I'd like to use the CompoundPropertyModel in Wicket for creating a user.
My user class looks like this:
public class User {
private String username;
...
private Address address;
...
}
public class Address{
private String street;
...
}
If I try to access the street of the address via the User's compoundproperty model, I get a nullpointerexception, of course: "user.address.street". So I have to instantiate the class "Address" on my own in advance. Is there a more elegant way to dynamically instantiate member fields?
Thanks
If a User must have an Address, you should create the instance of Address in the constructor for the User. Otherwise, you might do a null check in your getAddress() method and create a new instance if it's null...
public Address getAddress() {
if (address == null) {
address = new Address();
}
return address;
}
Related
How do I find all the person which are having city ="XYZ" in Address collection
public class Person {
#Id
private String id;
private String description
#DBRef
private Address address;
// Getters and Setters
}
public class Address
{
#Id
private String id;
private String area
private String city
// Getters and Setters
}
Mongo understands #DBRef as a reference to another document, in this case, an Address document and ultimately when the object is loaded from MongoDB, those references will be eagerly resolved and this will get populated to the user as a HATEOAS friendly link. You will get back a mapped object that looks the same as if it had been stored embedded within your master document.
You can define your repository, which will map the endpoints to your database, for the given object, like PersonRepository defined below as an example:
import com.mycompany.domain.Person;
import org.springframework.data.mongodb.repository.MongoRepository;
import org.springframework.data.repository.query.Param;
import java.util.List;
public interface PersonRepository extends MongoRepository<Person, String> {
List<Person> findByCity(#Param("city") String city);
}
Another way you could go around this using the query criteria methods is executing two queries.
First query would be to fetch the address documents which have the city = "XYZ". Resolve the ids from the list returned.
Generate another query on the Person entity using the ids from the previous operation.
The following demonstrates this approach
Query addressQuery = new Query(where("city").is("XYZ"));
addressQuery.fields().include("_id");
List<Address> addressList = mongoTemplate.find(addressQuery, Address.class, "address"); // get the addresses list that satisfy the given city criteria
// Resolve the ids for the addresses
final List<ObjectId> addressIds = new ArrayList<ObjectId>(addressList.length);
for(final Address address : addressList) {
addressIds.add(new ObjectId(address.getId()));
}
// Get the Person list using the ids from the previous operation
Query personQuery = new Query(where("address.$id").in(addressIds));
List<Person> list = mongoTemplate.find(personQuery, Person.class, "person");
If you knew the address id before hand you can then use a custom query:
public interface PersonRepository extends MongoRepository<Person, String> {
#Query("{ 'address': {'$ref': 'address', '$id': { '$oid': ?0 } } }")
List<Person> findByAddres(String addressIdAsString);
}
I am trying to use 1 class to change the values of another class.
My first class is Employees. My second class is address.
public class Employee {
private String name;
private Address address;
constructors:
public Employee(){
address = new Address();
name = "";
}
public Employee(String name){
this.name = name;
this.address = new Address();
}
public String getAddress(){
return address.getAddress();
}
public void changeAddress(String number, String street, String city, String province, String postalCode){
address.setNumber(number);
address.setStreet(street);
address.setCity(city);
address.setProvince(province);
address.setPostalCode(postalCode);
}
In my Address class I have a constructor and setters.
When I'm testing,
public static void main(String[] args){
Employee s1 = new Employee("John Doe");
s1.changeAddress("0141", "No5 Road", "Seattle", "WA", "65897");
This doesn't work, because I didn't create an address class.
so that made me try:
Address a1 = new Address();
but how do I link the new address and the employee class together?
I'm not even sure if I am supposed to manually create an address class using Address a1 = new Address() in my tester; or if I am able to include this in my Employee class so I am able to call the changeAddress method without typing out the new address class every time.
The change address method is in the employee class. The address class only has a constructor and setters.
I am trying to make a RESTful application in Java using Spring boot by following the tutorial here. I want to modify it so that I can extract an identifier from the URL and use it to serve requests.
So http://localhost:8080/members/<memberId> should serve me a JSON object with information about the member whose ID is <memberId>. I don't know how to
Map all http://localhost:8080/members/* to a single controller.
Extract the from the URL.
Should the logic of extracting the memberId and using it be part of the controller or a separate class, as per the MVC architecture?
I am new to Spring/Spring-boot/MVC. It is quite confusing to get started with. So please bear with my newbie questions.
Map all http://localhost:8080/members/* to a single controller.
You can use a placeholder in a request mapping to so it'll handle multiple URLs. For example:
#RequestMapping("/members/{id}")
Extract the id from the URL
You can have the value of a placeholder injected into your controller method using the #PathVariable annotation with a value that matches the name of the placeholder, "id" in this case:
#RequestMapping("/members/{id}")
public Member getMember(#PathVariable("id") long id) {
// Look up and return the member with the matching id
}
Should the logic of extracting the memberId and using it be part of the controller or a separate class, as per the MVC architecture?
You should let Spring MVC extract the member id from the URL as shown above. As for using it, you'll probably pass the URL to some sort of repository or service class that offers a findById method.
As you can see in the code below, service for customer are in one controller to get one and to add new customer.
