使用cglib动态为Java类添加方法
cglib（Code Generation Library）是一个强大的，高性能，高质量的Code生成类库，它可以在运行期扩展Java类与实现Java接口，Spring、Hibernate等很多著名的框架都使用了它。
http://cglib.sourceforge.net/
public class CGLibExample { @SuppressWarnings("unchecked") public static void main(String[] args) { // 定义一个参数是字符串类型的setCreatedAt方法 InterfaceMaker im = new InterfaceMaker(); im.add(new Signature("setCreatedAt", Type.VOID_TYPE, new Type[] { Type.getType(String.class) }), null); Class myInterface = im.create(); Enhancer enhancer = new Enhancer(); enhancer.setSuperclass(ExampleBean.class); enhancer.setInterfaces(new Class[] { myInterface }); enhancer.setCallback(new MethodInterceptor() { public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable { ExampleBean bean = (ExampleBean) obj; // 调用字符串类型的setCreatedAt方法时，转换成Date型后调用Setter if (method.getName().startsWith("setCreatedAt") && args[0] != null && args[0] instanceof String) { SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd"); Date date = null; try { date = sdf.parse((String) args[0]); } catch (final Exception e) { /* nop */ } bean.setCreatedAt(date); return null; } return proxy.invokeSuper(obj, args); } }); // 生成一个Bean ExampleBean bean = (ExampleBean) enhancer.create(); bean.setId(999); try { Method method = bean.getClass().getMethod("setCreatedAt", new Class[] {String.class}); method.invoke(bean, new Object[]{"20100531"}); } catch (final Exception e) { e.printStackTrace(); } System.out.printf("id : [%d] createdAt : [%s]\n", bean.getId(), bean.getCreatedAt()); }}class ExampleBean implements Serializable { private static final long serialVersionUID = -8121418052209958014L; private int id; private Date createdAt; public int getId() { return id; } public void setId(int id) { this.id = id; } public Date getCreatedAt() { return createdAt; } public void setCreatedAt(Date createdAt) { this.createdAt = createdAt; }}