`OAL` 直譯器實現

OAL 直譯器是基於 Antlr4 實現的，我們先來了解下 Antlr4

`Antlr4` 基本介紹

`Antlr4` 使用案例

參考Antlr4的使用簡介這篇文章，我們實現了一個簡單的案例：antlr案例：簡單的計算器，下面來講講這個案例。

首先，裝好ANTLR v4(IDEA外掛)外掛，這個之後驗證語法樹的時候會用到。

在 pom.xml 中配置 antlr4 的依賴和外掛

<dependency>

  <groupId>org.antlr</groupId>

  <artifactId>antlr4-runtime</artifactId>

  <version>4.7.1</version>

</dependency>

<plugin>

  <groupId>org.antlr</groupId>

  <artifactId>antlr4-maven-plugin</artifactId>

  <version>${antlr.version}</version>

  <executions>

    <execution>

      <id>antlr</id>

      <goals>

        <goal>antlr4</goal>

      </goals>

    </execution>

  </executions>

</plugin>

在 src/main/antlr4/com/switchvov/antlr/demo/calc 目錄下新增一個 Calc.g4 檔案

grammar Calc;   //名稱需要和檔名一致

root : expr EOF;   //解決問題: no viable alternative at input '<EOF>'

expr

    : expr '+' expr     #add   //標籤會生成對應訪問方法方便我們實現呼叫邏輯編寫

    | expr '-' expr     #sub

    | INT               #int

    ;

INT : [0-9]+                   //定義整數

    ;

WS : [ \r\n\t]+ -> skip      //跳過空白類字元

   ;

執行一下： mvn compile -Dmaven.test.skip=true ，在 target/generated-sources/antlr4 會生成相應的 Java 程式碼。

使用方式預設是監聽器模式，也可以配置成訪問者模式。

監聽器模式：主要藉助了 ParseTreeWalker 這樣一個類,相當於是一個 hook ，每經過一個樹的節點,便會觸發對應節點的方法。好處就算是比較方便,但是靈活性不夠,不能夠自主性的呼叫任意節點進行使用。

訪問者模式：將每個資料的節點型別高度抽象出來夠,根據你傳入的上下文型別來判斷你想要訪問的是哪個節點,觸發對應的方法

PS：結論，簡單語法監聽器模式就可以了，如果語法比較靈活可以考慮使用訪問者模式。

antlr4

├── Calc.tokens

├── CalcLexer.tokens

└── com

    └── switchvov

        └── antlr

            └── demo

                └── calc

                    ├── Calc.interp

                    ├── CalcBaseListener.java # 監聽模式下生成的監聽器基類，實現類監聽器介面，通過繼承該類可以實現相應的功能

                    ├── CalcLexer.interp

                    ├── CalcLexer.java  # 詞法解析器

                    ├── CalcListener.java # 監聽模式下生成的監聽器介面

                    └── CalcParser.java # 語法解析器

繼承 com.switchvov.antlr.demo.calc.CalcBaseListener ，實現計算器相應功能

package com.switchvov.antlr.demo.calc;

import java.util.ArrayDeque;

import java.util.Deque;

/**

 * @author switch

 * @since 2021/6/30

 */

public class CalcExecuteListener extends CalcBaseListener {

    Deque<Integer> queue = new ArrayDeque<>(16);

    @Override

    public void exitInt(CalcParser.IntContext ctx) {

        queue.add(Integer.parseInt(ctx.INT().getText()));

    }

    @Override

    public void exitAdd(CalcParser.AddContext ctx) {

        int r = queue.pop();

        int l = queue.pop();

        queue.add(l + r);

    }

    @Override

    public void exitSub(CalcParser.SubContext ctx) {

        int r = queue.pop();

        int l = queue.pop();

        queue.add(l - r);

    }

    public int result() {

        return queue.pop();

    }

}

測試一下

package com.switchvov.antlr.demo.calc;

import org.antlr.v4.runtime.CharStreams;

import org.antlr.v4.runtime.CodePointCharStream;

import org.antlr.v4.runtime.CommonTokenStream;

