ダイナミックエージェントソース解析

31000 ワード
Android java ダイナミックエージェント jdk 1.8 ソース分析
  • jdk 1.8.0に基づく分析
    • 動的エージェントDemo
    /**
 *      
 * Created by blacktoast on 2018/1/3.
 */

public interface ProxiedObject {
    public void doSomething1();
    public void doSomething2();
}
    import android.util.Log;

/**
 * Created by blacktoast on 2018/1/3.
 */

public class ConcreteProxiedObject implements ProxiedObject {
    @Override
    public void doSomething1() {
        Log.e("TAG", "doSomething1");
    }

    @Override
    public void doSomething2() {
        Log.e("TAG", "doSomething2");
    }
}
    import android.util.Log;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

/**
 * Created by blacktoast on 2018/1/3.
 */

public class ProxyHandler implements InvocationHandler {
    private Object proxied;

    public ProxyHandler(Object object) {
        this.proxied =object;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        Log.e("TAG", "do something before proxied object invoked.");
        Object invoke = method.invoke(proxied, args);
        Log.e("TAG", "do something after proxied object invoked.");
        return invoke;
    }
}
    import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import com.example.yinhua.aoptest.dl.ConcreteProxiedObject;
import com.example.yinhua.aoptest.dl.ProxiedObject;
import com.example.yinhua.aoptest.dl.ProxyHandler;

import java.lang.reflect.Proxy;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        testDyProxy();
    }

    public void testDyProxy() {
        ConcreteProxiedObject concreteProxiedObject = new ConcreteProxiedObject();
        ProxiedObject proxiedObject = (ProxiedObject) Proxy.newProxyInstance(ProxiedObject.class.getClassLoader(),
                new Class[]{ProxiedObject.class},//   concreteProxiedObject.getClass().getInterfaces()
                new ProxyHandler(concreteProxiedObject));
        proxiedObject.doSomething1();
        Log.e("TAG", "here:" + proxiedObject.getClass().getName());
    }

}
    Log  ：
E/TAG: do something before proxied object invoked.
E/TAG: doSomething1
E/TAG: do something after proxied object invoked.
E/TAG: here:$Proxy0

    注意事項
  • Interface修飾子はpublic修飾である必要があります.public修飾がない場合に生成されるclas.getName()は異なります.
  • で生成するエージェントクラスのバイトコードは、仮想マシンの実行時に動的に生成する
    • である.
  • 被エージェントオブジェクトはインタフェースを実現する必要があり、実質的にインタフェースのエージェント(私はそう理解している)
    • である.
    ダイナミックエージェントメカニズム
  • 動的プロキシプロセッサ/スケジューラInvocationHandler
    • を生成
  • Proxy静的手法によりプロキシオブジェクト
    • を生成する.
    ソース分析(==分析を注釈に書いた===)
  • Proxy.newProxyInstanceソース分析
    • ClassLoader、Interfaceでプロキシクラスタイプオブジェクトを生成します.生成エージェントインスタンスの反射(Reflection Generation Agent Instance)
    public static Object newProxyInstance(ClassLoader loader,
                                          Class>[] interfaces,
                                          InvocationHandler h)
        throws IllegalArgumentException
    {
        Objects.requireNonNull(h);

        //   Interface
        final Class>[] intfs = interfaces.clone();
        // Android-changed: sm is always null
        // final SecurityManager sm = System.getSecurityManager();
        // if (sm != null) {
        //     checkProxyAccess(Reflection.getCallerClass(), loader, intfs);
        // }

        /*
         * Look up or generate the designated proxy class.
         *   ClassLoader、Interface       
         * ------>           
         */
        Class> cl = getProxyClass0(loader, intfs);

        /*
         * Invoke its constructor with the designated invocation handler.
         */
        try {
            // Android-changed: sm is always null
            // if (sm != null) {
            //     checkNewProxyPermission(Reflection.getCallerClass(), cl);
            // }

            //           
            //             
            final Constructor> cons = cl.getConstructor(constructorParams);
            final InvocationHandler ih = h;
            //        public        
            if (!Modifier.isPublic(cl.getModifiers())) {
                // Android-changed: Removed AccessController.doPrivileged
                cons.setAccessible(true);
            }
            //     
            return cons.newInstance(new Object[]{h});
        } catch (IllegalAccessException|InstantiationException e) {
            throw new InternalError(e.toString(), e);
        } catch (InvocationTargetException e) {
            Throwable t = e.getCause();
            if (t instanceof RuntimeException) {
                throw (RuntimeException) t;
            } else {
                throw new InternalError(t.toString(), t);
            }
        } catch (NoSuchMethodException e) {
            throw new InternalError(e.toString(), e);
        }
    }
  • getProxyClass 0ソース分析
    • Class 
        private static Class> getProxyClass0(ClassLoader loader,
                                           Class>... interfaces) {
        //             65535    ，     ，   
        if (interfaces.length > 65535) {
            throw new IllegalArgumentException("interface limit exceeded");
        }

