使用Antlr4从Java生成Lexer

Question

使用Antlr4从Java生成Lexer

3

我知道大多数人让Antlr从命令行生成代码，但我想从Java中调用它。我也不能调用Tool类的main方法，因为该类使用了System.exit，这也会退出我的程序。

到目前为止，我尝试过以下方法：

        String g4Content = "My Grammar Content";            

        String[] arg0 = {pathOfG4File, "-package", "mypackage"};

        Tool tool = new Tool(arg0);

        GrammarRootAST ast = tool.parseGrammarFromString(g4Content)
        Grammar grammar = tool.createGrammar(ast);

        tool.process(grammar, true)

I get the following Exception:

java.lang.NoSuchMethodError: org.antlr.v4.parse.BlockSetTransformer.inContext(Ljava/lang/String;)Z
at org.antlr.v4.parse.BlockSetTransformer.setAlt(BlockSetTransformer.java:467)
at org.antlr.v4.parse.BlockSetTransformer.topdown(BlockSetTransformer.java:370)
at org.antlr.v4.parse.BlockSetTransformer.topdown(BlockSetTransformer.java:24)
at org.antlr.runtime.tree.TreeRewriter$2.rule(TreeRewriter.java:108)
at org.antlr.runtime.tree.TreeRewriter.applyOnce(TreeRewriter.java:61)
at org.antlr.runtime.tree.TreeRewriter$1.pre(TreeRewriter.java:92)
at org.antlr.runtime.tree.TreeVisitor.visit(TreeVisitor.java:28)
at org.antlr.runtime.tree.TreeVisitor.visit(TreeVisitor.java:33)
at org.antlr.runtime.tree.TreeVisitor.visit(TreeVisitor.java:33)
at org.antlr.runtime.tree.TreeVisitor.visit(TreeVisitor.java:33)
at org.antlr.runtime.tree.TreeVisitor.visit(TreeVisitor.java:33)
at org.antlr.runtime.tree.TreeRewriter.downup(TreeRewriter.java:95)
at org.antlr.runtime.tree.TreeRewriter.downup(TreeRewriter.java:86)
at org.antlr.v4.tool.GrammarTransformPipeline.reduceBlocksToSets(GrammarTransformPipeline.java:89)
at org.antlr.v4.tool.GrammarTransformPipeline.process(GrammarTransformPipeline.java:78)
at org.antlr.v4.Tool.process(Tool.java:360)
at java.util.Collections$UnmodifiableCollection.forEach(Collections.java:1080)
at de.ustutt.sidewise.editor.generator.BnfModelGenerator.doGenerate(BnfModelGenerator.java:53)
at org.eclipse.xtext.builder.BuilderParticipant.handleChangedContents(BuilderParticipant.java:524)
at org.eclipse.xtext.builder.BuilderParticipant.handleChangedContents(BuilderParticipant.java:513)
at org.eclipse.xtext.builder.BuilderParticipant.doGenerate(BuilderParticipant.java:498)
at org.eclipse.xtext.builder.BuilderParticipant.doBuild(BuilderParticipant.java:263)
at org.eclipse.xtext.builder.BuilderParticipant.build(BuilderParticipant.java:221)
at org.eclipse.xtext.builder.impl.RegistryBuilderParticipant$DeferredBuilderParticipant.build(RegistryBuilderParticipant.java:161)
at org.eclipse.xtext.builder.impl.RegistryBuilderParticipant.build(RegistryBuilderParticipant.java:69)
at org.eclipse.xtext.builder.impl.XtextBuilder.doBuild(XtextBuilder.java:252)
at org.eclipse.xtext.builder.impl.XtextBuilder.fullBuild(XtextBuilder.java:280)
at org.eclipse.xtext.builder.impl.XtextBuilder.build(XtextBuilder.java:117)
at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:734)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:205)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:245)
at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:300)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:303)
at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:359)
at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:382)
at org.eclipse.core.internal.events.AutoBuildJob.doBuild(AutoBuildJob.java:144)
at org.eclipse.core.internal.events.AutoBuildJob.run(AutoBuildJob.java:235)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

- Robin

实际上，我建议使用Maven或类似的构建工具在构建过程中构建您的解析器/词法分析器。 - Sean Patrick Floyd

@SeanPatrickFloyd 感谢您的评论，但这对我来说是不可能的。我动态生成.g4文件，并且必须从该文件生成Lexer。 - Robin

你可以将语法生成过程放在生命周期的早期阶段或者在一个独立的项目中完成，这都是可以的。 - Sean Patrick Floyd

@SeanPatrickFloyd 我需要在运行时完成它。我不确定，在运行时使用Maven或Ant似乎是错误的。难道没有其他解决方案吗？ - Robin

不，你说得对，这对我来说也是错误的。但在运行时生成Lexer也是如此 :-( - Sean Patrick Floyd

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1个回答

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- GRosenberg · Accepted Answer

这是一个已知的工作实现：

private void compileGrammar(IResource resource, IProgressMonitor monitor) {
    if (resource != null && resource instanceof IFile && (resource.getName().endsWith(".g4"))) {
        IFile file = (IFile) resource;

        try {
            String outputDirectory = determineBuildFolder(file).toString();
            Log.info(this, "Building  [file=" + file.getFullPath() + "]");
            Log.info(this, "Output to [dir= " + outputDirectory + "]");
            monitor.worked(1);

            Tool tool = new Tool(new String[] { "-o", outputDirectory });
            tool.removeListeners();
            ErrorListener toolErrs = new ErrorListener();
            tool.addListener(toolErrs);
            monitor.worked(1);

            // Prep and process the grammar file
            String loc = file.getLocation().toPortableString();
            Grammar g = tool.loadGrammar(loc);
            tool.process(g, true);
            monitor.worked(1);

            if (toolErrs.hasErrors()) {
                for (ANTLRMessage err : toolErrs.getErrList()) {
                    Log.error(this, err.toString());
                    AntlrDTCore.getDefault().showConsoleMessage(err.toString(), AntlrDTCore.MSG_ERROR);
                }
            }
            if (toolErrs.hasWarnings()) {
                for (ANTLRMessage warn : toolErrs.getWarnList()) {
                    Log.warn(this, warn.toString());
                    AntlrDTCore.getDefault().showConsoleMessage(warn.toString(), AntlrDTCore.MSG_WARNING);
                }
            }

            postCompileCleanup(file, monitor);
            monitor.worked(1);
        } catch (Exception e) {
            Log.error(this, "Build failed.", e);
        }
    }
}

顺便提一下，看起来你正在使用XText - 在我上次检查时它正在使用修改过的Antlr3实现。