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

import org.antlr.v4.runtime.tree.ParseTreeWalker;

import org.junit.Test;

/**

 * @author switch

 * @since 2021/6/30

 */

public class CalcTest {

    public static int exec(String input) {

        // 讀入字串

        CodePointCharStream cs = CharStreams.fromString(input);

        // 詞法解析

        CalcLexer lexer = new CalcLexer(cs);

        CommonTokenStream tokens = new CommonTokenStream(lexer);

        // 語法解析

        CalcParser parser = new CalcParser(tokens);

        // 監聽器觸發獲取執行結果

        ParseTree tree = parser.expr();

        ParseTreeWalker walker = new ParseTreeWalker();

        CalcExecuteListener listener = new CalcExecuteListener();

        walker.walk(listener, tree);

        return listener.result();

    }

    @Test

    public void testCalc() {

        String input = "1+2";

        // 輸出結果：3

        System.out.println(exec(input));

    }

}

`Antlr4 IDEA` 外掛使用

在 Calc.g4 語法定義檔案中，滑鼠右擊可以選擇 Test Rule root ，然後在 ANTLR Preview 的輸入框中填入 1 + 2 就可以校驗語法檔案是否 OK ，並且也可以看到相應的語法樹

`Antlr4` 在 `Skywalking` 的應用

通過“ Antlr4 基本介紹”一節，基本上對 Antlr4 使用有了個大概的認識。下面來看看 Skywalking 中 Antlr4 是如何使用的。

詞法定義

在 oap-server/oal-grammar/src/main/antlr4/org/apache/skywalking/oal/rt/grammar/OALLexer.g4 檔案中，我們能看到 OAL 的詞法定義

// Observability Analysis Language lexer

lexer grammar OALLexer;

@Header {package org.apache.skywalking.oal.rt.grammar;}

// Keywords

FROM: 'from';

FILTER: 'filter';

DISABLE: 'disable';

SRC_ALL: 'All';

SRC_SERVICE: 'Service';

SRC_SERVICE_INSTANCE: 'ServiceInstance';

SRC_ENDPOINT: 'Endpoint';

SRC_SERVICE_RELATION: 'ServiceRelation';

SRC_SERVICE_INSTANCE_RELATION: 'ServiceInstanceRelation';

SRC_ENDPOINT_RELATION: 'EndpointRelation';

SRC_SERVICE_INSTANCE_JVM_CPU: 'ServiceInstanceJVMCPU';

SRC_SERVICE_INSTANCE_JVM_MEMORY: 'ServiceInstanceJVMMemory';

SRC_SERVICE_INSTANCE_JVM_MEMORY_POOL: 'ServiceInstanceJVMMemoryPool';

SRC_SERVICE_INSTANCE_JVM_GC: 'ServiceInstanceJVMGC';

SRC_SERVICE_INSTANCE_JVM_THREAD: 'ServiceInstanceJVMThread';

SRC_SERVICE_INSTANCE_JVM_CLASS:'ServiceInstanceJVMClass';

SRC_DATABASE_ACCESS: 'DatabaseAccess';

SRC_SERVICE_INSTANCE_CLR_CPU: 'ServiceInstanceCLRCPU';

SRC_SERVICE_INSTANCE_CLR_GC: 'ServiceInstanceCLRGC';

SRC_SERVICE_INSTANCE_CLR_THREAD: 'ServiceInstanceCLRThread';

SRC_ENVOY_INSTANCE_METRIC: 'EnvoyInstanceMetric';

// Browser keywords

SRC_BROWSER_APP_PERF: 'BrowserAppPerf';

SRC_BROWSER_APP_PAGE_PERF: 'BrowserAppPagePerf';

SRC_BROWSER_APP_SINGLE_VERSION_PERF: 'BrowserAppSingleVersionPerf';

SRC_BROWSER_APP_TRAFFIC: 'BrowserAppTraffic';

