AnnotationProcessorをすこしさわってみた

InjectProcessor.java

package org.mikeneck.annotation;

import javax.annotation.processing.*;
import javax.inject.Inject;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.AnnotationMirror;
import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;
import javax.tools.Diagnostic;
import javax.tools.FileObject;
import javax.tools.StandardLocation;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Set;

/**
 * @author mike
 */
@SupportedSourceVersion(SourceVersion.RELEASE_7)
@SupportedAnnotationTypes({"javax.inject.Inject"})
public class InjectProcessor extends AbstractProcessor {

    private static final char comma = ',';

    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        if (annotations.size() == 0) return true;

        Messager messager = processingEnv.getMessager();
        Filer filer = processingEnv.getFiler();
        PrintWriter writer = null;

        try {
            FileObject fileObject = filer.createResource(StandardLocation.SOURCE_OUTPUT, "", "result.txt");
            writer = new PrintWriter(fileObject.openWriter(), true);

            // print supporting annotation
            writer.print(this.getClass().getCanonicalName());
            writer.println(" supports ");
            for (String type : this.getSupportedAnnotationTypes()) {
                writer.println("    " + type);
            }

            // print root elements information
            writer.println("====RoundEnvironment#getRootElements====");
            writer.println("  returns Set<? extends Element> contains");

            List<? extends Element> roots =
                    convertToUnmodifiableList(roundEnv.getRootElements());
            for (int index = 0, size = roots.size(); index < size; index += 1) {
                Element element = roots.get(index);
                scanEndPrintElement(index, writer, element);
            }
            writer.println("====RoundEnvironment#getRootElements====");
            writer.println("");

            // print annotations information
            writer.println("====Set<? extends TypeElement> annotations====");

            List<? extends TypeElement> list = convertToUnmodifiableList(annotations);
            for (int index = 0, size = list.size(); index < size; index += 1) {
                TypeElement element = list.get(index);
                scanEndPrintElement(index, writer, element);
            }
            writer.println("====Set<? extends TypeElement> annotations====");
            writer.println("");

            // print annotated elements information
            writer.println("====RoundEnvironment#getElementsAnnotatedWith====");
            writer.println("  " + Inject.class.getCanonicalName());

            List<? extends Element> elements =
                    convertToUnmodifiableList(roundEnv.getElementsAnnotatedWith(Inject.class));
            for (int index = 0, len = elements.size(); index < len; index += 1) {
                Element element = elements.get(index);
                scanEndPrintElement(index, writer, element);
            }
            writer.println("====RoundEnvironment#getElementsAnnotatedWith====");
            writer.println("");

        } catch (IOException e) {
            messager.printMessage(Diagnostic.Kind.ERROR, "cannot write file object.");
        } finally {
            if (writer != null) writer.close();
        }


        return true;
    }

    /**
     * convert {@code java.util.Set&lt;T&gt;} into {@code java.util.List&lt;T&gt;}
     * @param set source
     * @param <T> type
     * @return unmodifiable list of &lt;T&gt;
     */
    private <T> List<T> convertToUnmodifiableList (Set<T> set) {
        return Collections.unmodifiableList(new ArrayList<>(set));
    }

    /**
     * print {@code javax.lang.model.Element} information
     * @param index the number of elements
     * @param writer a writer object
     * @param element {@code javax.lang.model.Element} to be printed
     */
    private void scanEndPrintElement (int index, PrintWriter writer, Element element) {
        writer.println(index + " : " + element.getClass().getCanonicalName());
        writer.println("  asType             : " + element.asType());
        writer.println("  simpleName         : " + element.getSimpleName());
        printElement(writer, element);

        Element elm = element.getEnclosingElement();
        writer.println("  enclosingElement   : ");
        printElement(writer, elm);

        writer.println("  enclosingElements  :");
        for (Element e : element.getEnclosedElements()) {
            printElement(writer, e);
        }
        writer.println("  annotationMirrors :");
        for (AnnotationMirror mirror : element.getAnnotationMirrors()) {
            writer.println("    type : " + mirror.getAnnotationType());
        }
    }

    /**
     * print {@code javax.lang.model.Element} information
     * @param writer a writer object
     * @param e {@code javax.lang.model.Element} to be printed
     */
    private void printElement (PrintWriter writer, Element e) {
        writer.println("    class : " + e.getClass().getCanonicalName() + comma +
                " modifiers " + e.getModifiers() + comma +
                " kind : " + e.getKind() + comma +
                " type - kind : " + e.asType().getKind().name() + comma +
                " type : " + e.asType() + comma +
                " name : " + e.getSimpleName());
    }
}

