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简介

ANTLR是一款强大的语法分析器生成工具，可用于读取，处理，执行和翻译结构化的文本或二进制文件。它被广泛用于工业实践。大数据领域中熟知的hive,presto,spark都使用它来构建sql解析器。Twitter使用ANTLR进行语法分析，每天处理超过20亿次查询。

开发环境搭建

1.安装idea antlr4插件

下载地址：https://plugins.jetbrains.com/plugin/7358-antlr-v4-grammar-plugin/versions

2.生成代码

// Define a grammar called Hellogrammar Hello;r  : 'hello' ID ;         // match keyword hello followed by an identifierID : [a-z]+ ;             // match lower-case identifiersWS : [ \t\r\n]+ -> skip ; // skip spaces, tabs, newlines

配置ANTLR插件并生成响应的代码

代码实现

拷贝HelloBaseVisitor.java，HelloLexer.java，HelloListener.java，HelloParser.java，HelloVisitor.java到项目中

public class HelloVisitorImpl implements HelloVisitor {
       public Object visitR(HelloParser.RContext ctx) {
           return null;    }    public Object visit(ParseTree parseTree) {
           return null;    }    public Object visitChildren(RuleNode ruleNode) {
           return null;    }    public Object visitTerminal(TerminalNode terminalNode) {
           return null;    }    public Object visitErrorNode(ErrorNode errorNode) {
           return null;    }}

HelloVisitorImpl.java

public class HelloMain {
       public static void main(String[] args) {
           CharStream input = CharStreams.fromString("hello\nhaha");        // 实例化词法分析器        HelloLexer lexer=new HelloLexer(input);        CommonTokenStream tokens = new CommonTokenStream(lexer);        // 实例化解析器        HelloParser parser = new HelloParser(tokens);        ParseTree tree = parser.r();        HelloVisitorImpl myHelloVisitor = new HelloVisitorImpl();        myHelloVisitor.visit(tree);        System.out.println("result:"+ tree.toStringTree(parser));    }}

HelloMain.java

   	
    
     org.antlr
    	
    
     antlr4-runtime
    	
    
     4.8-1
    
   

pom.xml中添加antlr4-runtime依赖

运行结果：

"C:\Program Files\Java\jdk1.8.0_192\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2019.1.3\lib\idea_rt.jar=62242:C:\Program Files\JetBrains\IntelliJ IDEA 2019.1.3\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_192\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_192\jre\lib\rt.jar;E:\antlr4\target\classes;E:\repository\org\antlr\antlr4-runtime\4.8-1\antlr4-runtime-4.8-1.jar" cn.aiaudit.hello.HelloMainresult:(r hello haha)Process finished with exit code 0

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