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---
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icon: edit
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date: 2023-02-17
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category:
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- Java
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headerDepth: 5
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---
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# java 动态执行代码，可以从数据库·拉代码执行的方式例子
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```DynamicJavaCompilerUtil.java```
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```java
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import javax.tools.JavaCompiler;
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import javax.tools.ToolProvider;
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import java.io.File;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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import java.lang.reflect.InvocationTargetException;
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import java.lang.reflect.Method;
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import java.net.URL;
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import java.net.URLClassLoader;
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import java.util.Arrays;
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import java.util.stream.Collectors;
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public class DynamicJavaCompilerUtil {
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static String tmpPath = "./tmp";
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public static void Test() throws IOException {
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String code = new String("public class T4{ " +
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"static void print(String a){ " +
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"System.out.println(\"Hello world! \"+ a);" +
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"}" +
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"static void print(){ " +
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"System.out.println(\"Hello world! \");" +
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"}" +
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"static void print(Integer a,String b){ " +
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"System.out.println(\"Hello world! \"+a+b);" +
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"}" +
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"}");
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CompilerToRun(code, "T4", "print", 1, " 2");
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}
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/*
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* @param Code 代码字符串
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* @param ClassName 类名
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* @param MethodName 需要执行的方法名
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* @param MethodParam 需要执行的方法的参数
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*/
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public static void CompilerToRun(String Code, String ClassName, String MethodName, Object... MethodParam) throws IOException {
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isDirExists(new File(tmpPath));
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File file = new File(tmpPath + "/" + ClassName + ".java");
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RandomAccessFile accessFile = null;
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try {
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accessFile = new RandomAccessFile(file, "rw");
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accessFile.write(Code.getBytes());
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JavaCompiler compiler = ToolProvider.getSystemJavaCompiler(); //调用动态编译的工具
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int result = compiler.run(null, null, null, tmpPath + "/" + ClassName + ".java"); //进行动态编译，并返回结果
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if (result != 0) {
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throw new RuntimeException("编译失败");
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}
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//通过反射方法动态执行
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//1、首先构建文件的目录url地址，
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URL[] urls = new URL[]{new URL("file:" + tmpPath + "/")};
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//2、使用URLClassLoader对象的loadClass方法加载对应类
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URLClassLoader loder = new URLClassLoader(urls);
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//3、获取所加载类的方法
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Class clazz = loder.loadClass(ClassName);
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Class[] MethodParamClass = Arrays.asList(MethodParam).stream().map(Object::getClass).collect(Collectors.toList()).toArray(new Class[]{});
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// 4、传入方法所需的参数通过invoke运行方法
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Method method = clazz.getDeclaredMethod(MethodName, MethodParamClass);
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method.setAccessible(true);
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method.invoke(null, MethodParam); //当类型为String[]时，需要(Object)new String[] {}初始化
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} catch (IOException e) {
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throw new RuntimeException(e);
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} catch (ClassNotFoundException e) {
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throw new RuntimeException(e);
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} catch (InvocationTargetException e) {
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throw new RuntimeException(e);
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} catch (NoSuchMethodException e) {
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throw new RuntimeException(e);
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} catch (IllegalAccessException e) {
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throw new RuntimeException(e);
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} finally {
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accessFile.close();
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deleteFile(new File(tmpPath));
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}
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}
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private static void isDirExists(File file) {
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if (!file.exists()) {
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file.mkdir();
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}
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}
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private static Boolean deleteFile(File file) {
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//判断文件不为null或文件目录存在
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if (file == null || !file.exists()) {
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System.out.println("文件删除失败,请检查文件是否存在以及文件路径是否正确");
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return false;
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}
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//获取目录下子文件
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File[] files = file.listFiles();
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//遍历该目录下的文件对象
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for (File f : files) {
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//判断子目录是否存在子目录,如果是文件则删除
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if (f.isDirectory()) {
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//递归删除目录下的文件
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deleteFile(f);
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} else {
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//文件删除
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f.delete();
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//打印文件名
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System.out.println("文件名：" + f.getName());
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}
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}
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//文件夹删除
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file.delete();
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System.out.println("目录名：" + file.getName());
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return true;
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}
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}
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``` |