USE REFLECTION TO DETERMINE PRIMITIVE PROPERTIES

Java reflection is a powerful application program interface (API) for
examining and performing operations on objects at runtime. It allows 
the
coder to look at an unknown object and retrieve information about its
features, such as its methods, JavaBean properties, and inheritence 
trees.

Two types of values exist in Java. The first is the class type, which 
is
the building block of object-orientation that defines the object
properties within a class. The second is the primitive type. Reflection 
is most
commonly used with class values, but it's also easy to use with Java
primitives.

The primitive types in Java are derived from C-based syntax. They are:

boolean byte short int long float double char

There is a Java class associated with each primitive type. These 
classes
exist in the java.lang package, which is automatically imported into 
all
source files.

Special constants on the java.lang primitive class wrappers represent
the type of primitive instead of the class. For example, Integer.TYPE
represents the type 'int' rather than the type 'Integer' and Byte.TYPE
represents 'byte'. This makes it possible to create generic components 
that act
upon an unknown JavaBean.

Here's an example of a snippet that sets the values in a JavaBean from
an incoming HttpServletRequest:

// thrown Exceptions are left out for ease of reading...
Object bean = ....
BeanInfo bi = Introspector.getBeanInfo(bean.getClass( ));
PropertyDescriptor[ ] pds = bi.getPropertyDescriptors( );
for(int i=0; i<pds.length; i++) {
    String name = pds[i].getName( );
    String value = request.getParameter(name);
    if(value != null) {
        Method method = pds[i].getWriteMethod( );
        value = convert(value, method.getParameterType( )[0]);
        method.invoke(bean, new Object[ ] { value } );
    }
}

The only code that's missing is the convert method, which is defined as
follows:

public Object convert(Object value, Class type) {
    String name = type.getName( );
    if( "java.lang.String.equals(name) ) {
        return value.toString();
    } else
    if( "java.lang.Long".equals(name) || (type == Long.TYPE) ) {
        return convertToLong(value);
    } else
    if( "java.lang.Integer".equals(name) || (type == Integer.TYPE) ) {
        return convertToInteger(value);
    } else
        .....
}

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