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| 1 | +package org.springframework.lock.processor; |
| 2 | + |
| 3 | +import com.google.auto.service.AutoService; |
| 4 | +import com.sun.source.tree.Tree; |
| 5 | +import com.sun.tools.javac.api.JavacTrees; |
| 6 | +import com.sun.tools.javac.code.Flags; |
| 7 | +import com.sun.tools.javac.code.TypeTag; |
| 8 | +import com.sun.tools.javac.processing.JavacProcessingEnvironment; |
| 9 | +import com.sun.tools.javac.tree.JCTree; |
| 10 | +import com.sun.tools.javac.tree.TreeMaker; |
| 11 | +import com.sun.tools.javac.tree.TreeTranslator; |
| 12 | +import com.sun.tools.javac.util.Context; |
| 13 | +import com.sun.tools.javac.util.Names; |
| 14 | + |
| 15 | +import javax.annotation.processing.*; |
| 16 | +import javax.lang.model.SourceVersion; |
| 17 | +import javax.lang.model.element.Element; |
| 18 | +import javax.lang.model.element.ExecutableElement; |
| 19 | +import javax.lang.model.element.TypeElement; |
| 20 | +import javax.lang.model.type.TypeKind; |
| 21 | +import javax.tools.Diagnostic; |
| 22 | +import java.util.HashSet; |
| 23 | +import java.util.Set; |
| 24 | + |
| 25 | +import static com.sun.tools.javac.util.List.of; |
| 26 | +import static com.sun.tools.javac.tree.JCTree.*; |
| 27 | + |
| 28 | +/** |
| 29 | + * 乐观锁的处理器，用于将乐观锁编译进类成员 |
| 30 | + */ |
| 31 | +@SupportedAnnotationTypes("org.springframework.lock.annotation.OptimisticLock") |
| 32 | +@SupportedSourceVersion(SourceVersion.RELEASE_8) |
| 33 | +@AutoService(Processor.class) |
| 34 | +public class OptimisticLockProcessor extends AbstractProcessor { |
| 35 | + |
| 36 | + /** |
| 37 | + * 编译时输入日志的 |
| 38 | + */ |
| 39 | + private Messager messager; |
| 40 | + |
| 41 | + /** |
| 42 | + * 待处理的抽象语法树 |
| 43 | + */ |
| 44 | + private JavacTrees javacTrees; |
| 45 | + |
| 46 | + /** |
| 47 | + * 封装了AST节点的一些方法 |
| 48 | + */ |
| 49 | + private TreeMaker treeMaker; |
| 50 | + |
| 51 | + /** |
| 52 | + * 提供了创建标识符的方法 |
| 53 | + */ |
| 54 | + private Names names; |
| 55 | + |
| 56 | + /** |
| 57 | + * 初始化一些成员变量，方便下面使用 |
| 58 | + * @param processingEnv 环境 |
| 59 | + */ |
| 60 | + @Override |
| 61 | + public synchronized void init(ProcessingEnvironment processingEnv) { |
| 62 | + super.init(processingEnv); |
| 63 | + this.messager = processingEnv.getMessager(); |
| 64 | + this.javacTrees = JavacTrees.instance(processingEnv); |
| 65 | + Context context = ((JavacProcessingEnvironment) processingEnv).getContext(); |
| 66 | + this.treeMaker = TreeMaker.instance(context); |
| 67 | + this.names = Names.instance(context); |
| 68 | + } |
| 69 | + |
| 70 | + /** |
| 71 | + * 将乐观锁编译进类的成员变量 |
| 72 | + * @param annotations 注解 |
| 73 | + * @param roundEnv 有关当前和以前round的环境信息，可以从这里拿到可以处理的所有元素信息 |
| 74 | + * @return true——则这些注解已声明并且不要求后续Processor处理它们；false——则这些注解未声明并且可能要求后续 Processor处理它们。 |
| 75 | + */ |
| 76 | + @Override |
| 77 | + public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) { |
| 78 | + for (TypeElement annotation : annotations) { |
| 79 | + Set<TypeElement> cls = new HashSet<TypeElement>(); |
| 80 | + Set<? extends Element> elements = roundEnv.getElementsAnnotatedWith(annotation); |
| 81 | + // 找到都有哪些类里面的方法用到了这个注解 |
| 82 | + for (Element element : elements) { |
