ASM 库的 classVisitor 类解析

package org.objectweb.asm;

public abstract class ClassVisitor {
  // 实现的ASM的API版本。该字段的值必须为如下几个之一：Opcodes.ASM4，ASM5，ASM6，ASM7
  protected final int api;
  // 该类的方法可以委托给子类
  protected ClassVisitor cv;
  // 构造器 
  public ClassVisitor(final int api) {
    this(api, null);
  }
  // 构造器
  public ClassVisitor(final int api, final ClassVisitor classVisitor) {
    if (api != Opcodes.ASM6 && api != Opcodes.ASM5 && api != Opcodes.ASM4 && api != Opcodes.ASM7) {
      throw new IllegalArgumentException();
    }
    this.api = api;
    this.cv = classVisitor;
  }
  /**
  * 访问类头部信息
  *
  * @param version
  *            类版本
  * @param access
  *            类访问标识符public等
  * @param name
  *            类名称
  * @param signature
  *            类签名（非泛型为NUll）
  * @param superName
  *            类的父类
  * @param interfaces
  *            类实现的接口
  */
  public void visit(
      final int version,final int access,
      final String name, final String signature,
      final String superName,final String[] interfaces) {
    if (cv != null) {
      cv.visit(version, access, name, signature, superName, interfaces);
    }
  }
  /**
  * 访问类的源文件.
  *
  * @param source
  *            源文件名称
  * @param debug
  *            附加的验证信息，可以为空
  */
  public void visitSource(final String source, final String debug) {
    if (cv != null) {
      cv.visitSource(source, debug);
    }
  }

  public ModuleVisitor visitModule(final String name, final int access, final String version) {
    if (api < Opcodes.ASM6) {
      throw new UnsupportedOperationException("This feature requires ASM6");
    }
    if (cv != null) {
      return cv.visitModule(name, access, version);
    }
    return null;
  }

  public void visitNestHost(final String nestHost) {
    if (api < Opcodes.ASM7) {
      throw new UnsupportedOperationException("This feature requires ASM7");
    }
    if (cv != null) {
      cv.visitNestHost(nestHost);
    }
  }

  public void visitOuterClass(final String owner, final String name, final String descriptor) {
    if (cv != null) {
      cv.visitOuterClass(owner, name, descriptor);
    }
  }
  /**
  * 访问类的注解
  *
  * @param desc
  *            注解类的类描述
  * @param visible
  *            runtime时期注解是否可以被访问
  * @return 返回一个注解值访问器
  */
  public AnnotationVisitor visitAnnotation(final String descriptor, final boolean visible) {
    if (cv != null) {
      return cv.visitAnnotation(descriptor, visible);
    }
    return null;
  }
  /**
  * 访问标注在类型上的注解
  *
  * @param typeRef
  * @param typePath
  * @param desc
  * @param visible
  * @return
  */
  public AnnotationVisitor visitTypeAnnotation(
      final int typeRef, final TypePath typePath, final String descriptor, final boolean visible) {
    if (api < Opcodes.ASM5) {
      throw new UnsupportedOperationException("This feature requires ASM5");
    }
    if (cv != null) {
      return cv.visitTypeAnnotation(typeRef, typePath, descriptor, visible);
    }
    return null;
  }
  /**
  * 访问一个类的属性
  *
  * @param attribute
  *            类的属性
  */
  public void visitAttribute(final Attribute attribute) {
    if (cv != null) {
      cv.visitAttribute(attribute);
    }
  }

  public void visitNestMember(final String nestMember) {
    if (api < Opcodes.ASM7) {
      throw new UnsupportedOperationException("This feature requires ASM7");
    }
    if (cv != null) {
      cv.visitNestMember(nestMember);
    }
  }
  /**
  * 访问内部类信息
  * @param name
  * @param outerName
  * @param innerName
  * @param access
  */
  public void visitInnerClass(
      final String name, final String outerName, final String innerName, final int access) {
    if (cv != null) {
      cv.visitInnerClass(name, outerName, innerName, access);
    }
  }
  /**
  * 访问类的字段
  * @param access
  * @param name
  * @param desc
  * @param signature
  * @param value
  * @return
  */
  public FieldVisitor visitField(
      final int access,
      final String name,
      final String descriptor,
      final String signature,
      final Object value) {
    if (cv != null) {
      return cv.visitField(access, name, descriptor, signature, value);
    }
    return null;
  }
  /**
  * 访问类的方法
  * @param access
  * @param name
  * @param desc
  * @param signature
  * @param exceptions
  * @return
  */
  public MethodVisitor visitMethod(
      final int access,
      final String name,
      final String descriptor,
      final String signature,
      final String[] exceptions) {
    if (cv != null) {
      return cv.visitMethod(access, name, descriptor, signature, exceptions);
    }
    return null;
  }

  public void visitEnd() {
    if (cv != null) {
      cv.visitEnd();
    }
  }
}