Login.java

package org.mikeneck.annotation;

import javax.inject.Inject;
import java.util.Map;

/**
 * @author mike
 */
public class Login implements Redirectable {

    private static final String KEY = "name";

    @Inject
    private UserService service;

    /**
     * {@inheritDoc}
     */
    @Override
    public String getPage (Map<String, String> info) {
        if (service.isAuthorized()) {
            info.put(KEY, service.getName());
            return "index.html";
        } else {
            info.put(KEY, "guest");
            return "login.html";
        }
    }
}

Logout.java

package org.mikeneck.annotation;

import javax.inject.Inject;
import javax.inject.Named;
import java.util.Map;

/**
 * @author mike
 */
public class Logout implements Redirectable {

    private static final String KEY = "name";

    @Inject
    @Named(value = "out")
    private UserService service;

    /**
     * {@inheritDoc}
     */
    @Override
    public String getPage (Map<String, String> info) {
        service.logout();
        info.remove(KEY);
        return "logout.html";
    }
}

result.txt

org.mikeneck.annotation.InjectProcessor supports 
    javax.inject.Inject
====RoundEnvironment#getRootElements====
  returns Set<? extends Element> contains
0 : com.sun.tools.javac.code.Symbol.ClassSymbol
  asType             : org.mikeneck.annotation.Login
  simpleName         : Login
    class : com.sun.tools.javac.code.Symbol.ClassSymbol, modifiers [public], kind : CLASS, type - kind : DECLARED, type : org.mikeneck.annotation.Login, name : Login
  enclosingElement   : 
    class : com.sun.tools.javac.code.Symbol.PackageSymbol, modifiers [], kind : PACKAGE, type - kind : PACKAGE, type : org.mikeneck.annotation, name : annotation
  enclosingElements  :
    class : com.sun.tools.javac.code.Symbol.MethodSymbol, modifiers [public], kind : CONSTRUCTOR, type - kind : EXECUTABLE, type : ()void, name : <init>
    class : com.sun.tools.javac.code.Symbol.VarSymbol, modifiers [private, static, final], kind : FIELD, type - kind : DECLARED, type : java.lang.String, name : KEY
    class : com.sun.tools.javac.code.Symbol.VarSymbol, modifiers [private], kind : FIELD, type - kind : DECLARED, type : org.mikeneck.annotation.UserService, name : service
    class : com.sun.tools.javac.code.Symbol.MethodSymbol, modifiers [public], kind : METHOD, type - kind : EXECUTABLE, type : (java.util.Map<java.lang.String,java.lang.String>)java.lang.String, name : getPage
  annotationMirrors :
1 : com.sun.tools.javac.code.Symbol.ClassSymbol
  asType             : org.mikeneck.annotation.Logout
  simpleName         : Logout
    class : com.sun.tools.javac.code.Symbol.ClassSymbol, modifiers [public], kind : CLASS, type - kind : DECLARED, type : org.mikeneck.annotation.Logout, name : Logout
  enclosingElement   : 
    class : com.sun.tools.javac.code.Symbol.PackageSymbol, modifiers [], kind : PACKAGE, type - kind : PACKAGE, type : org.mikeneck.annotation, name : annotation
  enclosingElements  :
    class : com.sun.tools.javac.code.Symbol.MethodSymbol, modifiers [public], kind : CONSTRUCTOR, type - kind : EXECUTABLE, type : ()void, name : <init>
    class : com.sun.tools.javac.code.Symbol.VarSymbol, modifiers [private, static, final], kind : FIELD, type - kind : DECLARED, type : java.lang.String, name : KEY
    class : com.sun.tools.javac.code.Symbol.VarSymbol, modifiers [private], kind : FIELD, type - kind : DECLARED, type : org.mikeneck.annotation.UserService, name : service
    class : com.sun.tools.javac.code.Symbol.MethodSymbol, modifiers [public], kind : METHOD, type - kind : EXECUTABLE, type : (java.util.Map<java.lang.String,java.lang.String>)java.lang.String, name : getPage
  annotationMirrors :
2 : com.sun.tools.javac.code.Symbol.ClassSymbol
  asType             : org.mikeneck.annotation.UserServiceImpl
  simpleName         : UserServiceImpl
    class : com.sun.tools.javac.code.Symbol.ClassSymbol, modifiers [public], kind : CLASS, type - kind : DECLARED, type : org.mikeneck.annotation.UserServiceImpl, name : UserServiceImpl
  enclosingElement   : 
    class : com.sun.tools.javac.code.Symbol.PackageSymbol, modifiers [], kind : PACKAGE, type - kind : PACKAGE, type : org.mikeneck.annotation, name : annotation
  enclosingElements  :
    class : com.sun.tools.javac.code.Symbol.MethodSymbol, modifiers [public], kind : CONSTRUCTOR, type - kind : EXECUTABLE, type : ()void, name : <init>
    class : com.sun.tools.javac.code.Symbol.VarSymbol, modifiers [private], kind : FIELD, type - kind : BOOLEAN, type : boolean, name : authorized
    class : com.sun.tools.javac.code.Symbol.MethodSymbol, modifiers [public], kind : METHOD, type - kind : EXECUTABLE, type : ()boolean, name : isAuthorized
    class : com.sun.tools.javac.code.Symbol.MethodSymbol, modifiers [public], kind : METHOD, type - kind : EXECUTABLE, type : ()java.lang.String, name : getName
    class : com.sun.tools.javac.code.Symbol.MethodSymbol, modifiers [public], kind : METHOD, type - kind : EXECUTABLE, type : ()void, name : logout
  annotationMirrors :
3 : com.sun.tools.javac.code.Symbol.ClassSymbol
  asType             : org.mikeneck.annotation.UserService
  simpleName         : UserService
    class : com.sun.tools.javac.code.Symbol.ClassSymbol, modifiers [public, abstract], kind : INTERFACE, type - kind : DECLARED, type : org.mikeneck.annotation.UserService, name : UserService
  enclosingElement   : 
    class : com.sun.tools.javac.code.Symbol.PackageSymbol, modifiers [], kind : PACKAGE, type - kind : PACKAGE, type : org.mikeneck.annotation, name : annotation
  enclosingElements  :
    class : com.sun.tools.javac.code.Symbol.MethodSymbol, modifiers [public, abstract], kind : METHOD, type - kind : EXECUTABLE, type : ()boolean, name : isAuthorized
    class : com.sun.tools.javac.code.Symbol.MethodSymbol, modifiers [public, abstract], kind : METHOD, type - kind : EXECUTABLE, type : ()java.lang.String, name : getName
    class : com.sun.tools.javac.code.Symbol.MethodSymbol, modifiers [public, abstract], kind : METHOD, type - kind : EXECUTABLE, type : ()void, name : logout
  annotationMirrors :
====RoundEnvironment#getRootElements====

