在Java中动态执行字符串代码的方法小结

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
 
public class DynamicCodeExecution {
    public static void main(String[] args) {
        // 创建 ScriptEngineManager
        ScriptEngineManager manager = new ScriptEngineManager();
        
        // 获取 JavaScript 引擎
        ScriptEngine engine = manager.getEngineByName("JavaScript");
        
        // 要执行的字符串代码
        String code = "var a = 10; var b = 20; a + b;";
        
        try {
            // 执行代码并获取结果
            Object result = engine.eval(code);
            System.out.println("执行结果: " + result);
        } catch (ScriptException e) {
            e.printStackTrace();
        }
    }
}

import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.lang.reflect.Method;
 
public class DynamicCodeExecution {
    public static void main(String[] args) {
        String className = "DynamicClass";
        String methodName = "dynamicMethod";
        
        // 要动态编译和执行的 Java 代码
        String code = """
            public class DynamicClass {
                public static void dynamicMethod() {
                    System.out.println("动态代码执行成功！");
                }
            }
            """;
        
        File sourceFile = new File(className + ".java");
        
        try {
            // 将代码写入文件
            try (FileWriter writer = new FileWriter(sourceFile)) {
                writer.write(code);
            }
            
            // 获取 Java 编译器
            JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
            int result = compiler.run(null, null, null, sourceFile.getPath());
            
            if (result == 0) {
                System.out.println("编译成功");
                
                // 加载并执行编译后的类
                Class<?> dynamicClass = Class.forName(className);
                Method method = dynamicClass.getMethod(methodName);
                method.invoke(null);
            } else {
                System.out.println("编译失败");
            }
        } catch (IOException | ReflectiveOperationException e) {
            e.printStackTrace();
        } finally {
            // 清理生成的文件
            sourceFile.delete();
            new File(className + ".class").delete();
        }
    }
}

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import java.util.Scanner;
 
public class ExpressionCalculator {
    public static void main(String[] args) {
        // 创建 ScriptEngineManager
        ScriptEngineManager manager = new ScriptEngineManager();
        // 获取 JavaScript 引擎
        ScriptEngine engine = manager.getEngineByName("JavaScript");
        
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入表达式（输入 'exit' 退出）：");
 
        while (true) {
            System.out.print("> ");
            String expression = scanner.nextLine();
            
            if ("exit".equalsIgnoreCase(expression)) {
                break;
            }
 
            try {
                // 执行表达式并获取结果
                Object result = engine.eval(expression);
                System.out.println("结果: " + result);
            } catch (ScriptException e) {
                System.out.println("表达式错误: " + e.getMessage());
            }
        }
 
        scanner.close();
    }
}