java - 如何从JAVA文件中解析静态级别变量？

Question

我正在尝试从 JAVA 文件中解析静态变量值。但无法解析该变量。

我使用JavaParser来解析代码并获取变量的值。我成功获取了所有其他类级别变量和值，但无法解析静态字段。

Java 文件看起来像...

public class ABC {
    public string variable1 = "Hello How are you?";
    public boolean variable2 = false;
    public static String variable3;
    static{
    variable3 = new String("Want to Fetch this...");
    } 
    //Can't change this file, this is input.
    public static void main(String args[]){
    //....Other Code
    } 
}

我能够解析除“variabl3”之外的所有变量值。 Java文件的代码类似于上面的Java代码，我需要解析“variable3”的值。

我已经完成了下面的代码来解析类级别变量...

import java.util.HashMap;
import java.util.List;

import com.github.javaparser.ast.body.FieldDeclaration;
import com.github.javaparser.ast.body.VariableDeclarator;
import com.github.javaparser.ast.expr.VariableDeclarationExpr;
import com.github.javaparser.ast.visitor.VoidVisitorAdapter;


public class StaticCollector extends 
VoidVisitorAdapter<HashMap<String, String>> {

@Override
public void visit(FieldDeclaration n, HashMap<String, String> arg) {
    // TODO Auto-generated method stub
    List <VariableDeclarator> myVars = n.getVariables();
        for (VariableDeclarator vars: myVars){
            vars.getInitializer().ifPresent(initValue -> System.out.println(initValue.toString()));
            //System.out.println("Variable Name: "+vars.getNameAsString());
            }
}

}

主要方法...

public class Test {
public static void main(String[] args) {

    File file = new File("filePath");
    CompilationUnit compilationUnit = null;
    try {
        compilationUnit = JavaParser.parse(file);
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    HashMap<String, String> collector = new HashMap<String, String>();
    compilationUnit.accept(new StaticCollector(), collector);
} 
}

如何解析“variable3”的值，它是静态的并且在静态 block 内分配值？代码中可能还有其他变量，但我需要找到特定变量值的值(在本例中为 Variable3)。我是做错了什么还是需要添加其他方法，请提出建议。

Answer 1

Inspecting the AST as something that's easily readable, e.g., a DOT (GraphViz) image with PlantUML对解决此类问题有巨大帮助。请参阅this blog on how to generate the DOT as well as other formats .

这是概述，其中突出显示了“variable3”节点(我刚刚在 .dot 输出中搜索了它并添加了填充颜色)。您会看到它出现在两个位置:

放大右侧的节点空间，我们可以看到第二个子树位于InitializerDeclaration下。再往下，它是 AssignExpr 的一部分，其中值是 ObjectCreationExpr:

因此，我调整了您的 Visitor (它是一个内部类，使模块自包含)，您需要重写 visit(InitializerDeclaration n... 方法才能到达您想要的位置:

import com.github.javaparser.StaticJavaParser;
import com.github.javaparser.ast.CompilationUnit;
import com.github.javaparser.ast.body.FieldDeclaration;
import com.github.javaparser.ast.body.InitializerDeclaration;
import com.github.javaparser.ast.body.VariableDeclarator;
import com.github.javaparser.ast.stmt.Statement;
import com.github.javaparser.ast.visitor.VoidVisitorAdapter;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.HashMap;
import java.util.List;

public class Test {
    public static void main(String[] args) {

        File file = new File("src/main/java/ABC.java");
        CompilationUnit compilationUnit = null;
        try {
            compilationUnit = StaticJavaParser.parse(file);
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        HashMap<String, String> collector = new HashMap<String, String>();
        compilationUnit.accept(new StaticCollector(), collector);
    }

    private static class StaticCollector extends
            VoidVisitorAdapter<HashMap<String, String>> {
        @Override
        public void visit(FieldDeclaration n, HashMap<String, String> arg) {
            List<VariableDeclarator> myVars = n.getVariables();
            for (VariableDeclarator vars: myVars){
                vars.getInitializer().ifPresent(initValue -> System.out.println(initValue.toString()));
                //System.out.println("Variable Name: "+vars.getNameAsString());
            }
        }
        @Override
        public void visit(InitializerDeclaration n, HashMap<String, String> arg) {
            List<Statement> myStatements = n.getBody().getStatements();
            for (Statement s: myStatements) {
                s.ifExpressionStmt(expressionStmt -> expressionStmt.getExpression()
                        .ifAssignExpr(assignExpr -> System.out.println(assignExpr.getValue())));
            }
        }
    }
}

下面的输出还显示了静态 block 中 variable3 的初始化:

"Hello How are you?"
false
new String("Want to Fetch this...")