类文件解析器

Question

I have an assignment where i need to write a Java program that parses a .class file and retrieves things like :

1.name of the .java file

2.implemented interfaces

3.variables

4.constructors

5.methods

I don't have any ideeas where to begin from? For example,what kind of Data I/O structure should I use?

Answer 1

You don't need any external library, just use java.lang.Class . Write the name of your class:

[NameOfMyClass].class.getDeclaredFields();
[NameOfMyClass].class.getDeclaredConstructors();
[NameOfMyClass].class.getDeclaredMethods();

It's the same for interfaces and many other attributes.

Answer 2

There are already several libraries for classfile parsing out there. Objectweb ASM is the most popular.

If you have to do it from scratch, that I'd recommend starting by the JVM specification , which explains the binary layout of classfiles in detail. After that, parsing is just a simple matter of programming. I've written a classfile parser before, it's not that hard.

Answer 3

You can use Java Reflection. Here is a good tutorial -->

Java Reflection Tutorial

Answer 4

• You can you ClassParser which is available in Apache commons library. you can read the Javadoc here . You can download apache commons fromhere
• You can also use Java reflection API which provides method such as getDeclaredFileds , getDeclaredMethods etc.

Answer 5

OpenJDK actually comes with an API that lets you parse and manipulate class files programmatically that most programmers don't know about. It is located at the package com.sun.org.apache.bcel.internal .