bilibili-JVM學習筆記17 動態代理運作機制
The Java Virtual Machine Specification - Java SE 8 Edition
JVM學習筆記11 - Java字節碼初識
JVM學習筆記12 - 解讀筆記11中的attributes
JVM學習筆記13
JVM學習筆記14 異常
JVM學習筆記15 方法執行
JVM學習筆記16 字節碼執行
透過字節碼生成審視Java動態代理運作機制
package new_package.jvm.p57;
public interface Subject {
void request();
}
package new_package.jvm.p57;
public class RealSubject implements Subject {
@Override
public void request() {
System.out.println("RealSubject request");
}
}
package new_package.jvm.p57;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
public class DynamicSubject implements InvocationHandler {
private Object subject;
public DynamicSubject(Object object) {
this.subject = object;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("before calling: " + method);
method.invoke(this.subject, args);
System.out.println("after calling: " + method);
return proxy;
}
}
package new_package.jvm.p57;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
public class ProxyTest {
public static void main(String[] args) {
Subject subject = new RealSubject();
InvocationHandler handler = new DynamicSubject(subject);
Subject proxy = (Subject) Proxy.newProxyInstance(subject.getClass().getClassLoader(), subject.getClass().getInterfaces(), handler);
proxy.request();
System.out.println(proxy.getClass());
System.out.println(proxy.getClass().getSuperclass());
}
}
java.lang.reflect.Proxy
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. （生成代理類的字節碼）
*/
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());
}
}
}
sun.misc.ProxyGenerator
/**
* Generate a proxy class given a name and a list of proxy interfaces.
*
* @param name the class name of the proxy class
* @param interfaces proxy interfaces
* @param accessFlags access flags of the proxy class
*/
public static byte[] generateProxyClass(final String name,
Class<?>[] interfaces,
int accessFlags)
{
ProxyGenerator gen = new ProxyGenerator(name, interfaces, accessFlags);
final byte[] classFile = gen.generateClassFile();
if (saveGeneratedFiles) {
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction<Void>() {
public Void run() {
try {
int i = name.lastIndexOf('.');
Path path;
if (i > 0) {
Path dir = Paths.get(name.substring(0, i).replace('.', File.separatorChar));
Files.createDirectories(dir);
path = dir.resolve(name.substring(i+1, name.length()) + ".class");
} else {
path = Paths.get(name + ".class");
}
Files.write(path, classFile);
return null;
} catch (IOException e) {
throw new InternalError(
"I/O exception saving generated file: " + e);
}
}
});
}
return classFile;
}
/**
* Generate a class file for the proxy class. This method drives the
* class file generation process.
*/
private byte[] generateClassFile() {
/* ============================================================
* Step 1: Assemble ProxyMethod objects for all methods to
* generate proxy dispatching code for.
*/
/*
* Record that proxy methods are needed for the hashCode, equals,
* and toString methods of java.lang.Object. This is done before
* the methods from the proxy interfaces so that the methods from
* java.lang.Object take precedence over duplicate methods in the
* proxy interfaces.
*/
addProxyMethod(hashCodeMethod, Object.class);
addProxyMethod(equalsMethod, Object.class);
addProxyMethod(toStringMethod, Object.class);
/*
* Now record all of the methods from the proxy interfaces, giving
* earlier interfaces precedence over later ones with duplicate
* methods.
*/
for (Class<?> intf : interfaces) {
for (Method m : intf.getMethods()) {
addProxyMethod(m, intf);
}
}
/*
* For each set of proxy methods with the same signature,
* verify that the methods' return types are compatible.
*/
for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
checkReturnTypes(sigmethods);
}
/* ============================================================
* Step 2: Assemble FieldInfo and MethodInfo structs for all of
* fields and methods in the class we are generating.