SRC_BROWSER_APP_PAGE_TRAFFIC: 'BrowserAppPageTraffic';

SRC_BROWSER_APP_SINGLE_VERSION_TRAFFIC: 'BrowserAppSingleVersionTraffic';

// Constructors symbols

DOT:                                 '.';

LR_BRACKET:                          '(';

RR_BRACKET:                          ')';

LS_BRACKET:                          '[';

RS_BRACKET:                          ']';

COMMA:                               ',';

SEMI:                                ';';

EQUAL:                               '=';

DUALEQUALS:                          '==';

ALL:                                 '*';

GREATER:                             '>';

LESS:                                '<';

GREATER_EQUAL:                       '>=';

LESS_EQUAL:                          '<=';

NOT_EQUAL:                           '!=';

LIKE:                                'like';

IN:                                  'in';

CONTAIN:                            'contain';

NOT_CONTAIN:                        'not contain';

// Literals

BOOL_LITERAL:       'true'

            |       'false'

            ;

NUMBER_LITERAL :   Digits+;

CHAR_LITERAL:       '\'' (~['\\\r\n] | EscapeSequence) '\'';

STRING_LITERAL:     '"' (~["\\\r\n] | EscapeSequence)* '"';

DelimitedComment

    : '/*' ( DelimitedComment | . )*? '*/'

      -> channel(HIDDEN)

    ;

LineComment

    : '//' ~[\u000A\u000D]*

      -> channel(HIDDEN)

    ;

SPACE:                               [ \t\r\n]+    -> channel(HIDDEN);

// Identifiers

IDENTIFIER:         Letter LetterOrDigit*;

// Fragment rules

fragment EscapeSequence

    : '\\' [btnfr"'\\]

    | '\\' ([0-3]? [0-7])? [0-7]

    | '\\' 'u'+ HexDigit HexDigit HexDigit HexDigit

    ;

fragment HexDigits

    : HexDigit ((HexDigit | '_')* HexDigit)?

    ;

fragment HexDigit

    : [0-9a-fA-F]

    ;

fragment Digits

    : [0-9] ([0-9_]* [0-9])?

    ;

fragment LetterOrDigit

    : Letter

    | [0-9]

    ;

fragment Letter

    : [a-zA-Z$_] // these are the "java letters" below 0x7F

    | ~[\u0000-\u007F\uD800-\uDBFF] // covers all characters above 0x7F which are not a surrogate

    | [\uD800-\uDBFF] [\uDC00-\uDFFF] // covers UTF-16 surrogate pairs encodings for U+10000 to U+10FFFF

    ;

語法定義

在 oap-server/oal-grammar/src/main/antlr4/org/apache/skywalking/oal/rt/grammar/OALParser.g4 檔案中，我們能看到 OAL 的語法定義

parser grammar OALParser;

@Header {package org.apache.skywalking.oal.rt.grammar;}

options { tokenVocab=OALLexer; }

// Top Level Description

root

    : (aggregationStatement | disableStatement)*

    ;

aggregationStatement

    : variable (SPACE)? EQUAL (SPACE)? metricStatement DelimitedComment? LineComment? (SEMI|EOF)

    ;

disableStatement

    : DISABLE LR_BRACKET disableSource RR_BRACKET DelimitedComment? LineComment? (SEMI|EOF)

    ;

metricStatement

    : FROM LR_BRACKET source (sourceAttributeStmt+) RR_BRACKET (filterStatement+)? DOT aggregateFunction

    ;

filterStatement

    : DOT FILTER LR_BRACKET filterExpression RR_BRACKET

    ;

filterExpression

    : expression

    ;

source

    : SRC_ALL | SRC_SERVICE | SRC_DATABASE_ACCESS | SRC_SERVICE_INSTANCE | SRC_ENDPOINT |

      SRC_SERVICE_RELATION | SRC_SERVICE_INSTANCE_RELATION | SRC_ENDPOINT_RELATION |

      SRC_SERVICE_INSTANCE_JVM_CPU | SRC_SERVICE_INSTANCE_JVM_MEMORY | SRC_SERVICE_INSTANCE_JVM_MEMORY_POOL | SRC_SERVICE_INSTANCE_JVM_GC | SRC_SERVICE_INSTANCE_JVM_THREAD | SRC_SERVICE_INSTANCE_JVM_CLASS |// JVM source of service instance

