I need to consume this API: https://api.punkapi.com/v2/beers and after consuming, I have to store it in the database, but only with next fields: internal id, name, description and mean value of the temperature. Any ideas or advice?
The simplest approach would be to have your Model only containing those attributes so that Spring only deserialize them from JSON to object. Something like the following:
public class YourModel {
private long id;
private String name;
private String description;
}
Then in your Service you would have:
ResponseEntity<YourModel> response = restTemplate.getForEntity(url, YourModel.class);
You can then either save YourModel directly to the database (first you need to add some #Annotations if you want to rely on JPA) or you may build another more suited model to your use case.
Related
I have a spring app, that pushes data in an s3 bucket.
public class Ebook implements Serializable {
#Column(name= "cover_path", unique = true, nullable = true)
private String coverPath;
private String coverDownloadUrl;
#Value("${aws.cloudfront.region}")
private String awsCloudFrontDns;
#PostLoad
public void init(){
// I want to access the property here
System.out.println("PostConstruct");
String coverDownloadUrl = "https://"+awsCloudFrontDns+"/"+coverPath;
}
When a data is pushed, let's say my cover here, I get the key 1/test-folder/mycover.jpg which is the important part of the future http URL of the data.
When I read the data from database, I enter inside #PostLoad method and I want construct the complete URL using the cloudfront value. This value changes frequently so we don't want to save hardly in the database.
How could I do to construct my full path just after reading the data in database?
The only way to do this is to use a service that update the data after using repository to read it? For readbyId it can be a good solution, but for reading list or using other jpa methods, this solutions won't work because I have each time to create a dedicated service for the update.
It doesn't look good for Entity to depend on property.
How about EntityListener.
#Component
public class EbookEntityListener {
#Value("${aws.cloudfront.region}")
private String awsCloudFrontDns;
#PostLoad
void postload(Ebook entity) { entity.updateDns(awsCloudFrontDns); }
}
I recommend trying this way :)
Lets say in my dao class i have a method annotated with sql: SELECT id, name, lat, long FROM table WHERE id = :id.
i want to map that to object like (pseudo):
public class Something {
public string Id;
public string Name;
public GeoLocation Location;
public Something(id, name, lat, long) {
this.Id = id;
this.Name = name;
this.Location = new GeoLocation(lat, long);
}
}
so, point is that i want to map flat select result into model with children made from some of the return fields.
Important is that i don’t want to have public get/set for all fields that sql returns.
I also want to avoid any room annotations on Something if possible (i am aware of solutions that involve #Embedded annotations).
In room the only possible way to convert fields into POJO that has no boiler point is indeed #Embedded annotation. Thats the best and simplest way to do it.
You can convert your sql query to your desired model with some other few methods which are not feasible.
Intermediate Model. That is convert your SQL result to a model that one to one matches to your fields. i.e.
public class PreSomething {
public string id;
public string name;
public long lat;
public long long;
}
After converting to PreSomething, you can have it get converted Something with any fashion you like.
Another way would be TypeConverters which changes database schema and will require you have database migration.
So, the only possible way is infact #Embedded. Now coming to your requirements,
Important is that i don’t want to have public get/set for all fields
that sql returns.
Every field that's stored in the database needs to be either public or have a "getter" method. Since your fields are all public you don't have to have any get/set for the fields.
I also want to avoid any room annotations on Something if possible (i
am aware of solutions that involve #Embedded annotations).
You have to annotate #Embedded the GeoLocation object (not Something) in order to be able to map your fields to a POJO.
One other thing to note that you SQLite, in that fashion Room, is case sensitive so. If you have to specify your fields with lowercase if your columns are lowercase. Otherwise you have to annotate them with #ColumnInfo and correct column name.
I am trying to Map a JSON response to a Java POJO which has a different field name from different API.
I need an efficient way to do this reducing boilerplate codes.
I have tried mapping the JSON property field in Java POJO.