*/
try {
methods.add(generateConstructor());
for (List<ProxyMethod> sigmethods : proxyMethods.values()) {
for (ProxyMethod pm : sigmethods) {
// add static field for method's Method object
fields.add(new FieldInfo(pm.methodFieldName,
"Ljava/lang/reflect/Method;",
ACC_PRIVATE | ACC_STATIC));
// generate code for proxy method and add it
methods.add(pm.generateMethod());
}
}
methods.add(generateStaticInitializer());
} catch (IOException e) {
throw new InternalError("unexpected I/O Exception", e);
}
if (methods.size() > 65535) {
throw new IllegalArgumentException("method limit exceeded");
}
if (fields.size() > 65535) {
throw new IllegalArgumentException("field limit exceeded");
}
/* ============================================================
* Step 3: Write the final class file.
*/
/*
* Make sure that constant pool indexes are reserved for the
* following items before starting to write the final class file.
*/
cp.getClass(dotToSlash(className));
cp.getClass(superclassName);
for (Class<?> intf: interfaces) {
cp.getClass(dotToSlash(intf.getName()));
}
/*
* Disallow new constant pool additions beyond this point, since
* we are about to write the final constant pool table.
*/
cp.setReadOnly();
ByteArrayOutputStream bout = new ByteArrayOutputStream();
DataOutputStream dout = new DataOutputStream(bout);
try {
/*
* Write all the items of the "ClassFile" structure.
* See JVMS section 4.1.
*/
// u4 magic;
dout.writeInt(0xCAFEBABE);
// u2 minor_version;
dout.writeShort(CLASSFILE_MINOR_VERSION);
// u2 major_version;
dout.writeShort(CLASSFILE_MAJOR_VERSION);
cp.write(dout); // (write constant pool)
// u2 access_flags;
dout.writeShort(accessFlags);
// u2 this_class;
dout.writeShort(cp.getClass(dotToSlash(className)));
// u2 super_class;
dout.writeShort(cp.getClass(superclassName));
// u2 interfaces_count;
dout.writeShort(interfaces.length);
// u2 interfaces[interfaces_count];
for (Class<?> intf : interfaces) {
dout.writeShort(cp.getClass(
dotToSlash(intf.getName())));
}
// u2 fields_count;
dout.writeShort(fields.size());
// field_info fields[fields_count];
for (FieldInfo f : fields) {
f.write(dout);
}
// u2 methods_count;
dout.writeShort(methods.size());
// method_info methods[methods_count];
for (MethodInfo m : methods) {
m.write(dout);
}
// u2 attributes_count;
dout.writeShort(0); // (no ClassFile attributes for proxy classes)
} catch (IOException e) {
throw new InternalError("unexpected I/O Exception", e);
}
return bout.toByteArray();
}
sun.misc.ProxyGenerator.saveGeneratedFiles 系統變量設置爲 true
package new_package.jvm.p57;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
public class ProxyTest {
public static void main(String[] args) {
// debugging flag for saving generated class files
System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles","true");
Subject subject = new RealSubject();
InvocationHandler handler = new DynamicSubject(subject);
Subject proxy = (Subject) Proxy.newProxyInstance(subject.getClass().getClassLoader(), subject.getClass().getInterfaces(), handler);
proxy.request();
System.out.println(proxy.getClass());
System.out.println(proxy.getClass().getSuperclass());
}
}
在工程目錄下生成一個文件 com.sun.proxy.$Proxy0
javap -v com.sun.proxy.$Proxy0
Classfile /Users/kevin/Documents/opensource/gitee/java-read-sources-sample/com/sun/proxy/$Proxy0.class
Last modified 2020-6-13; size 1933 bytes