      SRC_SERVICE_INSTANCE_CLR_CPU | SRC_SERVICE_INSTANCE_CLR_GC | SRC_SERVICE_INSTANCE_CLR_THREAD |

      SRC_ENVOY_INSTANCE_METRIC |

      SRC_BROWSER_APP_PERF | SRC_BROWSER_APP_PAGE_PERF | SRC_BROWSER_APP_SINGLE_VERSION_PERF |

      SRC_BROWSER_APP_TRAFFIC | SRC_BROWSER_APP_PAGE_TRAFFIC | SRC_BROWSER_APP_SINGLE_VERSION_TRAFFIC

    ;

disableSource

    : IDENTIFIER

    ;

sourceAttributeStmt

    : DOT sourceAttribute

    ;

sourceAttribute

    : IDENTIFIER | ALL

    ;

variable

    : IDENTIFIER

    ;

aggregateFunction

    : functionName LR_BRACKET ((funcParamExpression (COMMA funcParamExpression)?) | (literalExpression (COMMA literalExpression)?))? RR_BRACKET

    ;

functionName

    : IDENTIFIER

    ;

funcParamExpression

    : expression

    ;

literalExpression

    : BOOL_LITERAL | NUMBER_LITERAL | IDENTIFIER

    ;

expression

    : booleanMatch | stringMatch | greaterMatch | lessMatch | greaterEqualMatch | lessEqualMatch | notEqualMatch | booleanNotEqualMatch | likeMatch | inMatch | containMatch | notContainMatch

    ;

containMatch

    : conditionAttributeStmt CONTAIN stringConditionValue

    ;

notContainMatch

    : conditionAttributeStmt NOT_CONTAIN stringConditionValue

    ;

booleanMatch

    : conditionAttributeStmt DUALEQUALS booleanConditionValue

    ;

stringMatch

    :  conditionAttributeStmt DUALEQUALS (stringConditionValue | enumConditionValue)

    ;

greaterMatch

    :  conditionAttributeStmt GREATER numberConditionValue

    ;

lessMatch

    :  conditionAttributeStmt LESS numberConditionValue

    ;

greaterEqualMatch

    :  conditionAttributeStmt GREATER_EQUAL numberConditionValue

    ;

lessEqualMatch

    :  conditionAttributeStmt LESS_EQUAL numberConditionValue

    ;

booleanNotEqualMatch

    :  conditionAttributeStmt NOT_EQUAL booleanConditionValue

    ;

notEqualMatch

    :  conditionAttributeStmt NOT_EQUAL (numberConditionValue | stringConditionValue | enumConditionValue)

    ;

likeMatch

    :  conditionAttributeStmt LIKE stringConditionValue

    ;

inMatch

    :  conditionAttributeStmt IN multiConditionValue

    ;

multiConditionValue

    : LS_BRACKET (numberConditionValue ((COMMA numberConditionValue)*) | stringConditionValue ((COMMA stringConditionValue)*) | enumConditionValue ((COMMA enumConditionValue)*)) RS_BRACKET

    ;

conditionAttributeStmt

    : conditionAttribute ((DOT conditionAttribute)*)

    ;

conditionAttribute

    : IDENTIFIER

    ;

booleanConditionValue

    : BOOL_LITERAL

    ;

stringConditionValue

    : STRING_LITERAL

    ;

enumConditionValue

    : IDENTIFIER DOT IDENTIFIER

    ;

numberConditionValue

    : NUMBER_LITERAL

    ;

`Antlr4` 生成 `Java` 程式碼

在 oap-server/oal-grammar 下執行 mvn compile -Dmaven.test.skip=true 會在 oap-server/oal-grammar/target/generated-sources/antlr4 目錄下生成相應的 Java 程式碼

.

