我正在使用 jdk.compiler 模块和启用了预览功能的 Java 15 编写 Java 编译器插件。根据 Oracle 的说法，Java 9 中引入的 jdk.compiler 模块包含我们过去在 java 8 的 tools.jar 中拥有的所有 API，除了 com.sun.tools.javac.tree 包。我想要做的是找到所有用我的注释注释的类并获取 value() 属性，在这种情况下为 Class<?> 类型。
插件代码：
public class ExtensionMethodPlugin implements Plugin{
@Override
public String getName() {
return "ExtensionMethodPlugin";
}
@Override
public void init(JavacTask task, String... args) {
task.addTaskListener(new TaskListener() {
@Override
public void started(TaskEvent event) {
}
@Override
public void finished(TaskEvent event) {
if (event.getKind() != TaskEvent.Kind.PARSE) {
return;
}
event.getCompilationUnit().accept(new TreeScanner<Void, Void>() {
@Override
public Void visitClass(ClassTree node, Void aVoid) {
var trees = Trees.instance(task);
var targetClass = InstrumentationUtils.findExtensionTargetForClass(node, trees, event.getCompilationUnit());
if (targetClass.isEmpty()) {
return super.visitClass(node, aVoid);
}
var methods = node
.getMembers()
.stream()
.filter(e -> e instanceof MethodTree)
.map(e -> (MethodTree) e)
.filter(tree -> tree.getReturnType() != null)
.filter(e -> InstrumentationUtils.shouldInstrumentMethod(e, targetClass.get()))
.collect(Collectors.toList());
throw new RuntimeException("Not implemented");
}
}, null);
}
});
}
}
InstrumentationUtils 的代码：
@UtilityClass
public class InstrumentationUtils {
public Optional<Class<?>> findExtensionTargetForClass(ClassTree node, Trees trees, CompilationUnitTree tree) {
return node
.getModifiers()
.getAnnotations()
.stream()
.filter(a -> Extension.class.getSimpleName().equals(a.getAnnotationType().toString()))
.findFirst()
.map(e -> InstrumentationUtils.findConstantTargetClassInAnnotationTree(e, trees, tree));
}
private Class<?> findConstantTargetClassInAnnotationTree(AnnotationTree tree, Trees trees, CompilationUnitTree compilationUnitTree) {
return tree
.getArguments()
.stream()
.filter(entry -> entry.getKind() == Tree.Kind.ASSIGNMENT)
.findFirst()
.map(e -> (AssignmentTree) e)
.map(e -> classForName(e, trees, compilationUnitTree))
.orElseThrow(() -> new RuntimeException("Cannot compile: Missing constant class target in annotation!"));
}
private Class<?> classForName(AssignmentTree tree, Trees trees, CompilationUnitTree compilationUnitTree){
//Don't know how to move from here
}
}
注释的代码：
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.SOURCE)
public @interface Extension {
Class<?> value();
}
我发现的唯一解决方案涉及使用 JCTree 类，但正如我之前所说，这些不再可用。我知道我可以很容易地强制在 jdk.compiler 模块中导出该包，但我更愿意找到更好的方法。我尝试使用 TreeScanner，但这无济于事：
tree.accept(new TreeScanner<Class<?>, Void>() {
// b.class
@Override
public Class<?> visitAssignment(AssignmentTree node, Void unused) {
return node.getExpression().accept(new TreeScanner<Class<?>, Void>(){
//.class
@Override
public Class<?> visitMemberSelect(MemberSelectTree node, Void unused) {
return node.getExpression().accept(new TreeScanner<Class<?>, Void>(){
// class ???
@Override
public Class<?> visitIdentifier(IdentifierTree node, Void unused) {
trees.printMessage(Diagnostic.Kind.WARNING, node.getName(), tree, compilationUnitTree);
return super.visitIdentifier(node, unused);
}
}, null);
}
}, null);
}
}, null);
提前致谢！