generate class and read json

gistfile1.java

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;

import org.apache.commons.beanutils.PropertyUtils;
import org.codehaus.jackson.JsonProcessingException;
import org.codehaus.jackson.map.ObjectMapper;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;



public class GenNewClassTest implements Opcodes {

    public static void main(String[] args) throws InstantiationException, IllegalAccessException, InvocationTargetException, NoSuchMethodException, JsonProcessingException, IOException {
        
        
        Class<? extends DBStatusHolder> generatedClass = generateClass(MyTestCase.class, "myProperty");

        ObjectMapper mapper = new ObjectMapper();
        DBStatusHolder dbQuery = mapper.reader(generatedClass).readValue(
                "{"
                + "\"statusId\": 1, "
                + "\"statusMsg\": \"hello\", "
                + "\"myProperty\":{"
                +                   "\"value\":\"Hello json world!\""
                +                 "}"
                + "}");
        
        System.out.println("DB Query: " + dbQuery);
        MyTestCase retrieved = (MyTestCase) PropertyUtils.getProperty(dbQuery, "myProperty");
        System.out.println(retrieved.getValue());
        
        
      }


    private static Class<? extends DBStatusHolder> generateClass(Class propType, String propName) {
        ClassWriter e = new ClassWriter(0);
        
        e.visit(V1_5, ACC_PUBLIC + ACC_SUPER, "MyFamousClass",null, "DBStatusHolder", null);
        createCtor(e);
        
            String internalName = "L" + propType.getName().replace('.', '/') + ";";
            e.visitField(0, propName, internalName, null, null).visitEnd();
            createSetter("MyFamousClass", propName, internalName, e);
            createGetter("MyFamousClass", propName, internalName, e);

        e.visitEnd();
        byte[] byteArray = e.toByteArray();
        Class loadedClass = loadClass("MyFamousClass", byteArray);
        return loadedClass;
    }
    
    static void createCtor( ClassWriter e) {
        MethodVisitor mv = e.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
        mv.visitCode();
        mv.visitVarInsn(ALOAD, 0);
        mv.visitMethodInsn(INVOKESPECIAL, "DBStatusHolder", "<init>", "()V");
        mv.visitInsn(RETURN);
        mv.visitMaxs(1, 1);
        mv.visitEnd();
     }
    
    static void createSetter(String className, String propertyName, String type, ClassWriter e) {
        String methodName = "set" + propertyName.substring(0, 1).toUpperCase() + propertyName.substring(1);
        MethodVisitor mv = e.visitMethod(ACC_PUBLIC, methodName, "(" + type + ")V", null, null);
        mv.visitCode();
        mv.visitVarInsn(ALOAD, 0);
        mv.visitVarInsn(Type.getType(type).getOpcode(ILOAD), 1);
        mv.visitFieldInsn(PUTFIELD, className, propertyName, type);
        mv.visitInsn(RETURN);
        mv.visitMaxs(2, 2);
        mv.visitEnd();
      }

      static void createGetter(String className, String propertyName, String returnType, ClassWriter e) {
        String methodName = "get" + propertyName.substring(0, 1).toUpperCase() + propertyName.substring(1);
        MethodVisitor mv = e.visitMethod(ACC_PUBLIC, methodName, "()" + returnType, null, null);
        mv.visitCode();
        mv.visitVarInsn(ALOAD, 0);
        mv.visitFieldInsn(GETFIELD, className, propertyName, returnType);
        mv.visitInsn(Type.getType(returnType).getOpcode(IRETURN));
        mv.visitMaxs(1, 1);
        mv.visitEnd();
      }
      
      private static Class loadClass(String className, byte[] b) {
          //override classDefine (as it is protected) and define the class.
          Class clazz = null;
          try {
            ClassLoader loader = ClassLoader.getSystemClassLoader();
            Class cls = Class.forName("java.lang.ClassLoader");
            java.lang.reflect.Method method =
              cls.getDeclaredMethod("defineClass", new Class[] { String.class, byte[].class, int.class, int.class });

            // protected method invocaton
            method.setAccessible(true);
            try {
              Object[] args = new Object[] { className, b, new Integer(0), new Integer(b.length)};
              clazz = (Class) method.invoke(loader, args);
            } finally {
              method.setAccessible(false);
            }
          } catch (Exception e) {
            e.printStackTrace();
            System.exit(1);
          }
          return clazz;
        }

}

class MyTestCase {

    
    String value;

    
    public MyTestCase() {
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }
  
    
    
    
}



class DBStatusHolder {

    private int statusId;
    private String statusMsg;
    
    
    public int getStatusId() {
        return statusId;
    }
    public void setStatusId(int statusId) {
        this.statusId = statusId;
    }
    public String getStatusMsg() {
        return statusMsg;
    }
    public void setStatusMsg(String statusMsg) {
        this.statusMsg = statusMsg;
    }
    @Override
    public String toString() {
        return "DBStatusHolder [statusId=" + statusId + ", statusMsg=" + statusMsg + "]";
    }
 
    
}