CGlib 入门

cglib github地址链接。
项目maven构建：


    cglib

    cglib

    3.1

/pre>
p>项目gradle构建：
/p>
pre class='language-javascript'>
dependencies { compile 'cglib:cglib:3.1' testCompile 'junit:junit:4.11' }/pre>
p>cglib不仅可以动态创建实现了接口类的代理对象，还可以为简单的POJO动态创建代理对象；而java只能动态创建实现了接口类的代理对象(使用Proxy类和InvocationHandler接口)。
/p>
h4>1，Enhancer和FixedValue
/h4>
p>cglib中最重要的就是net.sf.cglib.proxy.Enhancer这个类，与java中的Proxy类有异曲同工之妙，都可以创建代理对象。
/p>
p>下面就来简单实验一下：

首先新建一个简单的POJO类CGlibSample.java
/p>
pre class='language-javascript'>
public class CGlibSample { 

   



    public String test(String input){

        return input;

    }

}/pre>
p>测试类TestCG.java:
/p>
pre class='language-javascript'>
import net.sf.cglib.proxy.Enhancer;

import net.sf.cglib.proxy.FixedValue;

import org.junit.Assert;

import org.junit.Test;



public class TestCG { 

   



    @Test

    public void testFixedValue() throws Exception {



        Enhancer enhancer = new Enhancer();



        enhancer.setSuperclass(CGlibSample.class);



        /*enhancer.setCallback(new FixedValue() { @Override public Object loadObject() throws Exception { return "Hello cglib!"; } });*/



        //java lambda expression 与上面的代码段效果一样

        enhancer.setCallback((FixedValue)() -> {

            return "Hello cglib!";

        });



        CGlibSample proxy = (CGlibSample)enhancer.create();



        Assert.assertEquals("Hello cglib!",proxy.test("hello!"));

        Assert.assertEquals("Hello cglib!",proxy.toString());

        Assert.assertFalse("hello!".equals

        (proxy.test("hello!")));    



    }

}/pre>
p>这里的FixedValue接口相当于一个拦截器(interceptor)。  proxy.getClass()  输出结果为 class glib.CGlibSample
/p>
p>EnhancerByCGLIB
/p>
p>c9fa3aa1,明显可以看这是个有cglib产生的代理对象，目标对象为glib.CGlibSample  由以上代码可得cglib可以改变方法。  注意： 创建代理对象的目标对象(这里是CGlibSample)一定要有无参构造方法
/p>
h4>2，InvocationHandler
/h4>
p>这里的InvocationHandler接口并不是java反射包中的InvocationHandler，而是cglib中接口net.sf.cglib.proxy.InvocationHandler,其实里面的内容和java差不多，如下所示：
/p>
pre class='language-javascript'>
 public interface InvocationHandler extends Callback { 

   

    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable;



}/pre>
pre class='language-javascript'>
    @Test

    public void testInvocationHandler(){



        Enhancer enhancer = new Enhancer();



        enhancer.setSuperclass(CGlibSample.class);



        enhancer.setCallback(new InvocationHandler() {

            @Override

            public Object invoke(Object o, Method method, Object[] objects) throws Throwable {

                /** * method.getDeclaringClass() != Object.class 表示该方法不能是Object类中定义的方法，如：toString()。 * method.getReturnType() == String.class 表示方法的返回类型只能为String类型 */

                if (method.getDeclaringClass() != Object.class && method.getReturnType() == String.class) {

                    return "Hello cglib!";

                } else {

                    return "do not know what to do";

                }

            }

        });



        CGlibSample proxy = (CGlibSample) enhancer.create();



        Assert.assertTrue("Hello cglib!".equals(proxy.test("hello!")));



        Assert.assertTrue("do not know what to do".equals(proxy.toString()));



    }/pre>
h4>3，MethodInterceptor
/h4>
pre class='language-javascript'>
    @Test

    public void testMethodInterceptor(){



        Enhancer enhancer = new Enhancer();



        enhancer.setSuperclass(CGlibSample.class);

        enhancer.setCallback(new MethodInterceptor() {

            @Override

            public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {

                if (method.getDeclaringClass() != Object.class && method.getReturnType() == String.class) {

                    return "Hello cglib!";

                } else {

                    //这里有点像struts2中拦截器链

                    return proxy.invokeSuper(obj,args);

                }

            }

        });



        CGlibSample proxy = (CGlibSample) enhancer.create();



        Assert.assertTrue("Hello cglib!".equals(proxy.test("hello!")));



        Assert.assertFalse("do not know what to do".equals(proxy.toString()));