| 83 | + ExecutableElement method = (ExecutableElement) element; |
| 84 | + TypeElement clz = (TypeElement) method.getEnclosingElement(); |
| 85 | + messager.printMessage(Diagnostic.Kind.NOTE, "发现需要包含注解" + annotation.getQualifiedName() + "的类" + clz.getQualifiedName()); |
| 86 | + cls.add(clz); |
| 87 | + } |
| 88 | + for (TypeElement clz : cls) { |
| 89 | + JCTree tree = javacTrees.getTree(clz); |
| 90 | + tree.accept(new TreeTranslator() { |
| 91 | + @Override |
| 92 | + public void visitClassDef(JCTree.JCClassDecl jcClassDecl) { |
| 93 | + // 在抽象树中找出所有的变量 |
| 94 | + boolean foundOptimisticLock = false; |
| 95 | + for (JCTree jcTree : jcClassDecl.defs) { |
| 96 | + if (jcTree.getKind().equals(Tree.Kind.VARIABLE)) { |
| 97 | + JCVariableDecl var = (JCTree.JCVariableDecl) jcTree; |
| 98 | + if ("$opLock".equals("" + var.name)) { |
| 99 | + // 找到了类中的乐观锁，不修改语法树 |
| 100 | + messager.printMessage(Diagnostic.Kind.NOTE, "已发现" + clz.getQualifiedName() + "类中的乐观锁" + var.name); |
| 101 | + foundOptimisticLock = true; |
| 102 | + break; |
| 103 | + } |
| 104 | + } |
| 105 | + } |
| 106 | + // 修改语法树 |
| 107 | + if (!foundOptimisticLock) { |
| 108 | + messager.printMessage(Diagnostic.Kind.NOTE, "将为类" + clz.getQualifiedName() + "动态生成乐观锁"); |
| 109 | + JCVariableDecl lock = makeOptimisticLock(clz); |
| 110 | + jcClassDecl.defs = jcClassDecl.defs.append(lock); |
| 111 | + } |
| 112 | + super.visitClassDef(jcClassDecl); |
| 113 | + } |
| 114 | + }); |
| 115 | + } |
| 116 | + break; |
| 117 | + } |
| 118 | + return Boolean.TRUE; |
| 119 | + } |
| 120 | + |
| 121 | + /** |
| 122 | + * 制作乐观锁 |
| 123 | + * @return 变量声明 |
| 124 | + */ |
| 125 | + private JCVariableDecl makeOptimisticLock(TypeElement clz){ |
| 126 | + // 导入包 |
| 127 | + JCCompilationUnit imports = (JCCompilationUnit) this.javacTrees.getPath(clz).getCompilationUnit(); |
| 128 | + imports.defs = imports.defs.append(this.treeMaker.Import(this.treeMaker.Select(this.treeMaker.Ident(names.fromString("java.util.concurrent.atomic")), this.names.fromString("AtomicBoolean")), false)); |
| 129 | + // 声明变量 |
| 130 | + JCModifiers modifiers = this.treeMaker.Modifiers(Flags.PRIVATE + Flags.FINAL); |
| 131 | + JCVariableDecl var = this.treeMaker.VarDef( |
| 132 | + modifiers, |
| 133 | + this.names.fromString("$opLock"), |
| 134 | + this.memberAccess("java.util.concurrent.atomic.AtomicBoolean"), |
| 135 | + this.treeMaker.NewClass(null, of(memberAccess("java.lang.Boolean")), treeMaker.Ident(names.fromString("AtomicBoolean")), of(this.treeMaker.Literal(true)), null) |
| 136 | + ); |
| 137 | + return var; |
| 138 | + } |
| 139 | + |
| 140 | + /** |
| 141 | + * 制作声明类型 |
| 142 | + * @param components 声明类型的带包类名 |
| 143 | + * @return 声明类型 |
| 144 | + */ |
| 145 | + private JCExpression memberAccess(String components) { |
| 146 | + String[] componentArray = components.split("\\."); |
| 147 | + JCExpression expr = treeMaker.Ident(this.names.fromString(componentArray[0])); |
| 148 | + for (int i = 1; i < componentArray.length; i++) { |
| 149 | + expr = treeMaker.Select(expr, this.names.fromString(componentArray[i])); |
| 150 | + } |
| 151 | + return expr; |
| 152 | + } |
| 153 | +} |
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