Processor

com.prhythm.annotations.PrintUsageProcessor

Bar.java

package com.prhythm.foo;
 
import com.prhythm.annotations.PrintUsage;
 
/**
 * Test class
 * Created by nanashi07 on 15/12/2.
 */
public class Bar {
 
    @PrintUsage
    public void move(String name) {
 
    }
 
    @PrintUsage
    public long time() {
        return System.currentTimeMillis();
    }
 
}

build.gradle (foo)

group 'com.prhythm'
version '1.0-SNAPSHOT'
 
apply plugin: 'java'
 
sourceCompatibility = 1.6
 
repositories {
    mavenCentral()
}
 
dependencies {
    testCompile group: 'junit', name: 'junit', version: '4.11'
    compile project(':annotation-lib')
}

Enable annotation processor on preference

Build with gradle

gradle clean build

result

References:

Type Memo

Note: ==================================================
Note: TypeElement: com.prhythm.annotations.PrintUsage
Note: TypeElement.getClass(): class com.sun.tools.javac.code.Symbol$ClassSymbol
Note: TypeElement.getSimpleName(): PrintUsage
Note: TypeElement.getEnclosedElements(): 
Note: TypeElement.getEnclosingElement(): com.prhythm.annotations
Note: TypeElement.getInterfaces(): java.lang.annotation.Annotation
Note: TypeElement.getNestingKind(): TOP_LEVEL
Note: TypeElement.getQualifiedName(): com.prhythm.annotations.PrintUsage
Note: TypeElement.getSuperclass(): none
Note: TypeElement.getTypeParameters(): 
Note: TypeElement.getAnnotationMirrors(): 
Note: TypeElement.asType(): com.prhythm.annotations.PrintUsage
Note: TypeElement.getKind(): ANNOTATION_TYPE
Note: TypeElement.getModifiers(): [public, abstract]
Note: ----------------------------------------------------------
Note: Element: move(java.lang.String)
Note: Element.getModifiers(): [public]
Note: Element.getClass(): class com.sun.tools.javac.code.Symbol$MethodSymbol
Note: Element.getKind(): METHOD
Note: Element.getAnnotationMirrors(): @com.prhythm.annotations.PrintUsage
Note: Element.getSimpleName(): move
Note: Element.asType(): (java.lang.String)void
Note: Element.getEnclosedElements(): 
Note: Element.getEnclosingElement(): com.prhythm.foo.Bar
Note: ----------------------------------------------------------
Note: Element: time()
Note: Element.getModifiers(): [public]
Note: Element.getClass(): class com.sun.tools.javac.code.Symbol$MethodSymbol
Note: Element.getKind(): METHOD
Note: Element.getAnnotationMirrors(): @com.prhythm.annotations.PrintUsage
Note: Element.getSimpleName(): time
Note: Element.asType(): ()long
Note: Element.getEnclosedElements(): 
Note: Element.getEnclosingElement(): com.prhythm.foo.Bar
Note: ==================================================
Note: TypeElement: com.prhythm.annotations.Mark
Note: TypeElement.getClass(): class com.sun.tools.javac.code.Symbol$ClassSymbol
Note: TypeElement.getSimpleName(): Mark
Note: TypeElement.getEnclosedElements(): value(),names()
Note: TypeElement.getEnclosingElement(): com.prhythm.annotations
Note: TypeElement.getInterfaces(): java.lang.annotation.Annotation
Note: TypeElement.getNestingKind(): TOP_LEVEL
Note: TypeElement.getQualifiedName(): com.prhythm.annotations.Mark
Note: TypeElement.getSuperclass(): none
Note: TypeElement.getTypeParameters(): 
Note: TypeElement.getAnnotationMirrors(): 
Note: TypeElement.asType(): com.prhythm.annotations.Mark
Note: TypeElement.getKind(): ANNOTATION_TYPE
Note: TypeElement.getModifiers(): [public, abstract]
Note: ----------------------------------------------------------
Note: Element: com.prhythm.foo.Yahoo
Note: Element.getModifiers(): [public, abstract]
Note: Element.getClass(): class com.sun.tools.javac.code.Symbol$ClassSymbol
Note: Element.getKind(): INTERFACE
Note: Element.getAnnotationMirrors(): @com.prhythm.annotations.Mark("2323")
Note: Element.getSimpleName(): Yahoo
Note: Element.asType(): com.prhythm.foo.Yahoo
Note: Element.getEnclosedElements(): home(java.lang.String)
Note: Element.getEnclosingElement(): com.prhythm.foo
Note: ----------------------------------------------------------
Note: Element: home(java.lang.String)
Note: Element.getModifiers(): [public, abstract]
Note: Element.getClass(): class com.sun.tools.javac.code.Symbol$MethodSymbol
Note: Element.getKind(): METHOD
Note: Element.getAnnotationMirrors(): @com.prhythm.annotations.Mark("110"),@com.prhythm.core.generic.http.annotation.Get("https://tw.yahoo.com")
Note: Element.getSimpleName(): home
Note: Element.asType(): (java.lang.String)java.lang.String
Note: Element.getEnclosedElements(): 
Note: Element.getEnclosingElement(): com.prhythm.foo.Yahoo