编译原理

词法解析

// JavaParserpublic JCTree.JCCompilationUnit parseCompilationUnit() {        Token firstToken = token;        JCModifiers mods = null;        boolean consumedToplevelDoc = false;        boolean seenImport = false;        boolean seenPackage = false;        ListBuffer<JCTree> defs = new ListBuffer<>();        if (token.kind == MONKEYS_AT)            mods = modifiersOpt(); // 解析修饰符        if (token.kind == PACKAGE) { // 解析包声明            int packagePos = token.pos;            List<JCAnnotation> annotations = List.nil();            seenPackage = true;            if (mods != null) {                checkNoMods(mods.flags);                annotations = mods.annotations;                mods = null;            }            nextToken();            JCExpression pid = qualident(false);            accept(SEMI);            JCPackageDecl pd = toP(F.at(packagePos).PackageDecl(annotations, pid));            attach(pd, firstToken.comment(CommentStyle.JAVADOC));            consumedToplevelDoc = true;            defs.append(pd);        }        boolean checkForImports = true;        boolean firstTypeDecl = true;        while (token.kind != EOF) {            if (token.pos <= endPosTable.errorEndPos) {                // error recovery                skip(checkForImports, false, false, false);                if (token.kind == EOF)                    break;            }            if (checkForImports && mods == null && token.kind == IMPORT) { // 解析import                seenImport = true;                defs.append(importDeclaration());            } else { // 解析类主体                Comment docComment = token.comment(CommentStyle.JAVADOC); // 类doc注释                if (firstTypeDecl && !seenImport && !seenPackage) {                    docComment = firstToken.comment(CommentStyle.JAVADOC);                    consumedToplevelDoc = true;                }                if (mods != null || token.kind != SEMI)                    mods = modifiersOpt(mods);                if (firstTypeDecl && token.kind == IDENTIFIER) {                    ModuleKind kind = ModuleKind.STRONG; // 模块解析                    if (token.name() == names.open) {                        kind = ModuleKind.OPEN;                        nextToken();                    }                    if (token.kind == IDENTIFIER && token.name() == names.module) {                        if (mods != null) {                            checkNoMods(mods.flags & ~Flags.DEPRECATED);                        }                        defs.append(moduleDecl(mods, kind, docComment));                        consumedToplevelDoc = true;                        break;                    } else if (kind != ModuleKind.STRONG) {                        reportSyntaxError(token.pos, Errors.ExpectedModule);                    }                }                JCTree def = typeDeclaration(mods, docComment);                if (def instanceof JCExpressionStatement)                    def = ((JCExpressionStatement)def).expr;                defs.append(def);                if (def instanceof JCClassDecl)                    checkForImports = false;                mods = null;                firstTypeDecl = false;            }        }        JCTree.JCCompilationUnit toplevel = F.at(firstToken.pos).TopLevel(defs.toList());        if (!consumedToplevelDoc)            attach(toplevel, firstToken.comment(CommentStyle.JAVADOC));        if (defs.isEmpty())            storeEnd(toplevel, S.prevToken().endPos);        if (keepDocComments)            toplevel.docComments = docComments;        if (keepLineMap)            toplevel.lineMap = S.getLineMap();        this.endPosTable.setParser(null); // remove reference to parser        toplevel.endPositions = this.endPosTable;        return toplevel;    }

JavaParser 根据 Java 语言规范来解析.java文件进行词法解析

每调用一次nextToken 就会构造一个Token

语法分析

• 进行package词法分析的时候构建一个节点

JCExpression t = toP(F.at(token.pos).Ident(ident()));

• 进行import词法分析时构造的import语法树

protected JCTree importDeclaration() {    int pos = token.pos;    nextToken();    boolean importStatic = false;    if (token.kind == STATIC) {        importStatic = true;        nextToken();    }    JCExpression pid = toP(F.at(token.pos).Ident(ident()));    do {        int pos1 = token.pos;        accept(DOT);        if (token.kind == STAR) {            pid = to(F.at(pos1).Select(pid, names.asterisk));            nextToken();            break;        } else {            pid = toP(F.at(pos1).Select(pid, ident()));        }    } while (token.kind == DOT);    accept(SEMI);    return toP(F.at(pos).Import(pid, importStatic));}

• 类主体语法树构造

JCTree typeDeclaration(JCModifiers mods, Comment docComment) {    int pos = token.pos;    if (mods == null && token.kind == SEMI) {        nextToken();        return toP(F.at(pos).Skip());    } else {        return classOrRecordOrInterfaceOrEnumDeclaration(modifiersOpt(mods), docComment);    }}

最后会生成一颗完整的语法树

语义分析

打磨语法树

• Enter类

代码生成

• Gen类