First create a mapper :

import com.fasterxml.jackson.databind.ObjectMapper;// in play 2.3
ObjectMapper mapper = new ObjectMapper();

As Array:

MyClass[] myObjects = mapper.readValue(json, MyClass[].class);

As List:

List<MyClass> myObjects = mapper.readValue(jsonInput, new TypeReference<List<MyClass>>(){});

Another way to specify the List type:

List<MyClass> myObjects = mapper.readValue(jsonInput, mapper.getTypeFactory().constructCollectionType(List.class, MyClass.class));

First, define POJOs for mapping your request object:

public class RequestObj implements Serializable{

    private List<Long> ids;

    private UsuarioDTO user;

    /* getters and setters here */

}

public class UsuarioDTO implements Serializable{

    private String name;
    private String email;

    /* getters and setters here */

}

And then modify your endpoint:

@PostMapping(value = "/sendToOficial")
public ResponseEntity<?> sendToOficial(@RequestBody RequestObj payload) {

In this way you also do not need to use an ObjectMapper. Just call payload.getIds().

Consider also that in this way if payload changes you'll need only to change RequestObj definition, while using ObjectMapper would force you to update also your endpoint in an important way. It's better and safer to separate payload representation from control logic.

The problem is not in your code but in your json:

{"Compemployes":[{"id":1001,"name":"jhon"}, {"id":1002,"name":"jhon"}]}

this represents an object which contains a property Compemployes which is a list of Employee. In that case you should create that object like:

class EmployeList{
    private List<Employe> compemployes;
    (with getter an setter)
}

and to deserialize the json simply do:

EmployeList employeList = mapper.readValue(jsonString,EmployeList.class);

If your json should directly represent a list of employees it should look like:

[{"id":1001,"name":"jhon"}, {"id":1002,"name":"jhon"}]

Last remark:

List<Employee> list2 = mapper.readValue(jsonString, 
TypeFactory.collectionType(List.class, Employee.class));

TypeFactory.collectionType is deprecated you should now use something like:

List<Employee> list = mapper.readValue(jsonString,
TypeFactory.defaultInstance().constructCollectionType(List.class,  
   Employee.class));

You will need to pass a TypeReference to readValue with the desired result type:

ObjectMapper mapper = new ObjectMapper();
List<Map<String, Object>> data = mapper.readValue(json, new TypeReference<List<Map<String, Object>>>(){});

You are asking Jackson to parse a StudentList. Tell it to parse a List (of students) instead. Since List is generic you will typically use a TypeReference

List<Student> participantJsonList = mapper.readValue(jsonString, new TypeReference<List<Student>>(){});

The TypeFactory in Jackson allows to map directly to collections and other complex types:

String json = "[ \"abc\", \"def\" ]";
ObjectMapper mapper = new ObjectMapper();

List<String> list = mapper.readValue(json, TypeFactory.defaultInstance().constructCollectionType(List.class, String.class));

You can convert the result to an object list, or you can pass in a type parameter rather than the List class.

String jsonString = "[{\"id\": \"0\", \"ip\": \"123\", \"mac\": \"456\"}, {\"id\": \"1\", \"ip\": \"111\", \"mac\": \"222\"}]";

With Object

List<Object> items = objectMapper.readValue(
    jsonString,
    objectMapper.getTypeFactory().constructParametricType(List.class, Object.class)
);

With SlaveEntity

List<SlaveEntity> items = objectMapper.readValue(
    jsonString,
    objectMapper.getTypeFactory().constructCollectionType(List.class, SlaveEntity.class)
);

Update

This is what I have come up with, and it works.

EntityTest

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import com.fasterxml.jackson.databind.ObjectMapper;

public class EntityTest {
    public static void main(String[] args) {
        String json = "[{\"id\": \"0\", \"ip\": \"123\", \"mac\": \"456\"}, {\"id\": \"1\", \"ip\": \"111\", \"mac\": \"222\"}]";

        for (SlaveEntity entity : jsonToSlaveEntity(json)) {
            System.out.println(entity);
        }
    }

    public static List<SlaveEntity> jsonToSlaveEntity(String json) {
        ObjectMapper objectMapper = new ObjectMapper();

        try {
           return objectMapper.readValue(
                   json,
                objectMapper.getTypeFactory().constructCollectionType(List.class, SlaveEntity.class)
            );

        } catch (IOException e) {
            e.printStackTrace();
        }
        return new ArrayList<SlaveEntity>();
    }
}

BaseEntity

public class BaseEntity {
    private long id;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }
}

SlaveEntity

import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.FetchType;
import javax.persistence.OneToMany;

import com.fasterxml.jackson.annotation.JsonProperty;

public class SlaveEntity extends BaseEntity {
    private String ip;

    @JsonProperty("mac")
    private String macAddress;

    private String status;

    @OneToMany(mappedBy = "slave", targetEntity = PositionEntity.class, fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    private List<PositionEntity> positions;

    public String getIp() {
        return ip;
    }

    public void setIp(String ip) {
        this.ip = ip;
    }

    public String getMacAddress() {
        return macAddress;
    }

    public void setMacAddress(String macAddress) {
        this.macAddress = macAddress;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public List<PositionEntity> getPositions() {
        return positions;
    }

    public void setPositions(List<PositionEntity> positions) {
        this.positions = positions;
    }

    @Override
    public String toString() {
        return String.format(
                "SlaveEntity [id=%d, ip=%s, mac=%s, status=%s, positions=%s]",
                getId(), ip, macAddress, status, positions);
    }
}

PositionEntity

public class PositionEntity {
    // ?
}

Result

SlaveEntity [id=0, ip=123, mac=456, status=null, positions=null]
SlaveEntity [id=1, ip=111, mac=222, status=null, positions=null]