├── OALLexer.tokens

├── OALParser.tokens

└── org

    └── apache

        └── skywalking

            └── oal

                └── rt

                    └── grammar

                        ├── OALLexer.interp

                        ├── OALLexer.java # 詞法解析器

                        ├── OALParser.interp

                        ├── OALParser.java # 語法解析器

                        ├── OALParserBaseListener.java # 監聽器

                        └── OALParserListener.java

在 `Skywalking` 的使用

通過“ Antlr4 使用案例”一節，可以知道 Antlr4 有兩種功能實現方式：監聽器或者訪問器。

通過“ Antlr4 生成 Java 程式碼”一節，知道 Skywalking 使用的是監聽器模式。

Skywalking 關於 OAL 的相應的程式碼都在 oap-server/oal-rt 模組中。

org.apache.skywalking.oal.rt.grammar.OALParserBaseListener 的繼承類座標是 org.apache.skywalking.oal.rt.parser.OALListener

package org.apache.skywalking.oal.rt.parser;

import java.util.Arrays;

import java.util.List;

import org.antlr.v4.runtime.misc.NotNull;

import org.apache.skywalking.oal.rt.grammar.OALParser;

import org.apache.skywalking.oal.rt.grammar.OALParserBaseListener;

import org.apache.skywalking.oap.server.core.source.DefaultScopeDefine;

public class OALListener extends OALParserBaseListener {

    private List<AnalysisResult> results;

    private AnalysisResult current;

    private DisableCollection collection;

    private ConditionExpression conditionExpression;

    private final String sourcePackage;

    public OALListener(OALScripts scripts, String sourcePackage) {

        this.results = scripts.getMetricsStmts();

        this.collection = scripts.getDisableCollection();

        this.sourcePackage = sourcePackage;

    }

    @Override

    public void enterAggregationStatement(@NotNull OALParser.AggregationStatementContext ctx) {

        current = new AnalysisResult();

    }

    @Override

    public void exitAggregationStatement(@NotNull OALParser.AggregationStatementContext ctx) {

        DeepAnalysis deepAnalysis = new DeepAnalysis();

        results.add(deepAnalysis.analysis(current));

        current = null;

    }

    @Override

    public void enterSource(OALParser.SourceContext ctx) {

        current.setSourceName(ctx.getText());

        current.setSourceScopeId(DefaultScopeDefine.valueOf(metricsNameFormat(ctx.getText())));

    }

    @Override

    public void enterSourceAttribute(OALParser.SourceAttributeContext ctx) {

        current.getSourceAttribute().add(ctx.getText());

    }

    @Override

    public void enterVariable(OALParser.VariableContext ctx) {

    }

    @Override

    public void exitVariable(OALParser.VariableContext ctx) {

        current.setVarName(ctx.getText());

        current.setMetricsName(metricsNameFormat(ctx.getText()));

        current.setTableName(ctx.getText().toLowerCase());

    }

    @Override

    public void enterFunctionName(OALParser.FunctionNameContext ctx) {

        current.setAggregationFunctionName(ctx.getText());

    }

    @Override

    public void enterFilterStatement(OALParser.FilterStatementContext ctx) {

        conditionExpression = new ConditionExpression();

    }

    @Override

    public void exitFilterStatement(OALParser.FilterStatementContext ctx) {

        current.addFilterExpressionsParserResult(conditionExpression);

        conditionExpression = null;

    }

    @Override

    public void enterFuncParamExpression(OALParser.FuncParamExpressionContext ctx) {

        conditionExpression = new ConditionExpression();

    }

    @Override

    public void exitFuncParamExpression(OALParser.FuncParamExpressionContext ctx) {

        current.addFuncConditionExpression(conditionExpression);

        conditionExpression = null;