        // If the proxy class defined by the given loader implementing
        // the given interfaces exists, this will simply return the cached copy;
        // otherwise, it will create the proxy class via the ProxyClassFactory
        return proxyClassCache.get(loader, interfaces);
    }
  • proxyClassCache分析
    • new KeyFactory()とnew ProxyClassFactory()の2つのオブジェクトは、すべてのエージェントクラスのマッピングを処理します.
        /**
     * a cache of proxy classes
     *           
     *   ：new KeyFactory()、new ProxyClassFactory()     ，      
     */
    private static final WeakCache[], Class>>
        proxyClassCache = new WeakCache<>(new KeyFactory(), new ProxyClassFactory());
  • WeakCache getメソッド解析
    • mapによってClassLoaderに対応するマッピング関係valuesMapを取得する.valuesMapにはKeyとFactory間のマッピングが格納されます.Factory.get()メソッドは、ValueFactoryによってエージェントオブジェクトを取得する論理をカプセル化します.
        /**
     * WeakCache.get(loader, interfaces)
     */
    public V get(K key, P parameter) {
        Objects.requireNonNull(parameter);

        expungeStaleEntries();

        Object cacheKey = CacheKey.valueOf(key, refQueue);

        //   key（ClassLoader）      ， CacheKey Factory     
        // lazily install the 2nd level valuesMap for the particular cacheKey
        ConcurrentMap> valuesMap = map.get(cacheKey);
        if (valuesMap == null) {
            //        put map 
            ConcurrentMap> oldValuesMap
                = map.putIfAbsent(cacheKey,
                                  valuesMap = new ConcurrentHashMap<>());
            if (oldValuesMap != null) {
                //   map  valuesMap    oldValuesMap
                valuesMap = oldValuesMap;
            }
        }

        //   KeyFactory  Key，Key     interface hashcode    
        // create subKey and retrieve the possible Supplier stored by that
        // subKey from valuesMap
        Object subKey = Objects.requireNonNull(subKeyFactory.apply(key, parameter));
        //   Supplier  ，       ValueFactory         
        Supplier supplier = valuesMap.get(subKey);
        Factory factory = null;

        while (true) {
            if (supplier != null) {
                // supplier might be a Factory or a CacheValue instance
                //          
                V value = supplier.get();
                if (value != null) {
                    return value;
                }
            }
            // else no supplier in cache
            // or a supplier that returned null (could be a cleared CacheValue
            // or a Factory that wasn't successful in installing the CacheValue)

            // lazily construct a Factory
            if (factory == null) {
                factory = new Factory(key, parameter, subKey, valuesMap);
            }

            //   Supplier   Factory  ，    Key Factory     
            if (supplier == null) {
                supplier = valuesMap.putIfAbsent(subKey, factory);
                if (supplier == null) {
                    // successfully installed Factory
                    supplier = factory;
                }
                // else retry with winning supplier
            } else {
                if (valuesMap.replace(subKey, supplier, factory)) {
                    // successfully replaced
                    // cleared CacheEntry / unsuccessful Factory
                    // with our Factory
                    supplier = factory;
                } else {
                    // retry with current supplier
                    supplier = valuesMap.get(subKey);
                }
            }
        }
    }
  • Factoryソース分析
    • Factoryによるプロキシオブジェクトの生成
    private final class Factory implements Supplier<V> {

        private final K key;
        private final P parameter;
        private final Object subKey;
        private final ConcurrentMap> valuesMap;

        Factory(K key, P parameter, Object subKey,
                ConcurrentMap> valuesMap) {
            this.key = key;
            this.parameter = parameter;
            this.subKey = subKey;
            this.valuesMap = valuesMap;
        }

        @Override
        public synchronized V get() { // serialize access
            // re-check
            Supplier supplier = valuesMap.get(subKey);
            if (supplier != this) {
                // something changed while we were waiting:
                // might be that we were replaced by a CacheValue
                // or were removed because of failure ->
                // return null to signal WeakCache.get() to retry
                // the loop
                return null;
            }
            // else still us (supplier == this)

            // create new value
            V value = null;
            try {
                //   ValueFactory        
                value = Objects.requireNonNull(valueFactory.apply(key, parameter));
            } finally {
                if (value == null) { // remove us on failure
                    valuesMap.remove(subKey, this);
                }
            }
            // the only path to reach here is with non-null value
            assert value != null;

