Get from map, set in object using setter, but for too many fields?-CodePudding

Problem

Consider a Pojo class with a lot of fields. A HashMap is given. Get element from map and set in object (Update operation). Following should be considered:

The key name in HashMap and corresponding target field name are not exactly same (see example)
If a key is not present in map, don't update corresponding field
If key is present, update corresponding field (including updating with null)
Do not worry about ClassCastException, map values will be provided with appropriate class type, always.

Example:

Map and Pojo correspondence:

key in HashMap - > field name in Object

numberOfItems -> quantity
paidAmount -> price
adrLine1 -> house
adrLine2 -> road
adrLine3 -> area
adrLine4 -> city
...and 100s more

Pojo class:

private static class MyObject{
    private Integer quantity;
    private Double price;
    private String house;
    private String road;
    private String area;
    private String city;
    ...

    //getter-setters

}

A good old plain approach can be:

private void someMethod(Map<String, Object> updateRequest, MyObject obj){
    if(updateRequest.containsKey("numberOfItems")){
        obj.setQuantity((Integer) updateRequest.get("numberOfItems"));
    }
    if(updateRequest.containsKey("paidAmount")){
        obj.setPrice((Double) updateRequest.get("paidAmount"));
    }
    if(updateRequest.containsKey("adrLine1")){
        obj.setHouse((String) updateRequest.get("adrLine1"));
    }
    if(updateRequest.containsKey("adrLine2")){
        obj.setRoad((String) updateRequest.get("adrLine2"));
    }
    if(updateRequest.containsKey("adrLine3")){
        obj.setArea((String) updateRequest.get("adrLine3"));
    }
    if(updateRequest.containsKey("adrLine4")){
        obj.setCity((String) updateRequest.get("adrLine4"));
    }
    ...
}

But as you can see, this is neither efficient to code, nor comes with a good maintainability.

Something like this would be perfect:

Map<String, Object> updateRequest = //provided
MyObject obj = //provided

List.of(
        Pair.of("numberOfItems", "quantity"),
        Pair.of("paidAmount", "price"),
        Pair.of("adrLine1", "house"),
        Pair.of("adrLine2", "road"),
        Pair.of("adrLine3", "area"),
        Pair.of("adrLine4", "city")
).stream()
.filter(queryPair -> updateRequest.ContainsKey(queryPair.getKey()))
.forEach(queryPair -> obj. set ?? programmatically set field name ?? (updateRequest.get(queryPair.getKey())));

Also feel free to suggest any popular external library that already does this.

CodePudding user response：

Here's a solution that uses lambdas to reify the setters:

Map<String, Object> updateRequest = //provided
MyObject obj = //provided

Map<String, BiConsumer<MyObject, Object>> keyToSetter =
  Map.of(
    "numberOfItems", (o, v) -> o.setQuantity((Integer) v)
    // ...
  );

updateRequest.forEach((k, v) -> keyToSetter.get(k).accept(obj, v));

CodePudding user response：

You can convert your existing myObject instance to a map using ObjectMapper and then merge the two maps. Finally you just have to convert the map to MyObject.

ObjectMapper mapper = new ObjectMapper();
Map<String,Object> myObjectMap = mapper.convertValue(obj, HashMap.class);
inputMap.forEach((k,v)-> myObjectMap.merge(k,v, (v1,v2)-> v2));
MyObject resultObject = mapper.convertValue(myObjectMap , MyObject.class);

Notice the remapping function used above. It only sets value from the inputMap. If no value found for a key, it will keep the value in myObjectMap.