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首页ASM4开发手册：英文原版与CGLIB字节码库解析

ASM4开发手册：英文原版与CGLIB字节码库解析

cglib

java

动态代理

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ASM4.0是一款专为Java字节码操作而设计的Java字节码工程库，由Eric Bruneton开发并享有版权。该手册提供了深入的细节，展示了ASM在CGlib动态代理框架中的核心作用。CGlib是一个广泛使用的轻量级的Java代码生成库，它利用ASM对Java类的字节码进行分析和修改，实现了动态代理的功能，即在运行时动态创建和执行代理类。 ASM的核心特性包括低级别的字节码操作接口，允许开发者直接操作类文件的二进制表示，如方法调用、字段访问、指令插入和删除等。这使得在不改变源代码的情况下，能够实现诸如AOP（面向切面编程）中的动态代理功能，例如创建动态代理对象来拦截目标方法的执行，实现事务管理、日志记录等功能。在使用ASM4.0时，开发者需要注意以下几点： 1. 版权与许可：在使用ASM的源代码（例如XML或LaTeX格式）时，必须保留版权声明、条件列表以及免责声明，并确保未经作者明确书面许可，不得将作者的名字用于推广基于此文档的产品。 2. 使用限制：编译后的文档（如PDF、PostScript、HTML等）同样需要包含版权声明和免责声明，且不能暗示或保证其适用于特定目的的适销性或适合性。 3. 责任声明：作者提供的文档是"原样"提供的，不附带任何形式的明示或默示保证，包括但不限于适销性和特定用途的适用性。因此，在使用ASM时，用户需要自行承担风险，理解并接受可能存在的局限性。 ASM4.0开发手册为Java开发者提供了一把强大的字节码操作工具，通过理解并掌握其原理，可以实现高效、灵活的动态代理机制，提升软件的灵活性和可扩展性。然而，使用时务必遵守相关条款，尊重作者权益。

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2. Classes

• A compiled class does not contain comments, of course, but can contain

class, ﬁeld, method and code attributes that can be used to associate

additional information to these elements. Since the introduction of an-

notations in Java 5, which can be used for the same purpose, attributes

have become mostly useless.

• A compiled class does not contain a package and import section, so all

type names must be fully qualiﬁed.

Another very important structural diﬀerence is that a compiled class contains

a constant pool section. This pool is an array containing all the numeric, string

and type constants that appear in the class. These constants are deﬁned only

once, in the constant pool section, and are referenced by their index in all other

sections of the class ﬁle. Hopefully ASM hides all the details related to the

constant pool, so you will not have to bother about it. Figure 2.1 summarizes

the overall structure of a compiled class. The exact structure is described in

the Java Virtual Machine Speciﬁcation, section 4.

Modiﬁers, name, super class, interfaces

Constant pool: numeric, string and type constants

Source ﬁle name (optional)

Enclosing class reference

Annotation*

Attribute*

Inner class* Name

Field* Modiﬁers, name, type

Annotation*

Attribute*

Method* Modiﬁers, name, return and parameter types

Annotation*

Attribute*

Compiled code

Figure 2.1.: Overall structure of a compiled class (* means zero or more)

Another important diﬀerence is that Java types are represented diﬀerently in

compiled and source classes. The next sections explain their representation in

compiled classes.

2.1. Structure

2.1.2. Internal names

In many situations a type is constrained to be a class or interface type. For

instance the super class of a class, the interfaces implemented by a class, or

the exceptions thrown by a method cannot be primitive types or array types,

and are necessarily class or interface types. These types are represented in

compiled classes with internal names. The internal name of a class is just the

fully qualiﬁed name of this class, where dots are replaced with slashes. For

example the internal name of String is java/lang/String.

2.1.3. Type descriptors

Internal names are used only for types that are constrained to be class or

interface types. In all other situations, such as ﬁeld types, Java types are

represented in compiled classes with type descriptors (see Figure 2.2).

Java type Type descriptor

boolean Z

char C

byte B

short S

int I

float F

long J

double D

Object Ljava/lang/Object;

int[] [I

Object[][] [[Ljava/lang/Object;

Figure 2.2.: Type descriptors of some Java types

The descriptors of the primitive types are single characters: Z for boolean, C

for char, B for byte, S for short, I for int, F for float, J for long and D

for double. The descriptor of a class type is the internal name of this class,

preceded by L and followed by a semicolon. For instance the type descriptor

of String is Ljava/lang/String;. Finally the descriptor of an array type is

a square bracket followed by the descriptor of the array element type.

2. Classes

2.1.4. Method descriptors

A method descriptor is a list of type descriptors that describe the parameter

types and the return type of a method, in a single string. A method descriptor

starts with a left parenthesis, followed by the type descriptors of each formal

parameter, followed by a right parenthesis, followed by the type descriptor of

the return type, or V if the method returns void (a method descriptor does

not contain the method’s name or the argument names).

Method declaration in source ﬁle Method descriptor

void m(int i, float f) (IF)V

int m(Object o) (Ljava/lang/Object;)I

int[] m(int i, String s) (ILjava/lang/String;)[I

Object m(int[] i) ([I)Ljava/lang/Object;

Figure 2.3.: Sample method descriptors

Once you know how type descriptors work, understanding method descriptors

is easy. For instance (I)I describes a method that takes one argument of type

int, and returns an int. Figure 2.3 gives several method descriptor examples.