MD5 checksum 8b7db9cc13cf98eeeff555cb57c49163
public final class com.sun.proxy.$Proxy0 extends java.lang.reflect.Proxy implements new_package.jvm.p57.Subject
minor version: 0
major version: 49
flags: ACC_PUBLIC, ACC_FINAL
Constant pool:
#1 = Utf8 <init>
#2 = Utf8 (Ljava/lang/reflect/InvocationHandler;)V
#3 = Utf8 Code
#4 = Utf8 Exceptions
#5 = Utf8 java/lang/reflect/Proxy
#6 = Class #5 // java/lang/reflect/Proxy
#7 = NameAndType #1:#2 // "<init>":(Ljava/lang/reflect/InvocationHandler;)V
#8 = Methodref #6.#7 // java/lang/reflect/Proxy."<init>":(Ljava/lang/reflect/InvocationHandler;)V
#9 = Utf8 m1
#10 = Utf8 Ljava/lang/reflect/Method;
#11 = Utf8 equals
#12 = Utf8 (Ljava/lang/Object;)Z
#13 = Utf8 h
#14 = Utf8 Ljava/lang/reflect/InvocationHandler;
#15 = NameAndType #13:#14 // h:Ljava/lang/reflect/InvocationHandler;
#16 = Fieldref #6.#15 // java/lang/reflect/Proxy.h:Ljava/lang/reflect/InvocationHandler;
#17 = Utf8 com/sun/proxy/$Proxy0
#18 = Class #17 // com/sun/proxy/$Proxy0
#19 = NameAndType #9:#10 // m1:Ljava/lang/reflect/Method;
#20 = Fieldref #18.#19 // com/sun/proxy/$Proxy0.m1:Ljava/lang/reflect/Method;
#21 = Utf8 java/lang/Object
#22 = Class #21 // java/lang/Object
#23 = Utf8 java/lang/reflect/InvocationHandler
#24 = Class #23 // java/lang/reflect/InvocationHandler
#25 = Utf8 invoke
#26 = Utf8 (Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;
#27 = NameAndType #25:#26 // invoke:(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;
#28 = InterfaceMethodref #24.#27 // java/lang/reflect/InvocationHandler.invoke:(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;
#29 = Utf8 java/lang/Boolean
#30 = Class #29 // java/lang/Boolean
#31 = Utf8 booleanValue
#32 = Utf8 ()Z
#33 = NameAndType #31:#32 // booleanValue:()Z
#34 = Methodref #30.#33 // java/lang/Boolean.booleanValue:()Z
#35 = Utf8 java/lang/Error
#36 = Class #35 // java/lang/Error
#37 = Utf8 java/lang/RuntimeException
#38 = Class #37 // java/lang/RuntimeException
#39 = Utf8 java/lang/Throwable
#40 = Class #39 // java/lang/Throwable
#41 = Utf8 java/lang/reflect/UndeclaredThrowableException
#42 = Class #41 // java/lang/reflect/UndeclaredThrowableException
#43 = Utf8 (Ljava/lang/Throwable;)V
#44 = NameAndType #1:#43 // "<init>":(Ljava/lang/Throwable;)V
#45 = Methodref #42.#44 // java/lang/reflect/UndeclaredThrowableException."<init>":(Ljava/lang/Throwable;)V
#46 = Utf8 m2
#47 = Utf8 toString
#48 = Utf8 ()Ljava/lang/String;
#49 = NameAndType #46:#10 // m2:Ljava/lang/reflect/Method;
#50 = Fieldref #18.#49 // com/sun/proxy/$Proxy0.m2:Ljava/lang/reflect/Method;
#51 = Utf8 java/lang/String
#52 = Class #51 // java/lang/String
#53 = Utf8 m3
#54 = Utf8 request
#55 = Utf8 ()V
#56 = NameAndType #53:#10 // m3:Ljava/lang/reflect/Method;
#57 = Fieldref #18.#56 // com/sun/proxy/$Proxy0.m3:Ljava/lang/reflect/Method;
#58 = Utf8 m0
#59 = Utf8 hashCode
#60 = Utf8 ()I
#61 = NameAndType #58:#10 // m0:Ljava/lang/reflect/Method;
#62 = Fieldref #18.#61 // com/sun/proxy/$Proxy0.m0:Ljava/lang/reflect/Method;
#63 = Utf8 java/lang/Integer
#64 = Class #63 // java/lang/Integer
#65 = Utf8 intValue
#66 = NameAndType #65:#60 // intValue:()I
#67 = Methodref #64.#66 // java/lang/Integer.intValue:()I
#68 = Utf8 <clinit>
#69 = Utf8 java.lang.Object
#70 = String #69 // java.lang.Object
#71 = Utf8 java/lang/Class
#72 = Class #71 // java/lang/Class
#73 = Utf8 forName