However, the problem is I am fetching data from different sources.
Let's say I have below user class
Class User{
String name;
String contact;
}
The JSON I may receive from different sources can be
{"name": "ABC" , "contact": "123456"}
or
{"userName": "XYZ" , "mobileNo":"4354665"}
There may be more variations as we go on integrating more API's
Is there a way I can archive this?
above is just a simple example
there could be more complex JSON object I may need to read.
like List of User etc.
You can use the #JsonAlias() to give the variable more than one JSON key binding.
#JsonAlias is introduced in Jackson 2.9 release. #JsonAlias defines one or more alternative names for a property to be accepted during deserialization i.e. setting JSON data to Java object. But at the time of serialization i.e. while getting JSON from Java object, only actual logical property name is used and not alias. #JsonAlias is defined as follows.
#Entity
Class User{
#JsonProperty()
#JsonAlias({"name", "userName"})
String name;
#JsonProperty()
#JsonAlias({"contact", "mobileNo"})
String contact;
}
You could use the #JsonSetter annotation like :
public class User{
public String contact;
public String name;
#JsonSetter("name")
public void setName(String name) {
this.name = name;
}
#JsonSetter("userName")
public void setName(String name) {
this.name = name;
}
}
Instead of directly mapping to an entity class , you should have a DTO object or model in between to map the json response. Then, you can convert that into any entity you may choose.If you are fetching the data from different sources , it means you are calling different endpoints, why don't you create different DTO 's for that.In that way even if one of the endpoints introduce a change , it won't affect the rest of the endpoint calls.
Vice-versa you could have different DTO objects being returned from the two endpoints instead of returning the same Entity class as well, that way you can have control over which attributes should be there in the response.
To reduce the boiler plate code, you could use library such as MAP STRUCT to enable conversion between entity and DTO objects easily
Read here about the advantages of using a DTO .
Using spring-data-jpa and working on getting data out of table where there are about a dozen columns which are used in queries to find particular rows, and then a payload column of clob type which contains the actual data that is marshalled into java objects to be returned.
Entity object very roughly would be something like
#Entity
#Table(name = "Person")
public class Person {
#Column(name="PERSON_ID", length=45) #Id private String personId;
#Column(name="NAME", length=45) private String name;
#Column(name="ADDRESS", length=45) private String address;
#Column(name="PAYLOAD") #Lob private String payload;
//Bunch of other stuff
}
(Whether this approach is sensible or not is a topic for a different discussion)
The clob column causes performance to suffer on large queries ...
In an attempt to improve things a bit, I've created a separate entity object ... sans payload ...
#Entity
#Table(name = "Person")
public class NotQuiteAWholePerson {
#Column(name="PERSON_ID", length=45) #Id private String personId;
#Column(name="NAME", length=45) private String name;
#Column(name="ADDRESS", length=45) private String address;
//Bunch of other stuff
}
This gets me a page of NotQuiteAPerson ... I then query for the page of full person objects via the personIds.
The hope is that in not using the payload in the original query, which could filtering data over a good bit of the backing table, I only concern myself with the payload when I'm retrieving the current page of objects to be viewed ... a much smaller chunk.
So I'm at the point where I want to map the contents of the original returned Page of NotQuiteAWholePerson to my List of Person, while keeping all the Paging info intact, the map method however only takes a Converter which will iterate over the NotQuiteAWholePerson objects ... which doesn't quite fit what I'm trying to do.
Is there a sensible way to achieve this ?
Additional clarification for #itsallas as to why existing map() will not suffice..
PageImpl::map has
#Override
public <S> Page<S> map(Converter<? super T, ? extends S> converter) {
return new PageImpl<S>(getConvertedContent(converter), pageable, total);
}
Chunk::getConvertedContent has
protected <S> List<S> getConvertedContent(Converter<? super T, ? extends S> converter) {
Assert.notNull(converter, "Converter must not be null!");
List<S> result = new ArrayList<S>(content.size());
for (T element : this) {
result.add(converter.convert(element));
}
return result;
}
So the original List of contents is iterated through ... and a supplied convert method applied, to build a new list of contents to be inserted into the existing Pageable.
