一般注意事项
如果您已经在使用Lombok，则可以添加自定义Lombok转换批注和处理程序。
使用
@Target(FIELD)
和定义存在注释@Retention(SOURCE)
创建一个处理程序
@ProviderFor(JavacAnnotationHandler.class)
public class HandleExists extends JavacAnnotationHandler
{ …`
处理您的注释。处理程序类包必须以
lombok.前缀开头。如果除了javac之外还需要支持Eclipse等，则需要编写更多的处理程序来扩展适当的框架类。
- 在处理程序中，重写/实现是
handle()
通过AST操纵生成所需代码的方法。
您可以将@Getter实现作为示例：
注释：
Getter.java
处理程序：
HandleGetter.java
您还可以查看其他注释和处理程序的源，以了解如何生成特定代码。
您需要添加对Lombok（JDK tools.jar）的依赖。
一些资源：
在龙目岛，皮克与一帮自龙目注释的源项目，特别是FluentSetter.java，HandleFluentSetter.java / FluentSetterHandler.java
自定义转换概述
具有说明的简单注释示例。
注意，这里有几点要考虑
- 这是一堆要编写和维护的重要代码。如果您打算使用注释5至6次，那是不值得的。
- 您可能需要通过lombok升级来更改注释处理器的实现。
- lombok所依赖的编译器中的漏洞也可能被关闭（然后整个Lombok项目将发生巨大变化或不复存在；在这种情况下，如果您广泛使用Lombok，即使是@Getter，也将遇到更严重的问题）。
没有Lombok的更复杂的替代方案是使用标准注释处理进行代码生成，但是AFAIK，您不能更改原始类，而必须生成/使用扩展它们的类（除非您将使用与 Lombok
相同的后门或手段到CGLib或ASM之类的代码操作）。
龙目岛的例子
以下是一些用于创建自定义Lombok批注的工作代码，我将其称为 @Contains 。
它只是Javac实现，没有Eclipse等。我想为Eclipse或其他IDE创建类似的处理程序并不难。
它将生成 fieldName Contains（）成员方法，该成员方法委派给 fieldName .contains（）。
请注意，该代码只是快速而肮脏（但可以正常工作）的示例。对于生产级注释，您将需要处理许多边界条件，检查正确的类型，处理Lombok配置等，因为可以在lombok或lombok-
pg库源代码中看到它。
样本用法
SomeEnity.java
@Getter@Setterpublic class SomeEntity { @NonNull @Contains private Collection<String> fieldOne = new ArrayList<>(); @NonNull @Contains private Collection<String> fieldTwo = new ArrayList<>();}SomeEntityTest.java
public class SomeEntityTest { @Test public void test() { SomeEntity entity = new SomeEntity(); Collection<String> test1 = Arrays.asList(new String[] { "1", "2" }); entity.setFieldOne(test1); assertSame(test1, entity.getFieldOne()); Collection<String> test2 = new HashSet<String>(Arrays.asList(new String[] { "3", "4" })); entity.setFieldTwo(test2); assertSame(test2, entity.getFieldTwo()); assertTrue(entity.fieldoneContains("1")); assertTrue(entity.fieldoneContains("2")); assertFalse(entity.fieldoneContains("3")); assertFalse(entity.fieldoneContains("4")); assertFalse(entity.fieldTwoContains("1")); assertFalse(entity.fieldTwoContains("2")); assertTrue(entity.fieldTwoContains("3")); assertTrue(entity.fieldTwoContains("4")); try { entity.setFieldOne(null); fail("exception expected"); } catch (Exception ex) { } try { entity.setFieldTwo(null); fail("exception expected"); } catch (Exception ex) { } }}注释实现
包含.java
@Target({ElementType.FIELD})@Retention(RetentionPolicy.SOURCE)public @interface Contains { Class<?>[] types() default {}; Class<?>[] excludes() default {};}HandleContains.java
@ProviderFor(JavacAnnotationHandler.class) @HandlerPriority(65536) @ResolutionResetNeeded public class HandleContains extends JavacAnnotationHandler<Contains> { @Override public void handle(AnnotationValues<Contains> annotation, JCAnnotation ast, JavacNode annotationNode) { try { JavacNode node = annotationNode.up(); if (node.getKind() != Kind.FIELD) { annotationNode.addError("@Contains is allowed only on fields"); return; } Name delegateName = annotationNode.toname(node.getName()); JavacResolution reso = new JavacResolution(annotationNode.getContext()); JCTree member = node.get(); if (member.type == null) { reso.resolveClassMember(node); } Type delegateType = member.type; if (delegateType instanceof ClassType) { ClassType ct = (ClassType) delegateType; //TODO validate that this field is a collection type // if(!Collection) // annotationNode.addError("@Contains can only be used on collections"); final String methodName = "contains"; MethodSig methodSig = getMethodBinding(methodName, ct, annotationNode.getTypesUtil()); if (methodSig == null) throw new Exception("no method " + methodName + " in " + ct.tsym.name); JCMethodDecl methodDecl = createDelegateMethod(methodSig, annotationNode, delegateName); injectMethod(node.up(), methodDecl); } else { annotationNode.addError("@Contains can only use concrete class types"); return; } } catch (Exception ex) { //ex.printStackTrace(); annotationNode.addError("@Contains unexpected error: " + ex.getMessage()); } } public JCMethodDecl createDelegateMethod(MethodSig sig, JavacNode annotation, Name delegateName) throws TypeNotConvertibleException { JavacTreeMaker maker = annotation.getTreeMaker(); com.sun.tools.javac.util.List<JCAnnotation> annotations; if (sig.isDeprecated) { annotations = com.sun.tools.javac.util.List.of(maker.Annotation(genJavaLangTypeRef(annotation, "Deprecated"), com.sun.tools.javac.util.List.