測試代碼:

package dynamicproxy;public class DynamicProxy implements IHelloWorld {IHelloWorld helloWorld;public DynamicProxy(IHelloWorld helloWorld){this.helloWorld = helloWorld;}public void print(){System.out.println("Before Hello World!");helloWorld.print();System.out.println("After Hello World!");} }

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package dynamicproxy;import java.io.File; import java.io.FileWriter; import java.io.IOException; import java.io.Serializable; import java.io.Writer; import java.lang.reflect.Constructor; import java.net.URL; import java.net.URLClassLoader;import javax.tools.JavaCompiler; import javax.tools.JavaCompiler.CompilationTask; import javax.tools.JavaFileObject; import javax.tools.StandardJavaFileManager; import javax.tools.ToolProvider;class HelloWorldImp implements IHelloWorld {public void print() {System.out.println("Hello World");} }public class DynamicProxyDemo implements Serializable {private static final long serialVersionUID = 1L;public static void main(String[] arg) throws Exception {Class<?> c = getProxyClass();Constructor<?> constructor = c.getConstructor(IHelloWorld.class);IHelloWorld helloWorldImpl = new HelloWorldImp();IHelloWorld helloWorld = (IHelloWorld) constructor.newInstance(helloWorldImpl);helloWorld.print();}private static String getSourceCode() {String src = "package dynamicproxy;\n\n"+ "public class DynamicProxy implements IHelloWorld\n" + "{\n"+ "\tIHelloWorld helloWorld;\n\n"+ "\tpublic DynamicProxy(IHelloWorld helloWorld)\n" + "\t{\n"+ "\t\tthis.helloWorld = helloWorld;\n" + "\t}\n\n"+ "\tpublic void print()\n" + "\t{\n"+ "\t\tSystem.out.println(\"Before Hello World!\");\n"+ "\t\thelloWorld.print();\n"+ "\t\tSystem.out.println(\"After Hello World!\");\n" + "\t}\n"+ "}";return src;}private static String createJavaFile(String sourceCode) {String fileName = "C:\\Users\\i042416\\git\\JavaTwoPlusTwoEquals5\\src\\dynamicproxy\\DynamicProxy.java";File javaFile = new File(fileName);Writer writer;try {writer = new FileWriter(javaFile);writer.write(sourceCode);writer.close();} catch (IOException e) {e.printStackTrace();}return fileName;}private static void compile(String fileName) {try {JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();StandardJavaFileManager sjfm = compiler.getStandardFileManager(null, null, null);Iterable<? extends JavaFileObject> iter = sjfm.getJavaFileObjects(fileName);CompilationTask ct = compiler.getTask(null, sjfm, null, null, null, iter);ct.call();sjfm.close();} catch (IOException e) {e.printStackTrace();}}private static Class<?> loadClass() {URL[] urls;Class<?> c = null;try {urls = new URL[] { (new URL("file:\\"+ "C:\\Users\\i042416\\git\\JavaTwoPlusTwoEquals5\\src\\")) };URLClassLoader ul = new URLClassLoader(urls);c = ul.loadClass("dynamicproxy.DynamicProxy");System.out.println("Class loaded successfully: " + c.getName());ul.close();} catch (ClassNotFoundException | IOException e) {e.printStackTrace();}return c;}private static Class<?> getProxyClass() {String sourceCode = getSourceCode();String javaFile = createJavaFile(sourceCode);compile(javaFile);return loadClass();} }

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package dynamicproxy;import java.io.File; import java.io.FileWriter; import java.io.Serializable; import java.io.Writer; import java.lang.reflect.Constructor; import java.net.URL; import java.net.URLClassLoader;import javax.tools.JavaCompiler; import javax.tools.JavaCompiler.CompilationTask; import javax.tools.JavaFileObject; import javax.tools.StandardJavaFileManager; import javax.tools.ToolProvider;interface HelloWorld {void print(); }class HelloWorldImpl implements HelloWorld {public void print(){System.out.println("Hello World");} }public class DynamicProxyTest implements Serializable {private static final long serialVersionUID = 1L;private static void test() throws Exception{long start = System.currentTimeMillis();HelloWorld helloWorld = (HelloWorld) newProxyInstance();System.out.println("動態生成代理耗時：" + (System.currentTimeMillis() - start) + "ms");helloWorld.print();System.out.println();}public static void main(String[] arg) throws Exception{test();}public static Object newProxyInstance() throws Exception{String src = "package dynamicproxy;\n\n" + "public class StaticProxy implements HelloWorld\n" + "{\n" + "\tHelloWorld helloWorld;\n\n" + "\tpublic StaticProxy(HelloWorld helloWorld)\n" + "\t{\n" + "\t\tthis.helloWorld = helloWorld;\n" + "\t}\n\n" + "\tpublic void print()\n" + "\t{\n" + "\t\tSystem.out.println(\"Before Hello World!\");\n" + "\t\thelloWorld.print();\n" + "\t\tSystem.out.println(\"After Hello World!\");\n" + "\t}\n" + "}";/** 生成一段Java代碼 */String fileDir = System.getProperty("user.dir");String fileName = "C:\\Users\\i042416\\git\\JavaTwoPlusTwoEquals5\\src\\dynamicproxy\\StaticProxyDemo.java";File javaFile = new File(fileName);Writer writer = new FileWriter(javaFile);writer.write(src);writer.close();JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();StandardJavaFileManager sjfm = compiler.getStandardFileManager(null, null, null);Iterable<? extends JavaFileObject> iter = sjfm.getJavaFileObjects(fileName);CompilationTask ct = compiler.getTask(null, sjfm, null, null, null, iter);ct.call();sjfm.close();URL[] urls = new URL[] {(new URL("file:\\" + "C:\\Users\\i042416\\git\\JavaTwoPlusTwoEquals5\\dynamicproxy\\src"))};URLClassLoader ul = new URLClassLoader(urls);System.out.println("class loader for url");Class<?> c = ul.loadClass("dynamicproxy.StaticProxy");Constructor<?> constructor = c.getConstructor(HelloWorld.class);HelloWorld helloWorldImpl = new HelloWorldImpl();HelloWorld helloWorld = (HelloWorld)constructor.newInstance(helloWorldImpl);File classFile = new File(fileDir + "\\src\\com\\xrq\\proxy\\StaticProxy.class");javaFile.delete();classFile.delete();ul.close();return helloWorld;} }

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package dynamicproxy;public interface IHelloWorld {void print(); }

總結

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