https://github.com/cglib/cglib/cglib: cglib is a powerful, high performance and quality Code Generation Library, It is used to extend JAVA classes and implements interfaces at runtime. 
public class net.sf.cglib.beans.ImmutableBean$Generator extends net.sf.cglib.core.AbstractClassGenerator
  minor version: 0
  major version: 59
  flags: flags: (0x0021) ACC_PUBLIC, ACC_SUPER
  this_class: net.sf.cglib.beans.ImmutableBean$Generator
  super_class: net.sf.cglib.core.AbstractClassGenerator
{
  private static final net.sf.cglib.core.AbstractClassGenerator$Source SOURCE;
    descriptor: Lnet/sf/cglib/core/AbstractClassGenerator$Source;
    flags: (0x001a) ACC_PRIVATE, ACC_STATIC, ACC_FINAL

  private java.lang.Object bean;
    descriptor: Ljava/lang/Object;
    flags: (0x0002) ACC_PRIVATE

  private java.lang.Class target;
    descriptor: Ljava/lang/Class;
    flags: (0x0002) ACC_PRIVATE

  static void <clinit>();
    descriptor: ()V
    flags: (0x0008) ACC_STATIC
    Code:
      stack=3, locals=0, args_size=0
         0: .line 46
            new net.sf.cglib.core.AbstractClassGenerator$Source
            dup
            ldc Lnet/sf/cglib/beans/ImmutableBean;
            invokevirtual java.lang.Class.getName:()Ljava/lang/String;
            invokespecial net.sf.cglib.core.AbstractClassGenerator$Source.<init>:(Ljava/lang/String;)V
            putstatic net.sf.cglib.beans.ImmutableBean$Generator.SOURCE:Lnet/sf/cglib/core/AbstractClassGenerator$Source;
            return
      LocalVariableTable:
        Start  End  Slot  Name  Signature

  public void <init>();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
        start local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
         0: .line 51
            aload 0 /* this */
            getstatic net.sf.cglib.beans.ImmutableBean$Generator.SOURCE:Lnet/sf/cglib/core/AbstractClassGenerator$Source;
            invokespecial net.sf.cglib.core.AbstractClassGenerator.<init>:(Lnet/sf/cglib/core/AbstractClassGenerator$Source;)V
         1: .line 52
            return
        end local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    2     0  this  Lnet/sf/cglib/beans/ImmutableBean$Generator;

  public void setBean(java.lang.Object);
    descriptor: (Ljava/lang/Object;)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
        start local 1 // java.lang.Object bean
         0: .line 55
            aload 0 /* this */
            aload 1 /* bean */
            putfield net.sf.cglib.beans.ImmutableBean$Generator.bean:Ljava/lang/Object;
         1: .line 56
            aload 0 /* this */
            aload 1 /* bean */
            invokevirtual java.lang.Object.getClass:()Ljava/lang/Class;
            putfield net.sf.cglib.beans.ImmutableBean$Generator.target:Ljava/lang/Class;
         2: .line 57
            return
        end local 1 // java.lang.Object bean
        end local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    3     0  this  Lnet/sf/cglib/beans/ImmutableBean$Generator;
            0    3     1  bean  Ljava/lang/Object;
    MethodParameters:
      Name  Flags
      bean  

  protected java.lang.ClassLoader getDefaultClassLoader();
    descriptor: ()Ljava/lang/ClassLoader;
    flags: (0x0004) ACC_PROTECTED
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
         0: .line 60
            aload 0 /* this */
            getfield net.sf.cglib.beans.ImmutableBean$Generator.target:Ljava/lang/Class;
            invokevirtual java.lang.Class.getClassLoader:()Ljava/lang/ClassLoader;
            areturn
        end local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lnet/sf/cglib/beans/ImmutableBean$Generator;

  protected java.security.ProtectionDomain getProtectionDomain();
    descriptor: ()Ljava/security/ProtectionDomain;
    flags: (0x0004) ACC_PROTECTED
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
         0: .line 64
            aload 0 /* this */
            getfield net.sf.cglib.beans.ImmutableBean$Generator.target:Ljava/lang/Class;
            invokestatic net.sf.cglib.core.ReflectUtils.getProtectionDomain:(Ljava/lang/Class;)Ljava/security/ProtectionDomain;
            areturn
        end local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lnet/sf/cglib/beans/ImmutableBean$Generator;

