https://gitee.com/china-bin/vue-onlinecode
原理： 1.利用java里面有JavaComile 可以实现在程序里面编译允许其他的java代码
步骤： 1.利用JavaComile， 将java代码 编译到内存中 2.从内存中根据类名取出此类 3.通过java反射调用此类的方法
详细Demo代码如下：
import com.haiyang.onlinejava.complier.util.ClassClassLoader; import javax.tools.*; import java.io.ByteArrayOutputStream; import java.io.FileInputStream; import java.io.IOException; import java.lang.reflect.Method; import java.net.URI; import java.nio.ByteBuffer; import java.nio.channels.Channels; import java.nio.channels.FileChannel; import java.nio.channels.WritableByteChannel; import java.util.Arrays; /** * @author: bin * @email: 958615915@qq.com * @create: 2019-08-03 */ public class TestComiles { private String javaSource = "class Solution { " + " public static String sayHello() { return \"hello world\"; } " + "}"; private String javaSource2 = "class Solution { " + " public static String sayHello(int i) { return \"hello world\" + i; } " + "}"; private String className = "Solution"; private String methoName = "sayHello"; // path 是你想把.class 放在哪里的路径， private String path = "C:\\Users\\bin\\Desktop\\java\\"; public void comile() throws Exception { // javqComile 是java程序里的java编译器类 JavaCompiler javaCompiler = ToolProvider.getSystemJavaCompiler(); // StandardJavaFileManager 对象主要负责 // 编译文件对象的创建，编译的参数等等，我们只对它做些基本设置比如编译 CLASSPATH 等。 StandardJavaFileManager standardJavaFileManager = javaCompiler.getStandardFileManager(null, null, null); // JavaFileObject 为类文件上进行操作的工具的文件抽象 StringObject stringObject = new StringObject(className, javaSource2); JavaFileObject javaFileObject = stringObject; // Array Map Set 等都属于Itreable类型 Iterable options = Arrays.asList("-d", path); Iterable<? extends JavaFileObject> files = Arrays.asList(javaFileObject); // 通过一些选项，javafileObject， classPath 来获取JvaComiler.ComilationTask JavaCompiler.CompilationTask task = javaCompiler.getTask(null, standardJavaFileManager, null, options, null, files); // 将Class 在内存中编译 Boolean result = task.call(); // 通过类名 加载class ClassLoader classLoader = new ClassClassLoader(getClass().getClassLoader()); // ClassLoader classLoader = getClass().getClassLoader(); Class cls = classLoader.loadClass(className); // java反射机制 method.setAcessible 设置允许访问 Method method = cls.getMethod(methoName, int.class); method.setAccessible(true); Object[] args = new Object[]{2}; args[0] = 1; Object obj = method.invoke(null, args); System.out.println(obj.toString()); } public static void main(String[] args) { try { new TestComiles().comile(); } catch (Exception e) { e.printStackTrace(); } } private class StringObject extends SimpleJavaFileObject { private String contents = null; public StringObject(String clasName, String contents) throws Exception { super(URI.create("String:///" + clasName + Kind.SOURCE.extension), Kind.SOURCE); this.contents = contents; } @Override public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException { return contents; } } private class ClassClassLoader extends ClassLoader { ClassClassLoader(ClassLoader parent) { super(parent); } @Override protected Class<?> findClass(String name) throws ClassNotFoundException { //这个classLoader的主要方法 String classPath = name.replace(".", "\\") + ".class";//将包转为目录 String classFile = path + classPath;//拼接完整的目录 Class clazz = null; try { byte[] data = getClassFileBytes(classFile); clazz = defineClass(name, data, 0, data.length); if (null == clazz) {//如果在这个类加载器中都不能找到这个类的话，就真的找不到了 } } catch (Exception e) { e.printStackTrace(); } return clazz; } private byte[] getClassFileBytes(String classFile) throws Exception { //采用NIO读取 FileInputStream fis = new FileInputStream(classFile); FileChannel fileC = fis.getChannel(); ByteArrayOutputStream baos = new ByteArrayOutputStream(); WritableByteChannel outC = Channels.newChannel(baos); ByteBuffer buffer = ByteBuffer.allocateDirect(1024); while (true) { int i = fileC.read(buffer); if (i == 0 || i == -1) { break; } buffer.flip(); outC.write(buffer); buffer.clear(); } fis.close(); return baos.toByteArray(); } } }