I am stuck at converting Java Bean
to Map
. There are many resources on the internet, but unfortunately they all treat converting simple beans to Maps. My ones are a little bit more extensive.
There's simplified example:
public class MyBean {
private String firstName;
private String lastName;
private MyHomeAddress homeAddress;
private int age;
// getters & setters
}
My point is to produce Map<String, Object>
which, in this case, is true for following conditions:
map.containsKey("firstName")
map.containsKey("lastName")
map.containsKey("homeAddress.street") // street is String
map.containsKey("homeAddress.number") // number is int
map.containsKey("homeAddress.city") // city is String
map.containsKey("homeAddress.zipcode") // zipcode is String
map.containsKey("age")
I have tried using Apache Commons BeanUtils
. Both approaches BeanUtils#describe(Object)
and BeanMap(Object)
produce a Map which "deep level" is 1 (I mean that there's only "homeAddress"
key, holding MyHomeAddress
object as a value). My method should enter the objects deeper and deeper until it meets a primitive type (or String), then it should stop digging and insert key ie "order.customer.contactInfo.home"
.
So, my question is: how can it be easliy done (or is there already existing project which would allow me to do that)?
update
I have expanded Radiodef answer to include also Collections, Maps Arrays and Enums:
private static boolean isValue(Object value) {
final Class<?> clazz = value.getClass();
if (value == null ||
valueClasses.contains(clazz) ||
Collection.class.isAssignableFrom(clazz) ||
Map.class.isAssignableFrom(clazz) ||
value.getClass().isArray() ||
value.getClass().isEnum()) {
return true;
}
return false;
}
Here's a simple reflective/recursive example.
You should be aware that there are some issues with doing a conversion the way you've asked:
This example doesn't address those because I'm not sure how you want to account for them (if you do). If your beans inherit from something other than Object
, you will need to change your idea a little bit. This example only considers the fields of the subclass.
In other words, if you have
public class SubBean extends Bean {
this example will only return fields from SubBean
.
Java lets us do this:
package com.acme.util;
public class Bean {
private int value;
}
package com.acme.misc;
public class Bean extends com.acme.util.Bean {
private int value;
}
Not that anybody should be doing that, but it's a problem if you want to use String
as the keys, because there would be two keys named "value"
.
import java.lang.reflect.*;
import java.util.*;
public final class BeanFlattener {
private BeanFlattener() {}
public static Map<String, Object> deepToMap(Object bean) {
Map<String, Object> map = new LinkedHashMap<>();
try {
putValues(bean, map, null);
} catch (IllegalAccessException x) {
throw new IllegalArgumentException(x);
}
return map;
}
private static void putValues(Object bean,
Map<String, Object> map,
String prefix)
throws IllegalAccessException {
Class<?> cls = bean.getClass();
for (Field field : cls.getDeclaredFields()) {
if (field.isSynthetic() || Modifier.isStatic(field.getModifiers()))
continue;
field.setAccessible(true);
Object value = field.get(bean);
String key;
if (prefix == null) {
key = field.getName();
} else {
key = prefix + "." + field.getName();
}
if (isValue(value)) {
map.put(key, value);
} else {
putValues(value, map, key);
}
}
}
private static final Set<Class<?>> VALUE_CLASSES =
Collections.unmodifiableSet(new HashSet<>(Arrays.asList(
Object.class, String.class, Boolean.class,
Character.class, Byte.class, Short.class,
Integer.class, Long.class, Float.class,
Double.class
// etc.
)));
private static boolean isValue(Object value) {
return value == null
|| value instanceof Enum<?>
|| VALUE_CLASSES.contains(value.getClass());
}
}
You could always use the Jackson Json Processor . Like this:
import com.fasterxml.jackson.databind.ObjectMapper;
//...
ObjectMapper objectMapper = new ObjectMapper();
//...
@SuppressWarnings("unchecked")
Map<String, Object> map = objectMapper.convertValue(pojo, Map.class);
where pojo is some Java bean. You can use some nice annotations on the bean to control the serialization.
You can re-use the ObjectMapper.
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