====Set<? extends TypeElement> annotations====
0 : com.sun.tools.javac.code.Symbol.ClassSymbol
  asType             : javax.inject.Inject
  simpleName         : Inject
    class : com.sun.tools.javac.code.Symbol.ClassSymbol, modifiers [public, abstract], kind : ANNOTATION_TYPE, type - kind : DECLARED, type : javax.inject.Inject, name : Inject
  enclosingElement   : 
    class : com.sun.tools.javac.code.Symbol.PackageSymbol, modifiers [], kind : PACKAGE, type - kind : PACKAGE, type : javax.inject, name : inject
  enclosingElements  :
  annotationMirrors :
    type : java.lang.annotation.Target
    type : java.lang.annotation.Retention
    type : java.lang.annotation.Documented
====Set<? extends TypeElement> annotations====

====RoundEnvironment#getElementsAnnotatedWith====
  javax.inject.Inject
0 : com.sun.tools.javac.code.Symbol.VarSymbol
  asType             : org.mikeneck.annotation.UserService
  simpleName         : service
    class : com.sun.tools.javac.code.Symbol.VarSymbol, modifiers [private], kind : FIELD, type - kind : DECLARED, type : org.mikeneck.annotation.UserService, name : service
  enclosingElement   : 
    class : com.sun.tools.javac.code.Symbol.ClassSymbol, modifiers [public], kind : CLASS, type - kind : DECLARED, type : org.mikeneck.annotation.Login, name : Login
  enclosingElements  :
  annotationMirrors :
    type : javax.inject.Inject
1 : com.sun.tools.javac.code.Symbol.VarSymbol
  asType             : org.mikeneck.annotation.UserService
  simpleName         : service
    class : com.sun.tools.javac.code.Symbol.VarSymbol, modifiers [private], kind : FIELD, type - kind : DECLARED, type : org.mikeneck.annotation.UserService, name : service
  enclosingElement   : 
    class : com.sun.tools.javac.code.Symbol.ClassSymbol, modifiers [public], kind : CLASS, type - kind : DECLARED, type : org.mikeneck.annotation.Logout, name : Logout
  enclosingElements  :
  annotationMirrors :
    type : javax.inject.Inject
    type : javax.inject.Named
====RoundEnvironment#getElementsAnnotatedWith====

UserService.java

package org.mikeneck.annotation;

/**
 * @author mike
 */
public interface UserService {

    public boolean isAuthorized ();

    public String getName ();

    public void logout();
}