However I cannot convert a NotQuiteAWholePerson to a Person individually, as I cannot simply construct the payload... well I could, if I called out to the DB for each Person by Id in the convert... but calling out individually is not ideal from a performance perspective ...
After getting my Page of NotQuiteAWholePerson I am querying for the entire List of Person ... by Id ... in one call ... and now I am looking for a way to substitute the entire content list ... not interively, as the existing map() does, but in a simple replacement.
This particular use case would also assist where the payload, which is json, is more appropriately persisted in a NoSql datastore like Mongo ... as opposed to the sql datastore clob ...
Hope that clarifies it a bit better.
You can avoid the problem entirely with Spring Data JPA features.
The most sensible way would be to use Spring Data JPA projections, which have good extensive documentation.
For example, you would first need to ensure lazy fetching for your attribute, which you can achieve with an annotation on the attribute itself.
i.e. :
#Basic(fetch = FetchType.LAZY) #Column(name="PAYLOAD") #Lob private String payload;
or through Fetch/Load Graphs, which are neatly supported at repository-level.
You need to define this one way or another, because, as taken verbatim from the docs :
The query execution engine creates proxy instances of that interface at runtime for each element returned and forwards calls to the exposed methods to the target object.
You can then define a projection like so :
interface NotQuiteAWholePerson {
String getPersonId();
String getName();
String getAddress();
//Bunch of other stuff
}
And add a query method to your repository :
interface PersonRepository extends Repository<Person, String> {
Page<NotQuiteAWholePerson> findAll(Pageable pageable);
// or its dynamic equivalent
<T> Page<T> findAll(Pageable pageable, Class<T>);
}
Given the same pageable, a page of projections would refer back to the same entities in the same session.
If you cannot use projections for whatever reason (namely if you're using JPA < 2.1 or a version of Spring Data JPA before projections), you could define an explicit JPQL query with the columns and relationships you want, or keep the 2-entity setup. You could then map Persons and NotQuiteAWholePersons to a PersonDTO class, either manually or (preferably) using your object mapping framework of choice.
NB. : There are a variety of ways to use and setup lazy/eager relations. This covers more in detail.
Say I have the following Collections
public #Data class Customer {
#Id
private String id;
private String firstName;
private String lastName;
#DBRef
private List<Address> addressList= new ArrayList<Address>();
}
and
public #Data class Address {
#Id
private String id;
private String address;
private String type;
private String customerID;
}
And each Customer has multiple addresses, and I have implemented MongoRepository. Saving customer for the First time is working pretty well customerRepo.save(customerObject) and before calling the save I am persisting multiple Address Objects and then setting those to the addressList.
Next time when I am updating the same document and want to add a New set of Address to the existing list it is overwriting the whole addressList array. So basically what I have to do now to set new address like thisexistingCustomerObject.getAddressList().addAll(my new List of address) if there are thousand(or more than thousand) of elements or I am slicing the addressList array the following procedure won't be a good idea. My question is what is the best way to achieve this scenario? say if I don't want to use MongoTemplate. Is it possible Just using the MongoRepository
I don't think you can do it in that way. Previously i had the same situation, and I tried the following
1.org.springframework.core.convert.converter.Converter even I have managed to manipulate the DBObject but functions like $push or $set(wrapping them under key) does not work over there.
2.AbstractMongoEventListener by overriding onBeforeSave but Object manipulation was not taking place during save.
However you can try altering the mentioned
you can try override MongoRepository save method, It would better if someone point to the right direction.
Otherwise for my scenario I had to create Custom repository(To update and delete document) which is working parallel with MongoRepository (for Insert and retrieve data/document), but I believe thats an ugly workaround. There has to be a cleaner way to do it.