Create simple POJO classes (bytecode) at runtime (dynamically)

Question

I\'ve the following scenario..

I am writing some tool that run user-entered query against the database and return the result..

The simplest way is to return

Answer 1

Creating a simple POJO with getters and setters is easy if you use CGLib:

public static Class createBeanClass(
    /* fully qualified class name */
    final String className,
    /* bean properties, name -> type */
    final Map> properties){

    final BeanGenerator beanGenerator = new BeanGenerator();

    /* use our own hard coded class name instead of a real naming policy */
    beanGenerator.setNamingPolicy(new NamingPolicy(){
        @Override public String getClassName(final String prefix,
            final String source, final Object key, final Predicate names){
            return className;
        }});
    BeanGenerator.addProperties(beanGenerator, properties);
    return (Class) beanGenerator.createClass();
}

Test code:

public static void main(final String[] args) throws Exception{
    final Map> properties =
        new HashMap>();
    properties.put("foo", Integer.class);
    properties.put("bar", String.class);
    properties.put("baz", int[].class);

    final Class beanClass =
        createBeanClass("some.ClassName", properties);
    System.out.println(beanClass);
    for(final Method method : beanClass.getDeclaredMethods()){
        System.out.println(method);
    }

}

Output:

class some.ClassName
public int[] some.ClassName.getBaz()
public void some.ClassName.setBaz(int[])
public java.lang.Integer some.ClassName.getFoo()
public void some.ClassName.setFoo(java.lang.Integer)
public java.lang.String some.ClassName.getBar()
public void some.ClassName.setBar(java.lang.String)

But the problem is: you have no way of coding against these methods, as they don't exist at compile time, so I don't know what good this will do you.