  public java.lang.Object create();
    descriptor: ()Ljava/lang/Object;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=1
        start local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
         0: .line 68
            aload 0 /* this */
            getfield net.sf.cglib.beans.ImmutableBean$Generator.target:Ljava/lang/Class;
            invokevirtual java.lang.Class.getName:()Ljava/lang/String;
            astore 1 /* name */
        start local 1 // java.lang.String name
         1: .line 69
            aload 0 /* this */
            aload 1 /* name */
            invokevirtual net.sf.cglib.beans.ImmutableBean$Generator.setNamePrefix:(Ljava/lang/String;)V
         2: .line 70
            aload 0 /* this */
            aload 1 /* name */
            invokespecial net.sf.cglib.core.AbstractClassGenerator.create:(Ljava/lang/Object;)Ljava/lang/Object;
            areturn
        end local 1 // java.lang.String name
        end local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    3     0  this  Lnet/sf/cglib/beans/ImmutableBean$Generator;
            1    3     1  name  Ljava/lang/String;

  public void generateClass(org.objectweb.asm.ClassVisitor);
    descriptor: (Lorg/objectweb/asm/ClassVisitor;)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=7, locals=10, args_size=2
        start local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
        start local 1 // org.objectweb.asm.ClassVisitor v
         0: .line 74
            aload 0 /* this */
            getfield net.sf.cglib.beans.ImmutableBean$Generator.target:Ljava/lang/Class;
            invokestatic org.objectweb.asm.Type.getType:(Ljava/lang/Class;)Lorg/objectweb/asm/Type;
            astore 2 /* targetType */
        start local 2 // org.objectweb.asm.Type targetType
         1: .line 75
            new net.sf.cglib.core.ClassEmitter
            dup
            aload 1 /* v */
            invokespecial net.sf.cglib.core.ClassEmitter.<init>:(Lorg/objectweb/asm/ClassVisitor;)V
            astore 3 /* ce */
        start local 3 // net.sf.cglib.core.ClassEmitter ce
         2: .line 76
            aload 3 /* ce */
            bipush 52
         3: .line 77
            iconst_1
         4: .line 78
            aload 0 /* this */
            invokevirtual net.sf.cglib.beans.ImmutableBean$Generator.getClassName:()Ljava/lang/String;
         5: .line 79
            aload 2 /* targetType */
         6: .line 80
            aconst_null
         7: .line 81
            ldc "<generated>"
         8: .line 76
            invokevirtual net.sf.cglib.core.ClassEmitter.begin_class:(IILjava/lang/String;Lorg/objectweb/asm/Type;[Lorg/objectweb/asm/Type;Ljava/lang/String;)V
         9: .line 83
            aload 3 /* ce */
            bipush 18
            ldc "CGLIB$RWBean"
            aload 2 /* targetType */
            aconst_null
            invokevirtual net.sf.cglib.core.ClassEmitter.declare_field:(ILjava/lang/String;Lorg/objectweb/asm/Type;Ljava/lang/Object;)V
        10: .line 85
            aload 3 /* ce */
            iconst_1
            getstatic net.sf.cglib.beans.ImmutableBean.CSTRUCT_OBJECT:Lnet/sf/cglib/core/Signature;
            aconst_null
            invokevirtual net.sf.cglib.core.ClassEmitter.begin_method:(ILnet/sf/cglib/core/Signature;[Lorg/objectweb/asm/Type;)Lnet/sf/cglib/core/CodeEmitter;
            astore 4 /* e */
        start local 4 // net.sf.cglib.core.CodeEmitter e
        11: .line 86
            aload 4 /* e */
            invokevirtual net.sf.cglib.core.CodeEmitter.load_this:()V
        12: .line 87
            aload 4 /* e */
            invokevirtual net.sf.cglib.core.CodeEmitter.super_invoke_constructor:()V
        13: .line 88
            aload 4 /* e */
            invokevirtual net.sf.cglib.core.CodeEmitter.load_this:()V
        14: .line 89
            aload 4 /* e */
            iconst_0
            invokevirtual net.sf.cglib.core.CodeEmitter.load_arg:(I)V
        15: .line 90
            aload 4 /* e */
            aload 2 /* targetType */
            invokevirtual net.sf.cglib.core.CodeEmitter.checkcast:(Lorg/objectweb/asm/Type;)V
        16: .line 91
            aload 4 /* e */
            ldc "CGLIB$RWBean"
            invokevirtual net.sf.cglib.core.CodeEmitter.putfield:(Ljava/lang/String;)V
        17: .line 92
            aload 4 /* e */
            invokevirtual net.sf.cglib.core.CodeEmitter.return_value:()V
        18: .line 93
            aload 4 /* e */
            invokevirtual net.sf.cglib.core.CodeEmitter.end_method:()V
        19: .line 95
            aload 0 /* this */
            getfield net.sf.cglib.beans.ImmutableBean$Generator.target:Ljava/lang/Class;
            invokestatic net.sf.cglib.core.ReflectUtils.getBeanProperties:(Ljava/lang/Class;)[Ljava/beans/PropertyDescriptor;
            astore 5 /* descriptors */
        start local 5 // java.beans.PropertyDescriptor[] descriptors
        20: .line 96
            aload 5 /* descriptors */
            iconst_1
            iconst_0
            invokestatic net.sf.cglib.core.ReflectUtils.getPropertyMethods:([Ljava/beans/PropertyDescriptor;ZZ)[Ljava/lang/reflect/Method;
            astore 6 /* getters */
        start local 6 // java.lang.reflect.Method[] getters
        21: .line 97
            aload 5 /* descriptors */
            iconst_0
            iconst_1
