Jdk_Proxy代理生成过过程源码分析

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<Class<?>, 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.
                 */
                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();
                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 com.sun.proxy package
                proxyPkg = ReflectUtil.PROXY_PACKAGE + ".";
            }

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

            /*
             * Generate the specified proxy class.
             */
            byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
                proxyName, interfaces, accessFlags);
            try {
                return defineClass0(loader, proxyName,
                                    proxyClassFile, 0, proxyClassFile.length);
            } catch (ClassFormatError e) {
                /*
                 * A ClassFormatError here means that (barring bugs in the
                 * proxy class generation code) there was some other
                 * invalid aspect of the arguments supplied to the proxy
                 * class creation (such as virtual machine limitations
                 * exceeded).
                 */
                throw new IllegalArgumentException(e.toString());
            }
        }
    }

ProxyGenerator.generateProxyClass 源码分析:

public static byte[] generateProxyClass(final String var0, Class<?>[] var1, int var2) {
			 ProxyGenerator var3 = new ProxyGenerator(var0, var1, var2);
			 final byte[] var4 = var3.generateClassFile();
			 if (saveGeneratedFiles) {
					 AccessController.doPrivileged(new PrivilegedAction<Void>() {
							 public Void run() {
									 try {
											 int var1 = var0.lastIndexOf(46);
											 Path var2;
											 if (var1 > 0) {
													 Path var3 = Paths.get(var0.substring(0, var1).replace('.', File.separatorChar));
													 Files.createDirectories(var3);
													 var2 = var3.resolve(var0.substring(var1 + 1, var0.length()) + ".class");
											 } else {
													 var2 = Paths.get(var0 + ".class");
											 }

											 Files.write(var2, var4, new OpenOption[0]);
											 return null;
									 } catch (IOException var4x) {
											 throw new InternalError("I/O exception saving generated file: " + var4x);
									 }
							 }
					 });
			 }

			 return var4;
	 }

private byte[] generateClassFile() {
        this.addProxyMethod(hashCodeMethod, Object.class);
        this.addProxyMethod(equalsMethod, Object.class);
        this.addProxyMethod(toStringMethod, Object.class);
        Class[] var1 = this.interfaces;
        int var2 = var1.length;

        int var3;
        Class var4;
        for(var3 = 0; var3 < var2; ++var3) {
            var4 = var1[var3];
            Method[] var5 = var4.getMethods();
            int var6 = var5.length;

            for(int var7 = 0; var7 < var6; ++var7) {
                Method var8 = var5[var7];
                this.addProxyMethod(var8, var4);
            }
        }

        Iterator var11 = this.proxyMethods.values().iterator();

        List var12;
        while(var11.hasNext()) {
            var12 = (List)var11.next();
            checkReturnTypes(var12);
        }

        Iterator var15;
        try {
            this.methods.add(this.generateConstructor());
            var11 = this.proxyMethods.values().iterator();

            while(var11.hasNext()) {
                var12 = (List)var11.next();
                var15 = var12.iterator();

                while(var15.hasNext()) {
                    ProxyGenerator.ProxyMethod var16 = (ProxyGenerator.ProxyMethod)var15.next();
                    this.fields.add(new ProxyGenerator.FieldInfo(var16.methodFieldName, "Ljava/lang/reflect/Method;", 10));
                    this.methods.add(var16.generateMethod());
                }
            }

            this.methods.add(this.generateStaticInitializer());
        } catch (IOException var10) {
            throw new InternalError("unexpected I/O Exception", var10);
        }

        if (this.methods.size() > 65535) {
            throw new IllegalArgumentException("method limit exceeded");
        } else if (this.fields.size() > 65535) {
            throw new IllegalArgumentException("field limit exceeded");
        } else {
            this.cp.getClass(dotToSlash(this.className));
            this.cp.getClass("java/lang/reflect/Proxy");
            var1 = this.interfaces;
            var2 = var1.length;

            for(var3 = 0; var3 < var2; ++var3) {
                var4 = var1[var3];
                this.cp.getClass(dotToSlash(var4.getName()));
            }

            this.cp.setReadOnly();
            ByteArrayOutputStream var13 = new ByteArrayOutputStream();
            DataOutputStream var14 = new DataOutputStream(var13);

            try {
                var14.writeInt(-889275714);
                var14.writeShort(0);
                var14.writeShort(49);
                this.cp.write(var14);
                var14.writeShort(this.accessFlags);
                var14.writeShort(this.cp.getClass(dotToSlash(this.className)));
                var14.writeShort(this.cp.getClass("java/lang/reflect/Proxy"));
                var14.writeShort(this.interfaces.length);
                Class[] var17 = this.interfaces;
                int var18 = var17.length;

                for(int var19 = 0; var19 < var18; ++var19) {
                    Class var22 = var17[var19];
                    var14.writeShort(this.cp.getClass(dotToSlash(var22.getName())));
                }

                var14.writeShort(this.fields.size());
                var15 = this.fields.iterator();

                while(var15.hasNext()) {
                    ProxyGenerator.FieldInfo var20 = (ProxyGenerator.FieldInfo)var15.next();
                    var20.write(var14);
                }

                var14.writeShort(this.methods.size());
                var15 = this.methods.iterator();

                while(var15.hasNext()) {
                    ProxyGenerator.MethodInfo var21 = (ProxyGenerator.MethodInfo)var15.next();
                    var21.write(var14);
                }

                var14.writeShort(0);
                return var13.toByteArray();
            } catch (IOException var9) {
                throw new InternalError("unexpected I/O Exception", var9);
            }
        }
    }