Java 字節碼操控框架ASM（二）：Parsing class

解析類需要的ASM框架的類是：ClassReader

ClassPrinter.java

package com.asm.readclass;
import org.objectweb.asm.*;

/**
 * Created by ouer1994 on 2/19/2017.
 */
public class ClassPrinter extends ClassVisitor {
    public ClassPrinter() {
        super(Opcodes.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) {
        return null;
    }

    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) {
        System.out.println(" " + desc + " " + name);
        return null;
    }

    public MethodVisitor visitMethod(int access, String name,
                                     String desc, String signature, String[] exceptions) {
        System.out.println(" " + name + desc);
        return null;
    }

    public void visitEnd() {
        System.out.println("}");
    }
}

MainDo.java 執行這個類中的main方法，控制檯就會打印出結果。

package com.asm.readclass;
import org.objectweb.asm.ClassReader;
import java.io.IOException;

/**
 * Created by ouer1994 on 2/19/2017.
 */
public class MainDo {
    public static void main(String[] a) {
        try {
            ClassPrinter classPrinter = new ClassPrinter();
            ClassReader classReader = new ClassReader("java.lang.Runnable");
            classReader.accept(classPrinter, 0);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

打印結果：

java/lang/Runnable extends java/lang/Object {
 run()V
}