JAVA怎么给一个对象动态添加属性?

public class Student {

    private int age;

    private String name;

    public int getAge() {

        return age;

    }

    public void setAge(int age) {

        this.age = age;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }    

}

import org.objectweb.asm.ClassAdapter;

import org.objectweb.asm.ClassVisitor;

import org.objectweb.asm.FieldVisitor;



public class AddFieldAdapter extends ClassAdapter {

    private int accessModifier;

    private String name;

    private String desc;

    private boolean isFieldPresent;



    public AddFieldAdapter(ClassVisitor cv, int accessModifier, String name, String desc) {

        super(cv);

        this.accessModifier = accessModifier;

        this.name = name;

        this.desc = desc;

    }



    @Override

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

            String signature, Object value) {

        if (name.equals(this.name)) {

            isFieldPresent = true;

        }

        return cv.visitField(access, name, desc, signature, value);

    }



    @Override

    public void visitEnd() {

        if (!isFieldPresent) {

            FieldVisitor fv = cv.visitField(accessModifier, name, desc, null, null);

            if (fv != null) {

                fv.visitEnd();

            }

        }

        cv.visitEnd();

    }

}

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.OutputStream;



import org.objectweb.asm.ClassAdapter;

import org.objectweb.asm.ClassReader;

import org.objectweb.asm.ClassWriter;

import org.objectweb.asm.Opcodes;



public class AddField {



    private Class clazz = null;

    private ClassReader cr = null;

    private ClassWriter cw = null;

    private ClassAdapter ca = null;

    private File classFile = null;



    private final static String CLASS_FILE_SUFFIX = ".class";



    public AddField(Class clazz) {

        this.clazz = clazz;

    }



    /**

     * 添加一个 public 的类成员

     * @param fieldName     类成员名

     * @param fieldDesc     类成员类型描述

     */

    public void addPublicField(String fieldName, String fieldDesc) {

        if(cr == null) {

            try {

                cr = new ClassReader(clazz.getCanonicalName());

            } catch (IOException e) {

                e.printStackTrace();

            }

            cw = new ClassWriter(cr, ClassWriter.COMPUTE_MAXS);

        }

        if(ca == null) {

            ca = new AddFieldAdapter(cw, Opcodes.ACC_PUBLIC, fieldName, fieldDesc);

        } else {

            ca = new AddFieldAdapter(ca, Opcodes.ACC_PUBLIC, fieldName, fieldDesc);

        }

    }



    /**

     * 将字节码写入类的 .class 文件

     *

     */

    public void writeByteCode() {

        cr.accept(ca, ClassReader.SKIP_DEBUG);

        byte[] bys = cw.toByteArray();

        OutputStream os = null;

        try {

            os = new FileOutputStream(getFile());

            os.write(bys);

        } catch (IOException e) {

            e.printStackTrace();

        } finally {

            try {

                os.close();

            } catch (IOException e) {

                e.printStackTrace();

            }

        }

    }



    /**

     * 获得类文件的 File 对象

     * @return

     */

    private File getFile() {

        if(classFile == null) {

            StringBuffer sb = new StringBuffer();

            sb.append(clazz.getResource("/"))

                .append(clazz.getCanonicalName().replace(".", File.separator))

                .append(CLASS_FILE_SUFFIX);

            classFile = new File(sb.substring(6));

        }

        return classFile;

    }

}

public class PreCompileProcess {



    public static void main(String[] args) {



        // 为 Student 添加字段

        AddField add = new AddField(Student.class);



        // 添加一个名为 address，类型为 java.lang.String 的 public 字段 

        add.addPublicField("address", "Ljava/lang/String;");



        // 再增加一个名为 tel，类型为 int 的 public 方法

        add.addPublicField("tel", "I");



        // 重新生成 .class 文件

        add.writeByteCode();

    }

}

public class Test {



    public static void main(String[] args) {

        Student stu = new Student();

        stu.setAge(10);

        stu.setName("Tom");

        stu.address = "Beijing";    // 新增加的 address 字段

        stu.tel = 56;               // 新增加的 tel 字段

        System.out.println("Name:    " + stu.getName());

        System.out.println("Age:     " + stu.getAge());

        System.out.println("Address: " + stu.address);

        System.out.println("Tel:     " + stu.tel);

    }

}