2.2. Interfaces and components

2.2.1. Presentation

The ASM API for generating and transforming compiled classes is based on

the ClassVisitor abstract class (see Figure 2.4). Each method in this class

corresponds to the class ﬁle structure section of the same name (see Figure

2.1). Simple sections are visited with a single method call whose arguments

describe their content, and which returns void. Sections whose content can be

of arbitrary length and complexity are visited with a initial method call that

returns an auxiliary visitor class. This is the case of the visitAnnotation,

visitField and visitMethod methods, which return an AnnotationVisitor,

a FieldVisitor and a MethodVisitor respectively.

The same principles are used recursively for these auxiliary classes. For ex-

ample each method in the FieldVisitor abstract class (see Figure 2.5) corre-

sponds to the class ﬁle sub structure of the same name, and visitAnnotation

2.2. Interfaces and components

public abstract class ClassVisitor {

public ClassVisitor(int api);

public ClassVisitor(int api, ClassVisitor cv);

public void visit(int version, int access, String name,

String signature, String superName, String[] interfaces);

public void visitSource(String source, String debug);

public void visitOuterClass(String owner, String name, String desc);

AnnotationVisitor visitAnnotation(String desc, boolean visible);

public void visitAttribute(Attribute attr);

public void visitInnerClass(String name, String outerName,

String innerName, int access);

public FieldVisitor visitField(int access, String name, String desc,

String signature, Object value);

public MethodVisitor visitMethod(int access, String name, String desc,

String signature, String[] exceptions);

void visitEnd();

}

Figure 2.4.: The ClassVisitor class

returns an auxiliary AnnotationVisitor, as in ClassVisitor. The creation

and usage of these auxiliary visitors is explained in the next chapters: in-

deed this chapter is restricted to simple problems that can be solved with the

ClassVisitor class alone.

public abstract class FieldVisitor {

public FieldVisitor(int api);

public FieldVisitor(int api, FieldVisitor fv);

public AnnotationVisitor visitAnnotation(String desc, boolean visible);

public void visitAttribute(Attribute attr);

public void visitEnd();

}

Figure 2.5.: The FieldVisitor class

The methods of the ClassVisitor class must be called in the following order,

speciﬁed in the Javadoc of this class:

visit visitSource? visitOuterClass? ( visitAnnotation | visitAttribute )*

( visitInnerClass | visitField | visitMethod )*

visitEnd

This means that visit must be called ﬁrst, followed by at most one call to

visitSource, followed by at most one call to visitOuterClass, followed by

2. Classes

any number of calls in any order to visitAnnotation and visitAttribute,

followed by any number of calls in any order to visitInnerClass, visitField

and visitMethod, and terminated by a single call to visitEnd.

ASM provides three core components based on the ClassVisitor API to

generate and transform classes:

• The ClassReader class parses a compiled class given as a byte array,

and calls the corresponding visitXxx methods on the ClassVisitor

instance passed as argument to its accept method. It can be seen as an

event producer.

• The ClassWriter class is a subclass of the ClassVisitor abstract class

that builds compiled classes directly in binary form. It produces as

output a byte array containing the compiled class, which can be retrieved

with the toByteArray method. It can be seen as an event consumer.

• The ClassVisitor class delegates all the method calls it receives to

another ClassVisitor instance. It can be seen as an event ﬁlter.

The next sections show with concrete examples how these components can be

used to generate and transform classes.

2.2.2. Parsing classes

The only required component to parse an existing class is the ClassReader

component. Let’s take an example to illustrate this. Suppose that we would

like to print the content of a class, in a similar way as the javap tool. The ﬁrst

step is to write a subclass of the ClassVisitor class that prints information

about the classes it visits. Here is a possible, overly simpliﬁed implementation:

public class ClassPrinter extends ClassVisitor {

public ClassPrinter() {

super(ASM4);

}

public void visit(int version, int access, String name,

String signature, String superName, String[] interfaces) {

System.out.println(name + " extends " + superName + " {");

}

public void visitSource(String source, String debug) {

}

public void visitOuterClass(String owner, String name, String desc) {

}

public AnnotationVisitor visitAnnotation(String desc,

boolean visible) {

剩余153页未读，继续阅读

./configure --prefix=/home/lw/opencv_4/zwork --host=arm-linux-gnueabihf --cross-prefix=arm-linux-gnueabihf- --disable-asm --enable-shared

- `--prefix=/home/lw/opencv_4/zwork`：指定安装目录为`/home/lw/opencv_4/zwork`，你可以根据需要更改为你希望安装的目录。 - `--host=arm-linux-gnueabihf`：指定目标设备的架构为ARMv7，并使用相应的工具链进行...

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ASM4开发手册：英文原版与CGLIB字节码库解析

ASM使用指南-中文版

ASM4使用指南.

ASM4使用指南

oracleasm-support-2.1.8-1.el6.x86_64.rpm

./configure --prefix=/home/lw/opencv_4/zwork --host=arm-linux-gnueabihf --cross-prefix=arm-linux-gnueabihf- --disable-asm --enable-shared

oracleasm-support-2.1.8-3.el7.x86_64.rpm 下载

oracleasm-support-2.1.8-3.el7.x86_64.rpm

kmod-oracleasm-2.0.8-26.el7.x86_64.rpm

kmod-oracleasm-2.0.8-15.el6_9.x86_64安装包

oracleasm-support 安装

asm1061 数据手册

asm1166 数据手册

kmod-oracleasm-2.0.8-13.el6_8.x86_64.rpm

asm1064芯片手册

ASM1117数据手册

asm1083芯片手册

ubuntu /usr/include/asm-generic/目录没有上面的文件和文件夹asm/sysreg-defs.h

cmake fatal error: asm/sysreg-defs.h: No such file or directory

ln -s asm-$2 asm

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