Dynamically generating classes in memory using Javaassist __java

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Javassist is an Open-source class library for parsing, editing, and creating Java bytecode. was created by Shigeru Chiba (Thousand Yezi) of the Mathematics and Computer Science Department of the Tokyo University of Technology. It has joined the open source JBoss Application Server project to implement a dynamic "AOP" framework for JBoss by using javassist for bytecode operations.

Now let's learn how to use Javaassist.

Package wjc.javaassist;

Import javassist.*;
Import Java.lang.reflect.Method;

Import Java.net.URLDecoder; /** * <pre> * Test javaassist Direct operation of Java bytecode files * </pre> * Author: Wang Junshu * date:2018-02-21 22:21 * blog:http:
 BLOG.CSDN.NET/DERRANTCM * Github:https://github.com/wang-jun-chao * all Rights Reserved!!! */public class Classgeneration {public static void main (string[] args) {Classpool pool = Classpool.getdefau
        Lt ();

        Ctclass cc = Pool.makeclass ("Wjc.javaassist.bean.Boss");
            try {Ctfield f1 = ctfield.make ("private int id;", cc);
            Ctfield F2 = ctfield.make ("Private String name;", CC);

            Ctfield F3 = Ctfield.make ("private int age;", CC);
            Cc.addfield (F1);
            Cc.addfield (F2);

            Cc.addfield (F3);
            Ctmethod m1 = Ctmethod.make ("public int getId () {return id;}", CC);
            Ctmethod m2 = ctmethod.make ("public void setId (int id) {$0.id=$1;}", CC); Cc.addmEthod (M1);

            Cc.addmethod (m2);
            Ctmethod m3 = ctmethod.make ("Public String GetName () {return name;}", CC);
            Ctmethod M4 = Ctmethod.make ("public void SetName (String name) {$0.name=$1;}", CC);
            Cc.addmethod (m3);


            Cc.addmethod (M4);
            Parameterless Construction constructor Ctconstructor Constructor1 = new Ctconstructor (New ctclass[]{}, CC); Constructor1.setbody ("{$0.id=1; $0.name=\ "Wjc\";
            $0.age=20;} ");


            Cc.addconstructor (Constructor1); A parameter constructor ctconstructor Constructor2 = new Ctconstructor (new Ctclass[]{ctclass.inttype, Pool.get ("Java.lang.St
            Ring "), Ctclass.inttype}, CC);
            Constructor2.setbody ("{$0.id=$1;$0.name=$2;$0.age=$3;}");



            Cc.addconstructor (CONSTRUCTOR2);
            Takes the root path of the current application run String path = ClassGeneration.class.getClassLoader (). GetResource (""). GetPath (); Path = Path.contains (":")?
            Path.substring (1): path; Path = URldecoder.decode (Path, "Utf-8");

            Class is generated to the root path under cc.writefile (path); Create a parameterless instance through reflection and fetch the EM method///To prevent the compiler from making an error, use the O Declaration and keep using Object o = Class.forName ("Wjc.javaassist.bean.Boss
            "). newinstance ();
            Method getter = O.getclass (). GetMethod ("GetName");

        System.out.println (Getter.invoke (o));
        catch (Exception e) {e.printstacktrace ();
 }

    }
}

Run Result:

Generated classes