<JCexpression>nil())); } else { annotations = com.sun.tools.javac.util.List.nil(); } JCModifiers mods = maker.Modifiers(PUBLIC, annotations); JCexpression returnType = JavacResolution.typeToJCTree((Type) sig.type.getReturnType(), annotation.getAst(), true); boolean useReturn = sig.type.getReturnType().getKind() != TypeKind.VOID; ListBuffer<JCVariableDecl> params = sig.type.getParameterTypes().isEmpty() ? null : new ListBuffer<JCVariableDecl>(); ListBuffer<JCexpression> args = sig.type.getParameterTypes().isEmpty() ? null : new ListBuffer<JCexpression>(); ListBuffer<JCexpression> thrown = sig.type.getThrownTypes().isEmpty() ? null : new ListBuffer<JCexpression>(); ListBuffer<JCTypeParameter> typeParams = sig.type.getTypeVariables().isEmpty() ? null : new ListBuffer<JCTypeParameter>(); ListBuffer<JCexpression> typeArgs = sig.type.getTypeVariables().isEmpty() ? null : new ListBuffer<JCexpression>(); Types types = Types.instance(annotation.getContext()); for (TypeMirror param : sig.type.getTypeVariables()) { Name name = ((TypeVar) param).tsym.name; ListBuffer<JCexpression> bounds = new ListBuffer<JCexpression>(); for (Type type : types.getBounds((TypeVar) param)) { bounds.append(JavacResolution.typeToJCTree(type, annotation.getAst(), true)); } typeParams.append(maker.TypeParameter(name, bounds.toList())); typeArgs.append(maker.Ident(name)); } for (TypeMirror ex : sig.type.getThrownTypes()) { thrown.append(JavacResolution.typeToJCTree((Type) ex, annotation.getAst(), true)); } int idx = 0; String[] paramNames = sig.getParameterNames(); boolean varargs = sig.elem.isVarArgs(); for (TypeMirror param : sig.type.getParameterTypes()) { long flags = JavacHandlerUtil.addFinalIfNeeded(Flags.PARAMETER, annotation.getContext()); JCModifiers paramMods = maker.Modifiers(flags); Name name = annotation.toname(paramNames[idx++]); if (varargs && idx == paramNames.length) { paramMods.flags |= VARARGS; } params.append(maker.VarDef(paramMods, name, JavacResolution.typeToJCTree((Type) param, annotation.getAst(), true), null)); args.append(maker.Ident(name)); } JCexpression accessor = maker.Select(maker.Ident(annotation.toname("this")), delegateName); JCexpression delegateCall = maker.Apply(toList(typeArgs), maker.Select(accessor, sig.name), toList(args)); JCStatement body = useReturn ? maker.Return(delegateCall) : maker.Exec(delegateCall); JCBlock bodyBlock = maker.Block(0, com.sun.tools.javac.util.List.of(body)); StringBuilder generatedMethodName = new StringBuilder(delegateName); generatedMethodName.append(sig.name.toString()); generatedMethodName.setCharAt(delegateName.length(), Character.toUpperCase(generatedMethodName.charAt(delegateName.length()))); return recursiveSetGeneratedBy(maker.MethodDef(mods, annotation.toname(generatedMethodName.toString()), returnType, toList(typeParams), toList(params), toList(thrown), bodyBlock, null), annotation.get(), annotation.getContext()); } public static <T> com.sun.tools.javac.util.List<T> toList(ListBuffer<T> collection) { return collection == null ? com.sun.tools.javac.util.List.<T>nil() : collection.toList(); } public static class MethodSig { final Name name; final ExecutableType type; final boolean isDeprecated; final ExecutableElement elem; MethodSig(Name name, ExecutableType type, boolean isDeprecated, ExecutableElement elem) { this.name = name; this.type = type; this.isDeprecated = isDeprecated; this.elem = elem; } String[] getParameterNames() { List<? extends VariableElement> paramList = elem.getParameters(); String[] paramNames = new String[paramList.size()]; for (int i = 0; i < paramNames.length; i++) { paramNames[i] = paramList.get(i).getSimpleName().toString(); } return paramNames; } @Override public String toString() { return (isDeprecated ? "@Deprecated " : "") + name + " " + type; } } public MethodSig getMethodBinding(String name, ClassType ct, JavacTypes types) { MethodSig result = null; TypeSymbol tsym = ct.asElement(); if (tsym == null) throw new IllegalArgumentException("no class"); for (Symbol member : tsym.getEnclosedElements()) { if (member.getKind() != ElementKind.METHOD || !name.equals(member.name.toString())) { continue; } if (member.isStatic()) continue; if (member.isConstructor()) continue; ExecutableElement exElem = (ExecutableElement) member; if (!exElem.getModifiers().contains(Modifier.PUBLIC)) continue; ExecutableType methodType = (ExecutableType) types.asMemberOf(ct, member); boolean isDeprecated = (member.flags() & DEPRECATED) != 0; result = new MethodSig(member.name, methodType, isDeprecated, exElem); } if (result == null) { if (ct.supertype_field instanceof ClassType) { result = getMethodBinding(name, (ClassType) ct.supertype_field, types); } if (result == null) { if (ct.interfaces_field != null) { for (Type iface : ct.interfaces_field) { if (iface instanceof ClassType) { result = getMethodBinding(name, (ClassType) iface, types); if (result != null) { break; } } } } } } return result; }}
