从 HashMap 获取值并填充 Java 对象

Question

I have map populated from database Data. I need to get values from there to Object. Field names in POJO and key names in Map object are different. I did it as the below. is there any effective way to do this

 Map<String ,Object> map; //retrieved from database

Employee e = new Employee();
if(map!=null) {
    if(map.containsKey("name")) {
        e.setFirstName(map.get("name"));
    }
    if(map.containsKey("ads")) {
        e.setMyAddress(map.get("ads"));
    }
    if(map.containsKey("country")) {
        e.setDealCountry(map.get("country"));
    }
    if(map.containsKey("keyId")) {
        e.Id(map.get("keyId"));
    }
}



public class Employee {
    String firstName;
    String id;
    String myAdreess;
    String dealCountry;
//setter getters
}

Answer 1

You can take a look to Hibernate or other ORM's. They automatically do the mapping for you.

Here for example a link to the Hibernate ORM: https://hibernate.org/

It's easier and faster than make the mapping manuelly. ;)

Answer 2

You can use java8+'s BiConsumer to define a setter for each of the map's keys:

    Map<String, BiConsumer<Employee, String>> consumerMap = new HashMap<>();
    consumerMap.put("name", Employee::setFirstName);
    consumerMap.put("ads", Employee::setMyAddress);
    consumerMap.put("country", Employee::setDealCountry);
    //and so on

    Map<String, String> map = new HashMap<>();//the data from your database 
    Employee e = new Employee();
    if (map != null) {
        consumerMap.forEach((key, value) -> {
            if (map.containsKey(key)) {
                //value is the BiConsumer
                value.accept(e, map.get(key));
            }
        });
    }

The forEach iterates over all the the defined mappings, then checks if your Map from the database has the respective keys and applies the data.

This does not involve any (manual) reflection and the mapping from the map's key to the setter is very direct.