    }

    /////////////

    // Expression

    ////////////

    @Override

    public void enterConditionAttribute(OALParser.ConditionAttributeContext ctx) {

        conditionExpression.getAttributes().add(ctx.getText());

    }

    @Override

    public void enterBooleanMatch(OALParser.BooleanMatchContext ctx) {

        conditionExpression.setExpressionType("booleanMatch");

    }

    @Override

    public void enterStringMatch(OALParser.StringMatchContext ctx) {

        conditionExpression.setExpressionType("stringMatch");

    }

    @Override

    public void enterGreaterMatch(OALParser.GreaterMatchContext ctx) {

        conditionExpression.setExpressionType("greaterMatch");

    }

    @Override

    public void enterGreaterEqualMatch(OALParser.GreaterEqualMatchContext ctx) {

        conditionExpression.setExpressionType("greaterEqualMatch");

    }

    @Override

    public void enterLessMatch(OALParser.LessMatchContext ctx) {

        conditionExpression.setExpressionType("lessMatch");

    }

    @Override

    public void enterLessEqualMatch(OALParser.LessEqualMatchContext ctx) {

        conditionExpression.setExpressionType("lessEqualMatch");

    }

    @Override

    public void enterNotEqualMatch(final OALParser.NotEqualMatchContext ctx) {

        conditionExpression.setExpressionType("notEqualMatch");

    }

    @Override

    public void enterBooleanNotEqualMatch(final OALParser.BooleanNotEqualMatchContext ctx) {

        conditionExpression.setExpressionType("booleanNotEqualMatch");

    }

    @Override

    public void enterLikeMatch(final OALParser.LikeMatchContext ctx) {

        conditionExpression.setExpressionType("likeMatch");

    }

    @Override

    public void enterContainMatch(final OALParser.ContainMatchContext ctx) {

        conditionExpression.setExpressionType("containMatch");

    }

    @Override

    public void enterNotContainMatch(final OALParser.NotContainMatchContext ctx) {

        conditionExpression.setExpressionType("notContainMatch");

    }

    @Override

    public void enterInMatch(final OALParser.InMatchContext ctx) {

        conditionExpression.setExpressionType("inMatch");

    }

    @Override

    public void enterMultiConditionValue(final OALParser.MultiConditionValueContext ctx) {

        conditionExpression.enterMultiConditionValue();

    }

    @Override

    public void exitMultiConditionValue(final OALParser.MultiConditionValueContext ctx) {

        conditionExpression.exitMultiConditionValue();

    }

    @Override

    public void enterBooleanConditionValue(OALParser.BooleanConditionValueContext ctx) {

        enterConditionValue(ctx.getText());

    }

    @Override

    public void enterStringConditionValue(OALParser.StringConditionValueContext ctx) {

        enterConditionValue(ctx.getText());

    }

    @Override

    public void enterEnumConditionValue(OALParser.EnumConditionValueContext ctx) {

        enterConditionValue(ctx.getText());

    }

    @Override

    public void enterNumberConditionValue(OALParser.NumberConditionValueContext ctx) {

        conditionExpression.isNumber();

        enterConditionValue(ctx.getText());

    }

    private void enterConditionValue(String value) {

        if (value.split("\\.").length == 2 && !value.startsWith("\"")) {

            // Value is an enum.

            value = sourcePackage + value;

        }

        conditionExpression.addValue(value);

    }

    /////////////

    // Expression end.