            invokestatic net.sf.cglib.core.ReflectUtils.getPropertyMethods:([Ljava/beans/PropertyDescriptor;ZZ)[Ljava/lang/reflect/Method;
            astore 7 /* setters */
        start local 7 // java.lang.reflect.Method[] setters
        22: .line 99
            iconst_0
            istore 8 /* i */
        start local 8 // int i
        23: goto 32
        24: .line 100
      StackMap locals: net.sf.cglib.beans.ImmutableBean$Generator org.objectweb.asm.ClassVisitor org.objectweb.asm.Type net.sf.cglib.core.ClassEmitter net.sf.cglib.core.CodeEmitter java.beans.PropertyDescriptor[] java.lang.reflect.Method[] java.lang.reflect.Method[] int
      StackMap stack:
            aload 6 /* getters */
            iload 8 /* i */
            aaload
            invokestatic net.sf.cglib.core.ReflectUtils.getMethodInfo:(Ljava/lang/reflect/Member;)Lnet/sf/cglib/core/MethodInfo;
            astore 9 /* getter */
        start local 9 // net.sf.cglib.core.MethodInfo getter
        25: .line 101
            aload 3 /* ce */
            aload 9 /* getter */
            iconst_1
            invokestatic net.sf.cglib.core.EmitUtils.begin_method:(Lnet/sf/cglib/core/ClassEmitter;Lnet/sf/cglib/core/MethodInfo;I)Lnet/sf/cglib/core/CodeEmitter;
            astore 4 /* e */
        26: .line 102
            aload 4 /* e */
            invokevirtual net.sf.cglib.core.CodeEmitter.load_this:()V
        27: .line 103
            aload 4 /* e */
            ldc "CGLIB$RWBean"
            invokevirtual net.sf.cglib.core.CodeEmitter.getfield:(Ljava/lang/String;)V
        28: .line 104
            aload 4 /* e */
            aload 9 /* getter */
            invokevirtual net.sf.cglib.core.CodeEmitter.invoke:(Lnet/sf/cglib/core/MethodInfo;)V
        29: .line 105
            aload 4 /* e */
            invokevirtual net.sf.cglib.core.CodeEmitter.return_value:()V
        30: .line 106
            aload 4 /* e */
            invokevirtual net.sf.cglib.core.CodeEmitter.end_method:()V
        end local 9 // net.sf.cglib.core.MethodInfo getter
        31: .line 99
            iinc 8 /* i */ 1
      StackMap locals:
      StackMap stack:
        32: iload 8 /* i */
            aload 6 /* getters */
            arraylength
            if_icmplt 24
        end local 8 // int i
        33: .line 109
            iconst_0
            istore 8 /* i */
        start local 8 // int i
        34: goto 40
        35: .line 110
      StackMap locals:
      StackMap stack:
            aload 7 /* setters */
            iload 8 /* i */
            aaload
            invokestatic net.sf.cglib.core.ReflectUtils.getMethodInfo:(Ljava/lang/reflect/Member;)Lnet/sf/cglib/core/MethodInfo;
            astore 9 /* setter */
        start local 9 // net.sf.cglib.core.MethodInfo setter
        36: .line 111
            aload 3 /* ce */
            aload 9 /* setter */
            iconst_1
            invokestatic net.sf.cglib.core.EmitUtils.begin_method:(Lnet/sf/cglib/core/ClassEmitter;Lnet/sf/cglib/core/MethodInfo;I)Lnet/sf/cglib/core/CodeEmitter;
            astore 4 /* e */
        37: .line 112
            aload 4 /* e */
            getstatic net.sf.cglib.beans.ImmutableBean.ILLEGAL_STATE_EXCEPTION:Lorg/objectweb/asm/Type;
            ldc "Bean is immutable"
            invokevirtual net.sf.cglib.core.CodeEmitter.throw_exception:(Lorg/objectweb/asm/Type;Ljava/lang/String;)V
        38: .line 113
            aload 4 /* e */
            invokevirtual net.sf.cglib.core.CodeEmitter.end_method:()V
        end local 9 // net.sf.cglib.core.MethodInfo setter
        39: .line 109
            iinc 8 /* i */ 1
      StackMap locals:
      StackMap stack:
        40: iload 8 /* i */
            aload 7 /* setters */
            arraylength
            if_icmplt 35
        end local 8 // int i
        41: .line 116
            aload 3 /* ce */
            invokevirtual net.sf.cglib.core.ClassEmitter.end_class:()V
        42: .line 117
            return
        end local 7 // java.lang.reflect.Method[] setters
        end local 6 // java.lang.reflect.Method[] getters
        end local 5 // java.beans.PropertyDescriptor[] descriptors
        end local 4 // net.sf.cglib.core.CodeEmitter e
        end local 3 // net.sf.cglib.core.ClassEmitter ce
        end local 2 // org.objectweb.asm.Type targetType
        end local 1 // org.objectweb.asm.ClassVisitor v
        end local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
      LocalVariableTable:
        Start  End  Slot         Name  Signature
            0   43     0         this  Lnet/sf/cglib/beans/ImmutableBean$Generator;
            0   43     1            v  Lorg/objectweb/asm/ClassVisitor;
            1   43     2   targetType  Lorg/objectweb/asm/Type;
            2   43     3           ce  Lnet/sf/cglib/core/ClassEmitter;
           11   43     4            e  Lnet/sf/cglib/core/CodeEmitter;
           20   43     5  descriptors  [Ljava/beans/PropertyDescriptor;
           21   43     6      getters  [Ljava/lang/reflect/Method;
           22   43     7      setters  [Ljava/lang/reflect/Method;
           23   33     8            i  I
           25   31     9       getter  Lnet/sf/cglib/core/MethodInfo;
           34   41     8            i  I
           36   39     9       setter  Lnet/sf/cglib/core/MethodInfo;
    MethodParameters:
      Name  Flags
      v     