So, you will have 2 services:
http://localhost:8080/customer/
http://localhost:8080/customer/{id}
#RestController("customer")
public class SampleController {
#RequestMapping(value = "/{id}", method = RequestMethod.GET)
public Customer greetings(#PathVariable("id") Long id) {
Customer customer = new Customer();
customer.setName("Eddu");
customer.setLastname("Melendez");
return customer;
}
#RequestMapping(value = "/{id}", method = RequestMethod.POST)
public void add(#RequestBody Customer customer) {
}
class Customer implements Serializable {
private String name;
private String lastname;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public void setLastname(String lastname) {
this.lastname = lastname;
}
public String getLastname() {
return lastname;
}
}
}
class Person{
private String name;
private int age;
private String gender;
//......
}
class Student extends Person{
private String id;
private String schoolBelongTo;
//......
}
public void showInfoOf(Person person){
System.out.println(person.getName());
//......
}
When using function "showInfoOf" ,if an object of Peron is used as the param,OK.However,if it is the type Student,I cannot get access to the field id and schoolBelongTo.
So I am confused ,how to ?
Actually, I want to know is this one of its(Interface oriented programming's or Supper class oriented programming's) disadvantages???
Two possible solutions:
You can programatically check the type in showInfoOf (Person), and use a cast to access & print the desired fields; or,
You can define a method on Person which will print/provide the desired info -- and either replace showPersonInfo() with that entirely, or call it into it. This is the more OO way.
Example:
abstract class Person {
private String name;
private int age;
private String gender;
public void printInfo() {
System.out.println( name);
}
}
class Student extends Person{
private String id;
private String schoolBelongTo;
#Override
public void printInfo() {
super.printInfo();
System.out.println( id);
System.out.println( schoolBelongTo);
}
}
public void showInfoOf (Person person){
person.printInfo();
}
In this example, all functionality has moved to Person.printInfo() and there is no real functionality remaining in showInfoOf (Person).
However in the real-world, you'd probably want move versatility in a Person.provideInfo() function -- perhaps returning a LinkedHashMap of fields & values (since unlabelled values on their own, are not great design).
The showInfoOf (Person) function could then handle formatting & printing the values to the specific requirement, leaving the Person.provideInfo() function general & multi-purpose.
in showInfoOf() you would have to check that person is of type Student, then cast it as a Student to get id or schoolBelongsTo
First of all, I have read this post and did not find the answer for my problem.
I am not sure if this is an aggregated Model class or an aggregated ViewModel class, but this is what I have:
In my WPF (with Prism) application, I have a view 'Filter Customers View' that connects to a service and requests a list of 'Customer' objects, based on a filter.
The list that is returned from the service is this :
List<CustomerDTO> FilteredCustomers;
And the CustomerDTO looks like this:
public class CustomerDTO
{
public Guid CustomerId;
public String Name;
public String Address;
public String PhoneNumber;
public OrderInfoDTO LastOrderInformation;
public List<OtherClass> ListOfSomething;
}
And the OrderInfoDTO looks like this:
public class OrderInfoDTO
{
public Guid OrderId;
public DateTime OrderDate;
public int NumberOfProducts;
public double TotalAmountSpent;
}
And the OtherClass looks like this:
public class OtherClass
{
public Guid Id;
public String SomeText;
}
As you can see - the customer might or might not have a 'Last Order',
I would like to wrap the 'CustomerDTO' object in a ViewModel,
so that I can bind it to the view.
This is what I thought of doing :
public class CustomerViewModel : NotificationObject
{
private CustomerDTO _customerDTO;
public CustomerViewModel(CustomerDTO customerDTO)
{
_customerDTO = customerDTO;
}
public Guid CustomerId
{
get { return _customerDTO.CustomerId; }
set { _customerDTO.CustomerId = value; RaisePropertyChanged("CustomerId "); }
}
public String Name
{
get { return _customerDTO.Name; }
set { _customerDTO.Name = value; RaisePropertyChanged("Name"); }
}
public String Address
{
get { return _customerDTO.Address; }
set { _customerDTO.Address = value; RaisePropertyChanged("Address"); }
}
public String PhoneNumber
{
get { return _customerDTO.PhoneNumber; }
set { _customerDTO.PhoneNumber= value; RaisePropertyChanged("PhoneNumber"); }
}
}
.
Questions:
First of all - is 'CustomerDTO' what is known as a Model ? And is 'OrderInfoDTO' also a Model ? and what about 'OtherClass' ?
How do I treat the 'OrderInfoDTO' in my CustomerViewModel class ? Do I create a 'ViewModel' for it also ? where do I create the 'OrderInfoDTO' view-model ??? What happens if now someone updates the customer and sets the 'OrderInfoDTO' value ?
How do I treat the list of 'OtherClass' in my CustomerViewModel class ? Do I create an ObservableCollection for it ? What happens if someone will want to delete an item in it or update an item in it or add an item to it ?
Think about it this way:
The View is your UI that you would bind elements from the View Model to using the {Binding Path=, Mode=TwoWay -- If you want to update based upon the user input
The Model is only the data, this could a record set, file, database records etc. So CustomerDTO and OrderInfoDTO are models.
The View Model is your link between the data (Model) and the UI (View). It will allow to you change the data so it's easier to present on the UI
You would need to use ObservableCollection in all instances where there's a list that could change in the background.
You don't need a view model for OrderInfoDTO unless you need a view to update that data. If you are presenting a CustomerDTO info with OrderInfoDTO in it, then making it a property of the CustomerDTO view model would be fine.