    ////////////

    @Override

    public void enterLiteralExpression(OALParser.LiteralExpressionContext ctx) {

        if (ctx.IDENTIFIER() == null) {

            current.addFuncArg(new Argument(EntryMethod.LITERAL_TYPE, Arrays.asList(ctx.getText())));

            return;

        }

        current.addFuncArg(new Argument(EntryMethod.IDENTIFIER_TYPE, Arrays.asList(ctx.getText().split("\\."))));

    }

    private String metricsNameFormat(String source) {

        source = firstLetterUpper(source);

        int idx;

        while ((idx = source.indexOf("_")) > -1) {

            source = source.substring(0, idx) + firstLetterUpper(source.substring(idx + 1));

        }

        return source;

    }

    /**

     * Disable source

     */

    @Override

    public void enterDisableSource(OALParser.DisableSourceContext ctx) {

        collection.add(ctx.getText());

    }

    private String firstLetterUpper(String source) {

        return source.substring(0, 1).toUpperCase() + source.substring(1);

    }

}

簡單來說，就是通過監聽器封裝了個 org.apache.skywalking.oal.rt.parser.OALScripts 物件

package org.apache.skywalking.oal.rt.parser;

import java.util.LinkedList;

import java.util.List;

import lombok.Getter;

@Getter

public class OALScripts {

    // 解析出來的分析結果集合

    private List<AnalysisResult> metricsStmts;

    // 禁用表示式集合

    private DisableCollection disableCollection;

    public OALScripts() {

        metricsStmts = new LinkedList<>();

        disableCollection = new DisableCollection();

    }

}

org.apache.skywalking.oal.rt.parser.ScriptParser 類讀取 oal 檔案，使用 Antlr 生成的 Java 類進行解析

package org.apache.skywalking.oal.rt.parser;

import java.io.IOException;

import java.io.Reader;

import org.antlr.v4.runtime.CharStreams;

import org.antlr.v4.runtime.CommonTokenStream;

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

import org.antlr.v4.runtime.tree.ParseTreeWalker;

import org.apache.skywalking.oal.rt.grammar.OALLexer;

import org.apache.skywalking.oal.rt.grammar.OALParser;

/**

 * Script reader and parser.

 */

public class ScriptParser {

    private OALLexer lexer;

    private String sourcePackage;

    private ScriptParser() {

    }

    public static ScriptParser createFromFile(Reader scriptReader, String sourcePackage) throws IOException {

        ScriptParser parser = new ScriptParser();

        parser.lexer = new OALLexer(CharStreams.fromReader(scriptReader));

        parser.sourcePackage = sourcePackage;

        return parser;

    }

    public static ScriptParser createFromScriptText(String script, String sourcePackage) throws IOException {

        ScriptParser parser = new ScriptParser();

        parser.lexer = new OALLexer(CharStreams.fromString(script));

        parser.sourcePackage = sourcePackage;

        return parser;

    }

    public OALScripts parse() throws IOException {

        OALScripts scripts = new OALScripts();

        CommonTokenStream tokens = new CommonTokenStream(lexer);

        OALParser parser = new OALParser(tokens);

        ParseTree tree = parser.root();

        ParseTreeWalker walker = new ParseTreeWalker();

        walker.walk(new OALListener(scripts, sourcePackage), tree);

        return scripts;

    }

    public void close() {

    }

}

參考文件

分享並記錄所學所見

Skywalking-07：OAL原理——直譯器實現

Skywalking-07：OAL原理——直譯器實現

`OAL` 直譯器實現

`Antlr4` 基本介紹

`Antlr4` 使用案例

`Antlr4 IDEA` 外掛使用

`Antlr4` 在 `Skywalking` 的應用

詞法定義

語法定義

`Antlr4` 生成 `Java` 程式碼

在 `Skywalking` 的使用

參考文件

Skywalking-07：OAL原理——直譯器實現

Skywalking-07：OAL原理——直譯器實現

OAL 直譯器實現

Antlr4 基本介紹

Antlr4 使用案例

Antlr4 IDEA 外掛使用

Antlr4 在 Skywalking 的應用

詞法定義

語法定義

Antlr4 生成 Java 程式碼

在 Skywalking 的使用

參考文件

最新文章

`OAL` 直譯器實現

`Antlr4` 基本介紹

`Antlr4` 使用案例

`Antlr4 IDEA` 外掛使用

`Antlr4` 在 `Skywalking` 的應用

`Antlr4` 生成 `Java` 程式碼

在 `Skywalking` 的使用