  protected java.lang.Object firstInstance(java.lang.Class);
    descriptor: (Ljava/lang/Class;)Ljava/lang/Object;
    flags: (0x0004) ACC_PROTECTED
    Code:
      stack=6, locals=2, args_size=2
        start local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
        start local 1 // java.lang.Class type
         0: .line 120
            aload 1 /* type */
            getstatic net.sf.cglib.beans.ImmutableBean.OBJECT_CLASSES:[Ljava/lang/Class;
            iconst_1
            anewarray java.lang.Object
            dup
            iconst_0
            aload 0 /* this */
            getfield net.sf.cglib.beans.ImmutableBean$Generator.bean:Ljava/lang/Object;
            aastore
            invokestatic net.sf.cglib.core.ReflectUtils.newInstance:(Ljava/lang/Class;[Ljava/lang/Class;[Ljava/lang/Object;)Ljava/lang/Object;
            areturn
        end local 1 // java.lang.Class type
        end local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lnet/sf/cglib/beans/ImmutableBean$Generator;
            0    1     1  type  Ljava/lang/Class;
    MethodParameters:
      Name  Flags
      type  

  protected java.lang.Object nextInstance(java.lang.Object);
    descriptor: (Ljava/lang/Object;)Ljava/lang/Object;
    flags: (0x0004) ACC_PROTECTED
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
        start local 1 // java.lang.Object instance
         0: .line 125
            aload 0 /* this */
            aload 1 /* instance */
            invokevirtual java.lang.Object.getClass:()Ljava/lang/Class;
            invokevirtual net.sf.cglib.beans.ImmutableBean$Generator.firstInstance:(Ljava/lang/Class;)Ljava/lang/Object;
            areturn
        end local 1 // java.lang.Object instance
        end local 0 // net.sf.cglib.beans.ImmutableBean$Generator this
      LocalVariableTable:
        Start  End  Slot      Name  Signature
            0    1     0      this  Lnet/sf/cglib/beans/ImmutableBean$Generator;
            0    1     1  instance  Ljava/lang/Object;
    MethodParameters:
          Name  Flags
      instance  
}
SourceFile: "ImmutableBean.java"
NestHost: net.sf.cglib.beans.ImmutableBean
InnerClasses:
  public Generator = net.sf.cglib.beans.ImmutableBean$Generator of net.sf.cglib.beans.ImmutableBean
  protected Source = net.sf.cglib.core.AbstractClassGenerator$Source of net.sf.cglib.core.AbstractClassGenerator