            // wrap value with CacheValue (WeakReference)
            //            ，CacheValue  Supplier     hashcode equals  ，       ，    
            CacheValue cacheValue = new CacheValue<>(value);

            // try replacing us with CacheValue (this should always succeed)
            if (valuesMap.replace(subKey, this, cacheValue)) {
                // put also in reverseMap
                reverseMap.put(cacheValue, Boolean.TRUE);
            } else {
                throw new AssertionError("Should not reach here");
            }

            // successfully replaced us with new CacheValue -> return the value
            // wrapped by it
            return value;
        }
    }
  • KeyFactoryソース分析
    •     private static final class KeyFactory
        implements BiFunction<ClassLoader, Class>[], Object>
    {
        @Override
        public Object apply(ClassLoader classLoader, Class>[] interfaces) {
            switch (interfaces.length) {
                //   Key，Key      Object  
                case 1: return new Key1(interfaces[0]); // the most frequent
                case 2: return new Key2(interfaces[0], interfaces[1]);
                case 0: return key0;
                default: return new KeyX(interfaces);
            }
        }
    }
  • ProxyFactory(ValueFactory)ソースコード分析
    • private static final class ProxyClassFactory
        implements BiFunction<ClassLoader, Class>[], Class>>
    {
        // prefix for all proxy class names
        private static final String proxyClassNamePrefix = "$Proxy";

        // next number to use for generation of unique proxy class names
        private static final AtomicLong nextUniqueNumber = new AtomicLong();

        @Override
        public Class> apply(ClassLoader loader, Class>[] interfaces) {

            Map, Boolean> interfaceSet = new IdentityHashMap<>(interfaces.length);
            for (Class> intf : interfaces) {
                /*
                 * Verify that the class loader resolves the name of this
                 * interface to the same Class object.
                 */
                Class> interfaceClass = null;
                try {
                    interfaceClass = Class.forName(intf.getName(), false, loader);
                } catch (ClassNotFoundException e) {
                }

                if (interfaceClass != intf) {
                    throw new IllegalArgumentException(
                        intf + " is not visible from class loader");
                }
                /*
                 * Verify that the Class object actually represents an
                 * interface.
                 */
                //        ，      
                //             java      
                if (!interfaceClass.isInterface()) {
                    throw new IllegalArgumentException(
                        interfaceClass.getName() + " is not an interface");
                }
                /*
                 * Verify that this interface is not a duplicate.
                 */
                if (interfaceSet.put(interfaceClass, Boolean.TRUE) != null) {
                    throw new IllegalArgumentException(
                        "repeated interface: " + interfaceClass.getName());
                }
            }

            String proxyPkg = null;     // package to define proxy class in
            int accessFlags = Modifier.PUBLIC | Modifier.FINAL;

            /*
             * Record the package of a non-public proxy interface so that the
             * proxy class will be defined in the same package.  Verify that
             * all non-public proxy interfaces are in the same package.
             */
            for (Class> intf : interfaces) {
                int flags = intf.getModifiers();
                //   interface  public
                //   public   ，         +  $Proxy1
                if (!Modifier.isPublic(flags)) {
                    accessFlags = Modifier.FINAL;
                    String name = intf.getName();
                    int n = name.lastIndexOf('.');
                    String pkg = ((n == -1) ? "" : name.substring(0, n + 1));
                    if (proxyPkg == null) {
                        proxyPkg = pkg;
                    } else if (!pkg.equals(proxyPkg)) {
                        throw new IllegalArgumentException(
                            "non-public interfaces from different packages");
                    }
                }
            }

            if (proxyPkg == null) {
                // if no non-public proxy interfaces, use the default package.
                proxyPkg = "";
            }

            //       java    ，java       com.sun.proxy$Proxy1, Android       $Proxy1
            {
                // Android-changed: Generate the proxy directly instead of calling
                // through to ProxyGenerator.
                List methods = getMethods(interfaces);
                Collections.sort(methods, ORDER_BY_SIGNATURE_AND_SUBTYPE);
                validateReturnTypes(methods);
                List[]> exceptions = deduplicateAndGetExceptions(methods);

                Method[] methodsArray = methods.toArray(new Method[methods.size()]);
                Class>[][] exceptionsArray = exceptions.toArray(new Class>[exceptions.size()][]);

                /*
                 * Choose a name for the proxy class to generate.
                 */
                // $Proxy       ，           1
                //  nextUniqueNumber     1，          
                long num = nextUniqueNumber.getAndIncrement();
                String proxyName = proxyPkg + proxyClassNamePrefix + num;

                //           ， native   
                return generateProxy(proxyName, interfaces, loader, methodsArray,
                                     exceptionsArray);
            }
        }
    }
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