JavaParser使用指南

Myth丶恋晨 2021-09-28 12:34 598阅读 0赞

### JavaParser使用指南 ###

*  前言
 *  入门-Start
 *   *  JavaParser Class
     *  CompilationUnit Class
     *  Visitor Classes
     *  A Simple Visitor
 *  Comments
 *  Pretty Printing and Lexical Preservation
 *  Javaparser-Solving Symbols and References
 *   *  Ex1: 获取变量（引用）的类型
     *  Ex2: 使用absolute name直接解析类型
     *  Ex3 Resolving a Type in a context
     *  Ex4 Resolving method calls
     *  Ex5 Using the Combined Type Solver
     *  Ex6 Using the MemoryTypeSolver
 *  JavaSymbolSolver

# 前言 #

以下翻译自官网的书

# 入门-Start #

## JavaParser Class ##

用途：把Java源码转换成 JavaParser定义的Statement对象

Eg:

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

## CompilationUnit Class ##

用途：是一个完整的类文件的表示  
在AST中，你可以把这个类看成是AST的根节点

## Visitor Classes ##

用途：用于找到某个类型的节点

## 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方法能够将FILE\_PATH所定义的类文件编译成CompilationUnit（可以理解为AST树的根节点，存有被编译的源代码的一切信息），接下来我们就可以通过遍历CompilationUnit来获得我们想要得到的信息啦！

# Comments #

一个节点(node)只能有一个comment  
可以在他的comment域中访问

**comment的类型**

*  LineComment
 *  BlockComment
 *  JavadocComment

**Orphan Comment**:  
不能归为AST树中的某一个节点的Comment

# Pretty Printing and Lexical Preservation #

Pretty Printing: 打印出格式化的代码  
Lexical Preservation: 原来的代码什么样，现在的代码就什么样

# Javaparser-Solving Symbols and References #

[JavaParser开发者教程][JavaParser]

**Symbol的定义**：  
Java code中的所有name都可以称作为symbol

**TypeSolver的作用**：  
确定寻找类的位置

> 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的时候，我们需要知道这个symbol来自哪里（i.e. 是类内定义的，还是类外定义的…）,因此JavaSymbolSolver有这样几种类型去确定类来自哪里，

简单来说下面这些类就是 **JavaSymbolSolver查找类的方式**

**TypeSolver的类型**：

<table> 
 <thead> 
  <tr> 
   <th>类型</th> 
   <th>功能</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>JarTypeSolver</td> 
   <td>在.jar文件中寻找类，我们需要传入一个.jar文件的位置</td> 
  </tr> 
  <tr> 
   <td>JavaParserTypeSolve</td> 
   <td>在souce file中寻找文件，我们只需传入根目录即可</td> 
  </tr> 
  <tr> 
   <td>ReflectionTypeSolver</td> 
   <td>一些类作为语言的一部分被定义，比如 java.lang.Object</td> 
  </tr> 
  <tr> 
   <td>MemoryTypeSolver</td> 
   <td>简单地返回我们记录的文件，多用于测试</td> 
  </tr> 
  <tr> 
   <td>CombinedTypeSolver</td> 
   <td>将几个不同的solver合并成一个</td> 
  </tr> 
 </tbody> 
</table>

其他：

<table> 
 <thead> 
  <tr> 
   <th>类(com.github.javaparser.symbolsolver)</th> 
   <th>功能</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>JavaSymbolSolver</td> 
   <td>创建后插入CompilationUnit可以创建符号解析<br>使用方法：ParserConfiguration.setSymbolResolver(SymbolResolver)</td> 
  </tr> 
 </tbody> 
</table>

## Ex1: 获取变量（引用）的类型 ##

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直接解析类型 ##

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"));
    	}
    }

作用是返回以下三个包里面的 symbol是作为field还是method

*  java.lang.Object
 *  java.lang.String
 *  java.util.List

## Ex3 Resolving a Type in a context ##

这个例子应用如下的场景：  
解析一个变量的类型是来自哪里

懒得截代码了，大家自己找官网的pdf看吧

## Ex4 Resolving method calls ##

可以知道一个method调用的对应的函数签名(signature)

## Ex5 Using the Combined Type Solver ##

使用结合的type solver

## Ex6 Using the MemoryTypeSolver ##

# JavaSymbolSolver #

JavaSymbolSolver