[ASM教程]#2生成类

首发于Enaium的个人博客

public class Learn2 {
   
    public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
   
        ClassWriter classWriter = new ClassWriter(ClassWriter.COMPUTE_MAXS);
        classWriter.visit(V1_8, ACC_PUBLIC, "cn/enaium/learn/asm/learn2/Learn2Test", null, "java/lang/Object", null);//类信息
        MethodVisitor methodVisitor = classWriter.visitMethod(ACC_PUBLIC + ACC_STATIC, "render", "()V", null, null);//插入方法
        methodVisitor.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");//插入字段
        methodVisitor.visitLdcInsn("Hello ASM!");//插入LDC
        methodVisitor.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);//插入方法
        methodVisitor.visitMaxs(2, 1);//设置栈和局部变量大小
        methodVisitor.visitInsn(RETURN);//插入返回
        methodVisitor.visitEnd();//结束
        classWriter.visitEnd();//结束

        //生成类
        try {
   
            FileOutputStream out = new FileOutputStream(Learn2.class.getResource("/cn/enaium/learn/asm/learn2/").getPath() + "Learn2Test.class");
            out.write(classWriter.toByteArray());
            out.close();
        } catch (Exception e) {
   
            e.printStackTrace();
        }
    }
}