1.JDK代理
動態的由java提供的api在內存中構建字節碼類對象完成的動態代理.
使用JDK代理方式動態創建對象時,對象需要聲明接口並且實現接口;
1.1聲明接口:
package yzr.dyn_jdk;
public interface IPerson {
void SayHello();
}
package yzr.dyn_jdk;
public class PersonImpl implements IPerson {
private String name;
@Override
public void SayHello() {
System.out.println("Hello "+this.name);
}
public PersonImpl(){}
public PersonImpl(String name){this.name=name;}
}
package yzr.dyn_jdk;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class MyInvocationHandler implements InvocationHandler {
private Object target;
public MyInvocationHandler(){
super();
}
public MyInvocationHandler(Object target){
super();
this.target=target;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args){
Object Result=null;
try {
Result=method.invoke(target, args);
} catch (Exception e) {
e.printStackTrace();
}
return Result;
}
}
package yzr.dyn_jdk;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
public class TestUnit {
public static void main(String[] args) {
IPerson LYF=new PersonImpl("yzr");
InvocationHandler handler=new MyInvocationHandler(LYF);
IPerson LYFProxy = (IPerson)Proxy.newProxyInstance(
LYF.getClass().getClassLoader(),
LYF.getClass().getInterfaces(),
handler);
LYFProxy.SayHello();
}
}
@Override
public Object invoke(Object proxy, Method method, Object[] args){
Object Result=null;
try {
System.out.println("調用方法之前:");
Result=method.invoke(target, args);
System.out.println("調用方法之後:");
} catch (Exception e) {
e.printStackTrace();
}
return Result;
}2.cglib代理
需要三個jar包: asm-3.3.1.jar cglib-2.2.jar cglib-nodep-2.2.jar
2.1聲明對象
package yzr.dyn_cglib;
public class PersonImpl {
private String name;
public void SayHello() {
System.out.println("Hello "+this.name);
}
public PersonImpl(){}
public PersonImpl(String name){this.name=name;}
}
package yzr.dyn_cglib;
import java.lang.reflect.Method;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
public class CglibProxy implements MethodInterceptor {
@Override
public Object intercept(Object arg0, Method arg1, Object[] arg2,
MethodProxy arg3) throws Throwable {
System.out.println(arg1.getName());
System.out.println("調用方法之前");
Object result=arg3.invokeSuper(arg0, arg2);
System.out.println("調用方法之之後");
return result;
}
}
package yzr.dyn_cglib;
import yzr.dyn_jdk.PersonImpl;
import net.sf.cglib.proxy.Enhancer;
public class CglibUnit {
public static void main(String[] args) {
CglibProxy proxy=new CglibProxy();
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(PersonImpl.class);
enhancer.setCallback(proxy);
PersonImpl per = (PersonImpl)enhancer.create();
per.SayHello();
}
}像這樣的方式就可以不要求一定需要聲明接口就可以動態代理,但是不管是JDK代理或者CgLib代理,都需要事先聲明PersonImpl實體類,就是說被動態創建的對象都需要聲明好,假如說如果不想手動聲明這樣的一個實體類(被動態創建的對象),又或者說即使是聲明瞭類似於PersonImpl這樣的實體對象,但需要能夠動態的爲它新增一些新的屬性並且賦值,這些想法都可以實現.,下面說一下該怎麼做:
3.動態代理
一個動態Bean,讀取屬性文件內容作爲被創建對象的屬性,當然你也可以選擇不使用屬性文件,直接寫在代碼上也可以;
package yzr.dynamiceBean;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import net.sf.cglib.beans.BeanGenerator;
import net.sf.cglib.beans.BeanMap;
public class DynamicBean {
private Object object = null;//動態生成的類
private BeanMap beanMap = null;//存放屬性名稱以及屬性的類型
public DynamicBean() {
super();
}
public DynamicBean(Map propertyMap) {
this.object = generateBean(propertyMap);
this.beanMap = BeanMap.create(this.object);
}
public void setValue(Object property, Object value) {
beanMap.put(property, value);
}
public Object getValue(String property) {
return beanMap.get(property);
}
public Object getObject() {
return this.object;
}
private Object generateBean(Map propertyMap) {
BeanGenerator generator = new BeanGenerator();
Set keySet = propertyMap.keySet();
for (Iterator i = keySet.iterator(); i.hasNext();) {
String key = (String) i.next();
generator.addProperty(key, (Class) propertyMap.get(key));
}
return generator.create();
}
}
package yzr.dynamiceBean;
import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.io.InputStream;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Properties;
import java.util.Set;
public class ClassUtil {
public Object dynamicClass(Object object) throws Exception {
HashMap returnMap = new HashMap();
HashMap typeMap = new HashMap();
// 讀取配置文件
Properties prop = new Properties();
String sourcepackage = object.getClass().getName();
String classname = sourcepackage.substring(sourcepackage
.lastIndexOf(".") + 1);
InputStream in = ClassUtil.class
.getResourceAsStream("/Dynamic.properties");
prop.load(in);
Set<String> keylist = prop.stringPropertyNames();
Class type = object.getClass();
BeanInfo beanInfo = Introspector.getBeanInfo(type);
PropertyDescriptor[] propertyDescriptors = beanInfo
.getPropertyDescriptors();
//添加自身屬性
for (int i = 0; i < propertyDescriptors.length; i++) {
PropertyDescriptor descriptor = propertyDescriptors[i];
String propertyName = descriptor.getName();
if (!propertyName.equals("class")) {
Method readMethod = descriptor.getReadMethod();
Object result = readMethod.invoke(object, new Object[0]);
if (result != null) {
returnMap.put(propertyName, result);
} else {
returnMap.put(propertyName, "");
}
typeMap.put(propertyName, descriptor.getPropertyType());
}
}
// 加載配置文件中的屬性
Iterator<String> iterator = keylist.iterator();
while (iterator.hasNext()) {
String key = iterator.next();
returnMap.put(key, prop.getProperty(key));
typeMap.put(key, Class.forName("java.lang.String"));
}
// map轉換成實體對象
DynamicBean bean = new DynamicBean(typeMap);
// 賦值
Set keys = typeMap.keySet();
for (Iterator it = keys.iterator(); it.hasNext();) {
String key=it.next().toString();
bean.setValue(key, returnMap.get(key));
}
Object obj = bean.getObject();
return obj;
}
public static void main(String[] args) throws Exception {
Object object = new ClassUtil().dynamicClass(new Object());
Class c = object.getClass();
Method[] methods = c.getDeclaredMethods();// 得到方法
Field[] fs = c.getDeclaredFields();
for (int i = 0; i < fs.length; i++) {
Field f = fs[i];
f.setAccessible(true); // 設置些屬性是可以訪問的
Object val = f.get(object);// 得到此屬性的值
String type = f.getType().toString();// 得到此屬性的類型
System.out.println("type=" + type + "\t name:" + f.getName()
+ "\t value = " + val);
}
}
}
屬性文件Dynamic.properties:
name=YZR;
運行結果:
被動態創建對象中的屬性會帶有$cglib_prop前綴;
案例代碼下載:點擊下載案例
