antlr入门指南

文章目录

• 总体流程
• 下载antlr代码生成器
• 写g4文件
• 执行命令
• 添加maven依赖
• 写编译代码
• 测试

总体流程

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5. 测试验证

4. 项目开发与编译

3. 生成 Java 代码

2. 定义语法规则

1. 环境准备

开始

下载 ANTLR Java 生成器antlr-4.13.2-complete.jar

编写 json.g4 文件定义 Lexer 和 Parser 规则

包含: STRING, NUMBER, obj, arr, value 等规则

执行生成命令java -jar … -visitor json.g4

拷贝生成的 Java 文件到源代码包中

添加 Maven 依赖antlr4-runtime 4.9.3

编写 Main.java 编译代码实现 CharStream -> Lexer -> Parser -> Visitor/Print

准备测试数据 test.json

运行 Main 类

输出解析结果

示例输出:("name"="John","friends"={"Tom","Lily"})

下载antlr代码生成器

antlr java下载地址 https://github.com/antlr/antlr4/blob/master/doc/java-target.md

https://www.antlr.org/download/antlr-4.13.2-complete.jar

写g4文件

// 语法名称
grammar JSON;

// 解析器规则 (小写开头)
// 1. 入口规则：匹配任何合法的 JSON 值
json
: value
;

// 2. 定义 JSON 的值类型
value
: STRING # StringLiteral // 字符串
| NUMBER # NumberLiteral // 数字
| obj # JsonObject // 对象
| arr # JsonArray // 数组
| 'true' # TrueLiteral // 布尔值 true
| 'false' # FalseLiteral // 布尔值 false
| 'null' # NullLiteral // null 值
;

// 3. 定义 JSON 对象结构 { key: value, … }
obj
: '{' pair (',' pair)* '}'
| '{' '}' // 空对象
;

// 4. 定义键值对结构
pair
: STRING ':' value
;

// 5. 定义数组结构 [ value, value, … ]
arr
: '[' value (',' value)* ']'
| '[' ']' // 空数组
;

// 6. 词法分析规则 (大写开头)
// 字符串：双引号包围，支持转义字符
STRING
: '"' (ESC | ~["\\\\])* '"'
;

// 数字：支持负数、小数、科学计数法
NUMBER
: '-'? INT ('.' [0-9]+)? EXP?
;

// 跳过空白字符 (空格, 换行, 制表符)
WS
: [ \\t\\n\\r]+ -> skip
;

// 片段规则 (仅供其他词法规则使用，不会单独匹配)
// 转义字符处理
fragment ESC
: '\\\\' ["\\\\/bfnrt]
| UNICODE_ESCAPE
;

// Unicode 转义
fragment UNICODE_ESCAPE
: '\\\\' 'u' HEX HEX HEX HEX
;

// 十六进制字符
fragment HEX
: [0-9a-fA-F]
;

// 整数部分
fragment INT
: '0'
| [1-9] [0-9]*
;

// 科学计数法
fragment EXP
: [Ee] [+-]? [0-9]+
;

执行命令

java -jar .\\antlr-4.13.2-complete.jar -visitor json.g4

然后将获得的java文件拷贝到源代码相应的包中。

添加maven依赖

<dependency>
<groupId>org.antlr</groupId>
<artifactId>antlr4-runtime</artifactId>
<version>4.9.3</version>
</dependency>

写编译代码

package cn.edu.ncepu.antlr;

import org.antlr.v4.runtime.*;
import org.antlr.v4.runtime.tree.ParseTree;

import java.io.IOException;
import java.nio.file.Paths;
import java.util.List;

/**
* 测试
* 2026-03-02
*
* @author 醒过来摸鱼
*/
public class Main {
public static void main(String[] args) throws IOException {

CharStream input = CharStreams.fromPath(Paths.get("antlr-learn/test.json"));
JSONLexer lexEngine = new JSONLexer(input);
CommonTokenStream tokens = new CommonTokenStream(lexEngine);
JSONParser jsonParser = new JSONParser(tokens);
JSONParser.JsonContext json = jsonParser.json();
System.out.println(print(json.value()));
}

private static String print(ParserRuleContext json) {
if (json instanceof JSONParser.StringLiteralContext string) {
return string.STRING().toString();
}

if (json instanceof JSONParser.JsonArrayContext jsonArrayContext) {
return print(jsonArrayContext.arr());
}

if (json instanceof JSONParser.JsonObjectContext jsonObjectContext) {
return print(jsonObjectContext.obj());
}

if (json instanceof JSONParser.PairContext pairContext) {
return pairContext.STRING()+ "=" + print(pairContext.value());
}

if (json instanceof JSONParser.ArrContext arrContext) {
List<JSONParser.ValueContext> value = arrContext.value();
StringBuilder builder = new StringBuilder("{");
boolean first = true;
for (JSONParser.ValueContext valueContext : value) {
String print = print(valueContext);
if (print != null && !print.isBlank()) {
if (first) {
first = false;
} else {
builder.append(",");
}
builder.append(print);
}
}
builder.append("}");
return builder.toString();
}

StringBuilder builder = new StringBuilder("(");
boolean first = true;
for (int i = 0; i < json.getChildCount(); i++) {
ParseTree child = json.getChild(i);
if (child instanceof ParserRuleContext context) {
String print = print(context);
if (print != null && !print.isBlank()) {
if (first) {
first = false;
} else {
builder.append(",");
}
builder.append(print);
}
}
}
builder.append(")");
return builder.toString();

}
}

测试

我使用的测试数据如下：

{
"name": "John",
"friends": ["Tom", "Lily"]
}

测试结果：

("name"="John","friends"={"Tom","Lily"})