    }/pre>
h4>4，CallbackFilter
/h4>
p>接口CallbackFilter实现类CallbackHelper。
/p>
pre class='language-javascript'>
    @Test

    public void testCallbackFilter(){



        Enhancer enhancer = new Enhancer();



        CallbackHelper callbackHelper = new CallbackHelper(CGlibSample.class,new Class[0]) {

            @Override

            protected Object getCallback(Method method) {

                if (method.getDeclaringClass() != Object.class && method.getReturnType() == String.class) {

                    return new FixedValue() {

                        @Override

                        public Object loadObject() throws Exception {

                            return "Hello cglib!";

                        }

                    };

                } else {

                    return NoOp.INSTANCE;

                }

            }

        };



        enhancer.setSuperclass(CGlibSample.class);

        enhancer.setCallbackFilter(callbackHelper);

        enhancer.setCallbacks(callbackHelper.getCallbacks());



        CGlibSample proxy = (CGlibSample) enhancer.create();



        Assert.assertTrue("Hello cglib!".equals(proxy.test("hello!")));

        System.out.println(proxy.hashCode());

        Assert.assertFalse("do not know what to do".equals(proxy.toString()));/pre>
p>注意：不要使用非静态的匿名内部类，会造成内存泄露。本文使用非静态的匿名内部类是为了方便。
/p>
h4>5，Immutable Bean
/h4>
pre class='language-javascript'>
    @Test(expected = java.lang.IllegalStateException.class)

    public void testImmutableBean(){



        SampleBean sampleBean = new SampleBean();



        sampleBean.setValue("Hello cglib");



        SampleBean immutableBean = (SampleBean) ImmutableBean.create(sampleBean);



        Assert.assertTrue("Hello cglib".equals(immutableBean.getValue()));



        sampleBean.setValue("Hello cglib again");

        Assert.assertTrue("Hello cglib again".equals(immutableBean.getValue()));



        immutableBean.setValue("Hello World!");//throw Exception java.lang.IllegalStateException: Bean is immutable

    }/pre>
h4>6，Bean Generator
/h4>
pre class='language-javascript'>
    @Test

    public void testBeanGenerator() throws Exception{



        BeanGenerator beanGenerator = new BeanGenerator();



        beanGenerator.addProperty("value",String.class);



        Object bean = beanGenerator.create();

        //获取bean的setter方法

        Method setter = bean.getClass().getMethod("setValue",String.class);

        setter.invoke(bean,"Hello cglib");



        //获取bean的getter方法

        Method getter = bean.getClass().getMethod("getValue");



        Assert.assertTrue("Hello cglib".equals(getter.invoke(bean)));





    }/pre>
h4>7，Bean Copier
/h4>
p>OtherSampleBean:
/p>
pre class='language-javascript'>
public class OtherSampleBean { 

   



    private String value;



    public String getValue() {

        return value;

    }



    public void setValue(String value) {

        this.value = value;

    }

}/pre>
p>测试案例：
/p>
pre class='language-javascript'>
    @Test

    public void testBeanCopier(){



        BeanCopier copier = BeanCopier.create(SampleBean.class,OtherSampleBean.class,false);



        SampleBean sampleBean = new SampleBean();

        sampleBean.setValue("sample bean");



        OtherSampleBean otherSampleBean = new OtherSampleBean();

        copier.copy(sampleBean,otherSampleBean,null);



        Assert.assertTrue("sample bean".equals(otherSampleBean.getValue()));

    }/pre>
h4>8，Bulk Bean
/h4>
pre class='language-javascript'>
    @Test

    public void testBulkBean(){



        BulkBean bulkBean = BulkBean.create(SampleBean.class,

                new String[]{

  

  "getValue"},

                new String[]{

  

  "setValue"},

                new Class[]{String.class});



        SampleBean bean = new SampleBean();

        bean.setValue("sample bean");



        Assert.assertTrue(bulkBean.getPropertyValues(bean).length == 1);



        Assert.assertTrue("sample bean".equals(bulkBean.getPropertyValues(bean)[0]));



        bulkBean.setPropertyValues(bean,new Object[]{

  

  "bulk bean"});



        Assert.assertTrue("bulk bean".equals(bean.getValue()));

    }/pre>
h4>9，Bean Map
/h4>
pre class='language-javascript'>
    @Test

    public void testBeanMap(){



        SampleBean bean = new SampleBean();



        BeanMap map = BeanMap.create(bean);

        bean.setValue("bean mao");



        Assert.assertTrue("bean mao".equals(map.get("value")));



    }/pre>
CGlib 入门

CGlib 入门

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