#74 = Utf8 (Ljava/lang/String;)Ljava/lang/Class;
#75 = NameAndType #73:#74 // forName:(Ljava/lang/String;)Ljava/lang/Class;
#76 = Methodref #72.#75 // java/lang/Class.forName:(Ljava/lang/String;)Ljava/lang/Class;
#77 = String #11 // equals
#78 = Utf8 getMethod
#79 = Utf8 (Ljava/lang/String;[Ljava/lang/Class;)Ljava/lang/reflect/Method;
#80 = NameAndType #78:#79 // getMethod:(Ljava/lang/String;[Ljava/lang/Class;)Ljava/lang/reflect/Method;
#81 = Methodref #72.#80 // java/lang/Class.getMethod:(Ljava/lang/String;[Ljava/lang/Class;)Ljava/lang/reflect/Method;
#82 = String #47 // toString
#83 = Utf8 new_package.jvm.p57.Subject
#84 = String #83 // new_package.jvm.p57.Subject
#85 = String #54 // request
#86 = String #59 // hashCode
#87 = Utf8 java/lang/NoSuchMethodException
#88 = Class #87 // java/lang/NoSuchMethodException
#89 = Utf8 java/lang/NoSuchMethodError
#90 = Class #89 // java/lang/NoSuchMethodError
#91 = Utf8 getMessage
#92 = NameAndType #91:#48 // getMessage:()Ljava/lang/String;
#93 = Methodref #40.#92 // java/lang/Throwable.getMessage:()Ljava/lang/String;
#94 = Utf8 (Ljava/lang/String;)V
#95 = NameAndType #1:#94 // "<init>":(Ljava/lang/String;)V
#96 = Methodref #90.#95 // java/lang/NoSuchMethodError."<init>":(Ljava/lang/String;)V
#97 = Utf8 java/lang/ClassNotFoundException
#98 = Class #97 // java/lang/ClassNotFoundException
#99 = Utf8 java/lang/NoClassDefFoundError
#100 = Class #99 // java/lang/NoClassDefFoundError
#101 = Methodref #100.#95 // java/lang/NoClassDefFoundError."<init>":(Ljava/lang/String;)V
#102 = Utf8 new_package/jvm/p57/Subject
#103 = Class #102 // new_package/jvm/p57/Subject
{
public com.sun.proxy.$Proxy0(java.lang.reflect.InvocationHandler) throws ;
descriptor: (Ljava/lang/reflect/InvocationHandler;)V
flags: ACC_PUBLIC
Code:
stack=10, locals=2, args_size=2
0: aload_0
1: aload_1
2: invokespecial #8 // Method java/lang/reflect/Proxy."<init>":(Ljava/lang/reflect/InvocationHandler;)V
5: return
Exceptions:
throws
public final boolean equals(java.lang.Object) throws ;
descriptor: (Ljava/lang/Object;)Z
flags: ACC_PUBLIC, ACC_FINAL
Code:
stack=10, locals=3, args_size=2
0: aload_0
1: getfield #16 // Field java/lang/reflect/Proxy.h:Ljava/lang/reflect/InvocationHandler;
4: aload_0
5: getstatic #20 // Field m1:Ljava/lang/reflect/Method;
8: iconst_1
9: anewarray #22 // class java/lang/Object
12: dup
13: iconst_0
14: aload_1
15: aastore
16: invokeinterface #28, 4 // InterfaceMethod java/lang/reflect/InvocationHandler.invoke:(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;
21: checkcast #30 // class java/lang/Boolean
24: invokevirtual #34 // Method java/lang/Boolean.booleanValue:()Z
27: ireturn
28: athrow
29: astore_2
30: new #42 // class java/lang/reflect/UndeclaredThrowableException
33: dup
34: aload_2
35: invokespecial #45 // Method java/lang/reflect/UndeclaredThrowableException."<init>":(Ljava/lang/Throwable;)V
38: athrow
Exception table:
from to target type
0 28 28 Class java/lang/Error
0 28 28 Class java/lang/RuntimeException
0 28 29 Class java/lang/Throwable
Exceptions:
throws
public final java.lang.String toString() throws ;
descriptor: ()Ljava/lang/String;
flags: ACC_PUBLIC, ACC_FINAL
Code:
stack=10, locals=2, args_size=1
0: aload_0
1: getfield #16 // Field java/lang/reflect/Proxy.h:Ljava/lang/reflect/InvocationHandler;
4: aload_0
5: getstatic #50 // Field m2:Ljava/lang/reflect/Method;
