Is there a version of BeanUtils.describe(customer) that recursively calls the describe() method on the complex attributes of 'customer'.
class Customer {
String id;
Address address;
}
Here, I would like the describe method to retrieve the contents of the address attribute as well.
Currently, all I have can see the name of the class as follows:
{id=123, address=com.test.entities.Address@2a340e}
Funny, I would like the describe method to retrieve the contents of nested attributes as well, I don't understand why it doesn't. I went ahead and rolled my own, though. Here it is, you can just call:
Map<String,String> beanMap = BeanUtils.recursiveDescribe(customer);
A couple of caveats.
Also, fyi, this is roughly taken from a project I've been working on called, affectionately, java in jails so you could just download it and then run:
Map<String, String[]> beanMap = new SimpleMapper().toMap(customer);
Though, you'll notice that it returns a String[], instead of a String, which may not work for your needs. Anyway, the below code should work, so have at it!
public class BeanUtils {
public static Map<String, String> recursiveDescribe(Object object) {
Set cache = new HashSet();
return recursiveDescribe(object, null, cache);
}
private static Map<String, String> recursiveDescribe(Object object, String prefix, Set cache) {
if (object == null || cache.contains(object)) return Collections.EMPTY_MAP;
cache.add(object);
prefix = (prefix != null) ? prefix + "." : "";
Map<String, String> beanMap = new TreeMap<String, String>();
Map<String, Object> properties = getProperties(object);
for (String property : properties.keySet()) {
Object value = properties.get(property);
try {
if (value == null) {
//ignore nulls
} else if (Collection.class.isAssignableFrom(value.getClass())) {
beanMap.putAll(convertAll((Collection) value, prefix + property, cache));
} else if (value.getClass().isArray()) {
beanMap.putAll(convertAll(Arrays.asList((Object[]) value), prefix + property, cache));
} else if (Map.class.isAssignableFrom(value.getClass())) {
beanMap.putAll(convertMap((Map) value, prefix + property, cache));
} else {
beanMap.putAll(convertObject(value, prefix + property, cache));
}
} catch (Exception e) {
e.printStackTrace();
}
}
return beanMap;
}
private static Map<String, Object> getProperties(Object object) {
Map<String, Object> propertyMap = getFields(object);
//getters take precedence in case of any name collisions
propertyMap.putAll(getGetterMethods(object));
return propertyMap;
}
private static Map<String, Object> getGetterMethods(Object object) {
Map<String, Object> result = new HashMap<String, Object>();
BeanInfo info;
try {
info = Introspector.getBeanInfo(object.getClass());
for (PropertyDescriptor pd : info.getPropertyDescriptors()) {
Method reader = pd.getReadMethod();
if (reader != null) {
String name = pd.getName();
if (!"class".equals(name)) {
try {
Object value = reader.invoke(object);
result.put(name, value);
} catch (Exception e) {
//you can choose to do something here
}
}
}
}
} catch (IntrospectionException e) {
//you can choose to do something here
} finally {
return result;
}
}
private static Map<String, Object> getFields(Object object) {
return getFields(object, object.getClass());
}
private static Map<String, Object> getFields(Object object, Class<?> classType) {
Map<String, Object> result = new HashMap<String, Object>();
Class superClass = classType.getSuperclass();
if (superClass != null) result.putAll(getFields(object, superClass));
//get public fields only
Field[] fields = classType.getFields();
for (Field field : fields) {
try {
result.put(field.getName(), field.get(object));
} catch (IllegalAccessException e) {
//you can choose to do something here
}
}
return result;
}
private static Map<String, String> convertAll(Collection<Object> values, String key, Set cache) {
Map<String, String> valuesMap = new HashMap<String, String>();
Object[] valArray = values.toArray();
for (int i = 0; i < valArray.length; i++) {
Object value = valArray[i];
if (value != null) valuesMap.putAll(convertObject(value, key + "[" + i + "]", cache));
}
return valuesMap;
}
private static Map<String, String> convertMap(Map<Object, Object> values, String key, Set cache) {
Map<String, String> valuesMap = new HashMap<String, String>();
for (Object thisKey : values.keySet()) {
Object value = values.get(thisKey);
if (value != null) valuesMap.putAll(convertObject(value, key + "[" + thisKey + "]", cache));
}
return valuesMap;
}
private static ConvertUtilsBean converter = BeanUtilsBean.getInstance().getConvertUtils();
private static Map<String, String> convertObject(Object value, String key, Set cache) {
//if this type has a registered converted, then get the string and return
if (converter.lookup(value.getClass()) != null) {
String stringValue = converter.convert(value);
Map<String, String> valueMap = new HashMap<String, String>();
valueMap.put(key, stringValue);
return valueMap;
} else {
//otherwise, treat it as a nested bean that needs to be described itself
return recursiveDescribe(value, key, cache);
}
}
}
The challenge (or show stopper) is problem that we have to deal with an object graph instead of a simple tree. A graph may contain cycles and that requires to develop some custom rules or requirements for the stop criteria inside the recursive algorithm.
Have a look at a dead simple bean (a tree structure, getters are assumed but not shown):
public class Node {
private Node parent;
private Node left;
private Node right;
}
and initialize it like this:
root
/ \
A B
Now call a describe on root. A non-recursive call would result in
{parent=null, left=A, right=B}
A recursive call instead would do a
1: describe(root) =>
2: {parent=describe(null), left=describe(A), right=describe(B)} =>
3: {parent=null,
{A.parent=describe(root), A.left=describe(null), A.right= describe(null)}
{B.parent=describe(root), B.left=describe(null), B.right= describe(null)}}
and run into a StackOverflowError because describe is called with objects root, A and B over and over again.
One solution for a custom implementation could be to remember all objects that have been described so far (record those instances in a set, stop if set.contains(bean) return true) and store some kind of link in your result object.
You can simple use from the same commom-beanutils:
Map<String, Object> result = PropertyUtils.describe(obj);
Return the entire set of properties for which the specified bean provides a read method.
