java annotation processing 自动生成代码

package example;

import java.io.*;
import javax.tools.*;
import java.util.*;
import javax.annotation.processing.*;
import javax.lang.model.*;
import javax.lang.model.element.*;

@SupportedAnnotationTypes(value = { "*" })
@SupportedSourceVersion(SourceVersion.RELEASE_6)
public class ExampleProcessor extends AbstractProcessor {

private Filer filer;

public void init(ProcessingEnvironment env) {
filer = env.getFiler();
}

public boolean process(Set elements, RoundEnvironment env) {
// Discover anything marked with @SuppressWarnings
for (Element element : env
.getElementsAnnotatedWith(SuppressWarnings.class)) {
if (element.getKind() == ElementKind.METHOD) {
// For any methods we find, create an aspect:
String methodName = element.getSimpleName().toString();
String aspectText = "public aspect Advise_" + methodName
+ " {\n" + "  before(): execution(* " + methodName
+ "(..)) {\n" + "    System.out.println(\""
+ methodName + " running\");\n" + "  }\n" + "}\n";
try {
JavaFileObject file = filer.createSourceFile("Advise_"
+ methodName, element);
file.openWriter().append(aspectText).close();
System.out.println("Generated aspect to advise "
+ methodName);
} catch (IOException ioe) {
}
}
}
return true;
}
}