Java introspection: object to map

Question

I have a Java object obj that has attributes obj.attr1, obj.attr2 etc. The attributes are possibly accessed through an extra level of

Answer 1

None of these work for nested properties, object mapper does a fair job except that you have to set all values on all fields you want to see in map and even then you cannot avoid/ignore objects own @Json annotations easily in ObjectMapper basically skip some of the properties. So unfortunately, you have to do something like the following, it is only a draft to just give an idea.

/*
     * returns fields that have getter/setters including nested fields as
     * field0, objA.field1, objA.objB.field2, ... 
     * to take care of recursive duplicates, 
     * simply use a set to track which classes
     * have already been traversed
     */
    public static void getBeanUtilsNestedFields(String prefix, 
            Class clazz,  List nestedFieldNames) throws Exception {
        PropertyDescriptor[] descriptors = BeanUtils.getPropertyDescriptors(clazz);
        for(PropertyDescriptor descr : descriptors){
            // if you want values, use: descr.getValue(attributeName)
            if(descr.getPropertyType().getName().equals("java.lang.Class")){
                continue;
            }
            // a primitive, a CharSequence(String), Number, Date, URI, URL, Locale, Class, or corresponding array
            // or add more like UUID or other types
            if(!BeanUtils.isSimpleProperty(descr.getPropertyType())){
                Field collectionfield = clazz.getDeclaredField(descr.getName());
                if(collectionfield.getGenericType() instanceof ParameterizedType){
                    ParameterizedType integerListType = (ParameterizedType) collectionfield.getGenericType();
                    Class actualClazz = (Class) integerListType.getActualTypeArguments()[0];
                    getBeanUtilsNestedFields(descr.getName(), actualClazz, nestedFieldNames);
                }
                else{   // or a complex custom type to get nested fields
                    getBeanUtilsNestedFields(descr.getName(), descr.getPropertyType(), nestedFieldNames);
                }
            }
            else{
                nestedFieldNames.add(prefix.concat(".").concat(descr.getDisplayName()));
            }
        }
    }