8: aconst_null
9: invokeinterface #28, 4 // InterfaceMethod java/lang/reflect/InvocationHandler.invoke:(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;
14: checkcast #52 // class java/lang/String
17: areturn
18: athrow
19: astore_1
20: new #42 // class java/lang/reflect/UndeclaredThrowableException
23: dup
24: aload_1
25: invokespecial #45 // Method java/lang/reflect/UndeclaredThrowableException."<init>":(Ljava/lang/Throwable;)V
28: athrow
Exception table:
from to target type
0 18 18 Class java/lang/Error
0 18 18 Class java/lang/RuntimeException
0 18 19 Class java/lang/Throwable
Exceptions:
throws
public final void request() throws ;
descriptor: ()V
flags: ACC_PUBLIC, ACC_FINAL
Code:
stack=10, locals=2, args_size=1
0: aload_0
1: getfield #16 // Field java/lang/reflect/Proxy.h:Ljava/lang/reflect/InvocationHandler;
4: aload_0
5: getstatic #57 // Field m3:Ljava/lang/reflect/Method;
8: aconst_null
9: invokeinterface #28, 4 // InterfaceMethod java/lang/reflect/InvocationHandler.invoke:(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;
14: pop
15: return
16: athrow
17: astore_1
18: new #42 // class java/lang/reflect/UndeclaredThrowableException
21: dup
22: aload_1
23: invokespecial #45 // Method java/lang/reflect/UndeclaredThrowableException."<init>":(Ljava/lang/Throwable;)V
26: athrow
Exception table:
from to target type
0 16 16 Class java/lang/Error
0 16 16 Class java/lang/RuntimeException
0 16 17 Class java/lang/Throwable
Exceptions:
throws
public final int hashCode() throws ;
descriptor: ()I
flags: ACC_PUBLIC, ACC_FINAL
Code:
stack=10, locals=2, args_size=1
0: aload_0
1: getfield #16 // Field java/lang/reflect/Proxy.h:Ljava/lang/reflect/InvocationHandler;
4: aload_0
5: getstatic #62 // Field m0:Ljava/lang/reflect/Method;
8: aconst_null
9: invokeinterface #28, 4 // InterfaceMethod java/lang/reflect/InvocationHandler.invoke:(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;
14: checkcast #64 // class java/lang/Integer
17: invokevirtual #67 // Method java/lang/Integer.intValue:()I
20: ireturn
21: athrow
22: astore_1
23: new #42 // class java/lang/reflect/UndeclaredThrowableException
26: dup
27: aload_1
28: invokespecial #45 // Method java/lang/reflect/UndeclaredThrowableException."<init>":(Ljava/lang/Throwable;)V
31: athrow
Exception table:
from to target type
0 21 21 Class java/lang/Error
0 21 21 Class java/lang/RuntimeException
0 21 22 Class java/lang/Throwable
Exceptions:
throws
static {} throws ;
descriptor: ()V
flags: ACC_STATIC
Code:
stack=10, locals=2, args_size=0
0: ldc #70 // String java.lang.Object
2: invokestatic #76 // Method java/lang/Class.forName:(Ljava/lang/String;)Ljava/lang/Class;
5: ldc #77 // String equals
7: iconst_1
8: anewarray #72 // class java/lang/Class
11: dup
12: iconst_0
13: ldc #70 // String java.lang.Object
15: invokestatic #76 // Method java/lang/Class.forName:(Ljava/lang/String;)Ljava/lang/Class;
18: aastore
19: invokevirtual #81 // Method java/lang/Class.getMethod:(Ljava/lang/String;[Ljava/lang/Class;)Ljava/lang/reflect/Method;
22: putstatic #20 // Field m1:Ljava/lang/reflect/Method;
25: ldc #70 // String java.lang.Object
27: invokestatic #76 // Method java/lang/Class.forName:(Ljava/lang/String;)Ljava/lang/Class;
30: ldc #82 // String toString
32: iconst_0
33: anewarray #72 // class java/lang/Class
