Eclipse IDE Java 注解处理器 AnnotationMirror 示例

Here's a practical Eclipse IDE Java Annotation Processing demo using AnnotationMirror:

Project Structure:

AnnotationMirrorDemo/
├── src/
│   ├── annotations/
│   │   └── DataClass.java
│   ├── processors/
│   │   └── DataProcessor.java
│   └── demo/
│       └── User.java
├── resources/
│   └── META-INF/
│       └── services/
│           └── javax.annotation.processing.Processor
└── pom.xml (for Maven) or .classpath

Step 1: Create the Annotation

// File: src/annotations/DataClass.java
package annotations;
import java.lang.annotation.*;
@Retention(RetentionPolicy.SOURCE) // Only needed at compile time
@Target(ElementType.TYPE) // Can only be applied to classes
public @interface DataClass {
    String tableName() default "";
    boolean persistent() default true;
    String[] tags() default {};
    Class<?> repository() default Void.class;
}

Step 2: Create the Annotation Processor

// File: src/processors/DataProcessor.java
package processors;
import annotations.DataClass;
import javax.annotation.processing.*;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.*;
import javax.lang.model.type.DeclaredType;
import javax.lang.model.util.*;
import javax.tools.Diagnostic;
import javax.tools.JavaFileObject;
import java.io.Writer;
import java.util.*;
import java.util.stream.Collectors;

@SupportedAnnotationTypes("annotations.DataClass")
@SupportedSourceVersion(SourceVersion.RELEASE_11)
public class DataProcessor extends AbstractProcessor {
    private ProcessingEnvironment processingEnv;
    private Elements elementUtils;
    private Types typeUtils;
    private Filer filer;
    private Messager messager;

    @Override
    public synchronized void init(ProcessingEnvironment processingEnv) {
        super.init(processingEnv);
        this.processingEnv = processingEnv;
        this.elementUtils = processingEnv.getElementUtils();
        this.typeUtils = processingEnv.getTypeUtils();
        this.filer = processingEnv.getFiler();
        this.messager = processingEnv.getMessager();
        messager.printMessage(Diagnostic.Kind.NOTE, "DataProcessor initialized for @DataClass");
    }

    @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        for (TypeElement annotation : annotations) {
            Set<? extends Element> annotatedElements = roundEnv.getElementsAnnotatedWith(annotation);
            for (Element element : annotatedElements) {
                if (element.getKind() == ElementKind.CLASS) {
                    processDataClass((TypeElement) element);
                }
            }
        }
        return true; // Claim the annotation
    }

    private void processDataClass(TypeElement classElement) {
        try