腳本之家服務(wù)器常用軟件

快捷導(dǎo)航

Java中Parser的用法

更新時(shí)間：2023年05月25日 10:31:07 作者：web17886480312

這篇文章主要介紹了Java?Parser使用指南,本文通過(guò)實(shí)例代碼給大家介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或工作具有一定的參考借鑒價(jià)值，需要的朋友可以參考下

前言

以下翻譯自官網(wǎng)的書(shū)

入門(mén)-Start

JavaParser Class

用途：把Java源碼轉(zhuǎn)換成 JavaParser定義的Statement對(duì)象

Eg:

Statement expression = JavaParser.parseStatement("int a=0;");

CompilationUnit Class

用途：是一個(gè)完整的類文件的表示
在AST中，你可以把這個(gè)類看成是AST的根節(jié)點(diǎn)

Visitor Classes

用途：用于找到某個(gè)類型的節(jié)點(diǎn)

A Simple Visitor

package com.github.javaparser;
import com.github.javaparser.*;
import com.github.javaparser.ast.*;
import com.github.javaparser.ast.body.ClassOrInterfaceDeclaration;
import com.github.javaparser.ast.body.EnumDeclaration;
import com.github.javaparser.ast.body.MethodDeclaration;
import com.github.javaparser.symbolsolver.JavaSymbolSolver;
import com.github.javaparser.symbolsolver.javaparsermodel.JavaParserFacade;
import com.github.javaparser.symbolsolver.resolution.typesolvers.CombinedTypeSolver;
import com.github.javaparser.symbolsolver.resolution.typesolvers.JavaParserTypeSolver;
import com.github.javaparser.symbolsolver.resolution.typesolvers.ReflectionTypeSolver;
import com.github.javaparser.utils.SourceRoot;
import java.io.File;
public class VoidVisitorStarter {
	private static final String FILE_PATH = "ReversePolishNotation.java";
	public static void main(String[] args) throws Exception {
			CompilationUnit cu = JavaParser.parse(new File(FILE_PATH));
	}
}

上面的parse方法能夠?qū)ILE_PATH所定義的類文件編譯成CompilationUnit（可以理解為AST樹(shù)的根節(jié)點(diǎn)，存有被編譯的源代碼的一切信息），接下來(lái)我們就可以通過(guò)遍歷CompilationUnit來(lái)獲得我們想要得到的信息啦！

Comments

一個(gè)節(jié)點(diǎn)(node)只能有一個(gè)comment
可以在他的comment域中訪問(wèn)

comment的類型

LineComment
BlockComment
JavadocComment

Orphan Comment:
不能歸為AST樹(shù)中的某一個(gè)節(jié)點(diǎn)的Comment

Pretty Printing and Lexical Preservation

Pretty Printing: 打印出格式化的代碼
Lexical Preservation: 原來(lái)的代碼什么樣，現(xiàn)在的代碼就什么樣

Javaparser-Solving Symbols and References

JavaParser開(kāi)發(fā)者教程

Symbol的定義：
Java code中的所有name都可以稱作為symbol

TypeSolver的作用：
確定尋找類的位置

原文：What the hell is a Type Solver It is the object which knows where to look for classes. When processing source code you will typically have references to code that is not yet compiled, but it is just present in other source files. You could also use classes contained in JARs or classes from the Java standard libraries. You have just to tell to your TypeSolver where to look for classes and it will figure it out.

由于在解析symbol的時(shí)候，我們需要知道這個(gè)symbol來(lái)自哪里（i.e. 是類內(nèi)定義的，還是類外定義的…）,因此JavaSymbolSolver有這樣幾種類型去確定類來(lái)自哪里，

簡(jiǎn)單來(lái)說(shuō)下面這些類就是 JavaSymbolSolver查找類的方式

TypeSolver的類型：

類型

功能

JarTypeSolver

在.jar文件中尋找類，我們需要傳入一個(gè).jar文件的位置

JavaParserTypeSolve

在souce file中尋找文件，我們只需傳入根目錄即可

ReflectionTypeSolver

一些類作為語(yǔ)言的一部分被定義，比如 java.lang.Object

MemoryTypeSolver

簡(jiǎn)單地返回我們記錄的文件，多用于測(cè)試

CombinedTypeSolver

將幾個(gè)不同的solver合并成一個(gè)

其他：

類(com.github.javaparser.symbolsolver)

功能

JavaSymbolSolver

創(chuàng)建后插入CompilationUnit可以創(chuàng)建符號(hào)解析
使用方法：ParserConfiguration.setSymbolResolver(SymbolResolver)

Ex1: 獲取變量（引用）的類型

public class GetTypeOfReference {
private static final String FILE_PATH = "src/main/java/org/javaparser/exampl

4 es/chapter5/Bar.java";

public static void main(String[] args) throws FileNotFoundException {
	TypeSolver typeSolver = new CombinedTypeSolver();
	JavaSymbolSolver symbolSolver = new JavaSymbolSolver(typeSolver);
	JavaParser.getStaticConfiguration().setSymbolResolver(symbolSolver);
	CompilationUnit cu = JavaParser.parse(new File(FILE_PATH));
	cu.findAll(AssignExpr.class).forEach(ae -> {
		ResolvedType resolvedType = ae.calculateResolvedType();
		System.out.println(ae.toString() + " is a: " + resolvedType);
	});
}
}

Ex2: 使用absolute name直接解析類型

package com.github.awesomelemon;
import com.github.javaparser.resolution.declarations.ResolvedReferenceTypeDeclaration;
import com.github.javaparser.symbolsolver.model.resolution.TypeSolver;
import com.github.javaparser.symbolsolver.resolution.typesolvers.ReflectionTypeSolver;
public class UsingTypeSolver {
	private static void showReferenceTypeDeclaration(
			ResolvedReferenceTypeDeclaration resolvedReferenceTypeDeclaration) {
		System.out.println(String.format("== %s ==", resolvedReferenceTypeDeclaration.getQualifiedName()));
		System.out.println(" fields:");
		resolvedReferenceTypeDeclaration.getAllFields()
				.forEach(f -> System.out.println(String.format(" %s %s", f.getType(), f.getName())));
		System.out.println(" methods:");
		resolvedReferenceTypeDeclaration.getAllMethods()
				.forEach(m -> System.out.println(String.format(" %s", m.getQualifiedSignature())));
		System.out.println();
	}
	public static void main(String[] args) {
		TypeSolver typeSolver = new ReflectionTypeSolver();
		showReferenceTypeDeclaration(typeSolver.solveType("java.lang.Object"));
		showReferenceTypeDeclaration(typeSolver.solveType("java.lang.String"));
		showReferenceTypeDeclaration(typeSolver.solveType("java.util.List"));
	}
}

作用是返回以下三個(gè)包里面的 symbol是作為field還是method