36: invokevirtual #81 // Method java/lang/Class.getMethod:(Ljava/lang/String;[Ljava/lang/Class;)Ljava/lang/reflect/Method;
39: putstatic #50 // Field m2:Ljava/lang/reflect/Method;
42: ldc #84 // String new_package.jvm.p57.Subject
44: invokestatic #76 // Method java/lang/Class.forName:(Ljava/lang/String;)Ljava/lang/Class;
47: ldc #85 // String request
49: iconst_0
50: anewarray #72 // class java/lang/Class
53: invokevirtual #81 // Method java/lang/Class.getMethod:(Ljava/lang/String;[Ljava/lang/Class;)Ljava/lang/reflect/Method;
56: putstatic #57 // Field m3:Ljava/lang/reflect/Method;
59: ldc #70 // String java.lang.Object
61: invokestatic #76 // Method java/lang/Class.forName:(Ljava/lang/String;)Ljava/lang/Class;
64: ldc #86 // String hashCode
66: iconst_0
67: anewarray #72 // class java/lang/Class
70: invokevirtual #81 // Method java/lang/Class.getMethod:(Ljava/lang/String;[Ljava/lang/Class;)Ljava/lang/reflect/Method;
73: putstatic #62 // Field m0:Ljava/lang/reflect/Method;
76: return
77: astore_1
78: new #90 // class java/lang/NoSuchMethodError
81: dup
82: aload_1
83: invokevirtual #93 // Method java/lang/Throwable.getMessage:()Ljava/lang/String;
86: invokespecial #96 // Method java/lang/NoSuchMethodError."<init>":(Ljava/lang/String;)V
89: athrow
90: astore_1
91: new #100 // class java/lang/NoClassDefFoundError
94: dup
95: aload_1
96: invokevirtual #93 // Method java/lang/Throwable.getMessage:()Ljava/lang/String;
99: invokespecial #101 // Method java/lang/NoClassDefFoundError."<init>":(Ljava/lang/String;)V
102: athrow
Exception table:
from to target type
0 77 77 Class java/lang/NoSuchMethodException
0 77 90 Class java/lang/ClassNotFoundException
Exceptions:
throws
}
動態代理實現機制深層次分析與動態字節碼生成總結
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//
package com.sun.proxy;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;
import new_package.jvm.p57.Subject;
public final class $Proxy0 extends Proxy implements Subject {
private static Method m1;
private static Method m2;
private static Method m3;
private static Method m0;
public $Proxy0(InvocationHandler var1) throws {
super(var1);
}
public final boolean equals(Object var1) throws {
try {
return (Boolean)super.h.invoke(this, m1, new Object[]{var1});
} catch (RuntimeException | Error var3) {
throw var3;
} catch (Throwable var4) {
throw new UndeclaredThrowableException(var4);
}
}
public final String toString() throws {
try {
return (String)super.h.invoke(this, m2, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
public final void request() throws {
try {
super.h.invoke(this, m3, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
public final int hashCode() throws {
try {
return (Integer)super.h.invoke(this, m0, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
static {
try {
m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
m2 = Class.forName("java.lang.Object").getMethod("toString");
m3 = Class.forName("new_package.jvm.p57.Subject").getMethod("request");
m0 = Class.forName("java.lang.Object").getMethod("hashCode");
} catch (NoSuchMethodException var2) {
throw new NoSuchMethodError(var2.getMessage());
} catch (ClassNotFoundException var3) {
throw new NoClassDefFoundError(var3.getMessage());
}
}
}
動態代理
- java Proxy
- 必須是接口
- 生成代理類（extends Proxy implements XXX ），實現 InvocationHadler 接口，添加自己的業務邏輯
- cglib
- 非 final class
- 動態生成一個子類繼承該類，然後重新父類方法，添加自己的業務邏輯
- javassist